Abstract:
The invention relates to an invisible removable orthodontic repositioning appliance with a lower modulus inner lining for systematically aligning teeth from an initial tooth arrangement to a final tooth arrangement while minimizing propensity for root and bone resorption due to the lower modulus. The aligning of the teeth may be accomplished by taking impressions at various intervals for greater accuracy in the event of a distorted impression. Patient impression and/or model may then be digitally scanned. Using 3D software, tooth position may be incrementally modified toward idealized position and associated stress analyzed. Final modified model and associated appliance may be fabricated with for orthodontic movement using 3D printer. Each appliance may be numerically identified to maintain uniformity of application from start of treatment to completion. The forces required for the alignment may be from polymeric material used to fabricate the orthodontic appliances, the shape memory alloy, and/or micro-implants with various attachments, including magnetic attachments to allow for three potential types of cooperating forces toward optimal tooth movement.

Description:
[0001]    This application claims the benefit of U.S. Provisional Application No. 60/822,991 filed Aug. 21, 2006, which is incorporated herein by reference in its entirety. 
     
     BACKGROUND 
       [0002]    Orthodontic treatments involve repositioning misaligned teeth and improving bite configurations for improved cosmetic appearance and dental function. Repositioning teeth is accomplished by applying controlled forces to the teeth over an extended period of time. 
         [0003]    Currently, there are numerous techniques for orthodontic treatments for repositioning misaligned teeth and improving bite configurations. The conventional technique consists of requiring the patient to wear what are commonly referred to as “braces.” Braces comprise a variety of appliances such as brackets, bands, arch wires, ligatures, and O-rings. After they are bonded to the teeth, periodic meetings with the orthodontist are required to adjust the braces. This involves installing different arch wires having different force-inducing properties or by replacing or tightening existing ligatures. Between meetings, the patient may be required to wear supplementary appliances, such as elastic bands or headgear, to supply additional or extra oral forces. Conventional braces are often a tedious and time consuming process requiring many visits to the orthodontist&#39;s office. Moreover, from a patient&#39;s perspective, they are unsightly and uncomfortable. 
         [0004]    Another group of appliances are removable orthodontic appliances, which have been used since the early 20th century. One such appliance in this group is a tooth positioning appliance, as disclosed in U.S. Pat. No. 2,531,222. The tooth positioning appliance is one piece that moves the upper and lower teeth simultaneously. This type of appliance is very demanding on patients as it is bulky, uncomfortable, and prevents patients from speaking. Also in this group are appliances known as spring-alignment appliances. These appliances are designed to correct minor incisor rotations. This appliance is constructed over a model of the repositioned teeth. Labial and lingual wires are formed and labial and lingual plates are formed over the wires. The acrylic plates apply the pressure to the teeth. These appliances cannot be adjusted and are not particularly effective for tooth movement. 
         [0005]    Consequently, alternative orthodontic treatments have been developed. Recent patents, including U.S. Pat. No. 6,454,565 by inventor Phan and U.S. Pat. No. 6,790,036 by inventor Graham relies on the use of elastic positioning appliances for realigning teeth. In these alternative treatments an inner elastic modulus is significantly higher then the outer elastic modulus thereby creating greater potential for excess and localized force which in turn possesses greater propensity to cause iatrogenic damage to patient&#39;s teeth, dental roots, and periodontum. Although during routine orthodontic dental movement it is necessary to cause some resorption and apposition, otherwise teeth cannot move, one must limit such degradation of anatomical structure to thereby minimize the ultimate loss of teeth. The increased modulus to the inner aspect of the appliance does the opposite of what a periodontist (specialist in bone, soft tissue and dental health) wishes for any patient. Thus, there is a need in the art for an apparatus and method providing orthodontic treatments without causing periodontal destruction which is not necessary for dental movement. 
       SUMMARY 
       [0006]    The summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the subject matter, nor is it intended to be used to limit the scope of the subject matter. 
         [0007]    An aspect of the invention relates to an invisible removable orthodontic repositioning appliance with a lower modulus inner lining for systematically aligning teeth from an initial tooth arrangement to a final tooth arrangement while minimizing propensity for root and bone resorption. 
         [0008]    In another aspect of the invention relates to an invisible removable orthodontic repositioning appliance with an option to have incorporated in it Shape Memory Alloy (SMA) which is an alloy used in the aeronautic industry where once the material shape is set the material may be severely deformed and then returned to its original shape. 
