Patent Publication Number: US-11660167-B2

Title: Dental appliance with repositioning jaw elements

Description:
CROSS-REFERENCE 
     This application is a divisional application of U.S. application Ser. No. 14/186,856, filed Feb. 21, 2014, now U.S. Pat. No. 9,844,424, which is incorporated herein by reference in its entirety and to which application we claim priority under 35 USC § 120. 
    
    
     BACKGROUND 
     The present disclosure is related generally to the field of dental treatment. More particularly, the present disclosure is related to methods, instructions on a computing device readable medium, and devices with repositioning jaw elements. 
     Dental treatments may involve, for instance, restorative and/or orthodontic procedures. Restorative procedures may be designed to implant a dental prosthesis (e.g., a crown, bridge, inlay, onlay, veneer, etc.) intraorally in a patient. Orthodontic procedures may include repositioning misaligned teeth and changing bite configurations for improved cosmetic appearance and/or dental function. Orthodontic repositioning can be accomplished, for example, by applying controlled forces to one or more teeth over a period of time. 
     As an example, orthodontic repositioning may be provided through a dental process that uses positioning appliances for realigning teeth. Such appliances may utilize a thin shell of material having resilient properties, referred to as an “aligner,” that generally conforms to a patient&#39;s teeth but is slightly out of alignment with a current tooth configuration. 
     Placement of such an appliance over the teeth may provide controlled forces in specific locations to gradually move the teeth into a new configuration. Repetition of this process with successive appliances in progressive configurations can move the teeth through a series of intermediate arrangements to a final desired arrangement. 
     Such systems typically utilize materials that are light weight and/or transparent to provide as a set of appliances that can be used serially such that as the teeth move, a new appliance can be implemented to further move the teeth without having to take a new impression of the patient&#39;s teeth at every increment of tooth movement in order to make the successive appliance. 
     In various instances, teeth of a patient&#39;s upper jaw and teeth of the patient&#39;s lower jaw may contact in an incorrect or suboptimal manner (e.g., crowding, crossbite, deep bite). A proper fit of the occlusal surfaces of the teeth is necessary for proper biting and chewing, as well as desirable for aesthetic appearance. Otherwise, premature wear of the teeth, undesirable flexion of the teeth, and/or undesirable forces on dental restorations may be experienced by the patient. For instance, a proper fit can be a function of the relative positions of teeth and the mandible and maxilla, either of which may be retruded or protruded relative to the ideal position. The maxilla (e.g., the upper jaw) is a bone that is fixed to the skull. The mandible (e.g., lower jaw) is a bone that is attached to the skull by numerous muscles which guide its movement. The mandible articulates at its posterior upward extremities with the temporal bone to form the jaw joint. The jaw joint is a loosely connected joint that accommodates the variety of movements of the mandible relative to the maxilla during biting and chewing motions. The numerous muscles attaching the mandible to the skull control and power the complex movements involved in biting and chewing. 
     The position of the lower jaw is governed by at least two factors. The first factor is the best fit or seating of the condyles of the mandible within the joint housing of the temporal bone. The posterior superior most position of the condyle in the joint is usually an ideal position representing full seating. The second factor is the best fit of the teeth between the maxilla and the mandible. Ideally, the teeth fit together best in occlusion with the left and right jaw joint fully seated at the same time, but this is not a requirement. Sometimes, the teeth fit together best with the condyles slightly displaced from the joint. As a result, when the condyles are fully seated, the teeth may not be in their best fitting position. This condition is known as a shift between the centric relationship (condyles fully seated) and the centric occlusion (teeth best fitting). 
     Because the condylar relationship affords some flexibility in the positioning of the jaw, the lower jaw can be intentionally repositioned in accordance with the best fit of the teeth, for instance, by using an orthodontic appliance. The orthodontic appliance used may or may not be displeasing, both physically and aesthetically, to a patient undergoing treatment which intentionally repositions the lower jaw. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1 A  illustrates a side view of an upper jaw with a first repositioning jaw element and a lower jaw with a repositioning jaw element according to a number of embodiments of the present disclosure. 
         FIG.  1 B  illustrates a front view of an upper jaw with a first repositioning jaw element and a third repositioning jaw element and a lower jaw with a second repositioning jaw element and a fourth repositioning jaw element according to a number of embodiments of the present disclosure. 
         FIG.  1 C  illustrates a side view of a first shell with a first repositioning jaw element and a second shell with a second repositioning jaw element according to a number of embodiments of the present disclosure. 
         FIG.  2 A  illustrates a side view of an upper jaw with a first repositioning jaw element and a lower jaw with a second repositioning jaw element according to a number of embodiments of the present disclosure. 
         FIG.  2 B  illustrates a front view of an upper jaw with a first repositioning jaw element and a third repositioning jaw element and a lower jaw with a second repositioning jaw element and a fourth repositioning jaw element according to a number of embodiments of the present disclosure. 
         FIG.  3    illustrates an example of a method for separating an upper dentition from a lower dentition according to a number of embodiments of the present disclosure. 
         FIGS.  4 A- 4 C  illustrate examples of repositioning jaw elements according to a number of embodiments of the present disclosure. 
         FIGS.  5 A- 5 C  illustrate examples of repositioning jaw elements according to a number of embodiments of the present disclosure. 
         FIG.  6    illustrates an example computing device readable medium having executable instructions that can be executed by a processor to perform a method according to one or more embodiments of the present disclosure. 
         FIGS.  7 A- 7 D  illustrate examples of a plurality of devices for repositioning jaws according to a number of embodiments of the present disclosure. 
         FIGS.  8 A- 8 D  illustrate examples of repositioning jaw elements according to a number of embodiments of the present disclosure. 
         FIGS.  9 A- 9 B  illustrate examples of features of devices for repositioning jaws according to a number of embodiments of the present disclosure. 
         FIGS.  10 A- 10 C  illustrate examples of occlusal features of devices for repositioning jaws according to a number of embodiments of the present disclosure. 
         FIGS.  11 A- 11 B  illustrate examples of devices for repositioning jaws according to a number of embodiments of the present disclosure. 
         FIGS.  12 A- 12 B  illustrate examples of devices according to a number of embodiments of the present disclosure. 
         FIGS.  12 C- 12 D  illustrate examples of repositioning jaw elements according to a number of embodiments of the present disclosure. 
         FIGS.  13 A- 13 B  illustrate examples of side surface features according to a number of embodiments of the present disclosure. 
         FIGS.  14 A- 14 B  illustrate examples of repositioning jaw elements for adjusting a midline of a patient according to a number of embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     As discussed above, the present disclosure provides methods, instructions on computing device readable medium, and devices for repositioning jaw elements. Generally, the repositioning occurs during an orthodontic treatment which is a process of moving and reorienting teeth for functional and/or aesthetic purposes, although repositioning may be made for other purposes. 
     Simultaneous contacting of the upper and lower teeth on the right and left sides, and in the anterior and posterior occlusal areas with maximum interdigitation is desired for proper positioning of the lower jaw to the upper jaw in the mouth of a patient. An unbalanced occlusion, such as a malocclusion, is disruptive to the proper biting and chewing functions because excessive forces may be placed in a particular area that can lead to premature wear and/or restoration failure, or because undesirable forces such as flexion may lead to stresses which cause abfraction lesions and/or crowding/spacing of the teeth. The position of a patient&#39;s jaw can be changed, for instance, using an orthodontic appliance (e.g., a dental appliance). 
     Current approaches for jaw repositioning, such as those performed prior to fixed orthodontic treatment (i.e., “braces”) include having a treatment professional place an orthodontic appliance which may include block elements, wires, tensioning springs, horizontal stops, etc., which is firmly fixed to the teeth and which applies repositioning forces to move the jaw of the patient, thereby causing the relative positioning of the patient&#39;s upper and lower jaws to adjust. Some believe that this repositioning stimulates jaw growth in patients with growth potential remaining, while others believe that the muscles can re-learn a new position so long as the teeth are made to fit together well in the new jaw position. In some instances, prior approaches include a removable appliance with block elements. 
     Current appliances for jaw repositioning are not designed to reposition the teeth during the process of jaw repositioning. After adjustment of the position of the patient&#39;s jaw, further orthodontic treatment is performed to move and re-orientate the teeth of the patient for improved dental interdigitation, if necessary. Many of the current jaw repositioning devices can be displeasing to patients, both physically and aesthetically, because the patient does not have the option to remove the appliance even for a short period of time. Such appliances (e.g., Herbst appliance) are typically cemented into place on the patient&#39;s teeth. Depending on whether the jaw change is due to growth or muscular repositioning, realigning the teeth of a patient after repositioning the jaw can result in reversion of the position of the jaw if the teeth are not positioned and/or repositioned in a manner that best supports the new jaw position. This would occur, for example, if the teeth fit better in a jaw position different from the one which is accomplished through the jaw repositioning phase of the treatment. In this situation, the jaw would revert toward its original position or whatever position is most comfortable for the patient when biting since the jaw repositioning appliance has been removed. Therefore, the desire is to reposition the jaw to an optimal relation while at the same time arrange the teeth such that they fit together the best both in arch coordination between the upper and lower arches and in interdigitation between the arches. The interdigitation makes the patient more likely to keep the lower jaw in the new position since the teeth fit together the best in the interdigitated position. 
     Repositioning a jaw (e.g., separation of occlusal surfaces and/or moving forward or backward the position of a lower jaw) according to embodiments of the present disclosure can include utilizing a set of one or more appliances, such as positioners, retainers, and/or other removable appliances (e.g., clear shells and/or aligners) having a shell to be worn over the teeth of a patient and having a first repositioning jaw element thereon that is positioned to interface, interact, and/or engage a second repositioning jaw element on an appliance on an opposing jaw for separating occlusal surfaces of the patient&#39;s upper dentition and lower dentition and/or to reposition the patient&#39;s jaw. The repositioning jaw elements can place a force on the lower jaw of the patient to sagittally move the lower jaw. Sagittal movement of a jaw, as used herein, can include revising a position of a lower jaw relative to the upper jaw (e.g., in a forward or backward direction). For instance, the position of the patient&#39;s lower jaw can shift sagittally to stimulate jaw growth in patients with growth potential remaining and/or to allow muscles to re-learn a new position. 
     In various embodiments, the movement can be controlled to reposition the patient&#39;s jaw in an anterior-posterior plane with respect to the jaws of the patient. For example, the first repositioning jaw element and the second repositioning jaw element can be positioned to interface as the patient moves to a fully engaged sagittal jaw position of the patient&#39;s upper dentition and the patient&#39;s lower dentition and wherein this movement is designed to reposition the patient&#39;s jaw in an anteroposterior plane with respect to the jaws of the patient. 
     For example, one or more embodiments can include providing a virtual model of a dental appliance having a shell configured to reposition a number of teeth of a patient. The virtual model of the dental appliance can, for instance, be created from a virtual model of the jaw of the patient and/or from a physical mold of the jaw of the patient. A virtual repositioning jaw element can, for example, be positioned on the shell of the virtual model of the dental appliance parallel to a bite plane of the patient and/or can extend from a surface of the shell of the virtual model of the dental appliance. The positioning of the virtual repositioning jaw element and/or the design of the virtual repositioning jaw element can be based on and/or included in a treatment plan. For instance, the treatment plan can include a desired and/or final jaw position. The virtual model of the dental appliance with the revised position of the repositioning jaw element can be used to create a physical dental appliance, for instance, as discussed further herein. 
     A dental appliance, in accordance with some embodiments of the present disclosure, can include a first shell having a number of tooth apertures configured to receive and reposition a number of teeth of a patient&#39;s upper dentition and a second shell having a number of tooth apertures configured to receive and reposition a number of teeth of the patient&#39;s lower dentition. Each shell (e.g., the first shell and second shell) can have a repositioning jaw element extending from a surface of the shells. The repositioning jaw elements can be positioned in each respective shell to interact and/or interface at surfaces in the presence of a fully engaged sagittal jaw position of the patient&#39;s upper jaw and the patient&#39;s lower jaw in order to reposition the patient&#39;s jaw and/or separate occlusal surfaces of the patient&#39;s teeth for treatment purposes. A fully engaged sagittal jaw position, as used herein, can include a relationship of the mandible and the maxilla when the upper and lower jaw are closed as far as the dental appliance with the repositioning jaw elements will allow (e.g., a partial occlusal jaw position). 
     For example, the separation of occlusal surfaces of the patient&#39;s teeth can be used to treat sagittal malocclusions (including crossbites), deep bites, open bites, and/or other malocclusions, in various embodiments. The repositioning jaw elements can be positioned such that the repositioning jaw elements avoid interference with the shells of the dental appliance that are used to align the teeth. For instance, the separation of occlusal surfaces can include the occlusal surfaces of at least some of the teeth within and/or a portion of occlusal surfaces of the shells interacting with one or more surfaces of the repositioning jaw elements of a shell on an opposing jaw. In this manner, a dental appliance in accordance with embodiments of the present disclosure can be used to concurrently treat sagittal malocclusions, including crossbite and/or deep bite, while simultaneously repositioning a number of teeth of the patient. Further, in some embodiments, all of this tooth and jaw movement can be planned via computing device executable instructions and therefore, excessive or redundant movements between the two typically separate processes can be avoided. Additionally, a virtual model can be created and tested so that the patient does not have to be subjected to trial and error to achieve proper jaw and teeth positioning. The ability to visualize the repositioned jaws and establish the alignment in the repositioned configuration is advantageous because the best alignment of the teeth when the jaw is repositioned can be precisely established and can be different from the alignment when the jaws are not repositioned into an improved or optimal position. 
     In some embodiments, a plurality of appliances can be worn by a patient successively to achieve gradual simultaneous and/or sequential repositioning of the patient&#39;s jaw and/or gradual tooth movement. For instance, each of a plurality of dental appliance can reposition the patient&#39;s jaw in incremental distances. In such embodiments, the positions of the repositioning jaw elements can be adjusted to allow the treatment professional to fine tune the movement of the jaw symmetrically or asymmetrically and/or to move the teeth incrementally which may be less painful than with fixed appliances which may impart more sudden force in the initial period of the process than later in the process, among other benefits. 
     In the detailed description of the present disclosure, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration how one or more embodiments of the disclosure may be practiced. These embodiments are described in sufficient detail to enable those of ordinary skill in the art to practice the embodiments of this disclosure, and it is to be understood that other embodiments may be utilized and that process, electrical, and/or structural changes may be made without departing from the scope of the present disclosure. As used herein, the designator “N” and “P”, particularly with respect to reference numerals in the drawings, indicates that a number of the particular feature so designated can be included. As used herein, “a number of” a particular thing can refer to one or more of such things (e.g., a number of teeth can refer to one or more teeth). 
     The figures herein follow a numbering convention in which the first digit or digits correspond to the drawing figure number and the remaining digits identify an element or component in the drawing. Similar elements or components between different figures may be identified by the use of similar digits. For example, 106 may reference element “06” in  FIG.  1   , and a similar element may be referenced as  206  in  FIG.  2   . As will be appreciated, elements shown in the various embodiments herein can be added, exchanged, and/or eliminated so as to provide a number of additional embodiments of the present disclosure. In addition, as will be appreciated, the proportion and the relative scale of the elements provided in the figures are intended to illustrate certain embodiments of the present disclosure, and should not be taken in a limiting sense. 
       FIG.  1 A  illustrates a side view of an upper jaw  102  with a first repositioning jaw element  106  and a lower jaw  104  with a second repositioning jaw element  108  according to a number of embodiments of the present disclosure. The upper jaw  102 , the first repositioning jaw element  106 , the lower jaw  104 , and the second repositioning jaw element  108  illustrated in  FIG.  1 A  include virtual images of jaws and repositioning jaw elements, respectively (e.g., virtual jaws and/or virtual repositioning jaw elements), as discussed further herein. The upper jaw  102  can include a maxilla, its related soft and hard tissues, and can include a number of teeth of a patient&#39;s upper dentition. The lower jaw  104  can include a mandible, its related soft and hard tissues, and can include a number of teeth of the patient&#39;s lower dentition. 
     In some instances, the patient may exhibit abnormal occlusion or malocclusion. For instance, this may include a jaw (or both) that is protrusive, retrusive, or laterally displaced. As an example, positioning of the number of teeth of the patient&#39;s upper dentition and the number of teeth of the patient&#39;s lower dentition can be such that the best fit of the upper dentition with the lower dentition results in a misalignment of the lower jaw  104  relative to the upper jaw  102  either in positional relations or at the level of the jaw joint which connects the lower jaw  104  to the upper jaw  102 . The lower jaw  104  can be in a retruded position, for instance, resulting in a distance (e.g., space) between the front teeth of the upper dentition and the front teeth of the lower dentition (e.g., an increased overjet). Correction of the malocclusion can be beneficial to the patient in terms of improved chewing ability, reduced premature wear of the teeth, and/or improved facial aesthetics. 
