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Torque overcorrection model

Torque overcorrection model description/claims

This application claims benefit of U.S. Provisional Application 60/916,189, filed on May 4, 2007, which is incorporated herein by reference.

This application is related to:

U.S. Pat. No. 5,431,562 issued Jul. 11, 1995 and Published International Patent Application No. PCT/US00/35558, each of which is incorporated in their entirety herein.

International Patent Application No. WO2004/028391, which is assigned to the assignee hereof and hereby incorporated by reference in its entirety.

U.S. patent application Ser. No. 10/528,036, filed Mar. 16, 2005, which is a U.S. National Stage application of International Application No. PCT/US2003/030917, filed on Sep. 26, 2003, which claims the benefit of U.S. Provisional Patent Application Ser. No. 60/413,712, filed Sep. 26, 2002, both hereby expressly incorporated by reference herein.

U.S. patent application Ser. No. 09/941,591, which is a continuation of International Patent Application No. PCT/US00/35558, both filed Dec. 29, 2000, which is an International Application of U.S. Provisional Patent Application Ser. No. 60/173,890, filed Dec. 29, 1999, all of which are hereby expressly incorporated herein by reference in their entirety.

International Patent Application No. US2007/062965 filed Feb. 28, 2007, which claims priority to U.S. Provisional Application Ser. No. 60/777,483, filed Feb. 28, 2006, both of which are hereby expressly incorporated herein by reference in their entirety.

The present invention relates to computer-aided orthodontia, and in particular the computerized generation of orthodontic appliances that are individualized for a particular patient.

In orthodontics it is difficult to create a pure translational movement of a tooth, or to control rotation of the tooth in what is called the Y-Z plane. This problem is most acute when the archwire has a round cross-section, but is also observed with archwires of square and rectangular sections.

FIG. 1 provides a simplified illustration of an archwire, bracket and tooth, and their relative landmarks, and FIG. 2 provides a more detailed view of landmark points within the tooth. The tooth's Center of Resistance (CR.pt) and the archwire axis (which is herein identified as AW.pt), are typically not coincident. As a consequence, pressure from the archwire other than along the Crown Long Axis (CLA.ax) causes some amount of angular change in the position of the tooth. The amount of rotation force is related to the alignment of the force vector of the deflected wire to the tooth's CR.pt. FIG. 1 illustrates the resulting rotational effects on a tooth caused by archwire force in the gingival, occlusal, facial and lingual directions.

Rotation of the tooth under applied archwire force, increases the complexity of orthodontic correction and avoiding such rotations is an important part of orthodontic correction.

Clinicians have traditionally attempted to solve torque correction issues by wire bending. From the clinician's point of view when the case is submitted the clinician would intuit those areas that should be corrected, based on experience drawn from a menu of typical scenarios. However, this solution is not necessarily systematic nor consistent.

In accordance with principles of the present invention, a custom orthodontic appliance comprised of brackets to be positioned on a patient's teeth, and an archwire, is customized to provide a desired torque to a tooth by selecting an angle for the slot of at least one bracket so as to provide a torque interaction between that bracket slot and the archwire.

In preferred embodiments, the torque interaction is computed to compensate for tooth tilt resulting from misalignment of the force vector applied by the archwire with the tooth center of resistance. Furthermore, the torque interaction is computed at the desired final position of the teeth. In further specific embodiments, the slot angle is computed to provide for an applied torque even where the tooth is positioned in the desired final tooth position to compensate for force diminution in the archwire.

In the disclosed particular embodiment the material properties of the archwire and the relative archwire slot geometry are evaluated to determine an archwire/slot angular offset in which torque is applied to the bracket.

The above and other objects and advantages of the present invention shall be made apparent from the accompanying drawings and the description thereof.

• Provisional Patent
• Utility Patent

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