         [0009]    In another aspect of the invention, a repositioning appliance may be constructed from polymers with a lower elastic modulus inner lining than an outer lining. The lower elastic modulus on the inner layer may allow for greater patient comfort, less tooth, bone and root damage, and longer duration of active tooth movement by the repositioning appliance thereby requiring less number of appliances to achieve idealized alignment. 
         [0010]    In another aspect of the invention, a separate repositioning appliance may be made for a patient&#39;s upper, maxillary, teeth or for a patient&#39;s lower, mandibular, teeth. 
         [0011]    In an additional aspect of the invention, a separate mold may be taken of the patient&#39;s teeth at various intervals in the alignment process, and a new repositioning appliance may be made based on such molds. By creating numerous molds, a defect in one mold may not continue throughout the course of the patient&#39;s treatment. Each of the molds and associated appliances may be numerically identified to maintain uniformity of application from start of treatment to completion. 
         [0012]    In a further aspect of the invention, the repositioning appliance may comprise bars for greater control and attachment over a patient&#39;s teeth. The bars may be longitudinal, diagonal, or horizontal depending upon the type of orthodontic movement. The bars are achieved by placing grooves at the desired locations on the patient&#39;s model and upon fabrication of the repositioning appliance, grooves on the model would be translated into bars on the appliance. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  illustrates an occlusal view of a maxillary impression taken from a patient with anterior crowding prior to any treatment in accordance with an aspect of the invention. 
           [0014]      FIG. 2  illustrates an occlusal view of a maxillary stone model which has been poured from the maxillary impression in accordance with an aspect of the invention. 
           [0015]      FIG. 3  illustrates an occlusal view of a maxillary repositioning appliance which has been fabricated from the modified stone model referenced in  FIG. 2  in accordance with an aspect of the invention. 
           [0016]      FIG. 4  illustrates an occlusal view of the repositioning appliance on the maxillary model referenced in  FIG. 2  in accordance with an aspect of the invention. 
           [0017]      FIG. 5  illustrates an occlusal view of the maxillary stone model in  FIG. 2 , where the anterior teeth have been sequentially modified toward their idealized tooth position in accordance with an aspect of the invention. 
           [0018]      FIG. 6  illustrates an occlusal view of a mandibular impression taken from a patient with anterior crowding in accordance with an aspect of the invention. 
           [0019]      FIG. 7  illustrates an occlusal view of the mandibular stone model which has been poured from the mandibular impression, referenced in  FIG. 6  in accordance with an aspect of the invention. 
           [0020]      FIG. 8  illustrates an occlusal view of the mandibular repositioning appliance which has been fabricated from the modified stone model in accordance with an aspect of the invention. 
           [0021]      FIG. 9  illustrates an occlusal view of the repositioning appliance on the mandibular model referenced in  FIG. 7  in accordance with an aspect of the invention. 
           [0022]      FIG. 10  illustrates an occlusal view of the mandibular stone model in  FIG. 7 , where the anterior teeth have been slightly modified toward their idealized positions in accordance with an aspect of the invention. 
           [0023]      FIG. 11  illustrates an occlusal diagrammatic view of a patient&#39;s maxillary teeth where the anterior teeth have been sequentially aligned in accordance with an aspect of the invention. 
           [0024]      FIG. 12  illustrates an occlusal diagrammatic view of a patient&#39;s maxillary teeth of  FIG. 11  following use of the repositioning appliance where the anterior teeth have been partially aligned from a subsequent patient impression in accordance with an aspect of the invention. 
           [0025]      FIG. 13  illustrates an occlusal diagrammatic view of a patient&#39;s mandibular teeth of where the anterior teeth have been partially aligned, in accordance with an aspect of the invention. 
           [0026]      FIG. 14  illustrates an occlusal diagrammatic view of a patient&#39;s mandibular teeth of  FIG. 13  following the use of the repositioning appliance where the anterior teeth have been partially aligned from a subsequent patient impression in accordance with an aspect of the invention. 
           [0027]      FIGS. 15 and 16  illustrate schematic drawings representing the difference between low modulus (softer) inner aspects of the appliance compared to a higher modulus (harder) appliance at the tooth—appliance interface in accordance with an aspect of the invention. 