     In some embodiments, the upper jaw  102  and lower jaw  104  illustrated in  FIG.  1 A  can include a virtual model of the patient&#39;s upper jaw and lower jaw. A virtual model of one or more dental appliances (e.g., an appliance for the upper dentition and an appliance for the lower dentition which may also be connected together) each having a shell configured to reposition a number of teeth of the patient can be provided. The virtual model of the dental appliance can include a virtual model of a dental appliance configured to reposition the number of teeth of the patient. 
     Repositioning jaw elements can be positioned on occlusal, buccal, and/or lingual surfaces of a dental appliance to be placed over the patient&#39;s teeth. A repositioning jaw element, as used herein, can include a portion of material (e.g., a geometric shaped element, such as a block shape) extending from a surface of the shell of the appliance, as discussed further herein. For instance, a virtual repositioning jaw element can be positioned on the shell of the virtual model of the dental appliance parallel to a bite plane of the patient. A bite plane, as used herein, can include a surface from the incisal edges of the incisors and the tips of the occluding surfaces of the posterior teeth that is a mean of the curvature of the surface. 
     In some embodiments, the position of the virtual repositioning jaw element can be revised to align with a midline (e.g., middle) of at least one tooth of the number of teeth wherein the virtual repositioning jaw element extends from a surface of the shell of the virtual model of the dental appliance. However, embodiments in accordance with the present disclosure are not so limited and the virtual repositioning jaw elements may not be aligned with a midline of the at least one tooth in various embodiments. The virtual model of the dental appliance, including the virtual repositioning jaw element, can be used to determine a treatment plan for the patient and/or to form a physical dental appliance and/or physical repositioning jaw element (e.g., as discussed further herein). 
     The physical repositioning jaw element can be formed of a variety of material types. In some embodiments, the physical repositioning jaw element can be formed of the same material as the shell of the dental appliance (e.g., a polymeric material). For instance, the physical repositioning jaw element can be formed integrally with the shell and/or formed of a same material as the shell. 
     The repositioning jaw elements can also be positioned in different places, in some embodiments. For example, the first repositioning jaw element  106  and the second repositioning jaw element  108  can be positioned near occlusal surfaces of the teeth of the patient to advance the placement of the lower jaw  104  in an forward direction (e.g., in an anterior direction and/or toward a patient&#39;s lips) or in a backward direction (e.g., in an posterior direction and/or towards the back of the patient&#39;s head). For instance, occlusal surfaces of teeth of the upper jaw  102  and lower jaw  104  can be separated using the first repositioning jaw element  106  and the second repositioning jaw element  108  to move (e.g., to move sagittally) the lower jaw  104  of the patient from an articulation path during opening (e.g., the path that the jaw currently follows when opening) to a desired range of jaw opening extending from an advanced or forward position of occlusion, as described further herein. As an example, the first repositioning jaw element  106  can include a first surface  128  and the second repositioning jaw element  108  can include a second surface  130  to interface, interact, and/or otherwise engage with the first surface  128  of the first repositioning jaw element  106 , as discussed further herein. By moving the lower jaw  104 , muscles associated with movement of the lower jaw  104  can be retrained to a new position (generally in a forward and/or downward direction, or in a backward direction) or the lower jaw may be permitted to grow more fully if the patient has not fully developed skeletally. 
       FIG.  1 B  illustrates a front view of an upper jaw  102  with a first repositioning jaw element  106  and a third repositioning jaw element  110  and a lower jaw  104  with a second repositioning jaw element  108  and a fourth repositioning jaw element  112  according to a number of embodiments of the present disclosure. A front view, as used herein, can include an anterior view and/or a more anterior view of the jaws as compared to a side view. The upper jaw  102 , the first repositioning jaw element  106 , the third repositioning jaw element  110 , the lower jaw  104 , the second repositioning jaw element  108 , and the fourth repositioning jaw element  112  illustrated in  FIG.  1 B  can include virtual images of jaws and repositioning jaw elements, respectively (e.g., virtual jaws and/or virtual repositioning jaw elements), as discussed further herein. As illustrated by  FIG.  1 B , two repositioning jaw elements (e.g., the first repositioning jaw element  106  and the third repositioning jaw element  110 ) can be positioned near (e.g., adjacent to) occlusal surfaces of the upper jaw  102  and two repositioning jaw elements (e.g., the second repositioning jaw element  108  and the fourth repositioning jaw element  112 ) can be positioned near occlusal surfaces of the lower jaw  104 . 
     The first repositioning jaw element  106  can be positioned near the occlusal surfaces of the posterior teeth (in the embodiment illustrated by  FIG.  1 B , the molars and/or bicuspids) of the upper jaw  102  and the second repositioning element  108  can be positioned near the occlusal surfaces of the posterior teeth (in the embodiment illustrated by  FIG.  1 B , the bicuspids) of the lower jaw  104 . The first repositioning jaw element  106  and second repositioning jaw element  108  can be located near a first posterior side of the patient&#39;s dentition. 
     The first repositioning jaw element  106  and the second repositioning jaw element  108  can include surfaces that can interface, interact, and/or engage with a surface of a repositioning jaw element on a shell of an opposing jaw. For instance, a first surface of the first repositioning jaw element  106  can interface, interact, and/or engage with a second surface of the second repositioning jaw element  108 . A surface, as used herein, can include a side and/or end surface of a repositioning jaw element. In some embodiments, the first surface can include a slanted surface on a mesial-facing surface of the first repositioning jaw element  106  and/or the second surface can include a slanted surface on a distal-facing surface of the second repositioning jaw element  108 , for instance. For example, a mesial-facing surface can include a surface of a repositioning jaw element that is in a direction toward the anterior midline of the teeth. A distal-facing surface can include a surface of a repositioning jaw element that is in a direction toward the last tooth in each quadrant of a dental arch. However, embodiments in accordance with the present disclosure are not so limited. A mesial-facing surface, in some embodiments, can be facing toward the facial plane (e.g., normal to the facial plane), whereas a distal-facing surface can be facing away from the facial plane (e.g., normal to the facial plane but in the opposite direction). The surfaces of the repositioning jaw elements, in accordance with embodiments of the present disclosure, can be oriented in a variety of directions. 
     The third repositioning jaw element  110  can be positioned near the occlusal surfaces of the posterior teeth (in embodiment illustrated by  FIG.  1 B , molars and/or bicuspids) of the upper jaw  102  and the fourth repositioning jaw element  112  can be positioned near the occlusal surfaces of the posterior teeth (in the embodiment illustrated by  FIG.  1 B , bicuspids) of the lower jaw  104 . The third repositioning jaw element  110  and the fourth repositioning jaw element  112  can be located near a second posterior side of the patient&#39;s dentition. The third repositioning jaw element  110  and the fourth repositioning jaw element  112  can include surfaces that can interface, interact, and/or engage with a surface of a repositioning jaw element on an opposite jaw. For instance, a third surface of the third repositioning jaw element  110  can interface, interact, and/or engage with a fourth surface of the fourth repositioning jaw element  112 . The third surface can include a slanted surface on a mesial-facing surface of the third repositioning jaw element  110  and the fourth surface can include a slanted surface on a distal-facing surface of the fourth repositioning jaw element  112 , for instance. 
     However, embodiments in accordance with the present disclosure are not so limited. For instance, the surfaces of the repositioning jaw elements  106 ,  108 ,  110 ,  112  can be oriented in a variety of directions. For instance, the first surface of the first repositioning jaw element  106  and the third surface of the third repositioning jaw element  110  can include distal-facing slanted surfaces and/or the second surface of the second repositioning jaw element  108  and the fourth surface of the fourth repositioning jaw element  112  can include mesial-facing slanted surfaces, among other orientations. 
     The surfaces (e.g., that interact and/or interface) of the repositioning jaw elements  106 ,  108 ,  110 ,  112  can be angled, in various embodiments, to guide the lower jaw  104  into position and gain desired lateral or prevent unwanted lateral movement. The surfaces can be angled in buccal-lingual and/or mesial-distal direction, for example. The angle of interacting and/or interfacing surfaces (e.g., two surfaces that are designed to interface, interact, and/or engage with each other either actively or passively) can have the same degree and/or slant or a different degree and/or slant (e.g., as illustrated by the embodiment of  FIGS.  14 A- 14 B ). 
     For example, the first surface of the first repositioning jaw element  106  and the second surface of the second repositioning jaw element  108  can interface at a first slant. The slant can include, for instance, a degree of angle of the repositioning jaw elements. The third surface of the third repositioning jaw element  110  and the fourth surface of the fourth repositioning jaw element  112  can interface at a second slant. 
     The first slant and the second slant, in accordance with a number of embodiments, can include opposing angles. The opposing angles of slants on opposing posterior sides of the patient&#39;s dentition can facilitate desired lateral movement or limit and/or prevent unwanted lateral movement. In some embodiments, the sum of the opposing angles can include 180 degrees. As an example, if the first slant is 70 degrees then the second slant can include 110 degrees. 
     In accordance with some embodiments, the repositioning jaw elements  106 ,  108 ,  110 ,  112  extending from surfaces of a shell can be used to generate distalizing force on at least some of the teeth that are located within the shell. For example, when the repositioning jaw elements  106 ,  108 ,  110 ,  112  interface, the distalizing forces can be isolated to posterior teeth of the upper jaw. The distalizing forces can, in some embodiments, cause tooth movement of the upper jaw posterior teeth in a distal direction. As such, the repositioning jaw elements  106 ,  108 ,  110 ,  112  in various embodiments can be a substitute for Class II elastics. 
     In some embodiments, the repositioning jaw elements  106 ,  108 ,  110 ,  112  can include geometric features to engage with a repositioning jaw element on an opposing jaw. Geometric features, as used herein, can include a variety of protruding geometric shapes (e.g., cylinder, rectangular, etc.) and/or receding geometric shapes (e.g., negative space that matches the protruding geometric shape on a repositioning jaw element on an opposing jaw, as illustrated in the embodiment of  FIG.  8 A ). For example, a geometric feature on the first surface of the first repositioning jaw element  106  can include a convex cylindrical shaped feature and a geometric feature on the second surface of the second repositioning jaw element  108  can include a concave cylindrical shaped feature shaped to mate with the geometric feature on the first surface of the first repositioning jaw element  106 . 
     In some embodiments, the geometric features of a first repositioning jaw element and/or a second repositioning jaw element can include a protrusion and a socket. A socket, in various embodiments, can include a convex geometric shape that is shaped to mate with a geometric shape on an opposing jaw (e.g., as discussed further herein). For example, a first repositioning jaw element can include a protrusion extending from the first repositioning jaw element in a direction toward occlusal surfaces of the opposing jaw. The second repositioning jaw element can include a socket within the second repositioning jaw element. The protrusion of the first repositioning jaw element can fit into the socket of the second repositioning jaw element to assist in guiding the lower jaw into a forward position or a backward position. 
     Alternatively, the protrusion and/or socket can be located within and/or extend from a surface of the shell. In some instances, one or more sockets can be located within and/or extend from a surface of the first shell located behind anterior teeth of the upper jaw. In such an embodiment, the lower incisor teeth can fit into the one or more sockets to guide the lower jaw into a forward position or backward position. 
     Although the present embodiments discuss guiding a jaw into a forward position or backward position, embodiments in accordance with the present disclosure are not so limited. For example, embodiments in accordance with the present disclosure can include guiding a jaw in a variety of directions, such as a mesial-distal direction, as discussed further herein with regards to the embodiment illustrated in  FIGS.  14 A- 14 B . 
       FIG.  1 C  illustrates a side view of a first shell  114  with a first repositioning jaw element  106  and a second shell  116  with a second repositioning jaw element  108  according to a number of embodiments of the present disclosure. The side view can, for instance, include a profile view of the first shell  114  and the second shell  116 . The first shell  114  and the second shell  116 , in some embodiments, can include a removable dental appliance. 
     Appliances can include any positioners, retainers, and/or other removable dental appliances for finishing, inducing (e.g., causing small movements in teeth), or maintaining teeth position in connection with a dental treatment. These appliances may be utilized by the treatment professional in completing a treatment plan. For example, a treatment plan can include the use of a set of dental appliances, created according to models described herein. 
     An appliance can, for example, be fabricated from a polymeric shell, and/or formed from other material, having a number of cavities shaped (e.g. tooth apertures) to receive and apply force to reposition one or more teeth from one geometric tooth arrangement to one or more successive tooth arrangements. There may be several appliances that may be needed to move the teeth from the beginning of a dental treatment plan to the end of the plan. The shell may be designed to fit over a number of, or in many instances all, teeth present in the upper and/or lower jaw. For example, a shell can have a cavity that includes a number of tooth apertures for placement of teeth therein. Each tooth aperture can include an interior surface (e.g., directly adjacent to the surfaces of the teeth placed therein) and an exterior surface. The interior surface is configured to receive and reposition a number of teeth of the patient, for example. 
     The first shell  114  can include a number of tooth apertures configured to receive and reposition a number of teeth of a patient&#39;s upper dentition. As illustrated by  FIG.  1 C , a first repositioning jaw element  106  can extend from a surface of the first shell  114 . The first repositioning jaw element  106  can extend from an occlusal surface of the first shell  114 . An occlusal surface of a shell, as used herein, can include an exterior surface of the shell adjacent to and/or extending toward the occlusal surfaces of the teeth on an opposing jaw of the patient. 
     The second shell  116  can include a number of tooth apertures configured to receive and reposition a number of teeth of the patient&#39;s lower dentition. A second repositioning jaw element  108  can extend from a surface of the second shell  116 . For instance, the second repositioning jaw element  108  can extend from an occlusal surface of the second shell  116 . 
     The first repositioning jaw element  106  can include a first surface  128  and the second repositioning jaw element  108  can include a second surface  130  to interface with the first surface  128  of the first repositioning jaw element  106 . For example, as illustrated by the embodiment of  FIG.  1 C , the first repositioning jaw element  106  and the second repositioning jaw element  108  can be positioned to interface, interact, and/or otherwise engage in the presence of a fully engaged sagittal jaw position of the patient&#39;s upper dentition (e.g., the upper jaw  102  illustrated in  FIGS.  1 A- 1 B ) and the patient&#39;s lower dentition (e.g., the lower jaw  104  illustrated in  FIGS.  1 A- 1 B ) in a manner to reposition the patient&#39;s lower jaw. The reposition of the patient&#39;s lower jaw can, for instance, include moving (e.g., moving sagittally) a lower jaw of the patient from an existing articulation reflex path of opening to a desired more extended range of jaw opening whereby the lower jaw is moved forward or backward into a new sagittal jaw position. 
     Alternatively and/or in addition, the repositioning of the patient&#39;s jaw can include a separation of occlusal surfaces of the number of teeth of the patient&#39;s upper dentition from occlusal surfaces of the number of teeth of the patient&#39;s lower dentition as the patient moves to a fully engaged sagittal jaw position. For instance, separating occlusal surfaces can include separating occlusal surfaces to a threshold distance to prevent an occlusal surface of the first shell  114  from contacting or engaging an occlusal surface of the second shell  116 . The threshold distance can include a particular value. For example, the threshold distance can include one millimeter or less, among other values. As discussed above, the separation of occlusal surfaces can include the occlusal surfaces of at least some of the teeth within a shell and/or at least some of an occlusal surface of the shell contacting or engaging with one or more surfaces of the repositioning jaw element of a shell on an opposing jaw. 
     In some embodiments, the separation of occlusal surfaces can be used for treatment of sagittal malocclusion, including excess overjets and anterior crossbite, the correction of transverse malocclusions including lateral crossbites, and/or vertical problems such as deep bite. Malocclusions can be treated using the repositioning jaw elements  106 ,  108  (in addition to a third repositioning jaw element  110  and fourth repositioning jaw element  112  on the opposing posterior side of the jaw, in some embodiments, as illustrated by the embodiment of  FIG.  1 B ) to reposition the jaw of the patient. In some situations, such as anterior crossbite and deep bite can be treated using the repositioning jaw elements  106 ,  108  to allow for individual movement of teeth while the jaws are repositioned into a new relative relationship. 
     Patients with crossbites and/or deep bites can have anterior incisors in the upper jaw and/or the lower jaw that are difficult to move into the desired location because teeth in the opposing jaw are a physical obstruction and therefore can prevent the desired movement from taking place, in some instances. The repositioning jaw elements  106 ,  108  can provide separation of the upper jaw from the lower jaw (e.g., disclusion) by separating an occlusal surface of the first shell  114  from an occlusal surface of the second shell  116 . In various instances, the repositioning jaw elements  106 ,  108  used for the treatment of crossbites and deep bites can be the same buccal-lingual length and can extend from an occlusal, lingual, and/or buccal surface of the first shell  114  and the second shell  116 . 
