Abstract:
A variable extension spring with two anchoring ends. Each anchoring end connected to an anchoring mechanism having engagement mechanisms. Engagement mechanisms may be eyelets. Engagement of the engagement mechanisms to intraoral features at different engagement positions allows variability in the extension length of the spring. Such variability allows the user to adjust the force exerted by the spring on the intraoral features. As intraoral features move overtime due to the force exerted by the spring, the extension length of the spring may change. Adjustment of the spring extension length is accomplished by engaging a different engagement mechanism to provide an engagement position that will extend the spring the desired length. The user is able to reduce inventory by being able to use the same spring several times to provide a desired range of forces for adjusting orthodontia.

Description:
[0001]    This application claims the benefit of U.S. Provisional Application No. 61/311,125 filed on Mar. 5, 2010. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to the field of orthodontics, in particular an orthodontic coil spring. 
       BACKGROUND OF THE INVENTION 
       [0003]    Orthodontic coil springs are used to provide force to move individual teeth or segments of teeth. Coil springs most often contain attachment mechanisms, or “eyelets” which are designed to allow the ends of the coil spring to be attached to posts on brackets, archwires, temporary anchorage devices (TADs) or any other intraoral feature. 
         [0004]    Coil springs are commonly made from stainless steel, nickel-titanium, and other suitable materials and are typically designed to be extended to two to three times their original length upon clinical activation. Coil springs are most often available in a variety of lengths, internal lumens and wire diameters to accommodate a multitude of clinical situations that are well known to an orthodontic practitioner. For example, a shorter spring will be useful when moving an individual tooth or segments of teeth a short distance whereas a longer spring will be useful for moving the dentition a larger distance. Different types of teeth or groupings of teeth also require different levels of force to move in the manner desired by the clinician. The force used to move a patient&#39;s teeth must be great enough to allow for proper alignment, yet not exert too great a force to cause damage to or misalignment of the tooth or adjacent dentition. In cases where there is space between adjacent teeth, a coil spring may be used to bring the teeth closer together. Various internal lumens of the spring or actual wire diameters are well known to impart more or less force on the dentition. Each end of the coil springs is attached to stop fittings on adjacent teeth, archwires or suitable attachments. The force of the spring imparts a force to move the teeth toward each other or, when sufficient anchorage exists, one individual tooth into a predetermined space. 
         [0005]    As individual teeth or groups of teeth are pulled towards each other, the extended distance of the coil spring decreases, most often resulting in a corresponding decrease of the force exerted on the teeth by the spring. In order to maintain a suitable force to move the teeth, the coil spring is replaced with a new, usually shorter, spring to exert appropriate force when the amount of movement eliminates the usefulness of the initial spring length. 
         [0006]    Conventional coil springs provide only a single eyelet of various shapes and sizes on either end of the spring for attachment. The springs are therefore limited by the amount of extension that will be employed to create the optimal amount of clinical rebound force. A clinician must therefore maintain a relatively large inventory of spring lengths, lumens and/or wire diameters to meet varying clinical situations. 
         [0007]    The present inventor has recognized the need for a multipurpose spring which decreases inventory requirements. 
         [0008]    The present inventor has recognized the need for a spring which is capable of multiple uses for individual patients. 
         [0009]    The present inventor has recognized the need for a spring design that allows the clinician to select the appropriate amount of force imparted to the dentition. 
         [0010]    The present inventor has recognized the need for a spring which decreases the treatment time of a patient. 
       SUMMARY OF THE INVENTION 
       [0011]    A variable extension spring for orthodontics having at least one end of the spring with multiple engagement positions corresponding to different extension lengths of the spring is provided. 
         [0012]    In one embodiment, the variable extension spring comprises a coil spring with two anchoring ends. The coil spring connects to an anchoring mechanism at each anchoring end. The anchoring mechanism comprises a spring attachment region wherein the coil spring becomes attached to the anchoring mechanism. The spring attachment region is disposed at one end of the anchoring mechanism. In this embodiment, the spring attachment region comprises two channels through which coils of the spring are wound to securely connect the coil spring to the anchoring mechanism. 
         [0013]    Each anchoring mechanism comprises at least one engagement mechanism, such as an eyelet. Other suitable engagement mechanisms known to one skilled in the art, such as hooks, may also be used. At least one of the anchoring mechanisms comprises more than one engagement mechanism. Each engagement mechanism is disposed at an engagement position. 
