A novel technique to visualize TMJ kinematics with computer graphics

Objectives: Three-dimensional image that obtained from Computed Tomography (CT) enable us to evaluate static morphology of articulations. But it is sometime difficult to understand kinematic aspect of joint function with such static graphics. If functional movement of temporomandibular joint (TMJ) can be observed as a precise computer animation, it can provide valuable clinical information for the diagnosis TMJ pathologies. This research introduces a new method to produce 3-D TMJ movement graphics with combination of 3-D CT data and six-degree-of-freedom jaw movement data. Methods: 3-D TMJ image was obtained from an adult male volunteer (37-year-old) with spiral CT (Somatom Plus4, Siemens, Germany). Four ceramics balls, that makes spatial referential points to integrate morphologic and kinematics records, were attached to upper dentition with an acrylic jig. Location of these ceramic balls was arranged to avoid artificial effect on TMJ images. Occlusal surface of mandibular and maxillary dentition with the same subject was digitized by 3-D measuring instrument (Microcode FN503, Mitsutoyo Co, Japan). Jaw movement of this subject was recorded with an electromagnetic jaw-tracking device (CS-IIi). The positioning and posturing resolution of this device is level of 48µm for translation and 0.034 degree for rotation. Workstation computer (Octane2, SGI, USA) and graphics software (AVS/Express Developer, KGT Inc, Japan) were utilized to represent computer graphics animation of TMJ movement. Results: Detailed computer graphics of TMJ movement enables quantitative analysis of joint space during jaw movement. Conclusion: One of the unique features of this method is to present occlusal contacts graphics as well as TMJ movement. Such system enables us to evaluate TMJ loading during functional and para-functional jaw movement under occlusal contacts. Role of dental occlusion for specific TMJ problems may be clarified with this system in the near future.