     The repositioning jaw element  106 ,  108  can be positioned near posterior teeth, for instance, to allow for an anterior portion of the bite of the patient to open enough (e.g., disengage the occlusal interferences that may normally take place) to allow for easier treatment of the crossbite and/or deep bite. For instance, the separation of occlusal surfaces can be caused by preventing the cusp of the molars from sliding back into the fossae on the opposing molars. In such situations, the upper jaw and the lower jaw are held apart and avoid interfering with the prescribed treatment, for example. 
     In accordance with a number of embodiments of the present disclosure, an opening of 5-6 millimeter (mm) at the first premolar region can be desirable for treatment of deep bite, open bite, and/or other malocclusions. For example, an aim of repositioning jaw elements to treat a patient with Class II, Division 1 deep bite can be to cause a 2 mm inter-incisal clearance (e.g., space between the incisal teeth of the upper jaw and incisal teeth of the lower jaw) resulting in a 5-6 mm opening at the first premolar region (e.g., teeth). By contrast, an aim of repositioning jaw elements to treat a patient with Class II, Division II deep bite can be to cause 0 mm of inter-incisal clearance (e.g., portions of the dental appliance with incisal teeth therein contact) resulting in a 5-6 mm opening at the first premolar region. Further, an aim of repositioning jaw elements to treat a patient with Class II, open bite can be to increase the inter-incisal clearance, as compared to repositioning jaw elements for Class II, Division 1 deep bite, resulting in a 5-6 mm opening at the premolar region. For example, in a 2 mm anterior open bite patient, a 4 mm inter-incisal clearance can be optimal. In various embodiments, the repositioning jaw element  106 ,  108  can inherently cause disclusion of posterior teeth of the patient. 
     The repositioning jaw elements  106 ,  108  interfacing, interacting, and/or engaging can be used to reposition a patient&#39;s lower jaw (e.g., lower jaw  112  illustrated in the embodiment of  FIG.  1 A- 1 B ) by placing a force on the patient&#39;s jaw. The force can include a force on the jaws of patient for sagittal correction. The force can, for instance, sagittally move the patient&#39;s lower jaw (e.g., in an anterior or posterior direction) to reposition the patient&#39;s jaw. 
     In some embodiments, repositioning jaw elements, such as the first repositioning jaw element  106  and second repositioning jaw element  108 , can include occlusal surfaces of the repositioning jaw elements that substantially follow the contours of the occlusal surfaces of teeth on an opposing jaw of the patient (e.g., as illustrated in the embodiment of  FIG.  12 B ). For instance, the occlusal surface (e.g., the top surface) of the first repositioning jaw element  106  can substantially follow the contours of the occlusal surfaces of the posterior teeth of the lower jaw (e.g., the occlusal surfaces of the posterior teeth of the lower jaw that the first repositioning jaw element  106  may contact). The occlusal surface of the second repositioning jaw element  108  can substantially follow the contours of the occlusal surfaces of the posterior teeth of the upper jaw (e.g., the occlusal surfaces of posterior teeth of the upper jaw that the second repositioning jaw element  108  may contact). Shaping the occlusal surfaces of repositioning jaw elements based on the patient&#39;s dentition may, for instance, avoid interference between cusps of teeth that may otherwise hit interferences in an opposing jaw which could increase the likelihood of unwanted tooth and/or jaw movements. 
     Alternatively and/or in addition, in some embodiments, occlusal surfaces of the repositioning jaw elements and/or other occlusal surfaces of the removable dental appliance can have a geometry that differs from the contours of the occlusal surfaces of teeth that are of an opposing jaw of the patient (e.g., as illustrated in the embodiment of  FIG.  10 C ). For instance, the geometry can include a pattern to match a new jaw position (e.g., forward or backward lower jaw position) of the patient (e.g., as discussed further herein). 
     In accordance with some embodiments of the present disclosure, a removable dental appliance can include the first shell  114  and second shell  116 . The removable dental appliance can be configured to reposition a number of teeth of the patient&#39;s upper dentition and a number of teeth of the patient&#39;s lower dentition concurrently with repositioning of the patient&#39;s jaw. The simultaneous treatment of misalignment of a patient&#39;s jaw (e.g., Class II correction) in conjunction with teeth alignment issues (e.g., rotation, tipping, etc.) can shorten treatments times compared to sequential treatment protocols that first treat the misalignment of a patient&#39;s jaw before treating the misalignment of the patient&#39;s teeth. To help accomplish this objective, the repositioning jaw elements  106 ,  108 , in accordance with a number of embodiments, avoid and/or do not interfere with the engagement of the shell with the teeth contained therein. 
     The simultaneous treatment of misalignment of a patient&#39;s jaw concurrently with teeth misalignment can assist in the treatment of repositioning the patient&#39;s jaw. If untreated, teeth misalignment may encourage occlusion in the original jaw position instead of the desired jaw position (e.g., the intended or final jaw position), since the optimal interdigitation between the arches coincides with the original jaw position. Realignment of the teeth so that the teeth fit together best in the desired jaw position can reinforce the desired jaw position when the appliances are removed. Repositioning of the patient&#39;s jaw can include retraining the muscles associated with the movement of the lower jaw. Due to the misalignment of a patient&#39;s teeth, a lower jaw of the patient can be incorrectly positioned in a retruded position because the teeth position with the best fit may force the jaw into a more retruded position than physiologically comfortable. A treatment whereby the teeth fit better in an anteriorly positioned mandible can relieve the joint compression that may take place when the mandible is retruded. The jaw muscles of the patient can be retrained to hold the lower jaw in a more forward (and more comfortable) position. 
     In contrast, the removable dental appliance embodiments discussed herein can comprise a first shell  114 , a second shell  116 , a first repositioning jaw element  106  extending from a surface of the first shell  114 , and a second repositioning jaw element  108  extending from a surface of the second shell  116  and can concurrently treat misalignment of the patient&#39;s jaw and misalignment of the patient&#39;s teeth. Concurrent treatment can avoid and/or prevent reversion and/or retraining of the muscles in an incorrect position, among other benefits. Further, removable dental appliance embodiments, in accordance with the present disclosure, can result in fewer braces and/or elastics as compared to prior solutions. In growing patients, the concurrent treatment may also encourage growth of the jaw(s) in a more favorable direction. 
     Although the present embodiment of  FIGS.  1 A- 1 C  illustrates repositioning jaw elements extending from an occlusal surface of a shell and/or near an occlusal surface of one or more teeth of a patient, embodiments are not so limited. The repositioning jaw elements, in some embodiments, can extend from a buccal surface, a lingual surface, an occlusal surface, and/or a combination thereof. 
     In some embodiments, the repositioning jaw elements (e.g., first repositioning jaw element  106  and second repositioning jaw element  108  illustrated in  FIG.  1 C ) can be hollow and/or can be filed with a material, such as a tooth colored material, a clear material, an acrylic, and/or a composite, among other materials, including materials that are printed via a three-dimensional (3D) printer or a through a stereolithography process. The extra material can, for instance, provide additional compressive strength as compared to a hollow repositioning jaw element. 
     In some embodiments, the hollow space within the repositioning jaw element can be used as a reservoir for the disbursement of medications or other items within the patient&#39;s mouth. For example, breath freshening agents, medications to aid in moving of teeth and/or improvement of the condition of the teeth and/or gums of the patient may be provided therein and dispensed through holes and/or passages formed in the interior and/or exterior sides of the repositioning jaw element. 
     A hollow repositioning jaw element can increase the flexibility of the shell to which the repositioning jaw element is attached. The increased flexibility introduced can lower the functionality and/or the retention of the dental appliance in a vertical or horizontal direction. For example, as a patient moves to a fully engaged sagittal jaw position and the repositioning jaw elements interface, the force placed on the shell can result in a gingival line of the shell flaring (e.g., moving away) from the gum line of the patient. In a number of embodiments, a number of design features and/or elements can be used to reduce and/or eliminate the increase in flexibility, such as grooves and curved repositioning jaw elements (e.g., as discussed further herein in regards to the embodiment of  FIG.  4   , among other locations). 
     In some embodiments, the repositioning jaw elements can be shaped to minimize and/or prevent degrading the retention and/or functionality of the shell of the dental appliance. For example, the buccal-lingual width of a repositioning jaw element can be different on an occlusal surface of the repositioning jaw element (e.g., top surface) than on a buccal-lingual width of a surface of the repositioning jaw element adjacent to the shell (e.g., bottom surface). For instance, the buccal-lingual width of a repositioning jaw element can be wider on an occlusal surface of the repositioning jaw element than on a buccal-lingual width of a surface of the repositioning jaw element adjacent to the shell. Such a shape can be similar to the construction of an I-beam, as illustrated in the embodiment of  FIG.  12 D , with the wider buccal-lingual occlusal surface interfacing with an occlusal surface of a repositioning jaw element positioned on an opposing jaw. 
     In accordance with some embodiments of the present disclosure, the repositioning jaw elements can be positioned on the removable dental appliance near unerupted and/or removed 2 nd  and/or 3 rd  molar teeth. Repositioning jaw elements positioned on the removable dental appliance near the unerupted and/or removed 2 nd  and/or 3 rd  molar teeth can, for instance, provide increased area for tooth movements. Alternatively and/or in addition, a spring feature can be positioned on the removable dental appliance near unerupted and/or removed 2 nd  and/or 3 rd  molar teeth. For example, a spring feature can be positioned on a first removable dental appliance and a tab feature can be positioned on a second removable dental appliance to interface with the spring feature. The spring feature can guide the lower jaw of the patient to a position (e.g., a forward or backward position), for example (e.g., as illustrated in the embodiment of  FIG.  9 B ). 
     In a number of examples, a variety of features can be used in addition to and/or in place of repositioning jaw elements to guide the lower jaw to a position (e.g., a forward or backward position). Example features can include connecting the first shell and the second shell using material at posterior sides of the shells, a rigid structure, and/or ridges, among other features (e.g., as illustrated in the embodiments of  FIGS.  11 A and  11 B , as discussed further herein). 
       FIG.  2 A  illustrates a side view of an upper jaw  202  with a first repositioning jaw element  206  and a lower jaw  204  with a second repositioning jaw element  208  according to a number of embodiments of the present disclosure. The upper jaw  202 , the first repositioning jaw element  206 , the lower jaw  204 , and the second repositioning jaw element  208  illustrated in  FIG.  2 A  can include virtual images of jaws and repositioning jaw elements, respectively (e.g., virtual jaws and/or virtual repositioning jaw elements), as discussed further herein. As illustrated in the embodiment of  FIG.  2 A , the first repositioning jaw element  206  can be positioned near a buccal surface of the posterior teeth (e.g., molars and bicuspids) of the upper jaw  202  of the patient to move the position (e.g., to move sagittally) of the lower jaw  204  in a forward direction or backward direction. 
     Although not illustrated in  FIG.  2 A , the first repositioning jaw element  206  can extend from a buccal surface of a first shell of a dental appliance. A buccal surface of a shell, as used herein, can include an exterior surface of a shell near the buccal surface of the teeth therein. Further, in various embodiments, the first repositioning jaw element  206  can be positioned near a lingual surface of the first shell. A lingual surface of a shell can include an exterior surface of the shell near the lingual surface of the teeth therein. 
     The second repositioning jaw element  208  can be positioned near a buccal surface of the posterior teeth (e.g., bicuspids) of the lower jaw  204  of the patient to move the position of the lower jaw  204  in a forward direction or backward direction. Although not illustrated in  FIG.  2 A , the second repositioning jaw element  208  can extend from a buccal surface of a second shell of a dental appliance. 
     The first repositioning jaw element  206  and the second repositioning jaw element  208  can interface. For instance, a first surface  228  of the first repositioning jaw element  206  can interface with a second surface  230  of the second repositioning jaw element  208 . The first repositioning jaw element  206  and the second repositioning jaw element  208  can be positioned to interface in a presence of a temporary bite (e.g., a fully engaged sagittal jaw position of the patient&#39;s upper dentition and the patient&#39;s lower dentition) in a manner to reposition the patient&#39;s jaw. A fully engaged sagittal jaw position, as previously discussed, can include a relationship of the mandible and the maxilla when the upper and lower jaw are closed as far as the dental appliance with the repositioning jaw elements will allow (e.g., a partial occlusal jaw position). 
     For example, the first surface  228  of the first repositioning jaw element  206  interfacing with the second surface  230  of the second repositioning jaw element  208  can place a force on the patient&#39;s jaw to reposition the patient&#39;s jaw. The force can, for instance, sagittally move the patient&#39;s lower jaw  204 . 
     In various embodiments, at least one of the repositioning jaw elements  206 ,  208  can extend past an occlusal plane of the upper jaw  202  and/or lower jaw  204  of the patient. For example, the first repositioning jaw element  206  can extend past the occlusal plane of the upper jaw  202  to interface with the second repositioning jaw element  208 . The second repositioning jaw element  208  may not extend past the occlusal plane of the lower jaw  204 , for instance. Alternatively, the second repositioning jaw element  208  can extend past the occlusal plane of the lower jaw  204  to interface with the first repositioning jaw element  206  and the first repositioning jaw element  206  may not extend past the occlusal plane of the upper jaw  202 . Further, in some embodiments, both the first repositioning jaw element  206  and the second repositioning jaw element  208  can extend past the occlusal plane of the upper jaw  202  and the lower jaw  204 , respectively, to interface with one another. 
       FIG.  2 B  illustrates a front view of an upper jaw  202  with a first repositioning jaw element  206  and a third repositioning jaw element  210  and a lower jaw  204  with a second repositioning jaw element  208  and a fourth repositioning jaw element  212  according to a number of embodiments of the present disclosure. The upper jaw  202 , the first repositioning jaw element  206 , the third repositioning jaw element  210 , the lower jaw  204 , the second repositioning jaw element  208 , and the fourth repositioning jaw element  212  illustrated in  FIG.  2 B  can include virtual images of jaws and repositioning jaw elements, respectively (e.g., virtual jaws and/or virtual repositioning jaw elements), as discussed further herein. As illustrated by  FIG.  2 B , two repositioning jaw elements (e.g., the first repositioning jaw element  206  and the third repositioning jaw element  210 ) can be positioned near buccal surfaces of the upper jaw  202  and two repositioning jaw elements (e.g., the second repositioning jaw element  208  and the fourth repositioning jaw element  212 ) can be positioned near buccal surfaces of the lower jaw  204 . 
     For example, the first repositioning jaw element  206  can be positioned near the buccal surfaces of posterior teeth (e.g., molars and/or bicuspids) of the upper jaw  202  and the second repositioning jaw element  208  can be positioned near the buccal surfaces of posterior teeth (e.g., bicuspids) of the lower jaw  204 . The first repositioning jaw element  206  and the second repositioning jaw element  208  can be located near a first posterior side of the patient&#39;s dentition (e.g., positioned on a first posterior side of a first shell and a second shell). 
     The first repositioning jaw element  206  and the second repositioning jaw element  208  can include surfaces designed to interact, interface, and/or otherwise engage with one another. For instance, a first surface of the first repositioning jaw element  206  can interface with a second surface of a second repositioning jaw element  208 . The first surface can include a slanted surface on a mesial-facing surface of the first repositioning jaw element  206  and the second surface can include a slanted surface on a distal-facing surface of the first repositioning jaw element  208 , for example. 
     The third repositioning jaw element  210  can be positioned near the buccal surfaces of posterior teeth (e.g., molars and/or bicuspids) of the upper jaw  202  and the fourth repositioning jaw element  212  can be positioned near the buccal surfaces of posterior teeth (e.g., bicuspids) of the lower jaw  204 . The third repositioning jaw element  210  and the fourth repositioning jaw element  212  can be located near a second posterior side of the patient&#39;s dentition (e.g., positioned on a second posterior side of a shell of a first shell and a second shell). 
     The third repositioning jaw element  210  and the fourth repositioning jaw element  212  can include surfaces designed to interact, interface, and/or otherwise engage with one another. For instance, a third surface of the third repositioning jaw element  210  can interface with a fourth surface of the fourth repositioning jaw element  212 . The third surface can include a slanted surface on a mesial-facing surface of the third repositioning jaw element  210  and the fourth surface can include a slanted surface on a distal-facing surface of the fourth repositioning jaw element  212 , for example. 
     The surfaces of the repositioning jaw elements  206 ,  208 ,  210 ,  212  can be angled, in various embodiments, to guide the lower jaw  204  into the intended and/or final jaw position and/or prevent unwanted lateral movement. The surfaces can be angled in buccal-lingual and/or mesial-distal direction. The angle of the surfaces (e.g., two surfaces that are designed to interface) can be comprised of supplemental angles (e.g., have the same slants at the interface). 
