Abstract:
An orthodontic appliance such as a bracket or buccal tube has an overall, low profile shape. The appliance includes a base having a thickness that is less in regions adjacent the archwire slot as compared to remaining regions. In certain embodiments, the base is provided with protrusions that extend into the archwire slot for controlling rotation of the associated tooth. The resulting low profile of the appliance enhances its aesthetic appearance and helps to avoid impingement of the appliance and the attached archwire on adjacent soft tissue in the oral cavity.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention broadly relates to an appliance that is secured to a tooth during the course of orthodontic treatment. More particularly, the present invention is directed to an orthodontic appliance having a compact, low profile such that the appliance lies close to the tooth surface. 
   2. Description of the Related Art 
   Orthodontia is a specialized field within the general subject area of dentistry. Orthodontic treatment involves movement of malpositioned teeth to correct locations along the dental arch. Orthodontic treatment can result in improved occlusion for the patient as well as a more pleasing aesthetic appearance. 
   One type of orthodontic treatment involves the use of a set of components that are collectively known as “braces”. In this type of treatment, small slotted devices known as brackets are secured to the patient&#39;s anterior, cuspid and bicuspid teeth. An archwire is received in the slots of the brackets and forms a track to guide movement of the teeth to desired positions. 
   Each end of an orthodontic archwire is often received in an enclosed elongated passageway of a small device known as buccal tube. Buccal tubes are connected to the patient&#39;s molar teeth. The enclosed passageway helps prevent the end of the archwire from contacting the patient&#39;s soft tissue in the oral cavity, which might otherwise lead to pain and injury. In some instances, buccal tubes are provided with a convertible cap along one side of the passageway that can be opened in order to convert the tube into a bracket when desired. 
   Orthodontic appliances such as brackets and buccal tubes typically include a base, a body extending outwardly from the base and support structure for connecting the appliance to the archwire. One type of base, known as a “direct bond” base, is adapted to secure the appliance directly to the enamel surface of a tooth by an adhesive. Another type of base, known as a “welding base”, is adapted to be welded to a metallic orthodontic band that encircles the patient&#39;s tooth. 
   A variety of archwire support structures are also known. In the case of buccal tubes, the archwire support structure may be a cylindrical member having internal wall sections that define an enclosed archwire slot or passageway. Other types of buccal tubes have archwire support structure that comprises an elongated rectangular block with wall sections defining an archwire slot or passageway. Buccal tubes with convertible caps often have small wings known as tiewings that can be used to ligate the archwire to the buccal tube once the cap has been removed. 
   In the case of orthodontic brackets, the archwire support structure often includes wall sections that define three sides of the archwire slot while the fourth side is open for insertion of the archwire. In some instances, the wall sections are located between one or more pairs of tiewings. In other instances, the wall sections are located in the center of the bracket and offset from the tiewings. An example of the former construction is shown in U.S. Pat. No. 5,746,594, and an example of the latter construction is illustrated in U.S. Design Pat. No. 290,040. 
   Over the years, many attempts have been made to improve the aesthetic appearance of braces. To this end, manufacturers have reduced the size of the brackets so that they are more difficult to see when in place in the oral cavity. This reduction in size can also help increase patient comfort because it is less likely that the bracket will unduly impinge upon adjacent soft tissue. 
   A variety of low profile orthodontic appliances have been proposed in the past. In some appliances, manufacturers have reduced the overall depth of the bracket in a buccolabial direction (i.e., in a direction toward the patient&#39;s lips or cheeks) by reducing the size of the body located between the base of the appliance and the archwire support structure. Such construction results in the archwire support structure being located relatively close to the base. 
   In other instances, the manufacturers have eliminated the body that is conventionally located between the archwire support structure and the base. For example, one commercially available buccal tube appliance comprises an elongated, generally “U”-shaped structure resembling an inverted three-sided trough that is directly welded to a base. In this appliance, the buccolabial side of the base serves as the fourth wall for the archwire slot such that the archwire is surrounded on all four sides. 
   However, many of the low profile appliances known in the past are not considered satisfactory. For example, the appliance mentioned in the preceding paragraph is not entirely satisfactory because the buccolabial side of the base, including the portion of the base within the archwire slot, has a convex, curved configuration that matches the shape of the tooth. An archwire received in the archwire slot of this appliance may bear against the convex-shaped base along only a fraction of the length of the archwire slot. As a consequence, precise control over movement between the archwire and the appliance is difficult to attain and the teeth may not shift to desired positions. 
