A two-part orthodontic bracket comprises a base and a holding device produced separately therefrom, with the base and the holding device being connected to one another via a joint having a pivot axis. The holding device can be selectively moved about the pivot axis between open and closed positions relative to the base and slot. When in an open position, the holding device can also be tilted about at least one tilt axis lateral or perpendicular to the pivot axis in order to provide better clearance in the case of tooth crowding. A guide system may also be provided that reduces the ability of the holding device to tilt as it is moved toward the closed position.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The present invention relates to a two-part orthodontic bracket comprising a base and a holding device produced separately therefrom, with the base and the holding device being fastened to one another via a connection device. In use, the holding device covers at least one slot for a wire and is movable by a closing movement from an open position into a closed position in which the holding device latches on the base.

2. Relevant Technology

A two-part orthodontic bracket having a base, an arch wire slot and a holding device is disclosed in WO 00/33760. However, when a bracket of this design is attached to a tooth surface of a patient whose teeth have strong crowding, such crowding can inhibit or prevent the holding devices of one or more brackets from being opened widely enough to easily place or remove an arch wire from the arch wire slot.

One-piece orthodontic brackets are known which have a base, an arch wire slot, and a holding device, with the base and the holding device being interconnected via a film hinge. In such brackets, the holding device can be tilted about an axis perpendicular to the pivot axis due to the flexibility of the film hinge. The inclusion of the film hinge limits the types of materials that can be used to make such one-piece brackets, particularly the film hinge itself, which must be flexible enough to allow opening and closing of the holding device.

In view of this, there is a need for improved two-part brackets in which the holding device has increased range of motion, or degrees of freedom, relative to the base to address problems associated with tooth crowding.

SUMMARY OF THE INVENTION

The present invention generally relates to a two-part orthodontic bracket that includes a base and a holding device that are interconnected by a connection device or joint. The base includes at least one slot for a wire. The holding device is designed to move between an open non-ligating position and a closed ligating position relative to the slot.

The connection device or joint is configured so as to permit the holding device to have multiple degrees of freedom of movement relative to the base while in the open position. In one embodiment, a guide system is provided that reduces the degrees of freedom of movement as the holding device is moved toward the closed position.

In accordance with the invention, the joint which interconnects the base and the holding device of the two-part orthodontic bracket is designed so that the holding device is movable about a pivot axis when the holding device is initially opened. When in the open position, the holding device is not only movable about the pivot axis, but it is also freely movable about one or more tilt axes that are lateral or perpendicular to the pivot axis. The ability of the holding device to tilt about one or more tilt axes when partially or completely open allows for sufficient opening of the holding device and exposure of the slot in the case of even high tooth crowding. In this way, the holding device can be manipulated by moving it in an appropriate direction past an adjacent tooth.

In one embodiment, the free movability of the holding device relative to the base may be limited or reduced as the holding device is moved toward the closed position. In one embodiment, the degrees of freedom of the holding device are reduced during closing of the holding device by a guide system. When the holding device is latched to the base in the closed state, the wire is held in the slot and the holding device is simultaneously fixed substantially immovably to the base.

In accordance with a first embodiment, a guide system for limiting or reducing the degrees of freedom of the holding device relative to the base can be provided at, or as part of, the connection device. It is also possible for the guide system to form part of the base and/or holding device.

In accordance with a further embodiment, the guide system can be configured such that the reduction of free movability of the holding device is initiated independently of latching. In other words, the guide system can be designed so that the free movability of the holding device is already reduced before the holding device is actually closed and/or latched to the base.

In one embodiment, the guide system can be configured so that the base and holding device can only be latched in a precisely fixed or pre-defined spatial relationship to one another, i.e., the guide system helps define the position of the holding device relative to the base before and also after latching.

According to one embodiment, the at least partially open holding device is preferably tiltable about a tilt axis that is different from the pivot axis so as to be moveable about a tilt angle in a range of about 0.5° to about 10°, preferably in a range of about 1° to about 8°. A tilt angle within these ranges is sufficient in many cases to move the at least partially open holding device past an adjacent tooth, thus overcoming potential problems associated with tooth crowding.

With a horizontally arranged base, a tilt axis can extend substantially horizontally so that a holding device in a vertical position is tiltable in a vertical plane about the horizontal tilt axis. Alternatively, a tilt axis can extend substantially vertically with a horizontally arranged base so that a holding device in the vertical position is tiltable about the vertical axis. In one embodiment, the bracket can have horizontal and vertical tilt axes in order for a holding device in a vertical position to be selectively tiltable about one or both of the horizontal and vertical tilt axes.

In one embodiment, the joint can be made such that the at least partially open holding device is movable about any three desired axes perpendicular to one another. This configuration more easily permits the holding device to be manipulated so as to be movable past an adjacent tooth in order to permit sufficient opening of the holding device. This helps facilitate insertion or removal of an arch wire from the slot.

In accordance with an additional embodiment of the invention, the joint can form a movable bearing for the at least partially open holding device in order to ensure a sufficient or desired amount of tilting of the holding device relative to the base. Of course the holding device is typically not tilted when latched to the base.

In accordance with a further embodiment of the invention, the joint may comprise at least one spigot that is received at least partially within a link guide, with the spigot and the link guide being be arranged either on the base or on the holding device. In one aspect the link guide serves to permit pivoting of the holding device about the pivot axis so that it can be opened and closed relative to the base. In another aspect the link guide permits tilting of the holding device relative to the base about one or more tilt axes that are lateral or perpendicular to the pivot axis when the holding device is in an open position.

To maintain the holding device on the base in a latched or closed state substantially without clearance or movement, while also permitting tilting of the holding device when in an at least partially open position relative to the base, the link guide may have a first peripheral section having a curvature that corresponds to the curvature of the spigot and a second peripheral section having a curvature that is greater than the curvature of the first peripheral section. It is ensured in this embodiment that the spigot has close contact in the region of the first peripheral section of the link guide when the holding device is in a completely closed or latched state, while also permitting tilting of the spigot inside the link guide when the holding device is at least partially open.

In accordance with a further embodiment, the joint may comprise two spigots which are each received in a respective link guide, with at least one link guide not surrounding the associated spigot along its total periphery. In this embodiment, a passage opening is provided in the at least one link guide. This facilitates assembly of the holding device and base by permitting insertion of a connection web interconnecting the spigots through the passage opening during assembly of the two-part bracket.

In accordance with a further embodiment of the invention, a snap connection can be provided which securely holds the holding device to the base while still permitting free movement of the holding device about the various axes described herein. In one embodiment, the passage opening is ramped so as to cause the associated link guide to temporarily spread open during assembly, more particularly, as the connection web is inserted therethrough. Upon fully inserting the connection web into a space between the two link guides, the passage opening snaps back so as to lock the holding device to the base while also permitting free movement of the holding device about the various axes.

The bracket in accordance with the invention is preferably made of a bite-proof material, for example of metal, rigid plastic or ceramic. In one embodiment of the invention, the holding device comprises a cover.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention generally relates to a two-part orthodontic bracket including a base and a holding device that are interconnected in a manner that allows the holding device to move or tilt about a plurality of axes while in the open position. In this way, the holding device has multiple degrees of freedom so that it can be moved past an adjacent tooth when moved to the open position so as to expose a slot for an arch wire. Following are exemplary embodiments of two-part orthodontic brackets according to the invention.

FIG. 1shows a two-part orthodontic bracket8which consists of a base10and a holding device12which can be produced separately therefrom. The base10and holding device12are pivotally connected to each other via a joint13which has a horizontal pivot axis S about which the holding device12can be pivoted from its completely closed and latched position shown inFIG. 1into an open position (e.g., as shown inFIG. 2). The joint13is an example of a connection device according to the invention.

In the embodiment shown, the holding device12comprises a cover having a smooth, curved outer surface14. It will be appreciated that the holding device12can have other shapes as desired to yield an orthodontic bracket having a desired configuration and functionality.

As further illustrated inFIG. 1, the holding device12, while in a completely closed or latched state relative to the base10, covers or occludes a slot16designed to receive therein an arch wire (not shown). The holding device12is advantageously provided with an extension18designed to bear against and hold an arch wire in slot16when the holding device12is closed or latched relative to the base10, as better seen inFIG. 3.

In accordance with the invention, the joint13is formed between the holding device12and the base10in a manner so as to permit the holding device12to be tilted about at least one tilt axis that is lateral or perpendicular to the pivot axis S when the holding device12is at least partially open relative to the base10. In this way the holding device12, while in an at least partially open position, is movable relative to the base10about at least two axes that are lateral or perpendicular to each other. A guide (which is explained in more detail below) can be provided (e.g., as part of the joint or connection device) that progressively limits the ability of the holding device12to tilt relative to the base10as the holding device12is moved toward the closed or latched position.