         [0014]    In use, the orthodontist identifies an engagement position, which when engaged with a post on a bracket for example, exerts a desired level of force to pull teeth towards each other. As the teeth move toward each other over time, the original distance the spring is stretched decreases. Tooth movement eventually ceases, as the spring no longer retains sufficient force to overcome resistance. These force requirements will vary depending on the size of the individual crown, arch length, distance between teeth to be moved, or the number of teeth being moved as a group. To readjust the force exerted on the teeth, the orthodontist disengages the post from its engagement with the first engagement mechanism at the first engagement position, and selects a second engagement mechanism which provides a second engagement position, for example, the engagement mechanism adjacent to the first engagement mechanism, to provide a second appropriate force which is exerted on the teeth to move the teeth toward each other. 
         [0015]    Numerous other advantages and features of the present invention will be become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  illustrates an exemplary embodiment of a variable extension spring. 
           [0017]      FIG. 1A  illustrates the variable extension spring of  FIG. 1  extended between two anchors in a patient&#39;s mouth. 
           [0018]      FIG. 1B  illustrates the variable extension spring of  FIG. 1  engaging with an engagement mechanism adjacent to that of the one engaged in  FIG. 1A  after the outermost engagement mechanism has been removed. 
           [0019]      FIG. 2A  illustrates another exemplary embodiment of the variable extension spring comprising an anchoring mechanism with two engagement mechanisms. 
           [0020]      FIG. 2B  illustrates other exemplary embodiments of the variable extension spring comprising an anchoring mechanism with three non-equidistantly disposed engagement mechanisms. 
           [0021]      FIG. 2C  illustrates other alternative exemplary embodiments of the variable extension spring comprising at least two engagement mechanisms on each anchoring mechanism. 
           [0022]      FIG. 2D  illustrates another exemplary embodiment of the variable extension spring comprising anchoring mechanisms each with three engagement mechanisms on each end. 
           [0023]      FIG. 2E  illustrates other embodiments of the variable extension spring comprising engagement mechanisms of different sizes on either end of the coil spring. 
           [0024]      FIG. 3  illustrates a perspective view of an anchoring mechanism. 
           [0025]      FIG. 4  illustrates a perspective view of an alternate embodiment of the anchoring mechanism. 
           [0026]      FIG. 4A  illustrates yet another embodiment of the anchoring mechanism. 
           [0027]      FIG. 4B  illustrates another alternate embodiment of the anchoring mechanism. 
           [0028]      FIG. 5  illustrates a top view of the anchoring mechanism of  FIG. 3 . 
           [0029]      FIG. 6  illustrates a top view of an alternate anchoring mechanism with differently sized engaging mechanisms. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0030]    While this invention is susceptible of embodiment in many different forms, there are shown in the drawings, and will be described herein in detail, specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated. 
         [0031]      FIG. 1  illustrates an exemplary embodiment of the variable extension spring. The variable extension spring comprises a coil spring  10 , with two anchoring ends  20 ,  30 . The two anchoring ends  20 ,  30  are respectively attached to anchoring mechanisms  40 ,  50 . 
         [0032]    The anchoring mechanism  50  comprises engagement mechanisms  80 ,  86 ,  90 ,  100 . Anchoring mechanism  60  as illustrated in  FIG. 3  comprise engagement mechanisms  80 ,  90 ,  100 . At least one of the anchoring mechanisms comprises more than one engagement mechanism.  FIG. 1A  illustrates the variable extension spring of  FIG. 1  extended between two anchors  11 ,  12  in a patient&#39;s mouth to move teeth  13 ,  14  towards each other. 
         [0033]    The coil spring  10  may configured as be a tension spring or a compression spring. The coil spring may be made of stainless steel, nickel titanium, beta titanium, or other suitable alloys which provide adequate shape memory. Coil springs of various expansion capabilities, such as 6 mm, 9 mm, and 12 mm springs, may be used to exert the desired force on teeth. This generally depends on the span between teeth to be moved or the desired amount of space closure required for successful completion of the procedure. Each anchoring end  20 ,  30  of the coil spring  10  is connected to an anchoring mechanism at its spring attachment region  70  ( FIG. 3 ). 
