Patent Publication Number: US-2012028207-A1

Title: Orthodontic connector providing controlled engagement with an orthodontic wire

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to orthodontic connectors and related assemblies used in the course of orthodontic treatment. More particularly, the present invention is directed to orthodontic connectors and related assemblies for coupling a wire to a bite corrector, force module or other orthodontic auxiliaries in the oral cavity. 
     2. Description of the Related Art 
     Orthodontics is a specialized area in the field of dentistry associated with the supervision, guidance and correction of teeth to proper positions in the dental arch. Orthodontic therapy generally involves the judicious application of light continuous forces to move teeth into a proper bite configuration, or occlusion. One mode of therapy, known as “fixed appliance” treatment, is carried out using a set of tiny slotted appliances called brackets, which are affixed to the anterior, cuspid, and bicuspid teeth of a patient. In the beginning of treatment, a resilient orthodontic wire (or archwire) is received in each of the bracket slots. The end sections of the wire are typically anchored in appliances called buccal tubes, which are affixed to the patient&#39;s molar teeth. 
     When initially installed in the brackets and buccal tubes, the wire is deflected from its original shape, but then gradually returns to its original arcuate shape during treatment. In this manner, the wire applies gentle, therapeutic forces to move the teeth from maloccluded (or “crooked”) positions to orthodontically correct positions. Taken together, the brackets, buccal tubes, and wire are commonly referred to as “braces”. Braces are often prescribed to provide improved dental and facial aesthetics, improve the occlusion (bite) and mastication, and promote better dental hygiene. 
     Various orthodontic devices and assemblies may be prescribed during the course of treatment, based on the experience and expertise of the orthodontist. Orthodontic connectors, which couple one orthodontic device to another, play an important role in enabling these devices and assemblies to properly direct corrective forces to the teeth. Depending on the malocclusion being treated, these connectors can assist in directing forces between teeth within the upper or lower arch, between the upper and lower arches, or even between one or more teeth and a temporary anchorage device such as a mini-screw implanted into the jawbone. 
     Some of the especially challenging applications for orthodontic connectors are found in the area of orthodontic auxiliaries (accessory devices). These include intra-oral devices for correcting Class II malocclusions, where the mandibular first molars are located excessively distal (in the posterior direction) with respect to the maxillary first molars when the jaws are closed. Other exemplary auxiliaries include devices for correcting the opposite malocclusion, known as a Class III malocclusion, which occurs when mandibular first molars are located excessively mesial (in the anterior direction) with respect to the maxillary first molars when the jaws are closed. Both Class II and Class III malocclusions result in improper alignment between the teeth of the upper and lower arches. 
     Various intra-oral auxiliary devices for correcting Class II and Class III malocclusions have been reported in the art. For example, U.S. Pat. No. 5,964,588 (Cleary) describes an intra-oral bite corrector with a first member and a second member slidably received in the first member. A spring extends around the second member for urging the second member and the first member in directions away from each other. A third member is slidably received in the second member. Together, these members provide a force module device that urges the lower dental arch either in a forwardly or rearwardly direction relative to the upper dental arch in order to improve the occlusion. 
     Intra-oral correctors such as these are typically coupled to the teeth using connectors with flexible linkages that allow the device to pivot relative to the teeth as the patient&#39;s jaws open and close. One particular challenge in treating patients using these intra-oral correctors is that portions of the device can inadvertently pivot towards the adjacent oral tissue or into the occlusion during mastication. This can result in oral irritation or the patient biting down on the device, leading to patient discomfort, device breakage or both. Various approaches have been taken to address such undue rotational movements of associated components of the orthodontic corrector. 
     For example, pending U.S. Publication No. 2009/0035715 (Cleary), describes an orthodontic bite corrector with anti-rotation features. The disclosed couplings use a shank that is received in a passage of the buccal tube with a flexible, snap-in retention movement, along with rotation stops that are moved into operative positions as the shank is received in the passage. These rotation stops function to limit pivoting movement of the associated bite corrector so that the bite corrector does not contact adjacent oral tissue and cause irritation. However, there may be instances when treating certain malocclusions that the orthodontist prefers to avoid connecting the bite corrector to the buccal tube. 