   As can be appreciated, there is a need in the art for an orthodontic appliance that has a relatively low profile, and yet provides reliable, precise control over movement of the associated teeth. 
   SUMMARY OF THE INVENTION 
   The present invention overcomes the above noted disadvantages of conventional orthodontic appliances by provision of an appliance having a novel base. In one aspect of the invention, the base has a thickness that varies in different regions of the base so that the archwire can be received in a position closer to the tooth surface than might be otherwise possible. The variance in thickness in the base may be carried out by modifying the tooth-facing side of the base, or by modifying the opposite side of the base, or by modifying both sides. 
   In another aspect of the invention, the base of the appliance is provided with one or more protrusions that extend outwardly in a buccolabial direction. Examples of suitable protrusions include elongated ridges, rounded bumps, posts, ramps and platforms. The protrusions serve as a bearing surface for the adjacent side of the archwire so that firm, precise control over movement of the associated teeth can be attained. At the same time, the low profile characteristics of the appliance are maintained. 
   In more detail, the present invention is directed in one embodiment to an orthodontic appliance that comprises a base having a first tooth-facing side and a second side opposite that first side. The base also has a number of cavities that extend from the first side in a direction toward the second side, and the cavities have a certain depth in a buccolabial-lingual direction. An archwire support is connected to the base. The support has an occlusal wall section (i.e., a wall section located next to the outer tip of the tooth) and a gingival wall section (i.e., a wall section located next to the patient&#39;s gums or gingiva). An archwire slot extends between the occlusal wall section and the gingival wall section in a generally mesial-distal direction (i.e., in directions toward and away from the middle of the dental arch, following along the path of the arch). The archwire slot has a tooth-facing side. The base has a certain thickness in directions along a buccolabial-lingual reference axis between the first side and the second side. The thickness of the base in at least one region next to the tooth-facing side of the archwire slot is less than the thickness of the base in at least one remaining region of the base. The depth of at least some of the cavities varies in corresponding relationship to the variance of the thickness of the base. 
   In another embodiment of the invention, an orthodontic appliance comprises a base having a tooth-facing surface. The base also has a number of cavities with a certain depth in a buccolabial-lingual direction. An archwire support is connected to the base and has an occlusal wall section and a gingival wall section. An archwire slot extends between the occlusal wall section and the gingival wall section in a generally mesial-distal direction and has a tooth-facing side. The base has a certain thickness in directions along a buccolabial-lingual reference axis. The thickness of the base varies in regions located next to the tooth-facing side of the archwire slot. The depth of at least some of the cavities varies in corresponding relationship to the variance of the thickness of the base. 
   An orthodontic appliance according to another embodiment of the invention comprises a base having a first, tooth-facing side and a second side opposite the first side. The base also has a number of cavities extending from the first side in a direction toward the second side, and the cavities have a certain depth in a buccolabial-lingual direction. An archwire support is connected to the second side of the base. An archwire slot extends across the appliance in a generally mesial-distal direction. The archwire slot has a side next to the tooth that extends along a path located at least partially between the first side and the second side of the base. At least some of the cavities located in regions lingually of the archwire slot have a depth that is less than the depth of the cavities located in regions offset from the archwire slot. 
   The present invention in another embodiment is also directed to an orthodontic appliance. In this embodiment, the appliance comprises a base having a tooth-facing surface and an archwire support connected to the base for receiving an archwire. An archwire slot extends across the archwire support in a generally mesial-distal direction. The base includes a plurality of cavities having a certain depth in directions along a buccolabial-lingual reference axis. The depth of at least some of the cavities located in regions lingually of the archwire slot is less than the depth of at least some of the remaining cavities located in regions lingually of the archwire slot. 
   An additional embodiment of the invention is also directed toward an orthodontic appliance that comprises a base having a first, tooth-facing side and a second side opposite the first side. An archwire support is connected to the base and has an occlusal wall section and a gingival wall section. An archwire slot extends between the occlusal wall section and the gingival wall section in a generally mesial-distal direction and has a lingual side. The first side of the base includes at least one protrusion that extends in a direction toward the archwire slot. 
   Another embodiment of the invention is also directed toward an orthodontic appliance. In this embodiment, the appliance includes a first, tooth-facing side and a second side opposite the first side. At least two tiewings are directly connected to the base. Each of the tiewings has an overall, generally “L”-shaped configuration. An archwire slot extends between at least two of the tiewings in a generally mesial-distal direction and has a tooth-facing side defined by the base. 
