WO1999058078A1

WO1999058078A1 - Orthodontic bracket with tie wing reinforcement members

Info

Publication number: WO1999058078A1
Application number: PCT/US1999/008697
Authority: WO
Inventors: Robert C. Manemann; Oliver L. Puttler; John S. Kelly
Original assignee: 3M Innovative Properties Company
Priority date: 1998-05-11
Filing date: 1999-04-21
Publication date: 1999-11-18

Abstract

An orthodontic bracket has twin tie wings and at least one reinforcing member connected to one or more tie wings. Each reinforcing member is oriented to avoid substantial contact, if not all contact, with adjacent sides of an archwire when received in an archwire slot of the bracket. The resulting construction enables the size of the tie wings and hence the overall size of the bracket to be significantly reduced in comparison to conventional brackets without impairment of rotational control of the associated tooth.

Description

ORTHODONTIC BRACKET WITH TIE WING REINFORCEMENT MEMBERS

Background of the Invention

1. Field of the Invention

This invention broadly relates to an appliance used in orthodontic treatment. More particularly, this invention relates to an orthodontic bracket having one or more reinforcement members that serve to strengthen tie wings of the bracket.

2. Description of the Related Art

Orthodontic treatment involves movement of malpositioned teeth to orthodontically correct locations. During treatment, tiny orthodontic appliances known as brackets are affixed to incisal, cuspid and bicuspid teeth of the patient. An archwire is received in slots of the brackets and functions as a track to guide sliding movement of the brackets and the associated teeth along the archwire to desired positions. Ends of the archwire are often captured in buccal tubes that are mounted on the patient's molar teeth.

Orthodontic brackets often have one or more pairs of tie wings that are provided for ligating or tying the archwire to each bracket. In many conventional brackets, the tie wings have opposed portions that are located on opposite sides of the archwire slot. The opposed portions are shaped like tiny hooks and are oriented in opposite directions. The ligature extends around each tie wing portion and also over the archwire in order to secure the archwire in place in the archwire slot of the bracket.

Ligatures are often sold either as a length of small gauge wire or in the form of a tiny O-ring. When using wire ligatures, the ends of the wire are twisted together to form a loop after the wire has been placed around the tie wing portions and the adjacent section of the archwire. When O-ring ligatures are used, the practitioner typically hooks one portion

-1- of the O-ring around one of the tie wing portions and then stretches the O-ring to extend over the archwire and around the other tie wing portion.

Tie wings and ligatures provide an efficient, inexpensive connection for coupling the archwire to each bracket while also enabling replacement of the archwire when desired. For example, the orthodontist may prefer to change the archwire as treatment progresses in order to enhance movement of the teeth to precise, desired final positions. In that instance, the ligatures can be readily disconnected from the tie wings in order to permit removal of the archwire and insertion of an archwire with somewhat different physical properties when desired. Some orthodontic brackets are known as "single" tie wing brackets because they have only a single tie wing portion located on each side of the archwire slot. In particular, single tie wing brackets have a single hook-like occlusal tie wing portion that is located relative to the archwire slot in an occlusal direction (i.e., in a direction toward the outer tip of each tooth) and a single hook-like gingival tie wing portion that is located relative to the archwire slot in a gingival direction (i.e., in a direction toward the patient's gingiva or gums). Single tie wing brackets are sometimes preferred because they are smaller and therefore less conspicuous than brackets having additional tie wings.

However, many practitioners prefer to use brackets known as "twin" tie wing brackets that have two sets of spaced apart tie wings. More specifically, twin tie wing brackets have a mesial tie wing that is located on the mesial side of the bracket (i.e., on a side of the bracket facing the middle of the patient's dental arch) and a distal tie wing that is located on a distal side of the bracket (i.e., on a side of the bracket facing away from the middle of the patient's dental arch). Each of the mesial and distal tie wings has a hook-like occlusal portion and a hook-like gingival portion. Twin tie wing brackets are preferred by many orthodontists because the spaced- apart mesial and distal tie wings provide greater control over rotation of the tooth about its long axis as compared to single tie wing brackets. For example, one of the patient's teeth may need to be rotated slightly about its long axis and also moved in a labial direction (i.e., in a direction generally toward the patient's lips or cheeks) in order to bring that tooth into proper alignment with other teeth. The mesial and distal tie wings of twin brackets provide alternative off-center anchoring locations for the ligature. If the ligature is connected to only one of the tie wings, the malpositioned tooth is urged by the ligature in a rotative direction toward the ligated tie wing as the tooth is also moved labially and brought into alignment with other teeth of the dental arch.