     As an alternative, instead of coupling to the buccal tube, one or both ends of the intra-oral corrector may be coupled directly to the wire. U.S. Pat. No. 7,070,410 (Cacchiotti et al.) describes, for example, an orthodontic device with flexible members that clip onto a wire and includes a cap portion that receives and retains the force module. These flexible members can be displaced when the cap portion is placed over the wire and pressed into position, allowing the wire to be captured between them. However, these flexible members do not provide the rotational control of the device about the longitudinal axis of the wire. 
     SUMMARY OF THE INVENTION 
     There is a need for an orthodontic connector that can be used with a wide range of orthodontic appliances and auxiliaries, can be easily installed and removed, and can secure those auxiliaries in a precise and controlled manner throughout treatment. The present invention addresses these needs by providing a connector in which both rigid and flexible components independently engage the wire. The combination of rigid and flexible components allows the connector to easily engage and disengage from the wire, while simultaneously preventing the attached auxiliaries from unduly rotating about the longitudinal axis of the wire. Restricting this rotation in turn prevents the auxiliary from rolling into the occlusion, which risks breakage of the device, or into the patient&#39;s cheek, which causes irritation. 
     In one aspect, the present invention is directed to an orthodontic assembly comprising a set of brackets, a wire connected to the brackets, and a connector for coupling an orthodontic auxiliary to the wire, the connector comprising a body, a slot extending across the body, and a clip coupled to the body, wherein the clip releasably retains the wire in the slot and wherein the slot includes a pair of rigid and opposing walls that restrict rotation of the connector body about the longitudinal axis of the wire. 
     In another aspect, the invention is directed to an orthodontic assembly comprising a connector for coupling a wire to an orthodontic auxiliary, the connector comprising a body having a lingual side, a slot extending across the lingual side of the body, and a clip coupled to the body for releasably retaining a wire in the slot, wherein the slot includes a pair of rigid and opposing walls that restrict rotation of the connector body about the longitudinal axis of a wire relative to the body while the wire is retained in the slot. 
     In still another aspect, the invention is directed to an orthodontic connector comprising a body, a slot extending across the body, and a clip coupled to the body for releasably retaining a wire in the slot, wherein the slot includes a pair of rigid and opposing walls that restrict rotation of the connector body about the longitudinal axis of a wire relative to the body while the wire is retained in the slot, and further wherein the connector lacks a bonding base that is adapted for attaching the connector to the surface of a tooth. 
     In yet another aspect, the invention is directed to a method of coupling a force module to a wire comprising providing a force module coupled to a connector, moving the connector in a direction toward a wire, sliding a pair of rigid and opposing walls of the connector along opposite sides of the wire, and coupling the connector to the wire by engaging the wire with at least one resilient clip of the connector such that the sides of the wire are adjacent the rigid walls. 
     These and other aspects of the invention are described in more detail in the paragraphs that follow and are illustrated in the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of an orthodontic assembly according to one embodiment of the present invention as installed on a dental arch with fixed orthodontic appliances. 
         FIG. 2  is a perspective view of a connector in the orthodontic assembly of  FIG. 1 , looking at the lingual, mesial, and gingival sides. 
         FIG. 3  is a perspective view of the connector in  FIG. 2 , looking at the facial, mesial, and gingival sides. 
         FIG. 4  is a perspective view of the connector in  FIGS. 2 and 3  in exploded form. 
         FIG. 5  is a perspective view of a connector according to another embodiment of the invention, looking at the distal, lingual, and gingival sides. 
         FIG. 6  is an occlusal view of the connector in  FIG. 5 , looking at the occlusal side. 
         FIG. 7  is a facial view of the connector in  FIGS. 5 and 6 , looking at the lingual side. 
         FIG. 8  is a side view of an orthodontic assembly according to another embodiment of the present invention. 
     
    
    
     DEFINITIONS 
     As used herein:
 
“Mesial” means in a direction toward the center of the patient&#39;s curved dental arch.
 
“Distal” means in a direction away from the center of the patient&#39;s curved dental arch.
 
“Occlusal” means in a direction toward the outer tips of the patient&#39;s teeth.
 
“Gingival” means in a direction toward the patient&#39;s gums or gingiva.