     For example, the first surface of the first repositioning jaw element  206  and the second surface of the second repositioning jaw element  208  can interface at a first slant. The third surface of the third repositioning jaw element  210  and the fourth surface of the fourth repositioning jaw element  212  can interface at a second slant. 
     Although not illustrated by the embodiments of  FIG.  2 B , the first repositioning jaw element  206  can extend from a buccal surface of a first shell of a dental appliance and/or the second repositioning jaw element  208  can extend from a buccal surface of a second shell of the dental appliance. The first repositioning jaw element  206  and the second repositioning jaw element  208  can be located near a first side of the patient&#39;s dentition (e.g., the right side of the patient&#39;s dentition). The third repositioning jaw element  210  can extend from a buccal surface of the first shell of the dental appliance and the fourth repositioning jaw element  212  can extend from a buccal surface of the second shell of the dental appliance. The third repositioning jaw element  210  and the fourth repositioning jaw element  212  can be located near a second side of the patient&#39;s dentition (e.g., a left side of the patient&#39;s dentition). 
     In some embodiments, repositioning jaw elements can extend from a lingual surface of the shells. A lingual surface of a shell can include an exterior surface of the shell near the lingual surface of the teeth therein. For example, in some embodiments, the first repositioning jaw element  206  and third repositioning jaw element  210  can each extend from a lingual surface of the first shell and the second repositioning jaw element  208  and fourth repositioning jaw element  212  can each extend from a lingual surface of the second shell. Positioning the repositioning jaw elements on the lingual surface of the shell can, for instance, result in a dental appliance that is more aesthetically pleasing to the patient because the repositioning jaw elements are less visible to others (e.g., decreasing the prominence of the repositioning jaw elements). 
     Alternatively and/or in addition, a number of repositioning jaw elements can extend from a lingual surface of the shells and a number of repositioning jaw elements can extend from a buccal surface of the shell (e.g., as illustrated by  FIGS.  13 A- 13 B ). In such embodiments, the first repositioning jaw element  206 , the second repositioning jaw element  208 , the third repositioning jaw element  210 , and the fourth repositioning jaw element  212  can each extend from a buccal surface of the first shell and the second shell. In addition, a fifth repositioning jaw element can extend from a lingual surface of the first shell and a sixth repositioning jaw element can extend from a lingual surface of the second shell; a seventh repositioning jaw element can extend from a lingual surface of the first shell and a eighth repositioning jaw element can extend from a lingual surface of the second shell. The fifth repositioning jaw element and sixth repositioning jaw element can be located near the first side of the patient&#39;s dentition and the seventh repositioning jaw element and eight repositioning jaw element can be located near the second side of the patient&#39;s dentition. Positioning repositioning jaw elements on the lingual surface of the shells in addition to the buccal surface of the shells can, for instance, provide additional stability, decrease the aesthetic prominence of the repositioning jaw elements, and/or limit lateral movement, among other benefits. 
     In some embodiments, a plurality of repositioning jaw elements can extend from the buccal surface of the first shell and a plurality of repositioning jaw elements can extend from the buccal surface of the second shell. The plurality of repositioning jaw elements extending from buccal surfaces can, for instance, decrease the prominence of the repositioning jaw elements as compared to a single repositioning jaw element extending from each buccal surface. 
     In accordance with a number of embodiments, a repositioning jaw element extending from a buccal surface can be used to treat crossbite in a patient. For instance, a repositioning jaw element extending from a buccal surface of a first shell and a repositioning jaw element extending from a buccal surface of a second sell can interface to tip a molar tooth in a buccal direction to treat crossbite in a patient. 
       FIG.  3    illustrates an example of a method  320  for separating an upper dentition from a lower dentition according to a number of embodiments of the present disclosure. Separating the upper dentition from the lower dentition according to the method  320  can allow for treatment of malocclusions such as excessive or inadequate overjet, excessive or inadequate overbite, and/or crossbite, for instance. 
     At block  322 , the method  320  includes moving at least one tooth with a dental appliance having a first shell configured to receive a number of teeth of a patient&#39;s upper dentition, the number of teeth comprising the at least one tooth. That is, the first shell can include a shell configured to receive a number of teeth of the patient&#39;s upper dentition and reposition at least one tooth of the number of teeth of the patient&#39;s upper dentition. 
     At block  324 , the method  320  includes separating a patient&#39;s upper dentition from the patient&#39;s lower dentition utilizing the dental appliance. For instance, the separation can include separating the occlusal surfaces to a threshold distance to prevent an occlusal surface of the first shell from contacting an occlusal surface of a second shell. The second shell can include a shell configured to receive a number of teeth of the patient&#39;s lower dentition and reposition at least one tooth of the number of teeth of the patient&#39;s lower dentition. 
     The dental appliance, at block  326 , can interface a first surface of a first repositioning jaw element of the first shell with a second surface of a second repositioning jaw element of a second shell of the dental appliance. The second shell can, for instance, be configured to receive a number of teeth of the patient&#39;s lower dentition. The dental appliance can separate occlusal surfaces of the number of teeth of the patient&#39;s upper dentition from the occlusal surfaces of the number of teeth of the patient&#39;s lower dentition as the patient moves to a fully engaged sagittal jaw position, for example. The surface area of the repositioning jaw elements that engage the upper jaw/shell to the lower jaw/shell while the disengaged areas are separated may be built so that the engagement is a better fit than the existing occlusion (e.g., greater points or surfaces in contact) so that the preferred position of the patient is the engaged surface area instead of the current occlusion. 
     A sagittal jaw position can include a relationship of the mandible and the maxilla when the upper jaw and the lower jaw are closed and the teeth are in contact. A fully engaged sagittal jaw position, as used herein, can include a relationship of the mandible and the maxilla when the upper and lower jaw are closed as far as the dental appliance with the repositioning jaw elements will allow (e.g., as the first surface of a first repositioning jaw element interfaces, interacts, and/or engages the second surface of the second repositioning jaw element). That is, in a fully engaged sagittal jaw position, at least some of the teeth of the upper jaw and at least some of the teeth of the lower jaw are not in contact. Further, in some embodiments, at least some of the occlusal surface of the first shell and the occlusal surface of the second shell are not in contact in a fully engaged sagittal jaw position. 
     As previously discussed, the fully engaged sagittal jaw position may be needed in the treatment of malocclusion such as excess or insufficient overjet, excess or insufficient overbite, and/or crossbite. For instance, separating the occlusal surfaces can allow for moving a lower jaw of the patient or opening up the bite to a desired range of jaw opening extending from the current position of occlusion. It can also allow for decompression of a lower jaw forward from an undesirable backwards position into a more comfortable (and esthetically pleasing) anteriorly displaced position. The advancement can be unilateral or bilateral. 
     In a number of embodiments in accordance with the present disclosure, the occlusal surfaces can be separated to a threshold distance to prevent an occlusal surface of the first shell from contacting an occlusal surface of the second shell. An example threshold distance can be one millimeter, however, a treatment professional may determine another suitable distance and such distances are within the scope of the embodiments of the present disclosure. 
     In various embodiments, the method  320  can include separating the occlusal surfaces of the number of teeth the patient&#39;s upper dentition from the occlusal surfaces of the number of teeth of the patient&#39;s lower dentition as the patient moves to the fully engaged sagittal jaw position in a plurality of incremental distances utilizing a plurality of dental appliances. For example, the repositioning jaw elements can be designed to incrementally treat a malocclusion, such as excessive or inadequate overjet, excessive or inadequate overbite, and/or crossbite by using repositioning jaw elements provided on a plurality of dental appliances. In some embodiments, the increment can include a gradual movement (e.g., sagittal movement) of the lower jaw by shifting the position of the repositioning jaw elements and/or shifting the length of one or more repositioning jaw elements on each of a series of the plurality of dental appliances (e.g., as discussed further herein with regard to  FIG.  7   ). 
       FIGS.  4 A- 4 C  illustrate examples of repositioning jaw elements according to a number of embodiments of the present disclosure.  FIG.  4 A  illustrates an example of two repositioning jaw elements  406 ,  408 . The two repositioning jaw elements  406 ,  408  can be virtual repositioning jaw elements and/or physical repositioning jaw elements. The first repositioning jaw element  406  can include a first repositioning jaw element positioned on a first shell of the dental appliance. The second repositioning jaw element  408  can include a second repositioning jaw element positioned on a second shell of the dental appliance. 
     As illustrated by  FIG.  4 A , the first repositioning jaw element  408  can include a first surface  428  and the second repositioning jaw element  408  can include a second surface  430 . The first surface  428  can be a slanted surface on a mesial-facing surface of the first repositioning jaw element  406  and the second surface  430  can be a slanted surface on a distal-facing surface of the second repositioning jaw element  408 . The surfaces  428 ,  430  can interface at the slant (e.g., the angled surfaces), for instance. 
     In a number of embodiments, a repositioning jaw element can include a curved back surface. For instance, a back surface (a surface on the opposite side relative to the surface that is designed to interface, interact, and/or engage a repositioning jaw element on an opposing jaw) of a repositioning jaw element can be curved in a distal direction. As illustrated by  FIG.  4 A , the back surface of the first repositioning jaw element  406  is curved in a distal direction. The curving can, for instance, improve comfort for a patient due to the reduction in sharp surfaces exposed to the tongue and/or other soft tissues of the mouth. 
       FIG.  4 B  illustrates an example of a repositioning jaw element  434  according to a number of embodiments of the present disclosure. The repositioning jaw element  434  can include a virtual repositioning jaw element and/or a physical repositioning jaw element, for instance. The repositioning jaw element  434  can include four side surfaces  436 ,  438 ,  458  (e.g., the remaining side surface is facing away from the view). The first side surface  436  can include a surface that can interface, interact, and/or engage with another surface of a repositioning jaw element on a shell of an opposing jaw. As illustrated, the first side surface  436  can be slanted. The second side surface  438  can include a back surface that is curved. For instance, the second side surface  438  can be curved in a distal direction to improve comfort for the patient. 
     As illustrated by  FIG.  4 B , in various embodiments, a repositioning jaw element  434  can include a groove  440  on a top surface  452  of the repositioning jaw element  434 . For instance, a reinforcement groove and/or guide groove can be placed on a top surface  452  of a virtual and/or physical repositioning jaw element. The top surface  452  of a repositioning jaw element, as used herein, can include a surface of the repositioning jaw element extending toward an occlusal and/or coronal surface of teeth on an opposing side of the patient&#39;s jaw. A groove, as used herein, can include a hollow channel within a repositioning jaw element. The groove  440  on the top surface  452  of the repositioning jaw element  434  can extend in a horizontal direction (e.g., a mesial-distal direction), for instance. 
     Alternatively and/or in addition, in a variety of embodiments, a repositioning jaw element  434  can include a side groove on a buccal side surface and/or a lingual side surface (e.g., side surface  458 ) of a repositioning jaw element  434 . A buccal side surface of a repositioning jaw element, as used herein, can include a side of the repositioning jaw element extending toward and/or adjacent to the cheek of the patient. A lingual side surface of the repositioning jaw element, as used herein, can include a side of the repositioning jaw element extending toward and/or adjacent to the tongue of the user. Grooves (e.g., a top groove and/or number of side grooves) can, for example, increase a rigidity of the repositioning jaw element  434  as compared to a repositioning jaw element without grooves and/or can minimize and/or prevent degrading the retention and/or functionality of the shell of the dental appliance. A groove can also function on the shell of each jaw during treatment. 
     In various instances, a plurality of side grooves  442 - 1 ,  442 - 2 ,  442 - 3 ,  442 - 4 ,  442 - 5 ,  442 - 6  . . .  442 -N) can be placed on the buccal side surface and/or the lingual side surface (e.g., side surface  458 ) of the repositioning jaw element  434 . For example, the side grooves  442 - 1  . . .  442 -N can be placed on each of the buccal side surface and lingual side surface (e.g., side surface  458 ) of a virtual repositioning jaw element and/or a physical repositioning jaw element. The side grooves  442 - 1  . . .  442 -N can each include a hollow channel within the side surface of the repositioning jaw element  434 . The side grooves  442 - 1  . . .  442 -N can extend in vertical direction (e.g., an inferior-superior direction.) As illustrated by  FIG.  4 B , in some embodiments, a repositioning jaw element  434  can include a top groove  440  on a top surface  452  and side grooves  442 - 1  . . .  442 -N on side surfaces (e.g., side surface  458 ). 
     In some embodiments, the side grooves  442 - 1  . . .  442 -N can include coronal-apical grooves positioned at interproximal regions of at least one of the number of teeth that the repositioning jaw element  434  extends from. That is, each side groove can be placed at an interproximal region of two teeth. 
     Although the present embodiment of  FIG.  4 B  illustrates a top groove  440  and a plurality of side grooves  442 - 1  . . .  442 -N in a V-shape, embodiments in accordance with the present disclosure are not so limited. The grooves can include a variety of geometric shapes and sizes. For instance, the grooves can include portions of circles, hexagons, rectangles, and/or octagons, among other shapes and/or sizes. Geometric patterns may be used in lieu of grooves, so long as the pattern provides adequate structural rigidity that a groove or series of grooves may provide. 
       FIG.  4 C  illustrates an example of a repositioning jaw element  444  according to a number of embodiments of the present disclosure. The repositioning jaw element  444  can be a virtual repositioning jaw element and/or a physical repositioning jaw element, for instance. The repositioning jaw element  444  can include four side surfaces  436 ,  438 ,  446  (the remaining side surface is facing away from the view). The first side surface  436  can include a surface that can interface, interact, and/or engage with another surface. As illustrated, the first side surface  436  can be slanted. The second side surface  438  can include a back surface that is curved. For instance, the second side surface  436  can be curved in a distal direction to improve comfort for the patient. Further, as illustrated by the repositioning jaw element  444  of  FIG.  4 C , the repositioning jaw element  444  can include a top groove  440  in the top surface of the repositioning jaw element  444 . 
     In accordance with some embodiments, a repositioning jaw element  444  can include curved side surfaces. For instance, a buccal side surface and/or a lingual side surface (e.g., side surface  446 ) can be curved in at least one of a buccal and/or lingual direction. As illustrated by  FIG.  4 C , the curved side surface  446  can include a bowed curve. For instance, the curved side surface  446  can result in the top surface of the repositioning jaw element  444  being shaped in a bone shape. A curved side surface  446  can increase a rigidity of the repositioning jaw element  444  as compared to a non-curved side surface and/or can minimize and/or prevent degrading the retention and/or functionality of the shell of the dental appliance, for example, by allowing greater surface area of the shell to engage the teeth than if the side surfaces were not curved. 
       FIGS.  5 A- 5 C  illustrate examples of repositioning jaw elements according to a number of embodiments of the present disclosure.  FIGS.  5 A- 5 C  illustrate an example of a repositioning jaw element. The repositioning jaw element can be a virtual repositioning jaw element and/or a physical repositioning jaw element, in various embodiments. For instance,  FIG.  5 A  illustrates a top-down view  550  of the repositioning jaw element. The top-down view  550  of the repositioning jaw element can include a view of two side surfaces with side grooves  542 - 1 ,  542 - 2 ,  542 - 3 ,  542 - 4 ,  542 - 5 ,  542 - 6 ,  542 - 7 ,  542 - 8 ,  542 - 9  . . .  542 -P, a surface that can interface, interact, and/or engage with another surface  536 , a back surface  538 , and a top surface  552 . 
     In accordance with some embodiments, side surfaces can be beveled. For instance, the buccal side surface and lingual side surface with side grooves  542 - 1  . . .  542 -P can be beveled to include a different buccal-lingual width on a bottom than a top of the side surfaces of the repositioning jaw element. For example, the buccal-lingual width on the bottom can be wider than the buccal-lingual width on the top of the side surfaces of the repositioning jaw element. In such embodiments, the occlusal surface of the repositioning jaw element can have a narrower buccal-lingual width than a surface of the repositioning jaw element adjacent to and/or near the shell of the dental appliance (e.g., bottom surface of the repositioning jaw element). Beveling of the side surfaces can, for instance, include beveling the surface  536  and/or the back surface  538  to have a wider buccal-lingual width on the top than the bottom of the side surfaces (e.g., as discussed further with regard to  FIG.  5 B ). Beveling the side surfaces  536 ,  538  and side grooves  542 - 1  . . .  542 -P can, for example, assist in manufacturing the dental appliance where the appliance is built from a positive reference model (e.g., such as a 3D printed model or stereolithography (SLA) model). 