   These and other aspects of the invention will be 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 perspective view of a low profile orthodontic appliance that is constructed in accordance with one embodiment of the present invention, looking at the appliance in a direction toward its buccolabial, mesial and occlusal sides; 
       FIG. 2  is a perspective view of the orthodontic appliance shown in  FIG. 1 , looking at the appliance toward its lingual, mesial and occlusal sides; 
       FIG. 3  is a perspective view of a base alone of the appliance depicted in  FIGS. 1 and 2 , looking at the base in a direction toward its buccolabial, mesial and gingival sides; 
       FIG. 4  is a perspective cross-sectional view of the base illustrated in  FIG. 3 , looking at the base in the same direction as the illustration of  FIG. 3 ; 
       FIG. 5  is another perspective cross-sectional view of the base shown in  FIG. 3 , wherein the view is taken along a reference plane that is perpendicular to the plane of view of  FIG. 4 ; 
       FIG. 6  is a perspective view of a low profile orthodontic appliance according to another embodiment of the invention, looking at the appliance in a direction toward its buccolabial, mesial and gingival sides; 
       FIG. 7  is another perspective view of the appliance shown in  FIG. 6 , looking at the appliance in a direction toward its lingual, mesial and gingival sides; 
       FIG. 8  is a side cross-sectional view of the orthodontic appliance shown in  FIGS. 6-7 , looking at the appliance in a direction toward its distal side; 
       FIG. 9  is a perspective view of a low profile orthodontic appliance according to yet another embodiment of the invention, looking at the appliance in a direction toward its buccolabial, mesial and gingival sides; 
       FIG. 10  is a cross-sectional view of the orthodontic appliance depicted in FIG.  9  and taken along a reference plane that bisects an archwire slot of the appliance; 
       FIG. 11  is a view somewhat similar to  FIG. 10  except showing an orthodontic appliance in accordance with still another embodiment of the invention; and 
       FIG. 12  is a perspective cross-sectional view of the appliance illustrated in FIG.  11 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   An orthodontic appliance according to one embodiment of the present invention is illustrated in  FIGS. 1 and 2  and is broadly designated by the numeral  20 . The appliance  20  includes a base  22  and an archwire support  24  that is connected to the base  22 . An elongated archwire slot  26  extends through the archwire support  24  for receiving an archwire. 
   In more detail, the base  22  includes a first, tooth-facing side  28  that is illustrated in  FIG. 2 and a  second side  30  that is opposite to the first side  28 . The second side  30  is shown in FIG.  1 . In the illustrated example, the appliance  20  is adopted to be secured to a buccolabial side of a tooth. Consequently, the first side  28  of the base  22  in this example can also be deemed a lingual side (i.e., a side facing the patient&#39;s tongue) and the second side  30  can be deemed a buccolabial side (i.e., a side facing the patient&#39;s lips or cheeks). 
   As shown in  FIG. 2 , the first side  28  of the base  22  is provided with a series of cavities  32  for receiving a portion of an orthodontic adhesive that is used to affix the appliance  20  to the enamel of a patient&#39;s tooth. The cavities  32  are arranged in a rectangular array and have a square configuration when viewed in a buccolabial direction. However, other arrays and shapes are also possible. For example, the cavities could be arranged in a diagonal array and/or have a circular, oval or rectangular shape when viewed in a buccolabial direction. 
   Alternatively, the cavities  32  may comprise two or more series of elongated grooves instead of the discrete small cavities  32  shown in FIG.  2 . The grooves may be arranged in a parallel array or may be arranged in a cross-over array where some of the grooves intersect with other grooves. Examples of elongated grooves arranged in a cross-over array are described in U.S. Design Pat. No. 331,975 which is expressly incorporated by reference herein. As a further option, the cavities  32  may be interconnected by pores that extend through the interior of the base  22  or by open channels that lie along the exterior surface of the first side  28  of the base  22 . Additionally, the cavities  32  may be established by spaces between protrusions that extend outwardly from the first side  28  in a direction away from the second side  30 . 
   In addition, the base  22  including the cavities  32  may include additional structure or aspects that further enhance the bond of the appliance  20  to the patient&#39;s tooth surface. For example, the base  22  including the surfaces within the cavity  32  may be etched with a chemical etchant or with laser etching apparatus, or roughened with sandblasting apparatus. As an additional example, the base  22  including the cavities  32  may be coated with a primer or other composition that serves to enhance the bond between the orthodontic adhesive and the appliance  20 . 