         [0034]      FIG. 3  illustrates an anchoring mechanism  60 . The anchoring mechanism  60  may be made from the same or different material as the coil spring. The anchoring mechanism  60  can be made from ductile material, such as  304  or  302  series stainless steel that can be cut using dental cutting instruments. The anchoring mechanism  60  comprises a spring attachment region  70 , and at least one engagement mechanism  80 ,  90 ,  100 . The spring attachment region  70  can comprises two channels  71 ,  72  spaced a distance “S” apart ( FIG. 5 ), through which the anchoring ends of the coil spring is wound to attach the anchoring mechanism to the anchoring end of the coil spring. The channels  71 ,  72  are spaced apart a distance S such that the coil radius at the anchoring ends  25 ,  35  ( FIG. 6 ) is consistent with the coil radius at the body  45  of the coil spring  15 . Alternatively, the channels can be spaced a distance S apart such that the radius of the coil at the anchoring end when wounded though the channels  71 ,  72 , is greater or smaller than the radius of the body of the coil spring. Other types of spring attachment regions known to one skilled in the art can also be used to connect the anchoring ends of the coil spring to the anchoring mechanisms. For example, as illustrated in  FIG. 4 , the spring attachment region can comprise a hole  115  and notches  110   a ,  110   b  for attachment to an anchoring end of the coil spring. In another embodiment, the spring attachment region allows the anchoring mechanism to rotate about an axis parallel to the longitudinal axis of the coil spring. The anchoring mechanism may rotate about an axis in line with the longitudinal axis of the coil spring. Anchoring ends  25 ,  35  of the spring may be engaged to allow the anchoring mechanism and the coil spring to swivel with respect to each other. Alternatively, in yet another embodiment, the spring attachment region allows for the anchoring ends  25 ,  35  to engage with the anchoring mechanism such that the anchoring mechanism may rotate about an axis perpendicular to the longitudinal axis of the coil spring. 
         [0035]    In the embodiment illustrated in  FIG. 3 , the spring attachment region  70  extends from an adjacent engagement mechanism. The anchoring mechanism comprises three engagement mechanisms  80 ,  90 ,  100 . The engagement mechanisms can be eyelets as illustrated, or may be any other suitable engagement mechanism such as a bracket, hook or eyelets of various shapes or internal diameters. In use, each engagement mechanism  80 ,  90 ,  100  provides a corresponding engagement position. For example, engagement mechanism  100  provides a first engagement position, and engagement mechanism  90  provides a second engagement position. The engagement mechanisms illustrated in  FIG. 3  are spaced equidistant from each other, with bridges  130   a ,  130   b  connecting the engagement mechanisms  80 ,  90 ,  100  in series. Alternate arrangements for the engagement mechanisms are illustrated in  FIGS. 2A-2E .  FIG. 2A  illustrates a variable engagement spring comprising two engagement mechanisms on one of the anchoring mechanisms.  FIG. 2B  illustrates embodiment of the variable extension spring comprising three non-equidistantly disposed engagement mechanisms on one of the anchoring mechanisms.  FIG. 2C  illustrates a variable extension spring with at least two engagement mechanisms on each anchoring mechanism.  FIG. 2D  illustrates a variable extension spring comprising three engagement mechanisms on each anchoring mechanism.  FIG. 2E  illustrates a variable extension spring comprising differently sized engagement mechanisms. A larger engagement mechanism  85  may be used on one side of the coil spring to adapt for use with a temporary anchoring device or TAD (not shown). In one embodiment, the larger engagement mechanism  85  can have an inner diameter of 0.088″ (2.235 mm), and an outer diameter of a suitable size to appropriately engage with the TAD. 
         [0036]    In another embodiment, as illustrated in  FIG. 5 , the anchoring mechanism may be about 0.01″ (0.254 mm) in thickness, with an inner eyelet diameter of 0.058″ (1.473 mm), and an outer eyelet diameter of 0.088″ (2.235 mm). 
         [0037]    The bridge portions  130   a ,  130   b  span a distance “L” as illustrated in  FIG. 3 . Distance L should be of a sufficient length to allow for a cutting instrument to be positioned between two adjacent engagement mechanisms, such that the engagement mechanism(s) furthest away from the coiled spring may be disconnected from the rest of the anchoring mechanism when the engagement position(s) is no longer needed, but may also be of a shorter or longer distance. 
         [0038]    In the alternative embodiment illustrated in  FIG. 4 , the engagement mechanism uses a hook-type mechanism  125   a ,  125   b . The anchoring mechanisms can comprise one row of engagement mechanisms  125   a , or may have engagement mechanisms aligned in a pair of offset rows  120   a ,  120   b , such that more engagement positions are provided within the same distance span “D”. Additional alternative embodiments, illustrated in  FIGS. 4A , and  4 B show that the engagement mechanisms can be any shape, including non-symmetrical shapes, to better accommodate the various types of hooks or TAD&#39;s.  FIG. 4A  illustrates an anchoring mechanism  135  with diamond-shaped engagement mechanisms  140  on one end of a coil  145  having an anchoring mechanism  136  on the opposite end comprising a circular eyelet  141 .  FIG. 4B  illustrates an anchoring mechanism  137  with an oblong eyelet  150  on one end of a coil  155  having an anchoring mechanism  138  on the opposite end comprising a circular eyelet  151 . 
