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 tra ces of the kinematic center of the temporomandibular joint with that of 4 n earby condylar reference points. Methods: Jaw movement recordings were made with an optoelectronic jaw movement recording system. Four asymptomatic pa rticipants performed 14 to 18 open-close mandibular movements. The movement s were performed with deliberate alterations of the rotation/translation ra tio during opening. The kinematic center of the condyle and 4 nearby condyl ar points (the corner points of a square placed in the condylar sagittal pl ane, centered around the kinematic center, and with an edge length of 10 mm ) were used as reference points. The standard deviations in the downward di splacements at the halfway point in the mandibular opening of these referen ce points were calculated as a quantification of the variation in the movem ent 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 refe rence points, the movement traces of the kinematic center show the lowest s ensitivity to variations in the way mandibular movements are performed.