 
“Facial” means in a direction toward the patient&#39;s lips or cheeks.
 
“Lingual” means in a direction toward the patient&#39;s tongue.
 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Further described below are orthodontic devices and assemblies used for coupling an orthodontic wire to an orthodontic auxiliary. The term “orthodontic auxiliary”, as used herein, is defined as any accessory device or appliance that facilitates the application of forces in orthodontic treatment. Primary auxiliaries include bite correctors or force modules that apply therapeutic forces between two or more locations in the oral cavity. Auxiliaries used in Class II and Class III correction, for example, often employ force modules acting between appliances located on the upper and lower arches. However, auxiliaries may also exert and/or direct forces between two different portions within the same arch. As further alternative, auxiliaries may direct and/or exert forces between a wire and a fixed appliance such as a bracket, or between a bracket and a temporary anchorage device such as a mini-screw implant. 
     An exemplary embodiment of the present invention is shown in  FIG. 1 . This figure depicts an orthodontic assembly, which is designated herein by the numeral  100 . The assembly  100  is installed on the left side of the upper and lower jaws of a patient, which are illustrated in profile view. As shown, the teeth of the upper jaw include an upper central  10 , upper lateral  12 , upper cuspid  14 , upper first bicuspid  16 , upper second bicuspid  18 , upper first molar  20 , and upper second molar  22 . Similarly, the teeth of the lower jaw include a lower central  24 , lower lateral  26 , lower cuspid  28 , lower first bicuspid  30 , lower second bicuspid  32 , lower first molar  34  and lower second molar  36 . 
     Bonded orthodontic appliances are affixed to the respective teeth of both the upper and lower arches. Appliances attached to the upper arch include upper central bracket  38 , upper lateral bracket  40 , upper cuspid bracket  42 , upper first bicuspid bracket  43 , upper second bicuspid bracket  44 , and upper first buccal tube  46 . Appliances attached to the lower arch include lower anterior brackets  48 , lower cuspid bracket  50 , lower first bicuspid bracket  52 , lower second bicuspid bracket  54 , and lower first buccal tube  56 . Each bracket and buccal tube includes a base for bonding the appliance to the facial surface of its respective tooth. As shown, each bracket further includes an archwire slot with an opening oriented towards the facial direction. 
     Each of the upper appliances is connected to an upper wire  58  and each of the lower appliances is connected to a lower wire  60 . In this example, both upper and lower wires  58 , 60  have generally rectangular cross-sections in planes perpendicular to their longitudinal axes. An elastomeric O-ring ligature  57  extends around each of the bracket tiewings to retain the respective wire  58 , 60  in its archwire slot. Optionally, the distal ends of the wires  58 , 60  are bent as shown in  FIG. 1  in a location adjacent the distal side of the respective buccal tube  46 , 56 . 
     The assembly  100  includes a combination of elements that cooperate in applying a therapeutic force between the upper and lower dental arches. In the embodiment shown, the assembly  100  includes a connector  102  and a force module  108 , which are coupled to the upper and lower wires  58 , 60 , respectively. On one end, the connector  102  is coupled to the upper wire  58  between the upper second bicuspid bracket  44  and the upper buccal tube  46 . On the opposite end, the force module  108  couples to the lower wire  60  between the lower cuspid bracket  50  and lower first bicuspid bracket  52 . 
     In more detail, the connector  102  includes a body  104 , labeled ‘L’ to convey that this device is intended for use on the left side of the dental arch. An annular attachment loop  106  extends outwardly from the occlusal side of body  104 , thereby providing a means to couple the connector  102  to adjoining components. As an alternative to the attachment loop  106 , a hook, crimp, latch, or any other suitable coupling may be used. Unlike brackets and buccal tubes, the connector  102  lacks a bonding base that is adapted for attaching the connector  102  to the surface of a tooth. In particular, the connector  102  lacks a concave external bonding base surface that matches a convex tooth surface, and lacks a material for enhancing the bond to a tooth surface such as grooves, particles, recesses, undercuts or a chemical bond enhancement material. 
     Optionally and as shown, a generally “D”-shaped linkage  107  couples the attachment loop  106  to the force module  108 . The linkage  107  extends in a generally distal direction during use as shown in  FIG. 1  and provides a limited degree of freedom for the force module  108  to pivot with respect to the attachment loop  106  in directions about reference axes extending in generally facial-lingual directions and about reference axes generally parallel to the longitudinal axis of the force module  108 . Additional details pertaining to the linkage  107  are described in co-pending U.S. provisional patent application Ser. No. 61/168,960, filed Apr. 14, 2009. If further restriction of pivotal motion is desired, the attachment loop  106  may alternatively couple directly to the force module  108 . 
     Preferably, the force module  108  shares aspects with the bite corrector described in U.S. Pat. No. 5,964,588 (Cleary). In brief, the force module  108  includes a first elongated tubular member, a second elongated tubular member that is received in the first member in sliding, telescoping relation, and a third member  110  that is received in the second member. A helical compression spring  112  extends around the first tubular member and has an outer end that bears against a distal end cap  114  of the force module  108  that is fixed to the first member. The opposite end of the spring  112  bears against an annular fitting  116  that is secured to an outer end section of the second member. Optionally, the outer mesial end of the third member  110  is formed into a loop-type configuration as shown in  FIG. 1  that extends around a section of the lower wire  60 . Additional examples of loop-type configurations are set out in U.S. Pat. No. 6,669,474 (Vogt). Other constructions for connecting a force module to an orthodontic wire are described in co-pending U.S. provisional patent application Ser. No. 61/168,946, filed Apr. 14, 2009. In some embodiments, the outer end of the third member  110  also includes a line of weakness such as a recess or other area of reduced thickness for ease of bending the outer end section around the lower wire  40 . Examples of suitable commercially-available force modules  108  are included in the FORSUS brand fatigue resistant Class II correctors from 3M Unitek Corporation (Monrovia, Calif.). 
     When the assembly  100  is connected to the wires  58 , 60  in the manner described, the helical compression spring  112  urges the connector  102  and the third member  110  in directions away from each other. As a result, the connector  102  slides distally along the wire  58  until it bears against the mesial side of buccal tube  46 , while the third member  110  slides mesially along wire  60  until it bears against the distal side of the bracket  50 . Other aspects of operating the assembly  100  are similar to those of the appliance described in issued U.S. Pat. No. 6,558,160 (Schnaitter et al.). 
     The connector  102  of the assembly  100  may be used with other types of force modules as well, and its use need not be limited to telescopic force modules such as the force module  108  shown. For example, the attachment loop  106  of the connector  102  may be coupled to a flat spring made from a shape-memory alloy such as disclosed in issued U.S. Pat. No. 5,752,823 (Vogt). Likewise, the connector  102  may be coupled to any other resilient elongated body that is bendable in an arc about references axes perpendicular to its longitudinal axis. 
     The connector  102  is displayed in greater detail in  FIGS. 2 and 3 , which show aspects of the connector  102  as viewed in generally lingual and facial directions, respectively.  FIG. 4  additionally displays the connector  102  in an exploded configuration in order to further illuminate aspects of its constituent components. 
     As shown in  FIG. 2 , the connector  102  includes an outer section  120  and an inner section  122 , joined in mating engagement. The outer section  120  extends across the entire facial side of the inner section  122 , while further including mesial and distal end members  121 , 123  that extend in the lingual direction along the respective mesial and distal sides of the inner section  122 . An elongated wire slot  124 , having a generally “U”-shaped configuration in sections transverse to its longitudinal axis, extends across the lingual side of the inner section  122 . The inner section  122  further includes a pair of protrusions  126  extending outwardly in the mesial and distal directions from the section  122  along an axis parallel to the longitudinal axis of the slot  124 . As shown, the lingual sides of the protrusions  126  are co-planar with the bottom of the slot  124 . The lingual edges of the end members  121 , 123  include notches  136 , which are complemental to the protrusions  126 . The notches  136  receive the outer ends of the protrusions  126  of the inner section  122 , thereby providing mating surfaces by which the sections  120 , 122  precisely register with each other. 