     The repositioning jaw element illustrated in  FIG.  5 A  can include a plurality of side grooves  542 - 1  . . .  542 -P on a buccal side surface and/or a mesial side surface. Beveling the buccal side surface and/or lingual side surface can, for instance, include beveling the side grooves  542 - 1  . . .  542 -P. For instance, the buccal-lingual width of the bottom of the side grooves  542 - 1  . . .  542 -P (the surface adjacent to and/or near the shell) can be wider than the buccal-lingual width of the top of the side grooves  542 - 1  . . .  542 -P (the surface of the side grooves adjacent to and/or near the top surface  552  of the repositioning jaw element). 
       FIG.  5 B  illustrates a view  553  of the repositioning jaw element. The repositioning jaw element of  FIGS.  5 A and  5 B  can include the same and/or different repositioning jaw elements, in various instances. For example,  FIG.  5 B  can include a view of repositioning jaw element illustrated in the embodiment of  FIG.  5 A  from the point of view of arrow  541 . 
     The view  553  of the repositioning jaw element can include a view of the surface that can interface, interact, and/or engage with another surface (e.g., the surface  536  of  FIG.  5 A ). For instance, the surface can include a top adjacent to a top surface  552  of the repositioning jaw element, a bottom adjacent to a bottom surface  554  of the repositioning jaw element, and two sides adjacent to the buccal and/or lingual side surfaces  531 - 1 ,  531 - 2  of the repositioning jaw element. 
     As illustrated by  FIG.  5 B , the buccal-lingual width of the surface can be beveled. For instance, the buccal-lingual width of the bottom of the surface (e.g., adjacent to the bottom surface  554  of the repositioning jaw element) can be wider than the buccal-lingual width of the top of the surface (e.g., adjacent to the top surface  552  of the repositioning jaw element). 
     Further, as illustrated by the arrow  556 , the surface that can interface, interact, and/or engage with another surface can be slanted. For instance, the surface can be slanted at an angle in a mesial-distal direction. 
       FIG.  5 C  illustrates an example side view  560  of a repositioning jaw element. The repositioning jaw element can be a virtual repositioning jaw element and/or a physical repositioning jaw element, in some embodiments. The repositioning jaw element of  FIGS.  5 A,  5 B, and  5 C  can include the same and/or different repositioning jaw elements, in various instances. For example,  FIG.  5 C  can include a view of repositioning jaw element illustrated in the embodiment of  FIG.  5 A  from the point of view of arrow  543 . The side view  560  can include a view of a buccal and/or lingual side surface  558 . The buccal and/or lingual side surface  558  can include a top adjacent to a top surface  552  of the repositioning jaw element, a bottom adjacent to a bottom surface  554  of the repositioning jaw element, a first side adjacent to the surface that can interface, interact, and/or engage with another surface  536  of the repositioning jaw element, and a second side adjacent to a back surface  538  of the repositioning jaw element. The buccal and/or lingual side surface  558 , as illustrated by  FIG.  5 C , can include a plurality of side grooves. 
     As illustrated by  FIG.  5 C , repositioning jaw elements in accordance with the present disclosure can include a slant in height from the surface  536  to the back surface  538 . For instance, the slant in height can include a higher coronal-apical height of a repositioning jaw element in a mesial direction than a coronal-apical height of the repositioning jaw element in a distal direction. Such a slant can, for instance, create a more comfortable experience for the patient as the jaw of the patient may not close in a flat direction (e.g., not parallel to a horizontal plane). In other words, the vertical distance between the upper jaw and the lower jaw may be greater in the anterior region than in the posterior region for some patients or greater in the posterior region than in the anterior region for others, depending on the original positioned and the desired position (e.g., the intended and/or final position) of the jaw. By accommodating these variances, the patient may occlude in more points (and the temporary bite will be more stable) than if an even flat plane was designed into the temporary bite. 
       FIG.  6    illustrates an example computing device readable medium having executable instructions that can be executed by a processor to perform a method according to one or more embodiments of the present disclosure. For instance, a computing device  664  can have a number of components coupled thereto. The computing device  664  can include a processor  666  and a memory  668 . The memory  668  can have various types of information including data  670  and executable instructions  672 , as discussed herein. 
     The processor  666  can execute instructions  672  that are stored on an internal or external non-transitory computer device readable medium (CRM). A non-transitory CRM, as used herein, can include volatile and/or non-volatile memory. Volatile memory can include memory that depends upon power to store information, such as various types of dynamic random access memory (DRAM), among others. Non-volatile memory can include memory that does not depend upon power to store information. 
     Memory  668  and/or the processor  666  may be located on the computing device  664  or off the computing device  664 , in some embodiments. As such, as illustrated in the embodiment of  FIG.  6   , the computing device  664  can include a network interface  674 . Such an interface  674  can allow for processing on another networked computing device, can be used to obtain information about the patient, and/or can be used to obtain data and/or executable instructions for use with various embodiments provided herein. 
     As illustrated in the embodiment of  FIG.  6   , the computing device  664  can include one or more input and/or output interfaces  678 . Such interfaces  678  can be used to connect the computing device  664  with one or more input and/or output devices  680 ,  682 ,  684 ,  686 ,  688 . 
     For example, in the embodiment illustrated in  FIG.  6   , the input and/or output devices can include a scanning device  680 , a camera dock  682 , an input device  684  (e.g., a mouse, a keyboard, etc.), a display device  686  (e.g., a monitor), a printer  688 , and/or one or more other input devices. The input/output interfaces  678  can receive executable instructions and/or data, storable in the data storage device (e.g., memory), representing a virtual dental model of a patient&#39;s dentition. 
     In some embodiments, the scanning device  680  can be configured to scan one or more physical dental molds of a patient&#39;s dentition. In one or more embodiments, the scanning device  680  can be configured to scan the patient&#39;s dentition and/or dental appliance directly. The scanning device  680  can be configured to input data into the computing device  664 . 
     In some embodiments, the camera dock  682  can receive an input from an imaging device (e.g., a 2D or 3D imaging device) such as a digital camera, a printed photograph scanner, and/or other suitable imaging device. The input from the imaging device can, for example, be stored in memory  668 . 
     The processor  666  can execute instructions to provide a visual indication of a treatment plan, a dental appliance, and/or a repositioning jaw element on the display  686 . The computing device  664  can be configured to allow a treatment professional or other user to input treatment goals. Input received can be sent to the processor  666  as data  670  and/or can be stored in memory  668 . 
     Such connectivity can allow for the input and/or output of data and/or instructions among other types of information. Some embodiments may be distributed among various computing devices within one or more networks, and such systems as illustrated in  FIG.  6    can be beneficial in allowing for the capture, calculation, and/or analysis of information discussed herein. 
     The processor  666 , in association with the data storage device (e.g., memory  668 ), can be associated with the data  670 . The processor  666 , in association with the memory  668 , can store and/or utilize data  670  and/or execute instructions  672  for placing virtual repositioning jaw elements on a shell of a virtual model of a dental appliance. Such data can include the virtual dental model. The virtual model of the dental appliance with the repositioning jaw element can be used to create a physical dental appliance, for instance, as discussed further herein. 
     The processor  666  coupled to the memory  668  can cause the computing device  664  to perform a method including, for example, providing a virtual model of a dental appliance having a shell configured to reposition a number of teeth of a patient. In various embodiments of the present disclosure, the processor  666  coupled to the memory  668  can cause the computing device  664  to perform the method including positioning a virtual repositioning jaw element on the shell of the virtual model of the dental appliance parallel to a bite plane of the patient, wherein the repositioning jaw element extends from a surface of the shell of the virtual model of the dental appliance. 
     For instance, to position the virtual repositioning jaw element parallel to a bite plane can include, in some embodiments, removing a virtual image of the number teeth of the patient. With the teeth removed, a virtual representation of the bite plane of the patient can remain and the virtual repositioning jaw element can be positioned parallel to the bite plane. 
     Further, in some embodiments, the processor  666  coupled to the memory  668  can cause the computing device  664  to perform the method including revising the position of the virtual repositioning jaw element to align with a midline of at least one tooth of the number of teeth. For instance, in some embodiments, the virtual image of the number of teeth can be displayed (e.g., such as, after being removed) and the position of the virtual repositioning jaw element can be automatically revised to align with the midline of the at least one tooth that the virtual repositioning jaw element extends from. 
     In some embodiments, the processor  666  coupled to the memory  668  can cause the computing device  664  to perform the method including determining a degree of the patient&#39;s jaw alignment utilizing a virtual image of the jaw of the patient. The virtual image of the jaw of patient can include a virtual image of the mandible, its related soft and hard tissue, a number of teeth the patient&#39;s lower dentition, the maxilla, its related soft and hard tissues, and/or a number of teeth of the patient&#39;s lower dentition. The degree of the patient&#39;s jaw alignment can include, for instance, a path of articulation or jaw opening and closing. It may also include a repositioned location such as a protruded position, or a combination of semi-articulation and protrusion, for example. 
     A dental appliance can be made, for example, by thermal-forming a sheet of plastic over a physical dental mold. The physical dental mold, for instance, can represent an incremental position to which a patient&#39;s teeth are to be moved. The physical dental mold can be manufactured by downloading a computer-aided Design (CAD) virtual dental model to a rapid prototyping process, such as, for example, a computer-aided manufacturing (CAM) milling, stereolithography, and/or photolithography. The virtual dental mold can be hollowed out or “shelled” before sent for manufacturing to save on material cost, for example. 
     The dental mold (e.g., set of molded teeth) can be created from a virtual model of a number of teeth of a patient. A virtual model, for example, can include an initial virtual dental model and/or intermediate virtual dental model. A dental mold can be formed in accordance with a unique treatment file that identifies a patient, a stage of a treatment plan, the virtual model of the number of teeth, and/or whether the dental mold is of the upper and/or lower dental arch. 
     In some embodiments, a treatment file can be accessed by a rapid prototyping apparatus machine, such as a SLA or 3D printing, to form and/or create the dental mold. The result of the dental mold can include a set of molded teeth. The set of molded teeth can include at least a replica of the number of teeth of the patient. The dental mold can be used to make a dental appliance, for example, by creating a negative impression of the dental mold using polymeric sheets of material and vacuum forming the sheets over the dental mold, as discussed above. 
     For instance, a dental appliance can be formed by layering a thermoformable sheet of material and/or multiple sheets of one or more materials over the dental mold. The materials can include a polymeric material, for instance. Generally, the dental appliance is produced and/or formed by heating the polymeric thermoformable sheet and vacuum or pressure forming the sheet over the dental mold (e.g., a number of molded teeth). The shape of the sheet of material can change thickness on some portions of the sheet as it conforms to the mold shape. A dental appliance can, for example, include a negative impression of the dental mold. The appliance and/or parts thereof may be transparent, semi-transparent, or opaque in such a way as to emulate a nature tooth shade. However, embodiments in accordance with present disclosure are not so limited. For example, embodiments in accordance with the present disclosure can include forming a dental appliance utilizing a variety of techniques, such as SLA or 3D printing, among other techniques. 
     In a number of embodiments, the processor  666  coupled to the memory  668  can cause the computing device  664  to perform the method of providing a treatment plan. One or more appliances, including positioners, retainers, removable dental appliances, and/or other appliances for finishing and maintaining teeth positioning, can be utilized by a treatment professional in performing a treatment plan. The treatment plan can include the use of one or more dental appliances, as described herein. 
     For example, the processor  666  coupled to the memory  668  can cause the computing device  664  to perform the method comprising identifying a misaligned jaw of a patient from a virtual image of the patient&#39;s jaw. The identification can include, for instance, determining a degree of the patient&#39;s jaw alignment utilizing the virtual image of the patient&#39;s jaw. 
     In some embodiments, the processor  666  coupled to the memory  668  can cause the computing device  664  to perform the method comprising providing a treatment plan for the patient. The treatment plan can include a virtual model of a dental appliance having a first shell and a second shell configured to reposition at least one tooth of the patient. The at least one tooth can, for instance, include a tooth on a lower jaw and/or a tooth on an upper jaw of the patient. Further, the virtual model of the dental appliance can include repositioning jaw elements on the first shell and the second shell configured to move a position of the misaligned jaw of the patient (e.g., to move sagittally a position of the misaligned jaw of the patient). 
     The repositioning jaw elements on the first shell and the second shell can be designed based on an aim of repositioning the misaligned jaw of the patient. A particular repositioning jaw element can have a shape and angle specific to a treatment plan based on at least one of a final and/or intended jaw position, an intended use (e.g., Class I correction, Class II correction, and/or Class III correction), and/or an orientation of a tooth over which the repositioning jaw element is positioned. 
     According to a number of embodiments of the present disclosure, providing a treatment plan for the patient can include identifying a final jaw position of the patient. The final jaw position of the patient can include, for instance, an improved and/or optimized jaw position. For instance, the final jaw position may include simultaneous contacting of the upper and lower teeth on the right and left sides, and in the anterior and posterior occlusal areas with maximum interdigitation, a best fit or seating of the condyles of the mandible within the joint housing of the temporal bone, and/or correction of malocclusions. 
     The identified final jaw position can be used to design the virtual repositioning jaw elements. For instance, the virtual repositioning jaw elements can be designed to move the position of the misaligned jaw of the patient toward and/or to the final jaw position (e.g., to move sagittally). 
     Alternatively and/or in addition, a plurality of dental appliances (e.g., a series of dental appliances) can be used to move the position of the misaligned jaw of the patient toward and/or to the final jaw position. For example, in some embodiments, providing the treatment plan can include providing a virtual model of a plurality of dental appliances. The plurality of dental appliances can be configured to reposition the misaligned jaw in incremental distances according to a number of stages of a treatment plan (e.g., as discussed further with regard to the embodiments illustrated in  FIGS.  7 A- 7 D ). 
     The shape and angle of each of the repositioning jaw elements can be specific to a stage of a treatment plan for which the appliance was designed (e.g., successive appliances created according to a treatment plan may have differently positioned, angled, and/or shaped repositioning jaw elements). Repositioning jaw elements that have shapes and angles specific to particular stages of treatment can be advantageous over using generic and/or uniform repositioning jaw element that are not specific to treatment stages and therefore may not accurately provide the desired correction for the treatment stage during which they are used. Such inaccurate treatment can lead to lengthening treatment plans, a need for a revised treatment plan, and/or unnecessary user discomfort, among other drawbacks. In contrast, a number of embodiments of the present disclosure allow for more timely, accurate, and/or comfortable execution of treatment plans. 
     In various embodiments, the processor  666  coupled to the memory  668  can cause the computing device  664  to perform the method comprising virtually testing the jaw movement to occur by the patient wearing the dental appliance. The virtual testing can include testing jaw movement, in addition to movement of teeth, in a number of embodiments. The virtual repositioning jaw elements can be adjusted based on the virtual testing of the jaw movement. For instance, the virtual repositioning jaw elements can be adjusted to reach an intended jaw position and/or a final jaw position in a treatment plan. The virtual testing and/or adjustment, in some embodiments, can be across a number of stages of a treatment plan. 
     For example, for each stage of a treatment plan, the instructions can be executed to model forces applied to a virtual model of the jaw by an appliance corresponding to that stage (to simulate actual forces to be applied to a user&#39;s physical jaw by a physical appliance). Those forces can include forces applied to the virtual model of the jaw by the virtual repositioning jaw elements, by virtue of the appliance being slightly out of alignment with a current configuration of the virtual model of the teeth and/or include forces applied to the aligner by the user (e.g., when the user wears the physical dental appliance). 
     The instructions can be executed to position the virtual repositioning jaw elements on the digital teeth of the virtual model of the jaw at a particular stage of treatment and/or adjust a position of the virtual repositioning jaw elements for subsequent stages of treatment. The virtual model of the jaw can be different at each stage of treatment according to the treatment plan (e.g., positioning of the virtual teeth and/or jaw can change). The instructions can be executed to adjust the position of the virtual repositioning jaw elements according to changes to the virtual model of the jaw between treatment stages and/or according to anticipated changes in subsequent stages of treatment (e.g., to help effectuate a desired change to the virtual model of the jaw). 
     Positioning and/or adjustment of positioning of virtual repositioning jaw elements on a virtual model of a jaw can be automatic (e.g., by operation of software based on force modeling for a particular stage of treatment), manual (e.g., by operation of an operator interacting with the virtual model via an interface with a computing device), or a combination thereof. Likewise, the shape, size, orientation (e.g., various angles with respect to references), and/or attachment location (on the virtual teeth) of the virtual repositioning jaw elements can be automatically set by the software, by manual operation (e.g., an operator can specify the necessary criteria of the virtual repositioning jaw elements and/or modify default criteria provided by the software), or a combination thereof. 