   Preferably, the first side  28  of the base  22  has a shape that matches the configuration of the tooth surface for which the appliance  20  is intended. In the example shown in the drawings, the first side  28  has a concave, compound contour that is curved in directions adapted to mate with the convex shape of a molar tooth. One of the curves can be viewed in a reference plane parallel to the occlusal plane of the patient when the appliance  20  is mounted on a tooth, and this curve is depicted in perspective view in FIG.  4 . The remaining curve can be viewed in a reference plane perpendicular to the occlusal plane and is depicted in perspective view in FIG.  5 . However, in certain instances (such as in appliances intended for anterior teeth), the base may be curved along only one direction or alternatively have a flat configuration. 
   The archwire support  24  in this embodiment is a rectangular “U”-shaped member having three sides: an occlusal side  34 , a buccolabial side  36  and a gingival side  38 . The archwire support  24  extends in a longitudinal direction across the base  22 . A lingual edge of the occlusal side  34  and a lingual edge of the gingival side  38  are integrally connected directly to the second side  30  of the base  22 . As shown, the archwire support  24  does not include a lingual side that might otherwise be located adjacent the second side  30  of the base  22 . Optionally, the archwire support  24  is located laterally offset in an occlusal or gingival direction from the middle of the base  22 . 
   The occlusal side  34  of the archwire support  24  includes an occlusal wall section (not shown) and the gingival side  38  includes a gingival wall section  42  that is illustrated in FIG.  1 . The buccolabial side  36  of the archwire support  24  includes a buccolabial wall section  44  (FIG.  2 ). Preferably, but not necessarily, the wall sections are flat and have widths that match the shape of a selected rectangular archwire to be received in the archwire slot  26 . Additionally, the occlusal wall section and the gingival wall section  42  preferably are parallel to each other. 
   The archwire slot  26  is defined by the occlusal wall section, the gingival wall section  42 , the buccolabial wall section  44  as well as a tooth-facing or lingual wall section  46  that is shown in FIGS.  1  and  3 - 5 . The lingual wall section  46  is not part of the archwire support  24 , but instead is part of the base  22 . Preferably, the lingual wall section  46  is flat and extends in a reference plane that is parallel to the labial wall section  44 . 
   Alternatively, the lingual wall section  46  as well as one or more of the remaining wall sections may include one or more ridges or grooves (not shown) for engaging the archwire. Examples of such grooves are shown in FIGS. 8-11 of U.S. Design Pat. No. 315,957 which is incorporated by reference herein. Preferably, however, the wall sections contact the archwire in sufficient areas along the length of the archwire slot  26  so that good control between movement of the appliance  20  and movement of the archwire is afforded. 
   As shown in  FIGS. 1 ,  3 ,  4  and  5 , the lingual wall section  46  extends below the second side  30  of the base  22  in a lingual direction. Consequently, the thickness of the base  22  in regions located lingually of the lingual wall section  46  is less than the thickness of the base  22  in remaining regions of the base  22 . The thickness of the base  22  for this purpose is determined in directions parallel to a buccolabial-lingual reference axis. Optionally, the thickness of the base  22  is essentially uniform (ignoring the cavities  32 ) except for regions of the base  22  that are located lingually of the lingual wall section  46 . 
   In the illustrated embodiment, the second side  30  of the base  22  is convex and the thickness of the base  22  is smallest in regions next to the center of the lingual wall section  46  (for this purpose, the center of the wall section  46  is determined in directions along a mesial-distal reference axis). However, other constructions are also possible. For example, if the appliance  20  is intended to be placed on the tooth at a location that is offset the mesial-distal center of the tooth or if the appliance  20  is intended to provide what is known as offset rotation, the thickness of the base  22  may be smallest in regions that are located on the lingual side of the lingual wall section  46 , but adjacent the mesial or distal end of the same. In these examples, the thickness of the base  22  varies in regions located lingually of the lingual wall section  46  in accordance with the location of that region in directions along the longitudinal axis of the archwire slot  26 . 