           [0028]      FIG. 17  illustrates stress distributions in laminated and un-laminated repositioning appliances in accordance with an aspect of the invention. 
           [0029]      FIG. 18  illustrates grooves that may be used in various embodiments of a repositioning appliance in accordance with an aspect of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0030]      FIG. 1  illustrates an occlusal view of a maxillary impression  100  taken from a patient with anterior crowding. A maxillary impression  100  is an impression made of a patient&#39;s upper teeth. Anterior crowding is crowding of the front teeth. The maxillary impression  100  may be removed from the patient&#39;s mouth using tab  102 . 
         [0031]    A maxillary stone model  200  of the patient&#39;s maxillary teeth may be made using the maxillary impression  100 , as seen in  FIG. 2 . The stone model  200  of the maxillary impression  100  may be modified to create an appliance that will alter and align the patient&#39;s teeth. In  FIG. 2 , the anterior teeth  202 ,  204 ,  206 ,  208 ,  210 ,  212 ,  214 ,  216 , and posterior (rear) tooth  220  are not aligned. 
         [0032]      FIG. 3  illustrates maxillary repositioning appliance  300  that may be fabricated from a maxillary stone model. Maxillary repositioning appliance  300  may be the first repositioning appliance in a series of appliances that may be used to reach the alignment goal. Repositioning appliance  300  may be comprised of a single sheet of material that may be formed from a variety of materials, such as polymers and plastics including polycarbonates, polyacetates, polyolefins, polyamides, polystyrenes and epoxy resins among others. These materials may range in thickness from 0.020 inch to 0.080 inch, depending upon the material&#39;s physical characteristics. In an aspect of the invention, repositioning appliance  300  may be 0.030 inch thick polycarbonate with a lower modulus inner lining which has been thermo vacuum-formed over a model  406  of a patient&#39;s teeth. The polycarbonate with a lower modulus inner lining is tissue compatible and invisible making it aesthetically appealing to the patient during use. Those skilled in the art will realize that materials such as polycarbonates, polyacetates, polyolefins, polyamides, polystyrenes and epoxy resins among others also may be provided in clear forms. The 0.030 inch repositioning appliance  300  may be firm enough to move the patient&#39;s teeth and may be flexible enough to adapt to the patient&#39;s misaligned teeth. These characteristics may provide a sequential adjustment of the teeth from a new impression at each and every phase toward the ideal that will move the patient&#39;s teeth from misalignment to alignment on an incremental basis with each and every new impression taken at each treatment interval of about six weeks. Those skilled in the art will realize that treatment intervals may be shorter or longer than six weeks depending upon a variety of patient and treatment factors. 
         [0033]      FIG. 4  illustrates maxillary repositioning appliance  300  over modified maxillary stone model  406 . As shown in  FIG. 4 , maxillary repositioning appliance  300  does not have to extend over all maxillary teeth  400 . Repositioning appliance  300  may be formed over a patient&#39;s teeth  402  and adjacent soft tissue  404 . In an aspect of the invention, repositioning appliance  300  may have its best use when only the anterior teeth  202 ,  204 ,  206 ,  208 ,  210   212 ,  214 ,  216  require aligning and the posterior teeth  220 ,  222 ,  224 ,  226 ,  228 ,  230 , requiring no alignment, become an anchor for the repositioning appliance  300 . In an alternative embodiment, with other teeth acting as an anchor, the repositioning appliance  300  may be used to align posterior teeth  220 ,  222 ,  224 ,  226 ,  228 ,  230 . 
         [0034]    The process of taking a maxillary impression, creating a stone model therefrom, modifying that stone model to form a more ideal teeth alignment model, and creating a maxillary repositioning appliance may occur about every six weeks until the patient&#39;s teeth are in alignment. 
         [0035]    In an aspect of the invention, the repositioning appliance may be created using a 3-D scanner and printer. When using 3-D technology to fabricate a repositioning appliance, there may be greater accuracy using laminated aligners with soft inner lining then un-laminated aligners as the repositioning appliance with laminated soft liners demonstrates less stress in the supporting bone then un-laminated aligners when inserting over an un-orthodontically altered model. 
         [0036]    In an aspect of the invention, posterior teeth  220 ,  222 ,  224 ,  226 ,  228 ,  230  which may not require alignment may act as anchors for repositioning appliance  300  for use in aligning anterior teeth  204 ,  206 ,  208 ,  210 ,  212 ,  214 , and  216 . 