       FIGS.  7 A- 7 D  illustrate examples of a plurality of devices for repositioning jaws according to a number of embodiments of the present disclosure. In some embodiments of the present disclosure, a plurality of dental appliances can be used for treating misalignment of teeth of a patient and/or misalignment of the patient&#39;s jaw. For example, a treatment plan can be divided into multiple parts (also called stages) wherein dental appliances (in this case, an appliance having an upper shell and lower shell) are used in succession to move one or more of the patient&#39;s teeth and/or jaw from an initial position to a target position. And, wherein specialized dental appliances can be designed for each stage of treatment having cavities with particular dimensions and orientations in which teeth are placed to move one or more of the teeth to a particular position during the particular stage of treatment and/or to move the jaw to a new position when the jaw is closed (e.g., to aid the jaw in following a different path from an open to a closed position to change the path from an initial path to a target path wherein the different path results in a new position of the jaw when it is fully closed). Such a change in jaw path can be accomplished with one device or incrementally with several devices wherein the repositioning jaw elements are in different positions and/or orientations with respect to each other and/or the shell on which they are connected. Accordingly, as discussed above, each of the plurality of dental device appliances can include a treatment stage in an incremental treatment plan. 
     For example, the plurality of devices can include a series of dental appliances designed to incrementally implement a treatment plan. For instance, the series of dental appliances can incrementally move a position of the patient&#39;s jaw (when the jaw is viewed in its fully closed orientation) from stage to stage. The movement of the position of the jaw can include a revised position of the lower jaw of the patient relative to the upper jaw of the patient. Each stage of the treatment plan can move the position of the patient&#39;s jaw an incremental distance (e.g., 0.1 mm) from the previous position of the patient&#39;s jaw, as discussed further herein. From one stage to the next stage, the position of the patient&#39;s jaw can progress toward a final or target jaw position. 
     The incremental movement of the patient&#39;s jaw can occur based on the use of repositioning jaw elements that have slightly different positions or orientations on the shells from stage to stage. For example, the positioning of repositioning jaw elements extending from a first shell and/or second shell of a dental appliance can be revised from a first stage to a second stage. The revised positioning can include changing a mesial-distal length and/or a mesial-distal placement of a repositioning jaw element from one stage (e.g., a first dental appliance) to a next stage (e.g., a second dental appliance), as discussed further herein. 
     As used herein, a “first stage” does not necessarily mean the original stage of a treatment plan, but is a relative term with respect to other stages. For example, the “first stage” may be a second stage of a 50 stage treatment plan, while the “second stage” may be a tenth stage of the 50 stage treatment plan, while the “third stage” may be a 30th stage of the 50 stage treatment plan, and the “fourth stage” may be a 40th stage of the 50 stage treatment plan. 
     The treatment plan may just treat the position of the jaw or, in some embodiments, the treatment of the position of the jaws can be combined with the movement of one or more teeth on one or both jaws. For instance, the series of dental appliances can be used to incrementally (e.g., in increments of 0.1 mm) move a position of a misaligned jaw of a patient. This can be beneficial as typical current jaw alignment techniques move a jaw in large increments, such as 0.5 mm or greater, which may cause discomfort to the patient, among other issues.
 
As discussed above, one or more of the series of dental appliances can also be configured to reposition a number of teeth of the patient&#39;s dentition. In some embodiments, one or more of the series of dental appliances can be configured to reposition a number of teeth of the patient&#39;s dentition simultaneously with moving a position of a jaw of the patient.
 
     An example series of dental appliances can include a first dental appliance comprising a first shell having a first repositioning jaw element extending therefrom and a second shell having a second repositioning jaw element extending therefrom. The first dental appliance can be associated with and/or a part of an initial stage of a treatment plan (e.g., a first stage). The first dental appliance can be configured to move a misaligned jaw of the patient to a first incremental jaw position. Jaw positions can be compared when the jaw is positioned in a similar open-closed position along its path. For example, a comparison can be made when the jaw is in a fully engaged sagittal jaw position. Alternatively, a comparison could be made at other positions of the repositioning jaw elements, for example, when the repositioning jaw elements first contact each other. 
     The series of dental appliances can include a second dental appliance comprising a first shell having a first repositioning jaw element extending therefrom and a second shell having a second repositioning jaw element extending therefrom. The second dental appliance can be associated with and/or a part of a second stage of the treatment plan (e.g., a subsequent stage to the initial stage). The second dental appliance can be configured to move the misaligned jaw of the patient to a second incremental position. 
     For example, the second dental appliance can move the misaligned jaw based on the first repositioning jaw element and the second repositioning jaw element having a second position specific to a second stage of the treatment plan. In this manner, the movement induced by use of the repositioning jaw elements can be divided into increments which may allow the movement to be more precise, may allow for more complex movements, and may allow for less discomfort to the patient. 
     A non-engaged sagittal jaw position, as used herein, can include a position of the patient&#39;s upper jaw and lower jaw when the repositioning jaw elements of the first shell and the repositioning jaw elements of the second shell are not interfacing, interacting, and/or engaging (e.g., not touching). For instance, a non-engaged sagittal jaw position may include a position of the first shell and the second shell such that the repositioning jaw elements are not providing a force to move (e.g., sagittally) the patient&#39;s jaw. 
     An engaged sagittal jaw position, as used herein, can include a position of the patient&#39;s upper jaw and lower jaw when the repositioning jaw elements of the first shell and the repositioning jaw elements of the second shell are interfacing, interacting, and/or engaging. For example, an engaged sagittal jaw position may include a position of the first shell and the second shell such that the repositioning jaw elements are providing a force to move (e.g., sagittally) the patient&#39;s jaw. As discussed herein, in various embodiments, the dental appliance may move a jaw of the patient in one or more other directions in addition to sagittal movement. 
     Although the present embodiment illustrates two dental appliances in a series of dental appliances, embodiments in accordance with the present disclosure are not so limited. Treatment plans can include a variety of number of dental appliances, including more or less than two dental appliances. 
     As discussed above, each treatment stage can include a gradual movement of a lower jaw of a patient. The increments can occur based on changes in the mesial-distal length of the repositioning jaw elements and/or shifts in placement of the repositioning jaw elements on the shell (e.g. shift at least one repositioning jaw element in a mesial or distal direction). 
     For example, as illustrated in each embodiment of  FIGS.  7 A- 7 D , the treatment plan can include a number of treatment stages. The embodiments of  FIGS.  7 A- 7 D  each illustrate two treatment stages. Each of the treatment stages can include a removable dental appliance with a first shell (e.g., first shell  714 - 1  of the first stage and first shell  714 - 2  of the second stage of  FIGS.  7 A- 7 D , herein generally referred to as “first shell  714 ”) and a second shell (e.g., second shell  716 - 1  of the first stage and second shell  716 - 2  of the second stage of  FIGS.  7 A- 7 D , herein generally referred to as “second shell  716 ”). 
     Each first shell  714  can have a number of tooth apertures configured to receive and reposition a number of teeth of a patient&#39;s upper dentition and each second shell  716  can have a number of tooth apertures configured to receive and reposition a number of teeth of the patient&#39;s lower dentition. A first repositioning jaw element (e.g.,  706 - 1  of the first stage and  706 - 2  of the second stage of  FIGS.  7 A- 7 D , herein generally referred to as “first repositioning jaw element  706 ”) can extend from a surface the first shell  714  and can include a first surface. A second repositioning jaw element (e.g.,  708 - 1  of the first stage and  708 - 2  of the second stage of  FIGS.  7 A- 7 D , herein generally referred to as “second repositioning jaw element  708 ) can extend from a surface the second shell  716  and include a second surface to interface, interact, and/or engage with the first surface of the first repositioning jaw element  706 . 
     For instance, the first repositioning jaw element  706  and the second repositioning jaw element  708  of each dental appliance can be positioned to interface in the presence of a fully engaged sagittal jaw position of the patient&#39;s upper dentition and the patient&#39;s lower dentition in a manner to reposition the patient&#39;s jaw. For instance, the repositioning can include a forward and downward movement of the patient&#39;s lower jaw (e.g., to sagittally move). 
     Each dental appliance in the treatment plan (e.g., at each treatment stage) can be configured to reposition the number of teeth of the patient&#39;s upper dentition and the number of teeth of the patient&#39;s lower dentition and/or reposition of the patient&#39;s jaw. For instance, the repositioning of the patient&#39;s jaw can be incremental across the number of treatment stages. An incremental reposition of the patient&#39;s jaw can include, for instance, gradual advancement of the lower jaw. As described further herein, the gradual advancement can be achieved by shifting the placement of at least one of the repositioning jaw elements from a first stage (e.g., first dental appliance) to a second stage (e.g., second dental appliance) and/or changing the mesial-distal length of at least one of the repositioning jaw elements from a first stage to a second stage of the treatment plan. 
     The embodiments of  FIGS.  7 A- 7 D  can illustrate repositioning jaw elements  706 ,  708  oriented in a horizontal line. For instance, each horizontal line can represent a side view of (e.g., shells) a jaw pair (e.g., an upper jaw and a lower jaw). Although not illustrated by  FIG.  7 A- 7 D , the repositioning jaw elements  706 ,  708  can be positioned to extend from a surface of a shell  714 ,  716  that is shaped to substantially follow a dental arch of a patient. As such, the left end points of each of Figures of  7 A- 7 D represent a posterior direction  745  and/or regions of the jaws (e.g., of the patient when the dental appliance is worn) and the right end points of each of the  FIGS.  7 A- 7 D  represent anterior directions  747  and/or regions of the jaws (e.g., of the patient when the removable dental appliance is worn). The repositioning jaw elements  706 ,  708  extend from the surfaces of the shells. 
       FIG.  7 A  illustrates an example of a number of treatment stages to reposition a jaw of a patient in gradual advancements by changing a mesial-distal length of a first repositioning jaw element. Changing a mesial-distal length of a repositioning jaw element, as used herein, can include increasing or decreasing the length of the repositioning jaw element along a mesial-distal plane of teeth of the patient. For instance, the first treatment stage can include a first repositioning jaw element  706 - 1  that extends from a surface of a first shell  714 - 1  configured to receive and reposition a number of teeth of a patient&#39;s upper dentition. A second repositioning jaw element  708 - 1  can extend from a surface of a second shell  716 - 1  configured to receive and reposition a number of teeth of the patient&#39;s lower dentition. 
     The mesial-distal length of the first repositioning jaw element  706 - 1  and the second repositioning jaw element  708 - 1  can include particular lengths based on the first treatment stage. For instance, the length can be based on an incremental distance of the particular treatment stage. Based on the mesial-distal lengths of the first repositioning jaw element  706 - 1  and the second repositioning jaw element  708 - 1  of the first treatment stage, the patient&#39;s jaw can be repositioned to a first incremental position and/or distance. 
     In some embodiments, as illustrated by  FIG.  7 A-D , the first repositioning jaw elements  706  can include a longer mesial-distal length than the second repositioning jaw elements  708 . In some instances, a patient may have posterior teeth on the lower jaw that have not yet fully erupted. The longer mesial-distal length of the first repositioning jaw elements  706  on the first shell  714  can minimize and/or prevent the posterior teeth on the lower jaw from erupting farther than is desirable (e.g., super eruption) while still allowing the posterior teeth to erupt. 
     A second treatment stage can include a first repositioning jaw element  706 - 2  that extends from a surface of a first shell  714 - 2  configured to receive and reposition a number of teeth of the patient&#39;s upper dentition. A second repositioning jaw element  708 - 2  can extend from a surface of a second shell  716 - 2  configured to receive and reposition a number of teeth of the patient&#39;s lower dentition. 
     The mesial-distal length of the first repositioning jaw element  706 - 2  of the second treatment stage can be increased from the mesial-distal length of the first repositioning jaw element  706 - 1  of the first treatment stage. The increase in mesial-distal length can be based on the incremental distance of the particular treatment stage. The change can include, for example, a particular distance value x  791  (e.g., increase by particular distance value x  791 ) in which the mesial surface of repositioning jaw element  706 - 2  is extended by a distance “x” in the mesial direction. The second repositioning jaw element  708 - 2  of the second treatment stage can be the same mesial-distal length as the second repositioning jaw element  708 - 1  of the first treatment stage and/or can be increased, in various embodiments. Based on the mesial-distal lengths of the first repositioning jaw element  706 - 2  and the second repositioning jaw element  708 - 2  of the second treatment stage, the patient&#39;s jaw can be repositioned to a second incremental position and/or distance. 
       FIG.  7 B  illustrates an example of a number of treatment stages to reposition a jaw of a patient in gradual advancements by changing a mesial-distal length of a second repositioning jaw element. For instance, the first treatment stage can include a first repositioning jaw element  706 - 1  that extends from a surface of a first shell  714 - 1  configured to receive and reposition a number of teeth of a patient&#39;s upper dentition. A second repositioning jaw element  708 - 1  can extend from a surface of a second shell  716 - 1  configured to receive and reposition a number of teeth of the patient&#39;s lower dentition. 
     The mesial-distal length of the first repositioning jaw element  706 - 1  and the second repositioning jaw element  708 - 1  can include particular lengths based on the first treatment stage. The length can be based on an incremental distance of the particular treatment stage. Based on the mesial-distal lengths of the first repositioning jaw element  706 - 1  and the second repositioning jaw element  708 - 1  of the first treatment stage, the patient&#39;s jaw can be repositioned to a first incremental position and/or distance. 
     A second treatment stage can include a first repositioning jaw element  706 - 2  that extends from a surface of a first shell  714 - 2  configured to receive and reposition a number of teeth of the patient&#39;s upper dentition. A second repositioning jaw element  708 - 2  can extend from a surface of a second shell  716 - 2  configured to receive and reposition a number of teeth of the patient&#39;s lower dentition. 
     The mesial-distal length of the second repositioning jaw element  708 - 2  of the second treatment stage can be increased from the mesial-distal length of the second repositioning jaw element  708 - 1  of the first treatment stage. The increase in mesial-distal length can be based on the incremental distance of the particular treatment stage. The change can include, for example, a particular distance value x  792  (e.g., increase by distance value x  792 ) in which the mesial surface of repositioning jaw element  708 - 2  is extended by a distance “x” in the distal direction. The first repositioning jaw element  706 - 2  of the second treatment stage can be the same mesial-distal length as the first repositioning jaw element  706 - 1  of the first treatment stage and/or can be increased, in various embodiments. Based on the mesial-distal lengths of the first repositioning jaw element  706 - 2  and the second repositioning jaw element  708 - 2  of the second treatment stage, the patient&#39;s jaw can be repositioned to a second incremental position and/or distance. 
       FIG.  7 C  illustrates an example of a number of treatment stages to reposition a jaw of a patient in gradual advancements by shifting a mesial-distal placement (e.g., shift the placement of the repositioning jaw element in a mesial or distal direction) of the first repositioning jaw element. For instance, the first treatment stage can include a first repositioning jaw element  706 - 1  that extends from a surface of a first shell  714 - 1  configured to receive and reposition a number of teeth of a patient&#39;s upper dentition. A second repositioning jaw element  708 - 1  can extend from a surface of a second shell  716 - 1  configured to receive and reposition a number of teeth of the patient&#39;s lower dentition. 
     The mesial-distal placement of the first repositioning jaw element  706 - 1  and the second repositioning jaw element  708 - 1  can include a particular placement adjacent to posterior teeth therein based on the first treatment stage. For instance, the placement can be based on an incremental distance of the particular treatment stage. Based on the mesial-distal placement of the first repositioning jaw element  706 - 1  and the second repositioning jaw element  708 - 1  of the first treatment stage, the patient&#39;s jaw can be repositioned to a first incremental position and/or distance. 
     A second treatment stage can include a first repositioning jaw element  706 - 2  that extends from a surface of a first shell  714 - 2  configured to receive and reposition a number of teeth of the patient&#39;s upper dentition. A second repositioning jaw element  708 - 2  can extend from a surface of a second shell  716 - 2  configured to receive and reposition a number of teeth of the patient&#39;s lower dentition. 
     The mesial-distal placement of the first repositioning jaw element  706 - 2  of the second treatment stage can be shifted in a mesial direction from the mesial-distal placement of the first repositioning jaw element  706 - 1  of the first treatment stage. The shift in mesial-distal placement can be based on the incremental distance of the particular treatment stage. The shift can include, for example, a particular distance value x 793 (e.g., shift in a mesial direction by a distance value of x 793). The second repositioning jaw element  708 - 2  of the second treatment stage can be the same mesial-distal placement as the second repositioning jaw element  708 - 1  of the first treatment stage and/or can be shifted, in various embodiments. Based on the mesial-distal placements of the first repositioning jaw element  706 - 2  and the second repositioning jaw element  708 - 2  of the second treatment stage, the patient&#39;s jaw can be repositioned to a second incremental position and/or distance. 