   Additionally, the depth (i.e. the overall depth) of the cavities  32  in directions along a buccolabial-lingual reference axis varies in corresponding relationship to the thickness of the base  22 . In particular, the depth of the cavities  32  is the least in regions where the thickness of the base  22  is the smallest. In the embodiment illustrated in the drawings, and particularly with reference to  FIG. 4 , It can be observed that the depth of the cavities  32  that are located near the mesial-distal center of the archwire slot  26  is less than the depth of the remaining cavities  32 , including the cavities adjacent the mesial and distal ends of the lingual wall section  46 . The depth of at least some of the cavities  32  located in regions lingually of the archwire slot  26  is less than the depth of the cavities  32  that are located in regions offset from the archwire slot  26  in an occlusal or gingival direction. Optionally, the depth of the cavities  32  progressively increases as the thickness of the base  22  increases. As another option, the depth of the cavities  32  may progressively increase as the occlusal edge and/or gingival edge of the appliance  20  is approached. 
   The features of the appliance  20  described above provide a significant advantage in that the overall height of the appliance  20  in a buccolabial direction is smaller than might be otherwise possible. In particular, the lingual wall section  46 , being located below the second side  30  of the base  22  in a lingual direction, enables the archwire slot  26  to be relatively close to the first side  28  of the base  22 . The varying thickness of the base  22  as well as the varying depth of the cavities  32  also enables such advantages to be realized. 
   Importantly, control over movement of the appliance  20 , the archwire and the associated tooth need not be compromised by following the principles of the present invention. In particular, since the lingual wall section  46  is parallel with the buccolabial wall section  44 , the archwire maintains good bearing contact with the appliance  20 . As such, forces exerted by the archwire on the appliance  20  are transferred without undue tolerance or “slop” so that precise control over movement of the archwire or the associated teeth can be attained. 
   A low profile orthodontic appliance  20   a  according to another embodiment of the invention is illustrated in  FIGS. 6 ,  7  and  8 . The appliance  20   a  includes a base  22   a  that is essentially the same as the base  20  described above. 
   However, the appliance  20   a  has an archwire support  24   a  that is somewhat different than the archwire support  24  mentioned above. In particular, the archwire support  24   a  includes a mesial-occlusal tiewing  48   a,  a mesial-gingival tiewing  50   a,  a distal-occlusal tiewing  52   a  and a distal-gingival tiewing  54   a.  Each of the tiewings  48   a - 54   a  has a generally inverted “L”-shaped configuration and a lingual end section that is directly connected to a second or buccolabial side  30   a  of the base  22   a.    
   An archwire slot  26   a  extends in a generally mesial-distal direction across the appliance  20   a.  The archwire slot  26   a  passes through the space between the tiewings  48   a,    50   a  as well as through the space between the tiewings  52   a,    54   a.  The archwire slot  26   a  is defined by two occlusal wall sections  40   a  that are located on the tiewings  48   a,    52   a  respectively, and two gingival wall sections (not shown) that are located on the tiewings  50   a,    54   a  respectively. The archwire slot  26   a  is also defined by a lingual wall section  46   a  that is part of the base  22   a.    
   The appliance  20   a  is a bracket and, as with many brackets, the archwire slot  26   a  is open along its buccolabial side. In order to couple the archwire to the appliance  20   a,  a ligature (not shown) is placed across the buccolabial side of the archwire once the archwire is seated in the archwire slot  26   a.  The ligature is also placed around two or more of the tiewings  48   a - 54   a  in order to hold the ligature in place and secure the archwire to the appliance  20   a.  Conventional, commonly-known ligatures useful for ligating include small elastomeric O-rings and also sections of metallic wire that are formed into a loop by the practitioner. 
   Advantageously, the tiewings  48   a - 54   a  lack undercut areas or notches that are conventionally located on the lingual side of the portions of the tiewings that overhang the base. In other words, the overhanging portions do not have a recess that is located a distance further away from the buccolabial side  30   a  of the base  22   a  in a buccolabial direction than the distance between the outer, occlusal or gingival ends of the same tiewings from the buccolabial side  30   a  of the base  22   a.  Instead, the lingual sides of the overhanging portions of the tiewings  48   a - 54   a  are generally smooth and flat and extend along occlusal-gingival reference axes. Such construction is satisfactory in part due to the recessed lingual wall section  46   a,  which enables the archwire to be located closer to the first side  28   a  of the base  22   a  than might be otherwise possible. 
   Advantageously, the appliance  20   a  lacks a body that is conventionally provided between the tiewings and the base. Instead, the tiewings  48   a - 54   a  are directly connected to the buccolabial side of the base  22   a.  Preferably, the appliance  20   a  is integrally made as a unitary component by a metal injection molding process or a machining process. As an alternative, however, the tiewings  48   a - 54   a  maybe manufactured separately and then connected by a welding or brazing operation directly to the base  22   a.    