The appearance of orthodontic appliances can sometimes serve as a source of embarrassment to the patient, particularly among adolescent patients who may experience teasing from classmates. Unfortunately, twin tie wing brackets are typically larger in a mesial-distal direction than corresponding single tie wing brackets and consequently are more noticeable during orthodontic treatment than single tie wing brackets. Although twin tie wing brackets are more noticeable during treatment, many practitioners prefer to use twin tie wing brackets because of the enhanced control over rotational movement of the teeth as described above.

Much effort has been undertaken in recent years among manufacturers of orthodontic brackets to make the brackets less apparent in the oral cavity. Some brackets, for example, have been scaled down in proportion from larger brackets so that their overall size is relatively small. Generally, such scaled-down brackets are otherwise identical in many respects to their larger counterparts. In some cases, the archwire slot is cut into the body of the bracket in an attempt to reduce the labial-lingual height of the tie wings and hence also the overall labial-lingual dimension of the bracket.

Manufacturers have also attempted to make orthodontic brackets less conspicuous by making the brackets of materials other than metal. For example, some brackets are made of translucent polycrystalline alumina that tends to pick up the color and therefore blend in with the underlying tooth. Other brackets have been made of transparent, single crystal alumina as well as other colorless and colored ceramics and plastics.

However, orthodontic brackets must have sufficient strength to withstand the forces expected during orthodontic treatment. Tie wings are often subjected to considerable force during treatment, especially during the early stages of treatment if the tooth is initially positioned some distance from its intended final location. If the tie wings break during treatment, the bracket must be removed and replaced with a new bracket, a procedure that represents an expense and a time-consuming nuisance to both the orthodontist as well as to the patient. At present, there is a need in the art for a twin orthodontic bracket that is relatively small in order to present an improved aesthetic appearance during use in orthodontic treatment. Preferably, such a bracket could be made out of metal such as stainless steel, as well as other materials such as plastics or ceramics.

Summary of the Invention

One aspect of the present invention is directed to an orthodontic bracket that comprises a base and a body connected to the base. A mesial tie wing is connected to the body and has a labial side, a mesial side and a distal side. A distal tie wing is connected to the body and has a labial side, a mesial side and a distal side. An archwire slot extends through the mesial tie wing and the distal tie wing for receiving an orthodontic archwire. At least one reinforcing member is connected to the body and is connected to at least one of the distal side of the mesial tie wing and the mesial side of the distal tie wing. Each reinforcing member has a labial side and a side facing the archwire slot. At least a portion of the labial side of each reinforcing member is located lingually of a reference plane interconnecting the labial side of the mesial tie wing and the labial side of the distal tie wing adjacent the archwire slot. At least a portion of the side of each reinforcing member facing the archwire slot is spaced from the archwire slot. Another aspect of the present invention is directed toward an orthodontic bracket that comprises a base and a body connected to the base. A mesial tie wing is connected to the body and has a labial side, a mesial side and a distal side. A distal tie wing is connected to the body and has a labial side, a mesial side and a distal side. An archwire slot extends through the mesial tie wing and the distal tie wing for receiving an orthodontic archwire. A pair of reinforcing members is connected to the body on opposite sides of the archwire slot. Each reinforcing member is connected to the distal side of the mesial tie wing and to the mesial side of the distal tie wing. Each reinforcing member has a labial side and a side facing the archwire slot. At least a portion of the labial side of each reinforcing member is located lingually of a reference plane interconnecting the labial side of the mesial tie wing and the labial side of the distal tie wing adjacent the archwire slot.

-4- At least a portion of the side of each reinforcing member facing the archwire slot is spaced from the archwire slot.