     The inner section  120  further includes a pair of generally rectangular posts  125  that protrude in the lingual direction from the connector body  104  thereby providing the wire slot  124  with rigid and opposing walls  127  (as shown in  FIG. 2 ). The rigid and opposing walls  127  of slot  124  advantageously restrict relative rotation of the connector body  104  about the longitudinal axis of the rectangular wire  58  (such as shown in  FIG. 1 ) while the wire is retained in the slot  124 . By restricting the rotational freedom of the connector body  104 , this configuration presents a substantial improvement over previous approaches. Rotational restriction allows the intra-oral position of the force module  108  to be precisely controlled, including during mastication and other kinds of jaw movement. This in turn allows the connector  102  to be optimally oriented relative to the force module  108  for enhanced patient comfort while preventing the force module  108  from rotating into the occlusion. 
     Preferably the distance between the walls  127  is sufficiently large to allow the slot  124  to easily accommodate a full-sized rectangular wire, while sufficiently narrow to prevent significant rotation of the connector  102  about the longitudinal axis of the wire after installation. In most cases, this distance between walls  127  is approximately equivalent to the slot dimensions of the fixed appliances being used in treatment. For example, orthodontic brackets with a “022 slot” may be used with a connector  102  with a slot  124  having a 0.022 in. height in an occlusal-gingival direction, and brackets with a “018 slot” may be used with a connector  102  with a slot  124  having a 0.018 in. height in an occlusal-gingival direction. However, the occlusal-gingival height of the slot  124  may be intentionally enlarged by one or two hundredths of a millimeter to allow for some degree of rotation of the connector  102  about the longitudinal axis of the wire  58 . If desired, the entrance to the slot  124  may additionally include chamfered wall sections, thereby presenting a tapered (or funneled) lead-in to facilitate receiving the wire  58  in the slot  124 . 
     Sections  120 , 122  are preferably made from a stainless steel alloy and formed using a MIM (metal injection molding) process. However, other manufacturing methods such as milling, conventional molding, or investment casting may also be used. If desired, one or more of these parts can also be manufactured from other classes of materials, such as ceramics or polymeric composites. 
     The connector  102  further includes a pair of clips  128 , which have a generally “C”-shaped configuration and are located in the recesses formed between the inner and outer sections  122 , 120 . Each clip  128  includes a pair of arm portions  130  that extend in the lingual directions and then bend inwardly toward each other. Within each clip  128  is a wire-receiving region  132  that is aligned with the slot  124 . The protrusions  126  of the inner section  122  extend through the clips  128  in locations facial to the wire-receiving regions  132 , thereby retaining the clips  128  in the body  104 . 
     The pair of clips  128  are disposed adjacent to the respective mesial and distal sides of the connector  102  and releasably retain the wire  58  (not shown in  FIGS. 2-4 ) in the slot  124  when the assembly  100  is in operation as shown in  FIG. 1 . Using a dual clip configuration provides improved stability over using a single clip by leveraging two engagement points along the wire  58 . Having two engagement points helps prevent the connector  102  from rotating about its occlusal-gingival axis, thereby resulting in a more secure coupling. 
     The clips  128  are shown in their normal, relaxed orientations in  FIGS. 2 ,  3 , and  4 . However, the arm portions  130  of each clip  128  are movable away from each other in order to admit the wire  58  into a wire-receiving region  132  when so desired. The smooth, outer edge of the arm portions  130  enables each clip  128  to receive a wire by pressing the wire  58  against the outer curved edges of the arm portions  130 . As pressure is exerted by the wire  58  on the curved edges, the arm portions  130  deflect away from each other in order to admit the wire  58  into the wire-receiving region  132 . 
     Once the wire  58  is received in the wire-receiving region  132 , the inherent resiliency of each clip  128  enables arm portions  130  to spring back toward each other and toward their normal, relaxed configuration as shown in  FIGS. 2 ,  3 , and  4  to retain the wire  58  in the wire slot  124 . In some embodiments, the wire-receiving region  132  is somewhat larger than the cross-section of the wire in directions along both an occlusal-gingival reference axis as well as along a facial-lingual reference axis, thereby avoiding firm contact between each clip  128  and the wire  58 . 