         [0039]    In use, an orthodontist selects a variable extension spring with the appropriate coil spring expansion capability and anchoring mechanism to provide an appropriate number and spacing of engagement mechanisms. The location of the engagement mechanism corresponds to engagement positions which provide predetermined increments of force. For example, engaging an outermost engagement mechanism  100  in  FIG. 1  will exert less force on teeth than engaging the engagement mechanism  90  immediately adjacent. An orthodontist may select the correct engagement mechanism with which to begin treatment, and simply detach, if any, outer engagement mechanisms beyond the engagement mechanism selected. Alternatively, an orthodontist may select a variable extension spring wherein the outermost engagement mechanism  180  corresponds to the correct engagement position to provide the desired force. The distance between engagement mechanisms is also selected by the orthodontist in anticipation of the gradual movement of teeth as a result of the force of the spring exerted on the teeth between visits to the orthodontist office. As illustrated in  FIG. 1A , a variable extension spring with engagement mechanisms  80 ,  86 ,  90 , and  100  is selected for use. The anchor  12  on teeth  14  engages with the outermost engagement mechanism  100 . Engagement mechanism  90  is adjacent to engagement mechanism  100 . 
         [0040]    As treatment progresses, the force exerted by, for example, a tension spring such as the one illustrated in  FIG. 1A , causes teeth to move closer. As teeth move toward each other, the extension length, and correspondingly the force exerted by the spring on the teeth, decreases. A patient returns at the next appointment to readjust the spring to exert a desired force, such as the one provided by the adjacent engagement mechanism  90 , as illustrated in  FIG. 1B . Engagement mechanism  100  is removed by the orthodontist, leaving engagement mechanism  90  as the outermost engagement mechanism. Switching to engagement mechanism  90  for use with the anchor  12  allows more force to be exerted on the teeth  14  than engagement mechanism  100  in light of the movement of the teeth  14  over time, as indicated by the narrower gap  15  between teeth  13  and  14  in  FIG. 1B  as compared to  FIG. 1A . 
         [0041]    By having the anchoring mechanism provide more than one engagement position by way of having multiple engagement mechanisms, the orthodontist is able to adjust the force exerted on adjacent teeth by selecting a different engagement position, without having to replace the entire spring. The orthodontist is also able to select a variable extension spring that provides a suitable distance between the engagement mechanisms based on the force exerted by the spring and the anticipated movement of the teeth as a result of the force exerted by the spring on the teeth, to determine the time needed between visits to readjust the engagement mechanism. Alternatively, if a patient desires a certain time frame in the future for a next visit, the orthodontist may select a variable extension spring based on the factors above, to suit the patient&#39;s schedule. The demonstrated versatility of the variable extension spring allows for the user to reduce inventory, as a wider range of functions are able to be addressed with a fewer number of springs. Furthermore, time spent by the orthodontist adjusting the force exerted on the spring is decreased as the orthodontist need only disengage the previous engagement mechanism, and select a second engagement mechanism to provide the engagement position with the desired force. The user can then remove, by cutting, the engagement mechanism that provided the first engagement position, or the engagement mechanism beyond which engagement positions are no longer useful to provide the desired force. 
         [0042]    Some specific types of nickel titanium coil springs exhibit “superelastic” properties versus the more common variable force properties. Superelasticity denotes a relatively constant force regardless of the range of extension. Superelastic springs may, however, lose these properties if they are overextended. Superelastic springs will also lose their ability to move teeth once they return to or near their original shape. Conventional superelastic springs cannot be “reactivated” via multiple eyelets to overcome these limitations. However, having multiple eyelets for use with coil springs made of superelastic material provides the user with the benefit of reducing inventory. An orthodontist has the option of selecting the appropriate engagement mechanism with which to begin treatment, and simply detach, if any, outer engagement mechanisms beyond the engagement mechanism selected. Inventory is reduced because one variable extension spring can provide the orthodontist multiple extension distances from which a distance for beginning treatment can be selected. 
         [0043]    From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred.