Digitally modeling the deformation of gingival tissue during orthodontic treatment

#The invention relates generally to the fields of dentistry and orthodontics. Two-dimensional (2D) and three-dimensional (3D) digital image technology has recently been tapped as a tool to assist in dental and orthodontic treatment. Many treatment providers use some form of digital image technology to study the dentitions of patients. U.S. patent application Ser. No. 09/169,276, incorporated by reference above, describes the use of 2D and 3D image data in forming a digital model of a patient's dentition, including models of individual dentition components. That application also describes using the digital dentition models in developing an orthodontic treatment plan for the patient, as well as in creating one or more orthodontic appliances to implement the treatment plan.

#The invention provides computer-automated techniques for digitally modeling the gingival tissue of an orthodontic patient, including deformation of the gingival tissue during orthodontic treatment. These techniques are useful, for example, in creating orthodontic appliances that carry out the orthodontic treatment while fitting securely over the patient's teeth and gums. Modeling the gums and deformation of the gums helps ensure that the orthodontic appliances do not press too tightly against the patient's gums and cause discomfort or pain. Modeling how the gums react to treatment also provides a more complete understanding of what to expect during treatment. Moreover, computer-generated images and animations of the dentition during treatment are more complete and aesthetically pleasing when the gums are included.

#The invention involves using a computer to develop a course of treatment for an orthodontic patient. In one aspect, the computer first obtains a digital model of a patient's dentition, including a dental model representing the patient's teeth at a set of initial positions and a gingival model representing gum tissue surrounding the teeth. The computer then derives from the digital model an expected deformation of the gum tissue as the teeth move from the initial positions to another set of positions.

#FIGS. 1A, 1B, and 1C show the arrangement of a patient's teeth at an initial stage, an intermediate stage, and a final stage of orthodontic treatment.

#FIG. 2 shows a partial model of a patient's dentition, including a model of gingival tissue.

#FIG. 3 shows a model of the gum line around a tooth crown.

#U.S. patent application Ser. Nos. 09/169,276, now abandoned 09/264,547, and 09/311,716, now U.S. Pat. No. 6,514,074 describe techniques for generating 3D digital data sets containing models of individual components of a patient's dentition. These data sets include digital models of individual teeth and the gingival tissue surrounding the teeth. These applications also describe computer-implemented techniques for using the digital models in designing and simulating an orthodontic treatment plan for the patient. For example, one such technique involves receiving an initial data set that represents the patient's teeth before treatment, specifying a desired arrangement of the patient's teeth after treatment, and calculating transformations that will move the teeth from the initial to the final positions over desired treatment paths. U.S. application Ser. No. 09/169,276 also describes the creation of data sets representing the tooth positions at various treatment stages and the use of these data sets to produce orthodontic appliances that implement the treatment plan. One technique for producing an orthodontic appliance involves creating a positive mold of the patient's dentition at one of the treatment stages and using a conventional pressure molding technique to form the appliance around the positive mold. The design of orthodontic appliances from digital dentition models is described in U.S. application Ser. No. 09/169,034.

#FIGS. 1A, 1B, and 1C show a patient's dentition at three stages during a course of treatment. FIG. 1A illustrates the initial positions of the patient's teeth before treatment begins. A digital model of the teeth at these initial positions is captured in an initial digital data set (IDDS). The digital model contained in the IDDS also includes portions representing gingival tissue surrounding the patient's teeth. A computer segments the IDDS into digital models of individual teeth and the gingival tissue.

#FIG. 1B illustrates the patient's teeth at an intermediate stage in the treatment process, and FIG. 1C illustrates the teeth at their final positions. In many cases, a human operator manipulates the digital models of the patient's teeth to prescribe the final tooth positions. The computer then calculates one or more of the intermediate positions, taking into account any constraints imposed on the movement of the teeth by the human operator or by the natural characteristics of the teeth themselves. The computer also accounts for any collisions that might occur between teeth as the teeth move from one treatment stage to the next. Selecting the final and intermediate tooth positions and the treatment paths along which the teeth move is described in more detail in one or more of the applications incorporated by reference above.