         [0037]      FIG. 5  illustrates a maxillary stone model  500 , which has been sequentially modified from an impression made subsequent to use of a number of repositioning appliances, each designed to increasingly align the patient&#39;s teeth. As shown on stone model  500 , the patient&#39;s teeth  202 ,  204 ,  206 ,  208 ,  210 ,  212 ,  214 ,  216 ,  220  are much more aligned than they had been in the initial modified maxillary stone model  200 . Maxillary stone model  500  has been modified to a more ideal alignment, and it may be used to create a subsequent maxillary repositioning appliance. 
         [0038]    The entire process may also be done to the mandibular (lower) teeth.  FIG. 6  illustrates an occlusal view of a mandibular impression  600  taken from a patient with anterior crowding. A mandibular impression  600  is an impression made of a patient&#39;s lower teeth. Anterior crowding is crowding of the front teeth. The mandibular impression  600  may be removed from the patient&#39;s mouth using tab  602 . 
         [0039]    A mandibular stone model  700  of the patient&#39;s mandibular teeth may be made using the mandibular impression  600 , as shown in  FIG. 7 . The mandibular stone model of the mandibular impression  600  may be modified to create an appliance that may alter and align the patient&#39;s teeth.  FIG. 7  illustrates that the patient&#39;s teeth  702 ,  704 ,  706 ,  708 ,  710 ,  712 ,  714 ,  716 ,  718 ,  720 ,  722 ,  724 ,  726 ,  728  are not aligned. 
         [0040]      FIG. 8  illustrates a mandibular repositioning appliance  800  that may be fabricated from a mandibular stone model. The repositioning appliance  880  may be the first repositioning appliance in a series of appliances that may be used to reach the alignment goal. The repositioning appliance  800  may be comprised of a single sheet of material that may be formed from a variety of materials, such as polymers and plastics including polycarbonates, polyacetates, polyolefins, polyamides, polystyrenes and epoxy resins among others. These materials may range in thickness from 0.020 inch to 0.080 inch, depending upon the material&#39;s physical characteristics. In an aspect of the invention, the repositioning appliance  300  may be 0.030 inch thick polycarbonate with a lower modulus inner laminate which has been thermo vacuum-formed over a model  906  of a patient&#39;s teeth. The polycarbonate with a lower modulus inner laminate is tissue compatible and invisible which making it aesthetically appealing to the patient during its use. Those skilled in the art will realize that materials such as polycarbonates, polyacetates, polyolefins, polyamides, polystyrenes and epoxy resins among others may also be provided in clear forms. The 0.030 inch repositioning appliance  800  may be firm enough to move the patient&#39;s teeth and may be flexible enough to adapt to the patient&#39;s misaligned teeth. These characteristics provide a sequential adjustment of the teeth from a new impression at each and every phase toward the ideal that will move the patient&#39;s teeth from misalignment to alignment on an incremental basis with each and every new impression taken at each treatment interval of about six weeks. Those skilled in the art will realize that treatment intervals may be shorter or longer than six weeks depending upon a variety of patient and treatment factors. 
         [0041]      FIG. 9  illustrates mandibular repositioning appliance  800  over modified maxillary stone model  906 . Repositioning appliance  800  may be formed over a patient&#39;s teeth  902  and adjacent soft tissue  904 . 
         [0042]    The process of taking a mandibular impression, creating a stone model therefrom, modifying that stone model into a more ideal alignment, and creating a mandibular repositioning appliance may occur at an interval of six weeks until the patient&#39;s teeth are in ideal alignment. Those skilled in the art will realize that the interval may be longer or shorter depending upon a variety of patient and treatment factors. 
         [0043]      FIG. 10  illustrates a mandibular stone model  1000 , which has been sequentially modified from an impression made subsequent to use of a number of repositioning appliances, each designed to increasingly align the patient&#39;s teeth. As seen on stone model  1000 , the patient&#39;s teeth  702 ,  704 ,  706 ,  708 ,  710 ,  712 ,  714 ,  716 ,  718 ,  720 ,  722 ,  724 ,  726 ,  728  are much more aligned than they had been in the initial modified maxillary stone model  700 . Mandibular stone model  1000  has been modified to a more ideal alignment, and it may be used to create a subsequent mandibular repositioning appliance. 
         [0044]      FIGS. 11 and 12  are diagrammatic views of a patient&#39;s maxillary teeth at sequential stages in the process of aligning the teeth to the ideal position. The diagram of the initial teeth  1100  shows unaligned teeth. Teeth  1102 ,  1104 ,  1106 ,  1108 ,  1112 ,  1114 ,  1116 ,  1118 ,  1120 ,  1122  are protruding and crooked. In the subsequent diagram  1110 , the patient&#39;s teeth show improved alignment. The anterior incisor central teeth  1112 ,  1114  are less protruding, and anterior teeth  1102 ,  1104  are more aligned. Furthermore, anterior teeth  1116 ,  1118  show less overlap. In another more subsequent diagram  1200 , the patient&#39;s teeth show further improvement. The teeth are in alignment and there is less overlap in anterior teeth  1114 ,  1116 . 
         [0045]      FIGS. 13 and 14  are diagrammatic views of a patient&#39;s mandibular teeth at sequential stages in the process of aligning the teeth to the ideal position. The diagram of the initial teeth  1300  shows unaligned teeth. Teeth  1302 ,  1304 ,  1306 ,  1308 ,  1311 ,  1312 ,  1314 ,  1316 ,  1318 ,  1320  are overlapping and crooked. In the subsequent diagram  1310 , the patient&#39;s teeth show improved alignment. Teeth  1308 ,  1311 ,  1312 ,  1314 ,  1316  are less overlapping, and tooth  1320  is significantly more aligned with the other teeth. In another more subsequent diagram  1400 , the patient&#39;s teeth show further improvement. The teeth are in alignment and there is even less overlap in teeth  1308 ,  1311 ,  1312 ,  1314 ,  1316 . 
         [0046]      FIGS. 15 and 16  illustrate the benefits of having an inner layer with a lower elastic modulus than the outer layer. The elastic modulus of a material is the ratio of the increment of unit stress to an increment of unit deformation within the elastic limit. When a material is deformed within the elastic limit, the coiled polymer chains are stretched reversibly. The magnitude of the elastic modulus may be indicative of the atomic and molecular bonding forces. When the stress is relieved, the material returns to its original shape and therefore the deformation is nonpermanent. Different materials may have different elastic moduli based on their molecular structures. Some materials, such as certain polymers including polycarbonates, polyacetates, polyolefins, polyamides, polystyrenes and epoxy resins among others, may be specially produced to have different elastic moduli while retaining similar chemical compositions by using additives such as silicates, other polymers or fillers among other materials. In an embodiment, the liner may be a polymer such as Thermoplastic Polyurethane that is an aromatic polyether based grade, such as TEXIN® 990R resin with a shore hardness of approximately 90 A. The TEXIN® 990R resin may offer outstanding abrasive resistance, impact strength, toughness, structural memory and flexibility. Furthermore, the resin may also provide good hydrolytic stability, microbial resistance, and exceptional mold release characteristics. 
         [0047]    In the final appliance the elastic moduli of the different parts will generally range from 0.1 to 10 GigaPascal (GPa), although some parts of the appliance may be outside of this range. The elastic modulus of one part may differ from another part by 10% to 500%, or more. 
         [0048]    As shown in  FIG. 15 , if an appliance  1510  has a higher modulus on the inner layer than the outer layer, the pressure on the tooth  1500  is localized  1502 , thereby increasing the propensity for tooth and bone damage. Also, the harder material  1510  is less elastic thereby causing greater load for a shorter period of time with less tooth movement by each appliance. 
         [0049]      FIG. 16  demonstrates the effect on tooth  1500  with use of a repositioning appliance  1600  with an inner layer having a lower elastic modulus than the outer layer. The lower modulus inner layer repositioning appliance  1600  allows for the same amount of load to be distributed to a greater surface area of the tooth for less bone and root resorption. Additionally, the lower modulus inner layer repositioning appliance  1600  will give less force for a longer period of time. Therefore, not only is the lower modulus inner lining safer for the patient&#39;s teeth, but also, may allow the repositioning appliance to maintain a longer life. 
         [0050]    For example,  FIG. 17  illustrates the stresses developed at a crestal bone between central incisors with repositioning appliance having an inner layer with a lower elastic modulus than the outer layer as compared to a repositioning appliance without an inner layer (liner). 
         [0051]    Polyvinyl siloxane impressions were made and poured up in stone. The central incisors were modified to represent desired orthodontic movement. Two types of repositioning appliances were fabricated from the modified model. The first repositioning appliance was fabricated from a polycarbonate sheet. The second repositioning appliance was fabricated from a polycarbonate sheet laminated with lower modulus polyurethane. The laminated and un-laminated repositioning appliances were inserted on the model and resulting stresses observed in the field of the polariscope and photographed. Stress data for the two repositioning appliances was analyzed using a computer graphics program to quantify stress intensity by fringe number counting. 
         [0052]    As shown in  FIG. 17 , similar stress distributions were developed at the crestal bone between the central incisors with both repositioning appliances. However, the level of stress was significantly lower using the laminated repositioning appliance  1702  as compared to the un-laminated repositioning appliance  1704 . 
         [0053]    The stresses associated with the laminated repositioning appliance were of lower intensity as compared to the un-laminated repositioning appliance, which may alleviate problems of patient discomfort and difficulty during insertion and removal of un-laminated repositioning appliances. 
         [0054]    In another aspect of the invention relates to an invisible removable orthodontic repositioning appliance with an option to have incorporated in it Shape Memory Alloy (SMA) which is an alloy where once the material shape is set the material may be severely deformed and then returned to its original shape. In an embodiment, the SMA may be adapted to an idealized dental alignment and then realigned to the present misaligned dental position and adhered to the polymeric orthodontic shell to allow continual inherent movement of the teeth or adjusted by the dentist. SMA and polymeric technology may allow for two types of cooperating forces toward optimal tooth movement. SMA may be utilized under conditions needing greater force, more rapid movement and or severe cases. 
         [0055]    In an aspect of the invention, orthodontic shape memory alloy wire having properties may be adapted to the lingual aspect of a stone model prior to adaptation of the repositioning appliance  1600  thereby allowing continual inherent movement of the patient&#39;s teeth. The orthodontic wire may be comprised of an alloy having shape memory properties such as NiTi, CuZnAl, and CuAlNi. Moreover, the orthodontic wire may be adjusted to assist in repositioning of teeth to an optimal position. This adjustment may be a self adjustment or an adjustment based on temperature change. 
         [0056]    In yet another aspect of the invention, a micro-implant which may be approximately 1-5 mm in diameter may be utilized. The micro-implant may withstand immediate load unlike traditional implants which may require 6 months of bone integration (healing). The micro-implant may be attached or connected to the polymeric shell or a component of the shell for added orthodontic tooth movement. Micro-implant for orthodontic movement may be achieved by either attachment for example using a Hader-bar, male-female (ball and socket) or magnets to allow for greater force and greater control of orthodontic forces. This may allow for greater options under various orthodontic conditions. A technique for greater orthodontic force and or control may be with magnet attachment at the head (coronal aspect of the micro-implant). The micro-implant may be positioned with the positive pole of the magnet positioned into the bone or tooth for anchorage. The negative pole of the magnet may be imbedded into the SMA, a bracket or component of the polymeric shell or the polymeric matrix of the appliance to allow for greater control and force for orthodontic tooth movement. 
         [0057]    In a further aspect of the invention, the repositioning appliance may comprise bars for greater control and attachment over a patient&#39;s teeth. For example, placement of grooves on a patient&#39;s stone model which translates into bars on the appliance upon replication may be used in areas which require greater control and force. 
         [0058]      FIG. 18  illustrates the placement of various grooves such as an oblique groove  1802 , a vertical groove  1804 , a horizontal groove  1806 , and a lingual vertical groove  1808 . Those skilled in the art will realize that other geometric shaped grooves such as longitudinal, diagonal, or horizontal grooves may also be used depending upon the type of orthodontic movement. Upon fabrication of the appliance, the grooves may become extensions on the appliance to allow for greater control during orthodontic tooth movement. 
         [0059]    Placement of the grooves on a stone model which translate into bars on the appliance as compared to cementing brackets on patient&#39;s teeth may eliminate the need for invasive attachments to teeth such as clasps +/or brackets. In addition, the bars may eliminate propensity for damage to teeth during application of cement or during grinding of the brackets during removal. Moreover, the grooves may provide improved esthetic and greater ease of oral hygiene for the patient.