     The spaces between each clip  128  and the wire  58  provide what is referred to as a “passive” clip. When the wire  58  is retained in the slot  124 , a passive clip allows the connector  102  to slide freely along the wire  58 . If desired, the dimensions of the clips  128  may be modified to eliminate the spaces between each clip  128  and the wire  58 , resulting in an “active” clip. If one or more “active” clips are used, the clip may apply sufficient compressive force to the wire  58  to prevent movement of the connector  102  in directions along the longitudinal axis of the wire. Optionally, inner surfaces of the clips  128  may be roughened or knurled or provided with serrations, grooves or other structure to facilitate a secure, non-sliding connection between the clips  128  and the wire. 
     Using an active clip can be advantageous for several reasons. When sliding movement between the connector  102  and the wire  58  is prevented, the force module bears on the wire  58  rather than the buccal tube  46 . While it depends on the treatment plan contemplated by the orthodontist, such a re-direction of force may be used for clinical advantage—for example, to move all of the upper teeth en masse relative to the lower arch. As another potential benefit, the lack of sliding provides a more predictable force vector between the upper and lower arches. Finally, fixing the connector  102  to the wire  58  effectively eliminates the possibility of collision between the connector  102  and the bracket  44  or buccal tube  46  during treatment. Appliance bond failures attributable to these collisions would therefore be eliminated. 
     Each clip  128  (including the arm portions  130 ) is sufficiently stiff to retain the wire in the wire slot  124  during the course of treatment so long as the forces exerted by the wire on the connector  102  remain below a certain minimum value in a generally facial direction (or in a direction opposite to the direction of insertion of the wire into the wire slot  124 ). However, whenever the forces exerted by the wire on the connector  102  in the same direction are greater than the minimum value, the arm portions  130  can move apart from each other to open the clip  128  and release the wire from the wire slot  124 . Further details regarding clip forces are described in the aforementioned U.S. Pat. Nos. 6,302,688 (Jordan et al.) and 6,582,226 (Jordan et al.). 
     Each clip  128  preferably releases the wire from the wire slot  124  in a generally facial direction whenever the wire exerts a force in the same direction on the connector  102  that is in the range of about 0.2 lb (0.1 kg) to about 11 lb (5 kg), more preferably in the range of about 0.4 lb (0.2 kg) to about 5.5 lb (2.5 kg), and most preferably in the range of about 0.75 lb (0.34 kg) to about 3.0 lb (1.4 kg). Preferably, the minimum value is sufficiently high to prevent the wire from unintentionally releasing from the wire slot  124  during the normal course of orthodontic treatment. As such, the force module  108  can exert expansive forces on the connector  102  and the third member  110  sufficient to carry out the treatment program and move the associated teeth as desired. 
     To determine the force to release each clip  128 , a section of wire is selected having an area in longitudinally transverse sections that is complemental to (i.e., substantially fills) the cross-sectional area of the wire slot  124 . Next, a sling is constructed and is connected to the wire section at locations closely adjacent to, but not in contact with, the end members  121 , 123 . Optionally, the sling is welded or brazed to the wire section. Next, the sling is pulled away from the connector  102  while the connector  102  is held in a stationary position, taking care to ensure that the longitudinal axis of the wire section does not tip relative to the longitudinal axis of the wire slot  124 . The force to release each clip  128  may be determined by the use of an Instron testing apparatus connected to the sling, using a crosshead speed of 0.5 in/min (1.3 cm/min). Alternatively, a cyclic tester (such as Model 300 from APC Dynamics of Carlsbad, Calif.) may be used along with a force transducer (such as Model 208C01 from PCB of Buffalo, N.Y.) to measure the force. 
     Optionally, each of the clips  128  is cut from a flat section of metallic stock material. Suitable metallic materials include shape memory alloys such as alloys of nitinol and beta-titanium. The clips  128  may be cut from the stock material using a stamping, die cutting, chemical etching, EDM (electrical discharge machining), laser cutting or water jet cutting process. As another option, the clips  128  could be formed and then heat-treated to set its shape. The clips  128  may also be made from a suitable plastic such as described in issued U.S. Pat. No. 7,070,410 (Cacchiotti et al.). Other suitable clips and possible optional features are given in issued U.S. Pat. Nos. 7,252,505 (Lai) and 7,367,800 (Lai et al.). 
