Systems and methods for positioning teeth

#The present invention is related generally to the field of orthodontics, and more particularly to systems and methods for positioning teeth.

#One objective in orthodontics is to move a patient's teeth to positions where the teeth function optimally and aesthetically. Conventionally, appliances such as braces are applied to the teeth of the patient by an orthodontist. Each appliance exerts continual forces on the teeth and gradually urges the teeth toward their ideal positions. Over a period of time, a treating professional such as an orthodontist adjusts the appliances to move the teeth toward their final destination.

#Generally, the orthodontist specifies in a prescription the final tooth arrangement. The prescription is based on the orthodontist's knowledge and experience in selecting the intended final position of each tooth. The orthodontist or an assistant applies the treatment to move the teeth to their intended destination over a number of office visits. The process of attaching the braces to teeth is tedious and painful to the patient. Additionally, each visit reduces the “chair-time” available to the orthodontist that can be made available to another patient.

#FIG. 1 is an elevational diagram showing the anatomical relationship of the jaws of a patient.

#FIG. 2A illustrates in more detail the patient's lower jaw and provides a general indication of how teeth may be moved by the methods and apparatus of the present invention.

#FIG. 2B illustrates a single tooth from FIG. 2A and defines how tooth movement distances are determined.

#FIG.1 shows a skull 10 with an upper jaw bone 22 and a lower jaw bone 20. The lower jaw bone 20 hinges at a joint 30 to the skull 10. The joint 30 is called a temporal mandibular joint (TMJ). The upper jaw bone 22 is associated with an upper jaw 101, while the lower jaw bone 20 is associated with a lower jaw 100. A computer model of the jaws 100 and 101 is generated in accordance with the process of FIG. 3, and a computer simulation can model interactions among the teeth on the jaws 100 and 101. The computer simulation allows the system to focus on motions involving contacts between teeth mounted on the jaws. The computer simulation allows the system to render realistic jaw movements that are physically correct when the jaws 100 and 101 contact each other. Further, the model can be used to simulate jaw movements including protrusive motions, lateral motions, and “tooth guided” motions where the path of the lower jaw 100 is guided by teeth contacts rather than by anatomical limits of the jaws 100 and 101. Motions are applied to one jaw, but may also be applied to both jaws. Based on the occlusion determination, the final position of the teeth can be ascertained.

#Referring now to FIG. 2A, a visual representation of the digital data representing the computer model of the lower jaw 100 includes a plurality of teeth 102, for example. At least some of these teeth may be moved by the methods of the present invention from an initial tooth arrangement to a final tooth arrangement. As a frame of reference describing how a tooth may be moved, an arbitrary centerline (CL) may be drawn through the tooth 102. With reference to this centerline (CL), each tooth may be moved in orthogonal directions represented by axes 104, 106, and 108 (where 104 is the centerline). The centerline may be rotated about the axis 108 (root angulation) and the axis 104 (torque) as indicated by arrows 110 and 112, respectively. Additionally, the tooth may be rotated about the centerline, as represented by an arrow 114. Thus, all possible free-form motions of the tooth can be performed.

#FIG. 2B shows how the magnitude of any tooth movement may be defined in terms of a maximum linear translation of any point P on a tooth 102. Each point P1 will undergo a cumulative translation as that tooth is moved in any of the orthogonal or rotational directions defined in FIG. 2A. That is, while the point will usually follow a nonlinear path, there is a linear distance between any point in the tooth when determined at any two times during the treatment. Thus, an arbitrary point P1 may in fact undergo a true side-to-side translation as indicated by arrow d1, while a second arbitration point P2 may travel along an arcuate path, resulting in a final translation d2. Many aspects of the present invention are defined in terms of the maximum permissible movement of a point P1 induced on any particular tooth. Such maximum tooth movement, in turn, is defined as the maximum linear translation of that point P1 on the tooth that undergoes the maximum movement for that tooth in any treatment step.