   Other aspects of the appliance  20   a  are similar to the appliance  20  mentioned above, including the variance in thickness of the base  22   a  and the variance in the depth of cavities in the base  22   a.  Accordingly, the advantages realized in connection with the appliance  20  are afforded to the appliance  20   a  as well. 
   A low profile orthodontic appliance  20   b  according to another embodiment of the invention is illustrated in  FIGS. 9 and 10 . Except as described below, the appliance  20   b  is essentially the same as the appliance  20   a.    
   The appliance  20   b  has a base  22   b  with one or more protrusions  56   b  that extend in a direction toward an archwire slot  26   b.  In the illustrated embodiment, the base  22   b  includes two protrusions  56   b  in the general shape of rounded, semi-spherical bumps. One of the protrusions  56   b  is located adjacent a mesial end of the archwire slot  26   b,  and the remaining protrusion  56   b  is located adjacent the distal end of the archwire slot  26   b.  However, it is also possible to provide one or more protrusions that are located adjacent only one end of the archwire slot  26   b,  especially in instances where the appliance is intended to rotate the associated tooth about its long axis during the course of treatment. 
   Optionally, the protrusions  56   b  are formed during a metal injection molding process that is carried out when manufacturing the appliance  20   b.  As another option, the protrusions  56   b  maybe formed by use of a punch process, wherein a punch tool is placed in contact with a tooth-facing side of the base  22  and urged in a buccolabial direction. 
   Although not shown in the drawings, the appliance  20   b  may include an archwire slot that is defined in part by a lingual wall section which extends below the buccolabial side of the appliance base  22  in a lingual direction. For example, the lingual wall section may be similar to the lingual wall sections  46 ,  46   a  described above. In those instances, the protrusions  56   b  may extend in a buccolabial direction from the recessed lingual wall section. As an additional option, the protrusions  56   b  may be located on the mesial and/or distal side of the lingual wall section. 
   A low profile orthodontic appliance  20   c  according to another embodiment of the invention is partially shown in  FIGS. 11 and 12 .  FIG. 11  is a cross-sectional view of the appliance  20   c  taken in the same direction as the illustration of FIG.  10 . Except as set out below, the appliance  20   c  is the same as the appliance  20   b.    
   The appliance  20   c  has two protrusions  56   c  that extend in a buccolabial direction from a base  22   c  of the appliance  20   c.  In this embodiment, however, the protrusions  56   c  are in the form of a ramp of varying thickness in a buccolabial direction. In particular, the thickness decreases as the mesial-distal center of the archwire slot  26   c  is approached. 
   The buccolabial surface of each protrusion  56   c  in this example lies in a flat plane. Although the protrusions  56   c  vary in thickness, the protrusions  56   c  are located atop a convex buccolabial side  30   c  of the base  22   c.  The variance in thickness of the protrusions  56   c  is selected in accordance with the curvature of the buccolabial side  30   c  of the base  22   c  so that the outermost, buccolabial surfaces of the protrusions  56   c  lie in a common, flat plane. As a result, the protrusions  56   c  flatly contact the lingual side of the archwire and enable the archwire to exert firm, precise control over movement of the associated tooth. 
   As an alternative, the protrusions  56   c  may be of uniform thickness in a buccolabial direction. Such construction may be desirable, for example, when the buccolabial side  30   c  is essentially flat instead of convex as shown in the drawings. As an additional option, the protrusions  56   c  may be located on a recessed lingual wall section of the archwire slot, such as the recessed lingual wall sections  46 ,  46   a  described above. 
   The low profile orthodontic appliances according to the invention, including the appliances described in detail above, maybe made of any material that is suitable for use in the oral cavity and has sufficient strength to resist the stresses normally encountered during the course of orthodontic treatment. Examples of such materials include metallic materials such as alloys of stainless steel and titanium. Ceramic materials may also be employed, such as translucent polycrystalline alumina. A particularly preferred low profile orthodontic appliance is made of stainless steel series no. 17-4PH or 316L using a metal injection molding technique. 
   The orthodontic appliances that are described above are representative examples of the present invention and a number of other embodiments are also possible. For example, the appliances may be adapted for connection to the lingual side of the tooth instead of the labial tooth side as mentioned above. Furthermore, the appliance may be provided with additional features such as auxiliary slots, hooks, alignment marks and the like. Accordingly, the invention should not be deemed limited to the particular examples that are set out in detail, but instead only by a fair scope of the claims that follow along with their equivalents.