     The manner of assembly of the outer section  120 , inner section  122 , and clips  128  to form the connector  102  is shown by the spatial arrangement of these components in  FIG. 4 . In one exemplary method, assembly takes place in two steps. First, the clips  128  are aligned around the respective mesial and distal protrusions  126  of inner section  122 . Second, the inner section  122  and clips  128  are joined with the outer section  120  such that the protrusions  126  are received in the notches  136  and the clips  128  are captured between inner section  122  and the end members  121 , 123  of the outer section  120 . Preferably, there is a sufficient space between the facial surfaces of the clips  128  and the adjacent lingual surface of the outer section  120  for the clips  128  to flex open and closed without interference. 
     In some embodiments, the inner and outer sections  120 , 122  are subsequently welded to each other using a resistance or laser welding process. Alternatively, the sections  120 , 122  may be adhesively or chemically bonded to each other using, for example, a chemically-cured polymerizable epoxy or acrylic resin. As a further alternative, the sections  120 , 122  may be joined in press-fit, snap-fit or interference-fit relation such that subsequent separation does not occur. If an interference fit is desired, one or both sections  120 , 122  may have mating, interlocking structures that snap together when the sections  120 , 122  are fully engaged with each other. 
     As described above, the orthodontic assembly  100  applies corrective forces on the left side of the dental arch. It is understood, however, that mirror images of the configurations shown in  FIGS. 1-4  are likewise contemplated for treating the right side of the dental arch. Generally when treating Class II malocclusions, a pair of orthodontic assemblies  100  are symmetrically disposed on the left and right sides of the patient&#39;s arch. Depending on the patient&#39;s particular treatment plan, however, the orthodontist may choose to use the assembly  100  on only one side of the arch. As another option, the orthodontist may prescribe using a pair of assemblies  100  as described above but with an asymmetric activation of the force modules  108  on the left and right sides of the arch. 
     The configuration of connector  102  confers several advantages to the orthodontist. First, it provides a simple and convenient “snap-in” mechanism that releasably couples the distal end of the assembly  100  to the wire  58  without need for loose auxiliary pieces such as screws, ligature wire, or wrenches. The connector  102  can be readily engaged or disengaged from the wire  58  using a pair of standard orthodontic utility pliers such as Weingart or How pliers. This mode of installation is convenient and saves time for the orthodontist when compared with the installation procedures for other Class II correctors on the market. 
     As a second advantage, this engagement mechanism provides a high degree of control and predictability by constraining the position of the installed connector  102  relative to the wire  58 . Provided that the wire size is known, the allowable facial rotation of the force module and range of pivoting can be precisely controlled based on the dimensions of the space between the rigid and opposing walls  127 . Third, the clips  128  are not only oriented towards the lingual direction away from the patient&#39;s cheeks but also protected in the confines between the inner and outer sections  120 , 122 , thereby minimizing the risk of tissue irritation from the edges of the clips during treatment. 
     As a third advantage, the direction from which the connector  102  engages the wire  58  leads to enhanced rotational control. Since the opening of the slot  124  faces the lingual direction, or towards the short occlusal-gingival dimension of the wire  58 , the rigid and opposing walls  127  can flatly engage the wire  58  along the entire length of the long facial-lingual dimension. By engaging along the long dimension, rather than the short dimension, of the wire  58 , the connector  102  benefits from a high degree of rotational control about the longitudinal axis of the wire  58 . Engaging the wire  58  from the lingual direction also provides a convenient angle of approach for the installing orthodontist. 
     An alternative embodiment of the present invention is illustrated in  FIGS. 5 ,  6 , and  7 . These figures show a connector  200  in perspective view, occlusal view, and facial view, respectively. The connector  200  is similar in some respects to the connector  102  in  FIGS. 1-4 . For example, the connector  200  has a connector body  202 , an attachment loop  201  protruding in the occlusal direction from the body  202 , a wire slot  204  extending in the mesial-distal direction across the connector body  202 , and a pair of “C”-shaped clips  206  for releasably retaining a wire in the slot  204 . 
     Particular to this embodiment, a pair of mesial posts  208  and a pair of distal posts  210  extend outwardly from the lingual side of the body  202  such that the slot  204  extends between each of the pairs of posts  208 , 210 . The sides of the posts  208 , 210  adjacent to the slot  204  present opposing walls  212 . Together, the lingual side of  202  and walls  212  define three sides of the slot  204  that are rigid and restrict rotation of the body  202  relative to the longitudinal axis of a rectangular wire while the wire is retained in the slot  204 . 