FIG. 1further illustrates an orthodontic bracket8in which the holding device or cover12and the base10form, in the closed or latched state, a substantially uniformly curved surface14having no sharp or jagged corners or edges that might irritate a user of the bracket8. This prevents or reduces potential injury and discomfort to the patient, as well as the tendency of food or other foreign substances to catch or adhere to the bracket8.

The holding device12can be latched or locked to the base10in order to maintain the holding device12in a closed or latched state by means of a latch projection20provided at an end of the holding device12distal to the joint13. The latch projection20generally extends toward the base10and is configured so as to snap over a latch bump22provided at the base10in order to mechanically latch the holding device12to the base10.

As shown inFIGS. 1–4, an auxiliary slot24may be provided in the base10in the region of the latch projection24, which, in one embodiment, extends parallel to the main slot16and is likewise covered when the holding device12is completely closed or latched so as to fix or ligate an arch wire that may optionally be provided in the auxiliary slot24.

As best seen inFIG. 3, an engagement gap26may advantageously be provided at the anterior side of the bracket8between the base10and the holding device12when the holding device12is the completely closed or latched position. A dental tool (not shown) can be inserted into the engagement gap26in order to engage and unlatch the holding device12from the base10.

As best seen inFIGS. 3 and 4, the orthodontic bracket8further includes, in the embodiment shown, a pair of spigots28which are connected to the holding device12by means of a connection web30. In one embodiment, the spigots28have a cylindrical cross-section. The spigots28are each received in a respective link guide32and34connected to a base10. The spigots28and link guides32and34together comprise at least a portion of joint13. The interaction between the spigots28and link guides32and34allow the holding device12to be rotated about the pivot access S between the open and closed positions.

As best seen inFIG. 2, the link guides32and34are in a spaced-apart relationship and include opposing inner surfaces that together define a guide recess36. The inner surfaces of the link guides32and34also include chamfers38. In use, the connection web30of the holding device12can be inserted into the guide recess36while closing the holding device12relative to the base10. The guide recess36and the connection web30are configured so that, when the holding device12is completely closed, lateral displacement of the holding device12relative to the base10along the axis S is prevented or at least minimized within a desired range. The chamfers38cause or represent a narrowing of the guide recess36so as to thereby channel the connection web30from a region of greater width of the guide recess36to a region of narrower width as the holding device12is moved toward the closed position. This action is more clearly illustrated inFIGS. 7A–7C, which are discussed more fully below.

As illustrated more particularly inFIGS. 4A–4C, the joint13between the base10and the holding device12forms a movable bearing for the holding device12when at least partially open relative to the base10. The inner peripheral surface of the link guides32and34has a first peripheral section40and a second peripheral section42. The curvature of the first peripheral section40corresponds to the cylindrical curvature of the outer periphery of the spigots28, and the curvature of the second peripheral section42is greater than the curvature of the first peripheral section40. This curvature differential causes the spigots28to more tightly contact the first peripheral section40when the holding device12is in a completely closed position (FIGS. 3 and 6E) and also when the holding device is in a slightly open position (FIG. 6D). Conversely, the spigots32and34more loosely contact the second peripheral section42when the holding device12is in an open position.

In one embodiment, the position of the holding device12relative to the base10shown inFIGS. 3 and 4Adefines the pivot axis S. At the same time, however, it is possible when the holding device12is partially or completely open to move the spigots28within the link guides32and34so as to adopt other positions, such as those illustrated inFIGS. 4B,4C,5A and5B, in which the peripheral surfaces of the spigots28do not contact the first peripheral section40of one or both link guides32and34. The holding device12is therefore not limited to being pivoted about the pivot axis S only, but may also be tilted about different tilt axes different from the pivot axis S.

FIG. 5Ashows a plan view of the bracket shown inFIG. 2, with the holding device12, however, having been tilted about a vertical tilt axis such that (in the embodiment shown) a tilt angle α of approximately 5° results. In this position, the right hand spigot28inFIG. 5A, for example, would adopt a position inside the link guide36corresponding toFIG. 4Bor4C, whereas the left hand spigot28inFIG. 5Awould adopt the position corresponding toFIG. 4A.

FIG. 5Bshows an elevated view of the bracket shown inFIG. 2, with the holding device12, however, having been tilted about a horizontal tilt axis such that (in the embodiment shown) a tilt angle α′ of approximately 5° results. In this position, the right hand spigot28inFIG. 5B, for example, would adopt a position inside the link guide36corresponding toFIG. 4B, whereas the left hand spigot28inFIG. 5Bwould adopt a position corresponding toFIG. 4Aor4C.