       FIG.  7 D  an example of a number of treatment stages to reposition a jaw of a patient in gradual advancements by shifting a mesial-distal placement of the second repositioning jaw element. For instance, the first treatment stage can include a first repositioning jaw element  706 - 1  that extends from a surface of a first shell  714 - 1  configured to receive and reposition a number of teeth of a patient&#39;s upper dentition. A second repositioning jaw element  708 - 1  can extend from a surface of a second shell  716 - 1  configured to receive and reposition a number of teeth of the patient&#39;s lower dentition. 
     The mesial-distal placement of the first repositioning jaw element  706 - 1  and the second repositioning jaw element  708 - 1  can include a particular placement adjacent to posterior teeth therein based on the first treatment stage. For instance, the placement can be based on an incremental distance of the particular treatment stage. Based on the mesial-distal placement of the first repositioning jaw element  706 - 1  and the second repositioning jaw element  708 - 1  of the first treatment stage, the patient&#39;s jaw can be repositioned to a first incremental position and/or distance. 
     A second treatment stage can include a first repositioning jaw element  706 - 2  that extends from a surface of a first shell  714 - 2  configured to receive and reposition a number of teeth of the patient&#39;s upper dentition. A second repositioning jaw element  708 - 2  can extend from a surface of a second shell  716 - 2  configured to receive and reposition a number of teeth of the patient&#39;s lower dentition. 
     The mesial-distal placement of the second repositioning jaw element  708 - 2  of the second treatment stage can be shifted in a distal direction from the mesial-distal placement of the second repositioning jaw element  708 - 1  of the first treatment stage. The shift in mesial-distal placement can be based on the incremental distance of the particular treatment stage. The shift can include, for example, a particular distance value x  794  (e.g., shift in a distal direction by a distance value of x  794 ). The first repositioning jaw element  706 - 2  of the second treatment stage can be the same mesial-distal placement as the first repositioning jaw element  706 - 1  of the first treatment stage and/or can be shifted, in various embodiments. Based on the mesial-distal placements of the first repositioning jaw element  706 - 2  and the second repositioning jaw element  708 - 2  of the second treatment stage, the patient&#39;s jaw can be repositioned to a second incremental position and/or distance. 
     Although the present embodiments of  FIGS.  7 A- 7 D  illustrate two treatment stages of a treatment plan, embodiments in accordance with the present disclosure are not so limited. Treatment plans can include a variety of number of treatment stages, including more or less than two treatment stages. At least a portion of the treatment stages can include treatment for gradual advancement of the patient&#39;s jaw. Further, one or more of the treatment stages may not include repositioning jaw elements, in various embodiments. 
       FIGS.  8 A- 8 D  illustrate examples of repositioning jaw elements according to a number of embodiments of the present disclosure.  FIG.  8 A  illustrates, for instance, repositioning jaw elements  806 ,  808 ,  810 ,  812  that include geometric features  851 - 1 ,  851 - 2 ,  851 - 3 ,  851 - 4  to engage with a repositioning jaw element on an opposing jaw. 
     Geometric features  851 - 1  . . .  851 - 4 , as used herein, can include a variety of protruding geometric shapes (e.g., cylinder, rectangular, etc.) and/or receding geometric shapes (e.g., negative space that matches the protruding geometric shape on a repositioning jaw element on an opposing jaw). For example, a geometric feature  851 - 1  on the first surface of the first repositioning jaw element  806  of a first shell  814  can include a concave shaped feature and a geometric feature  851 - 2  on the second surface of the second repositioning jaw element  808  of a second shell  816  can include a convex shaped feature shaped to mate with the geometric feature  851 - 1  on the first surface of the first repositioning jaw element  806 . 
     Similarly, a geometric feature  851 - 3  on the third surface of the third repositioning jaw element  810  of the first shell  814  can include a concave shaped feature and a geometric feature  851 - 4  on the fourth surface of the fourth repositioning jaw element  812  of the second shell  816  can include a convex shaped feature shaped to mate with the geometric feature  851 - 3  on the third surface of the third repositioning jaw element  810 . 
       FIG.  8 B  illustrates a repositioning jaw element  803  on an occlusal surface of a removable dental appliance. As illustrated, the repositioning jaw element  803  can be located on an occlusal surface of a first shell  814  (e.g., an upper dentition). 
     The repositioning jaw element  803  can, for instance, include an occlusal surface that has a geometry shaped to mate with the contours of the occlusal surfaces of the second shell  816 . The mating can, for instance, be designed to reposition the jaw of the patient by guiding the lower jaw of the patient into a forward position or backward position (e.g., to move sagittally). 
       FIGS.  8 C- 8 D  illustrate example of repositioning jaw elements  806 ,  808  with magnets within. Repositioning jaw elements  806 ,  808  with magnets within can extend from occlusal, buccal, and/or lingual surfaces of shells  814 ,  816  of a removable dental appliance. 
     The magnets within the repositioning jaw elements  806 ,  808  on opposing jaws can be opposite poles and/or same poles to guide the lower jaw to a position. For example, opposite poles on magnets can be used to attract the lower jaw into the forward position and/or same poles on magnets can be used to push the lower jaw into the forward position. 
       FIG.  8 C  illustrates an example of repositioning jaw elements  806 ,  808  with magnets within that have opposite poles on opposite jaws to attract the lower jaw (e.g., the second shell  816 ) into the forward position. In contrast,  FIG.  8 D  illustrates an example of repositioning jaw elements  806 ,  808  with magnets within that have same poles on opposite jaws to push the lower jaw (e.g., the second shell  816 ) into the forward position. 
     Although the embodiments of  FIGS.  8 C and  8 D  illustrate attracting or pushing the lower jaw into a forward position (e.g., Class II correction), embodiments in accordance with the present disclosure are not so limited. For example, embodiments in accordance with the present disclosure can include magnets within repositioning jaw elements that attract or push the lower jaw into a backward position (e.g., Class III correction). 
       FIGS.  9 A- 9 B  illustrate examples of features of devices for repositioning jaws according to a number of embodiments of the present disclosure. The devices illustrated in  FIGS.  9 A- 9 C  can include removable dental appliances.  FIG.  9 A , for instance, illustrates an example repositioning jaw element  907  with a groove  953  on a first shell  914  and a geometric feature  909  on a second shell  916 . 
     The groove  953  of the repositioning jaw element  907  can include, for instance, a hollow channel located within and/or on a surface of the repositioning jaw element  907  that is angled (e.g., a surface of the repositioning jaw element  907  that is designed to interface, interact, and/or engage with another repositioning jaw element and/or shell). The groove  953  can be shaped to mate with a geometric feature  909  on a second shell  916  on an opposite jaw. The geometric feature  909  on the second shell  916  on the opposite jaw can include a cylinder shaped feature that can rotate and/or slide down the angled surface of the repositioning jaw element  907  of the first shell  914  until the groove  953  is reached. That is, the groove  953  can limit and/or stop movement of the geometric feature  909  on the second shell  916 . The groove  953  and geometric feature  909  combination can, for instance, allow for greater freedom of motion of the lower jaw while repositioning the lower jaw to a forward position or backward position. 
     In some embodiments, a first repositioning jaw element of a first shell  914  and a second repositioning jaw element of a second shell  916  can include geometric features. For instance, geometric features of a first repositioning jaw element and/or a second repositioning jaw element can include a protrusion and a socket. For example, a first repositioning jaw element can include a protrusion extending from the first repositioning jaw element in a direction toward occlusal surfaces teeth of the opposing jaw. The second repositioning jaw element can include a socket within the second repositioning jaw element. The protrusion of the first repositioning jaw element can fit into the socket of the second repositioning jaw element to assist in guiding the lower jaw into a forward position or a backward position. 
       FIG.  9 B  illustrates an example of a device with a first geometric feature  911  on a first shell  914  and a second geometric feature  913  on a second shell  916 . For instance, the second geometric feature  913  can include a spring feature positioned on the second shell  916  and the first geometric feature  911  can include a tab feature positioned on the first shell  914  to interface, interact, and/or engage with the spring feature (e.g., the second geometric feature  913 ). The spring feature can, for instance, guide the lower jaw of the patient to a forward position or backward position, for example. For instance, the first geometric feature  911  interfacing, interaction, and/or engaging with the second geometric feature  913  can provide a force on the lower jaw of the patient to move sagittally the position of the lower jaw. 
       FIGS.  10 A- 10 C  illustrate examples of occlusal features of devices for repositioning jaws according to a number of embodiments of the present disclosure. The devices illustrated in  FIGS.  10 A- 10 C  can include removable dental appliances. 
       FIG.  10 A  illustrates an example device with a plurality of ridges on the occlusal surfaces of the first shell  1014  and a plurality of ridges on the second shell  1016 . The ridges can be used to guide the lower jaw of the patient to a position, such as a forward position or a backward position. Ridges, as used herein, can include protrusions that extend in a coronal-apical direction and have a buccal-lingual width (e.g., 1 mm). The ridges on the first shell  1014  can protrude in an alternating order as the ridges on the second shell  1016 , for instance. 
       FIG.  10 B  illustrates an example of a device with a plurality of pairs of magnets within the occlusal surface of the first shell  1014  and the second shell  1016 . The magnets within the occlusal surfaces of the shells  1014 ,  1016  on opposing jaws can be opposite poles and/or same poles to guide the lower jaw to a forward position or backward position. The plurality of pairs of magnets can be used to distribute the force evenly across the arch and/or across posterior teeth. 
       FIG.  10 C  illustrates an example of a device with occlusal surfaces that have a geometry that differs from the contours of occlusal surfaces of teeth that are on an opposing jaw of the patient. For instance, the geometry of the occlusal surface of the first shell  1014  and the geometry of the occlusal surface of the second shell  1016  can include a pattern to match a forward lower or backward lower jaw position of the patient. As illustrated by  FIG.  10 C , in some embodiments, the geometry can be on occlusal surfaces of a device that does not include repositioning jaw elements and the geometry can retrain the muscles of the lower jaw to be positioned in a forward lower jaw position or a backward lower jaw position (e.g., to move sagittally). 
     Further, in various embodiments, a dental appliance of the present disclosure can include one or more repositioning jaw elements having a structure to indicate to a patient that the patient has positioned the first and second repositioning jaw elements of the first shell and second shell in a fully engaged sagittal jaw position. For example, in the embodiment of  FIG.  10 C , the points of the repositioning jaw structure  1016  will stop when they fully engage with the cooperating valleys of the opposing repositioning jaw structure  1014 . Other examples of these indicting type structures can be seen in various embodiments illustrated in the figures such as,  FIGS.  8 A,  8 B, and  12 B . 
       FIGS.  11 A- 11 B  illustrate examples of devices for repositioning jaws according to a number of embodiments of the present disclosure. The devices illustrated in  FIGS.  11 A- 11 B  can include removable dental appliances. 
     In a number of examples, a variety of features can be used in addition to and/or in place of repositioning jaw elements to guide the lower jaw to a position, such as a forward position or a backward position. Example features can include connecting the first shell and the second shell using material at the sides of the shells in the posterior region, a rigid or flexible connecting structure (e.g., as illustrated by  FIGS.  11 A and  11 B ), ridges (e.g., as illustrated by  FIG.  10 A ), magnets (e.g., as illustrated by  FIG.  10 B ), and/or occlusal surfaces (e.g., as illustrated by  FIG.  10 C ), among other features. 
       FIG.  11 A  illustrates an example of a device with a first shell  1114  and a second shell  1116  connected by a rigid or flexible connecting structure  1121  to advance a lower jaw of the patient to a position, such as a forward position or backward position (e.g., move a lower jaw of the patient or opening up the bite to a desired range of jaw opening extending from the current position of occlusion). The rigid or flexible connecting structure  1121  can form a hinge. 
     The rigid or flexible connecting structure  1121  can include a strip of material (e.g., an arm), such as metal, polymer, and/or other material, which can connect the first shell  1114  to the second shell  1116 . As illustrated by the embodiment of  FIG.  11 A , the rigid structure  1121  can be connected to the first shell  1114  and the second shell  1116  in a variety of ways. In some embodiments, the rigid or flexible connecting structure  1121  can be connected to the first shell  1114  and the second shell  1116  using magnetic materials  1123 - 1 ,  1123 - 2 , pins  1125 - 1 ,  1125 , and/or similar features. 
     These features can allow the connecting structure to be easily installed and removed by the patient. For instance, the rigid or flexible connecting structure  1121  can form a hinge that uses magnetic materials  1123 - 1 ,  1123 - 2 , pins  1125 - 1 ,  1125 , and/or similar features to hold the first shell  1114  and the second shell  116  together while allowing the first shell  1114  and the second shell  116  to rotate. When a patient places the first shell  1114  and the second shell  1116  over their teeth, the patient can place the rigid or flexible connecting structure  1121  near the appropriate location. The magnetic materials  1123 - 1 ,  1123 - 2 , in some embodiments, can snap the rigid or flexible connecting structure  1121  into the appropriate location (e.g., from a close and/or near appropriate location to the appropriate location). A wire can be placed on a lingual surface of the second shell  1116  (e.g., lower jaw) to distribute the load evening across the dental arch, in various embodiments. 
       FIG.  11 B  illustrates an example of a device with a first shell  1114  and a second shell  1116  formed as a single piece. The first shell  1114  (e.g., upper jaw) and the second shell  1116  (e.g., lower jaw) can be connected into one piece to advance a lower jaw of the patient or opening up the bite to a desired range of jaw opening extending from the current position of occlusion. For example, the first shell  1114  and the second shell  1116  can be connected by material  1129  at a right posterior side and a left posterior side of the first shell  1114  and the second shell  1116 . The material  1129  can include the same and/or different material than the material of the first shell  1114  and the second shell  1116 , for instance. The material  1129  can be flexible to allow jaw articulation while continuing to provide positioning guidance to the jaws. 
       FIGS.  12 A- 12 B  illustrate examples of devices according to a number of embodiments of the present disclosure. The repositioning jaw elements  1206 ,  1208  of the devices illustrated in  FIGS.  12 A- 12 B  can interface, interact, and/or engage with one another to move a position of a patient&#39;s jaw from a current position of occlusion to a target and/or final position of occlusion (e.g., to move sagittally). 
       FIG.  12 A  illustrates an example of a device with a first repositioning jaw element  1206  extending from a surface of a first shell  1214  and a second repositioning jaw element  1208  extending from a surface of a second shell  1216 . The first repositioning jaw element  1206  and the second repositioning jaw element  1208  can interface, interact, and/or engage in the presence of fully engaged sagittal jaw position of a patient. 
     As illustrated by the embodiment of  FIG.  12 A , in a number of embodiments, one or more of the repositioning jaw elements  1206 ,  1208  can include a layer of compressible material  1231 - 1 ,  1231 - 2  on a surface designed to interface, interact, and/or engage with another repositioning jaw element. For example, the compressible material  1231 - 1 ,  1231 - 2  can assist in guiding the lower jaw of a patient to a forward or backward position by being in a compressed state when the surfaces are initially interfacing, interacting, and/or engaged, then uncompressing to push the lower jaw forward or backward as the jaws relax. That is, the compressible material  1231 - 1 ,  1231 - 2  can be compressed when the jaws of the patient initially move to a fully engaged sagittal jaw position and, as the patient&#39;s jaws relax over a period of time, the compressive material  1231 - 1 ,  1231 - 2  can expand (e.g., increase in thickness from the compressed state) to push the lower jaw forward or backward. 
       FIG.  12 B  illustrates an example of a device with a first repositioning jaw element  1206  extending from a surface of a first shell  1214  and a second repositioning jaw element  1208  extending from a surface of a second shell  1216 . In some embodiments, at least one of the repositioning jaw elements (e.g., the first repositioning jaw element  1206  and the second repositioning jaw element  1208 ) can include occlusal surfaces that substantially follow the contours of the occlusal surfaces of teeth on an opposing jaw of the patient. 
     For instance, as illustrated by the embodiment of  FIG.  12 B , the occlusal surface (e.g., the top surface) of the first repositioning jaw element  1206  can substantially follow the contours of the occlusal surfaces of the posterior teeth of the lower jaw (e.g., the occlusal surfaces of the posterior teeth of the lower jaw that the first repositioning jaw element  1206  may contact). The occlusal surface of the second repositioning jaw element  1208  can substantially follow the contours of the occlusal surfaces of the posterior teeth of the upper jaw (e.g., the occlusal surfaces of posterior teeth of the upper jaw that the second repositioning jaw element  1208  may contact). Shaping the occlusal surfaces of repositioning jaw elements based on the patient&#39;s dentition may, for instance, avoid interference between cusps of teeth that may otherwise hit interferences in an opposing jaw which could increase the likelihood of unwanted tooth and/or jaw movements. 