     The clips  206  are retained against the body  202  by protrusions  214  which project from the body  202  and extend through each respective clip  206 . Each protrusion  214  terminates with an oversized end cap  218 . End caps  218  retain the clips  206  along the mesial and distal sides of the body  202  and prevent undesirable sliding movement of the clips  206  along the longitudinal axes of the protrusions  214 . 
     A cover plate  216  extends across the facial side of body  202 . Optionally and as shown in  FIG. 6 , the cover plate  216  extends across the entire mesial-distal width of connector  200 . For a secure attachment, it is preferable that the cover plate is welded or adhesively bonded to the facial side of each end cap  218  along with the facial side of body  202 . Also preferably, the facial side of the cover plate  216  has smooth, rounded contours for patient comfort. As shown in  FIGS. 5-7 , the cover plate  216  overlaps the facial sides of the clips  206 , thereby preventing the clips  206  from sliding off the protrusions  214  in the facial direction. Preferably and as shown, there are gaps  220  between the facial side of each clip  206  and the cover plate  216  to allow room for the clip  206  to freely flex between open and closed positions. 
     Other variations are possible. For example, the cover plate  216  may be omitted altogether and clip  206  replaced with a self-retaining clip, such as described in issued U.S. Pat. Nos. 7,252,505 (Lai), 7,217,125 (Lai et al.), and 7,377,777 (Lai et al.). Such clips can be mechanically retained on the protrusions  214  of the connector body  202  without need for additional structure on the facial side of the clip. Other aspects of connector  200  are similar to those of the connector  102  and will not be repeated here. 
       FIG. 8  shows an orthodontic assembly  300  according to another embodiment of the invention. Assembly  300  is shown coupled to upper and lower wires  306 , 307 , and differs from assembly  100  in that it includes a mesial connector  304  releasably coupled to the lower wire  307  using resilient clips. The mesial loop at the end of the third section  308  is oriented slightly differently to engage with the mesial connector  304 . Advantageously, both distal connector  302  and the mesial connector  304  resiliently “snap-on” to respective upper and lower wires  306 , 307 , providing even further enhanced ease-of-use. Other aspects of assembly  300  are similar to those previously discussed. 
     In alternative embodiments, one or more of the orthodontic assemblies above are adapted to correct a Class III malocclusion. Such correction may be achieved, for example, by connecting the one end of the assembly to the wire  58  between the upper cuspid  42  and upper first bicuspid  43  and the other end of the assembly to the wire  60  distal to the lower first buccal tube  56 . Similar configurations to treat Class III malocclusions are described in issued U.S. Pat. No. 6,558,160 (Schnaitter et al.). 
     In further alternative embodiments, the connector  102 , 202  is coupled to a segment of orthodontic wire extending along only a portion of the upper or lower dental arch. 
     Orthodontic brackets need not be present in these configurations. For example, the connector may be coupled to a short segment of rectangular wire whose ends are adhesively bonded to the facial surfaces of two adjacent teeth. As another example, the connector may be coupled to a segment of wire with a rectangular cross-section protruding from a fixed appliance bonded to the surface of a tooth. 
     In still further alternative embodiments, one or more of the assemblies above are adapted for connection to two different locations within the same arch. 
     Further variants of the devices and assemblies above are contemplated in which the connector engages the wire from other directions besides the facial direction. These devices and assemblies could, for example, be implemented with one or more clips that are coupled to the connector and engage the wire from either the occlusal or gingival directions. If this were desired, the clip dimensions should be properly modified to accommodate the long dimension (facial-lingual dimension) of the wire. Such a connector configuration may be advantageously used on either the mesial or distal end of the force module to provide an overall lower profile appliance. 
     All of the patents and patent applications mentioned above are hereby expressly incorporated by reference. The embodiments described above are illustrative of the present invention and other constructions are also possible. Accordingly, the present invention should not be deemed limited to the embodiments described in detail above and shown in the accompanying drawings, but instead only by a fair scope of the claims that follow along with their equivalents.