In another aspect, the present invention directed toward an orthodontic bracket that comprises a base and a body connected to the base. A mesial tie wing is connected to the body and has a labial side, a mesial side and a distal side. A distal tie wing is connected to the body and has a labial side, a mesial side and a distal side. An archwire extends through the mesial tie wing and the distal tie wing for receiving an orthodontic archwire. A pair of reinforcing members is connected to the body along one side of the archwire slot. One of the reinforcing members is connected to the distal side of the mesial tie wing and the other reinforcing member is connected to the mesial side of the distal tie wing. Each reinforcing member has a labial side and a side facing archwire slot. At least a portion of the labial side of each reinforcing member is located lingually of a reference plane interconnecting the labial side of the mesial tie wing and the labial side of the distal tie wing adjacent the archwire slot. In the various embodiments of the invention, the bracket provides an improvement over prior art conventional brackets in that each reinforcing member increases the strength of the associated tie wing or tie wings and thus reduces the likelihood that the tie wing(s) will unduly deform or fracture during the course of orthodontic treatment. Moreover, each reinforcing member is oriented so as to avoid impairing the function of the bracket as a true twin tie wing bracket, so that that traditional advantages of twin tie wing brackets including substantial rotational control of the associated tooth are not impaired. Brackets constructed in accordance with the present invention can be significantly reduced in overall size in comparison to conventional brackets. Consequently, the brackets of this invention are less apparent when in place in the oral cavity and therefore provide enhanced aesthetic qualities relative to known brackets.

Further details of the invention are defined in the features of the claims.

Brief Description of the Drawings

-5- Fig. 1 is a perspective view of an orthodontic bracket constructed in accordance with one embodiment of the present invention, looking at the bracket toward its occlusal, distal and labial sides;

Fig. 2 is an elevational view of the bracket shown in Fig. 1 and looking toward the labial side of the bracket;

Fig. 3 is a side cross-sectional view of the bracket shown in Figs. 1 and 2, taken in a direction along lines 3-3 of Fig. 2;

Fig. 4 is a view somewhat similar to Fig. 2 except that an orthodontic archwire has been placed in an archwire slot of the bracket and a ligature has been placed around a distal tie wing of the bracket in order to secure the archwire to the bracket;

Fig. 4a is a view somewhat similar to Fig. 4 except that the ligature is not shown and the archwire has been replaced with a smaller archwire;

Fig. 5 is a side cross-sectional view of the bracket, archwire and ligature illustrated in Fig. 4 and taken along lines 5-5 of Fig. 4; Fig. 6 is a perspective view of an orthodontic bracket constructed in accordance with another embodiment of the present invention, looking in a direction toward occlusal, distal and labial sides of the bracket;

Fig. 7 is an elevational view of the bracket shown in Fig. 6 and looking in a direction toward its labial side; Fig. 8 is a side cross-sectional view of the bracket shown in Figs. 6-7 and taken along lines 8-8 of Fig. 7;

Fig. 9 is a perspective view of an orthodontic bracket constructed in accordance with yet another embodiment of the invention, taken in a view looking toward occlusal, distal and labial sides of the bracket; Fig. 10 is an elevational view of the bracket shown in Fig. 9 and looking in a direction toward the labial side of the bracket;

Fig. 11 is a side cross-sectional view of the bracket shown in Figs. 9 and 10 and taken along lines 11-11 of Fig. 10;

Fig. 12 is a plan view of the bracket shown in Figs. 9-11 and taken in a direction looking toward the occlusal side of the bracket;

-6- Fig. 13 is a perspective view of an orthodontic bracket constructed in accordance with still another embodiment of the present invention, taken in a direction looking toward occlusal, distal and labial sides of the bracket;

Fig. 14 is an elevational view of the bracket shown in Fig. 14, taken in a direction looking toward its labial side; and

Fig. 15 is a side cross-sectional view of an orthodontic bracket according to another embodiment of the invention.

Detailed Description of the Preferred Embodiments

An orthodontic bracket constructed in accordance with one embodiment of the present invention is illustrated in Figs. 1-5 and is designated broadly by the numeral 20. The bracket 20 includes a base 22 that preferably has a compound contour that matches the convex shape of the outer surface of the tooth for which it is intended. Although not shown in the drawings, the base 22 may optionally include a mesh surface, a roughened surface, a surface with upstanding pegs, projections with enlarged, outer heads or other structure in order to enhance bonding of the bracket 20 directly to the outer surface of the tooth.

