Variation in movement traces of the kinematic center of the temporomandibular joint.

AIM: The purpose of this study was to compare the variation in movement traces of the kinematic center of the temporomandibular joint with that of 4 nearby condylar reference points. METHODS: Jaw movement recordings were made with an optoelectronic jaw movement recording system. Four asymptomatic participants performed 14 to 18 open-close mandibular movements. The movements were performed with deliberate alterations of the rotation/translation ratio during opening. The kinematic center of the condyle and 4 nearby condylar points (the corner points of a square placed in the condylar sagittal plane, centered around the kinematic center, and with an edge length of 10 mm) were used as reference points. The standard deviations in the downward displacements at the halfway point in the mandibular opening of these reference points were calculated as a quantification of the variation in the movement tracings of these points. RESULTS: The movement traces of the kinematic center showed the smallest variation in comparison to the traces of the 4 nearby reference points (2-way analysis of variance and subsequent contrast analysis; P = 0.0026). CONCLUSION: In comparison to 4 nearby condylar reference points, the movement traces of the kinematic center show the lowest sensitivity to variations in the way mandibular movements are performed.