Computer-monitored radionuclide tracking of three-dimensional mandibular movements. Part III: Multiple point sources--toward mapping of tooth contacts.

A method of tracking mandibular movements has been refined using a computer-assisted radionuclide kinematics technique. Several sites of interest on the same tooth of complete dentures mounted on an articulator have been simultaneously labeled with radioactive material. Accurate reproduction of the movements of the various radioactive markers was observed. The mapping of the relative displacements of the mate teeth was investigated by labeling upper and lower reciprocating teeth with a thin layer of a different radioactive material. Computer image-enhancement programs allow for following the relative trajectory in various open-close movements with increased precision and allow us to draw preliminary conclusions on the possible application of multiple sources labeling to the identification of deflective contacts.

Computer-monitored radionuclide tracking of three-dimensional mandibular movements. Part II: experimental setup and preliminary results--Posselt diagram.

This article described a new method to track mandibular movements using a computer-assisted radionuclide kinematics technique. The usefulness of various image-enhancement techniques is discussed, and the reproduction of physiologic displacements is shown. Vertical, lateral, and protrusive envelopes of motion of a point on a tooth of a complete denture mounted on a semiadjustable articulator were measured. A demonstrative example of the validity of this approach is reproducing the motion of the mental point, which clearly evidences the Posselt diagram.

Computer-monitored radionuclide tracking of three-dimensional mandibular movements. Part I: theoretical approach.

A new technique for the three-dimensional recording of a person's mandibular movement is described. A small and harmless radioactive source is fixed on the patient's skin at the point of interest or sealed in a tooth cavity. Using the proper collimation, the motion of the point source is recorded via a gamma camera and minicomputer. Long-term storage on a magnetic device offers playback, slow motion facilities, and data analysis through the use of sophisticated computer languages. Simultaneous recordings using two cameras, or postsynchronization of two different views of an experiment, enable the three-dimensional restitution of mandibular movements. Superimposition of a grid of radioactive spots spaced at measured intervals during the recording permits a straightforward calibration of the patient's motion. Multiple sources in a single experiment may be recorded to describe the displacement of several points of interest. This method, derived from nuclear medicine techniques, offers a powerful tool of general interest for the tracking of dynamic events in many fields of dentistry such as temporomandibular joint dysfunction and prosthetic restorative techniques. Further considerations on our experimental settings and results will be published in part II.