The bracket 20 also includes a body 24 that is connected to the base 22. The body 24 extends away from the base 22 in a labial direction (i.e., in a direction toward the patient's lips or cheeks). The body 24 may be integrally connected to the base 22 or optionally may be coupled by other types of joining techniques such as welding, brazing, adhesive bonding and the like, depending in part upon the material chosen for the body 24 and the base 22. The bracket 20 also includes a mesial tie wing 26 that has an occlusal tie wing portion 28 and an opposed gingival tie wing portion 30. The bracket 20 also includes a distal tie wing 32 that has an occlusal tie wing portion 34 and an opposed gingival tie wing portion 36. An archwire slot 38 extends in a mesial-distal direction through aligned channels of the mesial tie wing 26 and the distal tie wing 32, and separates the occlusal tie wing portions 28, 34 from the gingival tie wing portions 30, 36 respectively. In this regard, the archwire slot 38 is considered as the passage bounded by a first reference plane that contains the coplanar gingival walls of the tie wing channels, a second reference plane that contains the coplanar occlusal walls of the tie wing channels, and a third reference plane that contains the coplanar lingual walls of the tie wing channels.

Each of the tie wings 26, 32, and more specifically each of the tie wing portions 28, 30, 34 and 36, includes a labial side 40, a mesial side 42 and a distal side 44. Moreover, each of the tie wing portions 28, 30, 34, 36 has a generally hook-like configuration with a concave surface for receiving a section of a ligature. The concave, ligature-receiving surface of the occlusal tie wing portions 28, 34 is located occlusally of the body 24 and labially of the base 22, while the concave, ligature-receiving surface of the gingival tie wing portions 30, 36 is located gingivally of the body 24 and labially of the base 22.

The bracket 20 includes at least one, and preferably includes two reinforcing cross members 46, 48 as depicted in Figs. 1-5. The reinforcing cross member 46 extends along the gingival side of the archwire slot 38, and preferably has a longitudinal axis that is parallel to the longitudinal axis of the archwire slot 38. The reinforcing cross member 48 extends along the occlusal side of the archwire slot 38, and preferably extends in a direction parallel to the direction of extension of the reinforcing cross member 46. As illustrated, each of the reinforcing members 46, 48 has a bar-like configuration with a rectangular cross-sectional shape, although other configurations are also possible.

A lingual side (i.e., a side facing the patient's tongue) of each reinforcing member 46, 48 is connected to a labial side of the body 24. The gingival reinforcing member 46 has a distal end that is connected to the mesial side 42 of the gingival tie wing portion 36 and a mesial end that is connected to the distal side 44 of the gingival tie wing portion 30. Additionally, the occlusal reinforcing member 48 has a mesial end that is connected to the distal side 44 of the occlusal tie wing portion 28 and a distal end that is connected to the mesial side 42 of the occlusal tie wing portion 34.

As shown for example in Figs. 1 and 3, each of the reinforcing members 46, 48 has a labial surface that is spaced in a labial direction from the labial side of the body 24. The labial surfaces of the reinforcing members 46, 48 may be flat and co-planer as shown in the drawings or alternatively may have a curved configuration. Such a curved configuration may be present in cross-sections taken perpendicularly to the archwire slot

-8- 38, or in cross sections taken perpendicularly of an occlusal-gingival reference axis extending through the bracket 20, or in both cross-sections.

In Figs. 4 and 5, an archwire 50 has been placed in the archwire slot 38 of the bracket 20 in order to illustrate one possible use of the bracket 20. The archwire 50 in this example fully occupies the archwire slot 38 and is secured to the distal tie wing 32 by an elastomeric O-ring ligature 52. The ligature 52 is received in the concave surfaces beneath the occlusal tie wing portion 34 and the gingival tie wing portion 36, and also extends over a labial side of the archwire 50 in order to secure the archwire 50 in place.

As can be appreciated by reference to Figs. 3 and 5, a gingival side of the archwire slot 38 and a gingival side of the archwire 50 is spaced from a facing, occlusal side of the gingival reinforcing member 46. Likewise, an occlusal side of the archwire slot 38 and an occlusal side of the archwire 50 is spaced from a facing, gingival side of the occlusal reinforcing member 48. Examples of suitable spacing of the archwire slot 38 and the reinforcing members 46, 48 include about 0.002 inch (0.05 mm) to about 0.005 inch (0.12 mm), and preferably about 0.003 inch (0.075 mm) or about 0.004 inch (0.12 mm). Other spacings are also possible.

Preferably, the lingual side of the archwire 50 is spaced in a labial direction from the adjacent, underlying labial surface of the body 24. A suitable spacing includes, for example, about 0.003 inch (0.075 mm), and preferably is at least 0.001 inch (0.025 mm). In addition, the labial side of the archwire 50 when fully seated in the archwire slot 38 is spaced in a labial direction from a reference plane containing the labial sides of the reinforcing members 46, 48. As a result, the ligature 52 bears on the archwire 50 without undue hindrance from the reinforcing members 46, 48.

The spacing of the archwire slot 38 and consequently of the archwire 50 from the reinforcing members 46, 48 and the body 24 as described above enables the bracket 20 to function as a true twin tie wing bracket that provides a significant degree of control over rotation of the associated tooth. For example, when the ligature 52 is connected to the bracket 20 as illustrated in Figs. 4 and 5, the archwire 50 tends to urge the associated tooth in a rotative direction about its longitudinal axis such that the distal side of the tooth is rotated toward the archwire 50. In practice, the practitioner can elect to ligate the bracket 20 to the archwire 50 using either one or both of the tie wings 26, 32 and observe good rotational mechanics over movement of the associated tooth that is similar to the rotational mechanics provided by conventional twin tie wing brackets.

Fig. 4a is an illustration somewhat similar to Fig. 4 except that the ligature 50 has been removed from view and the rectangular archwire 50 has been replaced with an archwire 51 having a circular cross-sectional configuration. In this example, the diameter of the archwire 51 is substantially smaller than the occlusal-gingival width of the archwire slot 38, such that the archwire 51 can bend in an arc as shown under certain circumstances. For instance, the archwire 51 may bend as shown in Fig. 4a when the orthodontist attempts to "tip" the associated tooth (i.e., attempts to move the tooth such that the longitudinal axis of the tooth is rotated in a mesial-distal direction). Tipping movements are often carried out during initial leveling stages of treatment using, for example, an archwire having a relatively small diameter (e.g. about 0.014 inch (0.35 mm)) in a bracket having a larger archwire slot (e.g., a slot with an occlusal-gingival width of about 0.022 inch (0.56 mm)). As can be appreciated by reference to Fig. 4a, the spacing between the gingival side of the archwire slot 38 and the occlusal side of the gingival reinforcing member 46 is advantageous in that the archwire 51 when bent in the arc as illustrated avoids contact with the reinforcing member 46. Consequently, such spacing affords better control over tipping movements and also reduces the amount of friction between the reinforcing member 46 and the archwire 51 that might otherwise be present. Similar results are observed in connection with the occlusal reinforcement member 48 when the archwire 51 is bent in an opposite direction.

It has also been discovered that the shape of the tie wings 26, 32 when made of a shiny, reflective material such as highly polished stainless steel serves to provide an illusion that the bracket 20 is smaller than it is in reality. As shown in Figs. 1-5, the outer, labial surface of each tie wing 26, 32 is curved in two dimensions (in particular, is curved about a mesial-distal reference axis as well as about an occlusal-gingival reference axis). Such curved surfaces function as small convex mirrors and present smaller reflected images than might otherwise be possible with relatively flat tie wings. The domed shape of the tie wings 26, 32 also serves to increase the effectiveness of the tumble polishing process that is typically undertaken during the final stages of manufacture.

-10- Another embodiment of the invention is shown in Figs. 6-8, wherein a bracket 20a is essentially identical to the bracket 20 described above except for the differences pointed out below. As such, a detailed description of common elements of the brackets 20, 20a need not be repeated. The bracket 20a differs from the bracket 20 in that only a single reinforcing member 46a is provided. In the embodiment shown, the reinforcing member 46a extends along a gingival side of the archwire slot, and there is no counterpart reinforcing member that extends along the occlusal side of the archwire slot. The gingival reinforcing member 46a is identical to the gingival reinforcing member 46 described above. As another alternative, and although not shown, the reinforcing member 46a of the bracket 20a may instead extend along the occlusal side of the archwire slot, with a reinforcing member absent from the gingival side of the archwire slot.

An orthodontic bracket 20b constructed in accordance with another embodiment of the invention is illustrated in Figs. 9-12. Except as noted below, the orthodontic bracket 20b is essentially identical to the bracket 20 described above and hence a detailed description of the common elements need not be repeated.

The bracket 20b has four reinforcing members 46b, 47b, 48b and 49b instead of the two reinforcing members 46, 48 as shown in connection with the bracket 20. The reinforcing members 46b, 47b are located on a gingival side of the archwire slot, while the reinforcing members 48b, 49b are located on an occlusal side of the archwire slot. Each of the reinforcing members 46b-49b has a generally triangular configuration when viewed along an occlusal-gingival reference axis. An outer, labial side of the reinforcing members 46b-49b (i.e., the side representing the hypotenuse of the triangular shape of the reinforcing members 46b-49b) may have a flat configuration as shown in Figs. 9-12 or alternatively may have a curved configuration in one or more directions. For example, the labial face of each reinforcing member 46b-49b may have a concave configuration when viewed along an occlusal-gingival reference axis, and/or may have a convex configuration when viewed in directions along a mesial-distal reference axis.

The gingival reinforcing members 46b, 47b are spaced apart from each other. Alternatively, however, the adjacent ends of the members 46b, 47b may contact each other at a location next to the base. Similarly, the occlusal reinforcing members 48b, 49b are

-11- spaced from each other or alternatively are touching each other in areas next to the base. The mesial sides of the reinforcing members 46b, 48b contact the distal sides of the gingival and occlusal tie wing portions respectively of the mesial tie wing 26b, and the distal sides of the reinforcing members 47b, 49b contact the mesial sides of the gingival and occlusal tie wing portions respectively of the distal tie wing 32b.

Preferably, but not necessarily, the occlusal side of the gingival reinforcing members 46b, 47b is spaced from the archwire slot and an archwire when received in the archwire slot. Similarly, the gingival side of the occlusal reinforcing members 48b, 49b is preferably, but not necessarily, spaced from the occlusal side of the archwire slot and an archwire received in the archwire slot. Preferably, all or at least a substantial portion of the labial side of each reinforcing member 46b-49b is spaced in a lingual direction of a reference plane that interconnects the labial side of the mesial tie wing and the distal tie wing adjacent to the archwire slot.

Figs. 13 and 14 are illustrations of a bracket 20c constructed in accordance with another embodiment of the invention. The bracket 20c is essentially identical to the bracket 20b with the exceptions noted below, and as such a detailed description of the common elements need not be repeated.

The bracket 20c includes a pair of gingival reinforcing members 46c, 47c, but lacks occlusal reinforcing members such as members 48b and 49b shown in Figs. 9-12. As an alternative, however, the pair of reinforcing members 46c, 47c may be instead located along the occlusal side of the archwire slot.

Fig. 15 depicts a bracket 20d constructed according to another embodiment of the invention. The bracket 20d is essentially identical to the bracket 20 except for the differences noted below, and as such a detailed description of the common elements need not be repeated. The bracket 20d has an archwire slot 38d with a convex lingual wall presenting a raised platform 39d. The platform 39d is located in the archwire channel of the mesial tie wing and the distal tie wing, and serves to reduce the amount of sliding friction that might otherwise be present between the lingual side of the archwire and the lingual side of the archwire slot 38d. The platform 39d retains the lingual side of the archwire at a distance spaced from the underlying labial surface of the bracket body. An

-12- example of a suitable spacing is about 0.002 inch (0.05 mm), although other spacings are also possible.

Other embodiments are also possible. For example, a bracket may be provided with a pair of reinforcing members similar to the reinforcing members 46b, 47b along the gingival side of the archwire slot, and a rectangular, bar-like reinforcing member similar to the reinforcing member 48 may extend along the occlusal side of the archwire slot. As another option, a bracket may have a pair of reinforcing members similar to members 48b, 49b located along the occlusal side of the archwire slot and a bar-like reinforcing member similar to member 46 located along the gingival side of the archwire slot. The present invention is particularly useful for twin tie wing brackets having an occlusal-gingival or "vertical" slot that is provided for receiving an auxiliary appliance such as an uprighting spring, a hook or the like. Vertical slots are commonly located in the bracket body next to the base and extend along a reference plane oriented equidistantly between the mesial and distal tie wings. Although not shown in the drawings, the reinforcement members significantly increase the strength of the tie wings on brackets with vertical slots and help enable the brackets to be manufactured with smaller lingual- labial overall dimensions that might not otherwise be possible.

Brackets constructed according to the present invention may be made of any one or more of a variety of materials and manufactured by any one of a number of processes. Preferably, the bracket body, tie wings and reinforcement member(s) are integral. The bracket may be made of metal using, for example, conventional metal injection molding processes wherein stainless steel powder (such as AISI-630) and a binder (such as polystyrene or polystyrene and waxes) are injected into a mold. The molded article is then heated to volatilize the binder and sinter the powder particles together. The brackets may also be made using a casting process.

As other alternatives, brackets constructed in accordance with the principles of the present invention may be made of ceramics such as single crystal alumina or polycrystalline alumina. Polycrystalline alumina brackets are preferably made using an injection molding process. The brackets may also be made of any one of a number of plastic materials such as polycarbonate and are preferably made using a molding process.

^■13- Optionally, the reinforcing member(s) may comprise part of a framework that is embedded in a second material such as a plastic material. Aesthetic plastic brackets with load bearing frameworks are known and are described, for example, in U.S. Patent No. 5,597,302. Preferably, the reinforcing members are connected to the mesial and distal portions of the framework that are located in tiewing regions of the bracket and extend in directions parallel to the longitudinal axis of the archwire slot of the bracket. The reinforcing members optionally include lingual sections that are connected to a portion of the framework that extends parallel to the archwire slot between the archwire slot and the bracket base. Advantageously, the reinforcing members as described above in the different embodiments provide significant strength to the bracket, and serve to reinforce the associated tie wings in order to hinder undue bending or breakage of the tie wings during use in orthodontic treatment. As a consequence, the reinforced tie wings can be made having somewhat smaller overall dimensions than tie wings made of similar materials but without reinforcement. Reduction in size the tie wings enables the overall size of the bracket to be reduced, such that the bracket is less visibly apparent when mounted in place in the oral cavity.

In all the various embodiments described above, however, the reinforcing members do not significantly, if at all, engage the archwire even when the archwire is fully seated in the archwire slot. The resultant spacing of the reinforcing members relative to the archwire enables the bracket to function as a true twin tie wing bracket, and provides the bracket with good control over tipping movement and rotational movement of the associated tooth as may be needed. The archwire relief provided by such spacing also reduces the amount of friction that might otherwise serve to hinder sliding movement of the bracket along the archwire.

Those skilled in the art may recognize that a number of modifications and additions may be made to the brackets described above without departing from the spirit of the invention. Accordingly, the invention should not be deemed limited to the particular embodiments described in detail above, but only by a fair scope of the claims that follow along with their equivalents.

■14-

Claims

CLAIMS:

1. An orthodontic bracket comprising: a base; a body connected to the base; a mesial tie wing connected to the body and having a labial side, a mesial side and a distal side; a distal tie wing connected to the body and having a labial side, a mesial side and a distal side; an archwire slot extending through the mesial tie wing and the distal tie wing for receiving an orthodontic archwire; and at least one reinforcing member connected to the body and connected to at least one of the distal side of the mesial tie wing and the mesial side of the distal tie wing, each reinforcing member having a labial side and a side facing the archwire slot, wherein at least a portion of the labial side of each reinforcing member is located lingually of a reference plane interconnecting the labial side of the mesial tie wing and the labial side of the distal tie wing adjacent the archwire slot, and wherein at least a portion of the side of each reinforcing member facing the archwire slot is spaced from the archwire slot.

2. The orthodontic bracket of claim 1 wherein each reinforcing member extends between the mesial side of the distal tie wing and the distal side of the mesial tie wing.

3. An orthodontic bracket according to claim 2 wherein each reinforcing member has a bar-like configuration.

4. An orthodontic bracket according to claim 1 wherein the bracket includes two reinforcing members located on opposite sides of the archwire slot.

5. An orthodontic bracket according to claim 4 wherein the two reinforcing members extend in parallel directions.

-15-

6. An orthodontic bracket according to claim 4 wherein each reinforcing member has a labial side, and the labial sides of the reinforcing members extend in a common reference plane.

7. An orthodontic bracket according to claim 1 wherein at least one reinforcing member has a generally triangular configuration.

8. An orthodontic bracket according to claim 7 wherein each reinforcing member has a generally curved labial side when viewed along an occlusal-gingival reference axis.

9. An orthodontic bracket according to claim 7 wherein each reinforcing member has a generally flat labial side.

10. An orthodontic bracket according to claim 1 wherein the bracket includes four reinforcing members, two of which are located on an occlusal side of the archwire slot and are connected to the mesial tie wing and the distal tie wing respectively and wherein the other two reinforcing members are. located on the gingival side of the archwire slot and are connected to the mesial tie wing and the distal tie wing respectively.

11. An orthodontic bracket according to claim 10 wherein each reinforcing member is spaced from the other reinforcing members.

12. An orthodontic bracket according to claim 11 wherein each reinforcing member has a generally triangular configuration.

13. An orthodontic bracket according to claim 1 wherein the labial side of each reinforcing member is located lingually of a reference plane containing an adjacent labial wall portion of an archwire when an archwire is received in the archwire slot.

14. An orthodontic bracket comprising: a base;

Γûá16- a body connected to the base; a mesial tie wing connected to the body and having a labial side, a mesial side and a distal side; a distal tie wing connected to the body and having a labial side, a mesial side and a distal side; an archwire slot extending through the mesial tie wing and the distal tie wing for receiving an orthodontic archwire; and a pair of reinforcing members connected to the body on opposite sides of the archwire slot, each reinforcing member connected to the distal side of the mesial tie wing and to the mesial side of the distal tie wing, each reinforcing member having a labial side and a side facing the archwire slot, wherein at least a portion of the labial side of each reinforcing member is located lingually of a reference plane interconnecting the labial side of the mesial tie wing and the labial side of the distal tie wing adjacent the archwire slot, and wherein at least a portion of the side of each reinforcing member facing the archwire slot is spaced from the archwire slot.

15. An orthodontic bracket according to claim 14 wherein each reinforcing member has a bar-like configuration.

16. An orthodontic bracket according to claim 14 wherein the two reinforcing members extend in parallel directions.

17. An orthodontic bracket according to claim 14 wherein each reinforcing member has a labial side, and the labial sides of the reinforcing members extend in a common reference plane.

18. An orthodontic bracket according to claim 14 wherein the labial side of each reinforcing member is located lingually of a reference plane containing an adjacent labial wall portion of an archwire when an archwire is received in the archwire slot.

19. An orthodontic bracket comprising:

-17- a base; a body connected to the base; a mesial tie wing connected to the body and having a labial side, a mesial side and a distal side; a distal tie wing connected to the body and having a labial side, a mesial side and a distal side; an archwire slot extending through the mesial tie wing and the distal tie wing for receiving an orthodontic archwire; and a pair of reinforcing members connected to the body along one side of the archwire slot, one of the reinforcing members connected to the distal side of the mesial tie wing and the other reinforcing member connected to the mesial side of the distal tie wing, each reinforcing member having a labial side and a side facing the archwire slot, wherein at least a portion of the labial side of each reinforcing member is located lingually of a reference plane interconnecting the labial side of the mesial tie wing and the labial side of the distal tie wing adjacent the archwire slot.

20. An orthodontic bracket according to claim 19 and including an additional pair of reinforcing members connected to the body along the other side of the archwire slot, one of the additional pair of reinforcing members connected to the mesial side of the distal tie wing and the other reinforcing member of the additional pair connected to the distal side of the mesial tie wing.

21. An orthodontic bracket according to claim 19 wherein at least one reinforcing member has a generally triangular configuration.

22. An orthodontic bracket according to claim 19 wherein each reinforcing member has a generally curved labial side when viewed along an occlusal-gingival reference axis.

23. An orthodontic bracket according to claim 19 wherein each reinforcing member has a generally flat labial side.

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24. An orthodontic bracket according to claim 19 wherein each reinforcing member is spaced from the other reinforcing members.

25. An orthodontic bracket according to claim 19 wherein the labial side of each reinforcing member is located lingually of a reference plane containing an adjacent labial wall portion of an archwire when an archwire is received in the archwire slot.

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