It should be understood that the particular conformations or positions of the holding device12relative to the base shown inFIGS. 5A and 5Bare merely illustrative and that various other conformations or positions are possible in order to maximize the ability to compensate for tooth crowding. Thus, it can be seen fromFIGS. 4 and 5that not only a tilting of the holding device12about a vertical tilt axis is possible, but also, within the limit pre-determined by the second peripheral section42, any desired tilting of the holding device12relative to the base10and/or pivot axis S is possible.

Notwithstanding the ability of the holding device12to tilt in various ways when the holding device12is in a fully open position relative to the base10, the degrees of freedom of such tilting may advantageously become progressively reduced as the holding device12is moved toward a closed position relative to the base10. More particularly, as a result of the positioning and size of the link guides32and34relative to the positioning and size of a corresponding inner surface of the holding device12, as well as the positioning and size of the connection web30relative to the guide recess36, the degrees of freedom of the holding device12can be reduced as the holding device12is progressively moved toward the closed position. As the holding device12is closed it can be guided through the interaction of the link guides32and34, inner surface of holding device12, connection web30and guide recess36so as to adopt a precisely defined position relative to the base10prior to and after being completely latched to the base10.

FIGS. 6A–6Billustrate the interaction between the link guides32and34and the corresponding surfaces of the holding device12in incrementally restricting the degrees of freedom or tiltability of the holding device12relative to the base10as the holding device is progressively moved towards the closed position according to one embodiment. As shown inFIG. 6A, a relatively large space44exists between an undersurface46of the holding device12and an outer surface48of link guide32. The size of space44at least partially defines the amount of tiltability or degrees of freedom that exist between the holding device12and the base10.

FIG. 6Bshows a diminution in the size of space44as the holding device12is moved to an intermediate position between the fully opened and fully closed positions. The diminished size of space44limits the tiltability or degrees of freedom of the holding device12relative to the base10.FIGS. 6C–6Eshow a further reduction in the size of space44until none remains when the holding device12is in the fully latched position (FIG. 6E) and in a position just prior to being latched (FIG. 6D).

FIGS. 7A–7Billustrate the interaction between the inner surfaces of the link guides32and34defining the guide recess36and the connection web30of the holding device12. As shown inFIG. 7A, when the holding device12is in the fully open position relative to the base10, a pair of relatively large spaces50exist between inner surfaces52of link guides32and34and outer surfaces54of connection web30.

FIG. 7Bshow a reduction in the size of spaces50as the holding device12is moved toward the closed position, particularly as the outer surfaces54of the connection web30pass by the chamfers38that define a narrowing of the space between the guide recess36. As the size of spaces50diminishes, the ability of the holding device12to tilt relative to the base32and34and outer surfaces54of connection web30is correspondingly reduced.FIG. 7Bshow a reduction in the size of spaces50as the holding device12is moved toward the closed position, particularly as the outer surfaces54of the connection web30pass by the chamfers38that define a narrowing of the space within the guide recess36. As the size of spaces50diminishes, the ability of the holding device12to tilt relative to the base10is correspondingly diminished.

As illustrated inFIG. 8, to facilitate assembly of the holding device12with the base10, at least one of link guides32and34can be provided with a passage opening56which is dimensioned such that the spigots28can be pushed therethrough along the pivot axis S when the holding device12is in the completely open position (seeFIGS. 2 and 4).

Link guide32further includes a secondary opening58having a ramped surface60that is inclined so as to cause the link guide32to be slightly stretched elastically so as to permit passage of the connection web30through the auxiliary passage58. After the connection web30is fully inserted through the auxiliary passage58, the link guide32snaps back to its original configuration, thereby forming a snap connection that captively retains the holding device12to the base10. The auxiliary passage58is more clearly seen inFIGS. 6A through 6E.

It should be appreciated that the joint or of the aforesaid embodiment can also be realized in other manners. It is only necessary that the holding device12is freely movable relative to the base10about at least two different axes while in the open position, with a reduction of free movability preferably taking place as a result of guide system as the holding device12is moved toward the closed position.

The orthodontic brackets according to the invention may comprise any material. Preferably, the base and/or holding device may consist of a bite-proof material such as metal, ceramic or rigid plastic whose stiffness would not ordinarily permit torsion in the region of a joint.