       FIGS.  12 C- 12 D  illustrate examples of repositioning jaw elements  1206 ,  1208  according to a number of embodiments of the present disclosure. The upper jaw  1202 , the first repositioning jaw element  1206 , the lower jaw  1204 , and the second repositioning jaw element  1208  illustrated in  FIGS.  12 C- 12 D  can include virtual images of jaws and repositioning jaw elements, respectively (e.g., virtual jaws and/or virtual repositioning jaw elements), and/or a physical mold. The virtual images and/or physical mold of the jaws  1202 ,  1204  and repositioning jaw elements  1206 ,  1208  can be used to determine a treatment plan for the patient and/or to form a physical dental appliance and/or physical repositioning jaw element. 
       FIG.  12 C  illustrates a side view of an upper jaw  1202  with a first repositioning jaw element  1206  and a lower jaw  1204  with a second repositioning jaw element  1208  according to a number of embodiments of the present disclosure. In a number of embodiments, one or more attachment elements  1233 - 1 ,  1233 - 2 ,  1233 - 3 ,  1233 - 4 ,  1233 - 5  can be virtually and/or physically attached to a surface of at least some of the virtual teeth, set of molded teeth, and/or physical teeth of a patient. The attachment elements  1233 - 1  . . .  1233 - 5  can be used to minimize and/or prevent degrading the retention and/or functionality of the shell of the dental appliance. 
     For instance, the attachment elements  1233 - 1  . . .  1233 - 5  can be added directly to a buccal/facial and/or lingual surface of a patient&#39;s tooth. An attachment element, as used herein, can include an attachment sub-device with a small base extending across a mesial-distal and/or incisal-gingival-crown surface of the tooth. The attachment elements  1233 - 1  . . .  1233 - 5  can be bonded to any surface of the tooth (and be made either indirectly (e.g. a light or chemical-cured dental composite) or directly (e.g. prefabricated plastic, composite, or porcelain object)). An attachment element bonded to a lingual surface of a tooth of the patient can be more aesthetically pleasing to a patient (and less noticeable to others than an attachment element bonded to a buccal/facial surface). The attachment elements  1233 - 1  . . .  1233 - 5  can also be attached to at least some of the anchoring teeth. The attachment elements  1233 - 1  . . .  1233 - 5  can include a variety of geometric shapes, such as ovoid, tear-drop, ramp, hexagonal, and/or rectangular, among other shapes. 
     The one or more attachment elements  1233 - 1  . . .  1233 - 5  can be designed to work with a virtual model of a removable dental appliance and/or a physical removable dental appliance. The shell can be shaped, for instance, to be placed over the attachment element(s)  1233 - 1  . . .  1233 - 5  to minimize and/or prevent vertical displacement of the shell. For example, the shell can include a ridge on the shell used to retain the dental appliance on the teeth. The attachment elements  1233 - 1  . . .  1233 - 5  can, for instance, provide friction between the dental appliance and the teeth to increase retention of the dental appliance. That is, the attachment elements  1233 - 1  . . .  1233 - 5  can create greater retention of the dental appliance in a particular direction. 
       FIG.  12 D  illustrates a front view of an upper jaw  1202  with a first repositioning jaw element  1206  and a third repositioning jaw element  1210  and a lower jaw  1204  with a second repositioning jaw element  1208  and a fourth repositioning jaw element  1212  according to a number of embodiments of the present disclosure. 
     In various embodiments, at least one of the repositioning jaw elements  1206 ,  1208 ,  1210 ,  1212  can be shaped to minimize and/or prevent degrading the retention and/or functionality of the shell of the dental appliance. For example, as illustrated in the embodiment of  FIG.  12 D , the buccal-lingual width of a repositioning jaw element (e.g., the repositioning jaw elements  1206 ,  1208 ,  1210 ,  1212 ) can be different on an occlusal surface of the repositioning jaw element (e.g., top surface) than on a buccal-lingual width of a surface of the repositioning jaw element adjacent to the shell (e.g., bottom surface). That is, the side surfaces of the repositioning jaw elements can be tapered inward toward the bottom surface. For instance, the buccal-lingual width of a repositioning jaw element can be wider on an occlusal surface of the repositioning jaw element than on a buccal-lingual width of a surface of the repositioning jaw element adjacent to the shell. Such a shape can be similar to the construction of an I-beam with the wider buccal-lingual occlusal surface interfacing with an occlusal surface of a repositioning jaw element positioned on an opposing jaw. 
       FIGS.  13 A- 13 B  illustrate examples of side surface features according to a number of embodiments of the present disclosure. The side surface features and jaws illustrated in  FIGS.  13 A- 13 B  can include virtual side surface features and virtual jaws of a patient or physical molds of a patient&#39;s jaws with side surface features, in some embodiments. 
     A side surface feature, as used herein, can extend beyond the occlusal plane of a removable dental appliance to engage with buccal and lingual coronal side surfaces of at least one tooth and/or a removable dental appliance on the opposite jaw of the patient. The side surface features can, for instance, add retention to molar teeth to balance movement created by the repositioning jaw elements and/or prevent and/or limit a posterior surface of the removable dental appliance from contacting molars. That is, although not illustrated by the embodiments of  FIGS.  13 A- 13 B , the side surface features can be used in addition to repositioning jaw elements, such as repositioning jaw elements  106 ,  108  illustrated in  FIG.  1 A . 
       FIG.  13 A  illustrates posterior view of an upper jaw  1302  and a lower jaw  1304  with a number of side surface features  1335 - 1 ,  1335 - 2 ,  1337 - 1 ,  1337 - 2 ,  1337 - 3  according to a number of embodiments of the present disclosure. As illustrated by  FIG.  13 A , the number of side surface features can include buccal side surface features  1335 - 1 ,  1335 - 2  and lingual side surface features  1337 - 1 ,  1337 - 2 ,  1337 - 3 . 
       FIG.  13 B  illustrates a view of a posterior side of the upper jaw  1302  and the lower jaw  1304  with the number of side surface features  1335 - 1 ,  1335 - 2 ,  1337 - 1 ,  1337 - 2 . The upper jaw  1302 , the lower jaw  1304 , and the number of side surface features  1335 - 1 ,  1335 - 2 ,  1337 - 1 ,  1337 - 2  illustrated in  FIG.  13 B  can include the same or different jaws and side surface features as illustrated in  FIG.  13 A , in various embodiments. 
     The side surface features  1335 - 1 ,  1335 - 2 ,  1337 - 1 ,  1337 - 2 , as illustrated by  FIG.  13 B , can include a pair of side surface features (e.g., a first buccal side surface feature  1335 - 1  and a first lingual side surface feature  1337 - 1 ) on the first posterior side of the upper jaw  1302  and a pair of side surface features (e.g., a second buccal side surface feature  1335 - 2  and a second lingual side surface feature  1337 - 2 ) on the second posterior side of lower jaw  1304 . Each pair of side surface features (e.g., the first buccal side surface feature  1335 - 1  and the first lingual side surface feature  1337 - 1 ) can engage with side surfaces of at least one tooth and/or a removable dental appliance on the opposite jaw of the patient. 
       FIGS.  14 A- 14 B  illustrate examples of repositioning jaw elements for adjusting a midline of a patient according to a number of embodiments of the present disclosure. The repositioning jaw elements and jaws illustrated in  FIGS.  14 A- 14 B  can include virtual repositioning jaw elements and virtual jaws of a patient or physical molds of a patient&#39;s jaws with repositioning jaw elements, for instance. 
     In accordance with a number of embodiments of the present disclosure, the repositioning jaw elements can be used to adjust a midline of a patient. A midline of a patient, as used herein, can include a midsagittal line of the teeth of the upper jaw and the teeth of the lower jaw of the patient. 
     For instance, repositioning jaw elements can be placed on the right and left posterior side of a shell for the upper jaw and the right and left posterior side of a shell for the lower jaw. The surfaces of repositioning jaw elements on the shell of each jaw that are designed to interface, interact, and/or engage surfaces of repositioning jaw elements on an opposing jaw can be angled at the same angle and/or opposite angles, in various instances. For example, for minor adjustment to the midline of a patient, the surfaces of repositioning jaw elements on the shell of a jaw (e.g., upper or lower) can be angled at opposing angles. In contrast, for larger adjustments to the midline of the patient, the surfaces of repositioning jaw elements (e.g., the right and left posterior side) on the shell of a jaw (e.g., upper or lower) can be angled at the same angle. 
       FIG.  14 A  illustrates an example of a side view of an upper jaw  1402  with a first repositioning jaw element  1406  and a third repositioning jaw element  1410  and a lower jaw  1404  with a second repositioning jaw element  1408  and a fourth repositioning jaw element  1412 . The first repositioning jaw element  1406  and second repositioning jaw element  1408 , and the third repositioning jaw element  1410  and the fourth repositioning jaw element  1412 , respectively, can be designed to interface, interface, and/or engage in the present of a fully engaged sagittal jaw position to guide the lower jaw  1404  of the patient in a mesial-distal direction. 
     In various embodiments, the guidance of the lower jaw  1404  in a mesial-distal direction can be concurrent with guiding the lower jaw  1404  in a forward or backward direction (e.g., anterior-posterior direction). That is, the midline of the patient can be adjusted concurrently with adjusting the sagittal jaw position of the patient using the repositioning jaw elements  1406 ,  1408 ,  1410 ,  1412 . 
       FIG.  14 B  illustrates an example of a view of an upper jaw  1402  with a first repositioning jaw element  1406  and a third repositioning jaw element  1410  and a lower jaw  1404  with a second repositioning jaw element  1408  and a fourth repositioning jaw element  1404 . The jaws  1402 ,  1404  and repositioning jaw elements  1406 ,  1408 ,  1410 ,  1412  illustrated in  FIG.  14 B  can include the same or different jaws/repositioning jaw elements as illustrated in  FIG.  14 A , in various embodiments. 
     As illustrated by the embodiment of  FIG.  14 B , in a number of embodiments, the surfaces of the repositioning jaw elements (e.g., the right and left posterior side) on the shell of a jaw (e.g., upper or lower) can be angled at the same angle. For instance, the first repositioning element  1406  and the third repositioning jaw element  1410  of the first jaw  1402  are angled at the same angle (e.g., a first angle). Similarly, the second repositioning jaw element  1408  and the fourth repositioning jaw element  1412  are angled at the same angle (e.g., a second angle), which can be an opposite angle as the first repositioning jaw element  1406  and the third repositioning jaw element  1410 . However, embodiments in accordance with the present disclosure are not so limited. For instance, the surfaces of repositioning jaw elements on the shell of a jaw (e.g., upper or lower) can be angled at opposing angles, in a number of embodiments. 
     Further, the embodiments illustrated by  FIGS.  14 A- 14 B  can include repositioning jaw elements  1406 ,  1408 ,  1410 ,  1412  that adjust the midline of a patient toward the patient&#39;s right side. However, embodiments in accordance with the present disclosure are not so limited and can include repositioning jaw elements designed to adjust the midline of a patient toward the patient&#39;s left side. 
     Listing of Exemplary Embodiments 
     A. A removable dental appliance comprising:
         a. a first shell having a number of tooth apertures configured to receive and reposition a number of teeth of a patient&#39;s upper dentition;   b. a second shell having a number of tooth apertures configured to receive and reposition a number of teeth of the patient&#39;s lower dentition;   c. a first repositioning jaw element that extends from a surface of the first shell and includes a first surface;   d. a second repositioning jaw element that extends from a surface of the second shell and includes a second surface to interface with the first surface of the first repositioning jaw element;   e. wherein the first repositioning jaw element and the second repositioning jaw element are positioned to interface in a presence of a fully engaged sagittal jaw position of the patient&#39;s upper dentition and the patient&#39;s lower dentition in a manner to reposition the patient&#39;s jaw; and   f. wherein the removable dental appliance is configured to reposition the number of teeth of the patient&#39;s upper dentition and the number of teeth of the patient&#39;s lower dentition concurrently with the repositioning of the patient&#39;s jaw.       

     B. The removable dental appliance of claim A, wherein at least one of the first repositioning jaw element and the second repositioning jaw element are positioned to generate distalizing force on at least some of the teeth within. 
     C. The removable dental appliance of claim A, wherein:
         a. the first repositioning jaw element includes a first geometric feature; and   b. the second repositioning jaw element includes a second geometric feature shaped to mate with the first geometric feature.       

     D. The removable dental appliance of claim C, wherein the first geometric feature includes a protrusion and the second geometric feature includes a socket. 
     E. The removable dental appliance of claim A, wherein at least one of the first repositioning jaw element and the second repositioning jaw element include a layer of compressible material on a surface. 
     F. The removable dental appliance of claim A, wherein at least one of the first surface and the second surface are angled to adjust a midline of patient. 
     G. The removable dental appliance of claim A, wherein the first repositioning jaw element and the second repositioning jaw elements include occlusal surfaces to follow contours of occlusal surfaces of teeth on an opposing jaw. 
     H. The removable dental appliance of claim A, wherein at least one of the first repositioning jaw element and the second repositioning jaw element include side surface features that extend beyond the occlusal plane of the removable dental appliance to engage with at least one of a buccal and a lingual side surfaces of a shell of an opposite jaw. 
     I. The removable dental appliance of claim A, wherein the first repositioning jaw element and the second repositioning jaw element are positioned near at least one of an unerupted and a removed molar tooth of the patient. 
     J. The removable dental appliance of claim A, wherein the first shell and the second shell include a plurality of repositioning jaw elements extending from at least one of a buccal and lingual surface of the first shell and the second shell. 
     K. The removable dental appliance of claim A, wherein the first repositioning jaw element and the second repositioning jaw element include at least a magnet within to interact and guide the lower jaw into a position. 
     L. The removable dental appliance of claim A, wherein at least one of the first repositioning jaw element and the second repositioning jaw element includes a top surface with a wider buccal-lingual width than a buccal-lingual width of a bottom surface. 
     M. A removable dental appliance comprising:
         a. a first shell having a number of tooth apertures configured to receive and reposition a number of teeth of a patient&#39;s upper dentition;   b. a second shell having a number of tooth apertures configured to receive and reposition a number of teeth of the patient&#39;s lower dentition;   c. wherein the first shell and the second shell interface in a presence of a fully engaged sagittal jaw position of the patient&#39;s upper dentition and the patient&#39;s lower dentition in a manner to reposition the patient&#39;s jaw; and   d. wherein the removable dental appliance is configured to reposition the number of teeth of the patient&#39;s upper dentition and the number of teeth of the patient&#39;s lower dentition concurrently with the repositioning of the patient&#39;s jaw.       

     N. The removable dental appliance of claim M, wherein:
         a. the first shell includes a protrusion; and   b. the second shell includes a socket shaped to mate with the protrusion to move a lower jaw of the patient from an articulation path of opening to a desired range of jaw opening extending from a current occluding position.       

     O. The removable dental appliance of claim M, wherein the first shell and the second shell include occlusal surfaces with a geometry that differs from the contours of the occlusal surfaces of the teeth of an opposing jaw. 
     P. The removable dental appliance of claim M, wherein:
         a. the first shell includes a spring; and   b. the second shell includes a tab to interact with the spring.       

     Q. The removable dental appliance of claim M, wherein the first shell and the second shell each include a plurality of ridges on occlusal surfaces to guide the jaw into a position. 
     R. The removable dental appliance of claim M, wherein the first shell and the second shell include pairs of magnets within occlusal surfaces of the first shell and the second shell to interact and guide the jaw of the patient into a position. 
     S. The removable dental appliance of claim M, wherein occlusal surfaces of the first shell and the second shell include a geometry to match a jaw position. 
     T. The removable dental appliance of claim M, wherein the first shell and the second shell are connected by a rigid or flexible connecting structure to move a lower jaw into a position. 
     U. The removable dental appliance of claim M, wherein the first shell and the second shell are connected by material at a right posterior side and a left posterior side of the first shell and the second shell. 
     V. The removable dental appliance of claim M, wherein:
         a. the first shell includes a repositioning jaw element with a groove; and   b. the second shell includes a geometric feature to interact with the groove.       

     Although specific embodiments have been illustrated and described herein, those of ordinary skill in the art will appreciate that any arrangement calculated to achieve the same techniques can be substituted for the specific embodiments shown. This disclosure is intended to cover any and all adaptations or variations of various embodiments of the disclosure. 
     It is to be understood that the above description has been made in an illustrative fashion, and not a restrictive one. Combination of the above embodiments, and other embodiments not specifically described herein will be apparent to those of skill in the art upon reviewing the above description. The scope of the various embodiments of the disclosure includes any other applications in which the above structures and methods are used. Therefore, the scope of various embodiments of the disclosure should be determined with reference to the appended claims, along with the full range of equivalents to which such claims are entitled. 
     In the foregoing Detailed Description, various features are grouped together in example embodiments illustrated in the figures for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the embodiments of the disclosure require more features than are expressly recited in each claim. 
     Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment.