[Evaluation of reproducibilty of the hinge-axis and it's positional relation to condyles]

The aim of this paper was to study the reproducibility of the positions of hinge-axis of mandibular retruded small open-closed movements, and the positional relationship between the hinge-axis and condyles. Fourteen normal students were tested by a six degrees of freedom mandibular movement recorder MT1602 (Germany). The result showed that: the hinge-axis could not be exactly repeated and movable instantaneous centers of rotation (ICR) were recorded. These rotation centers distributed almost evenly around the condyles, the mean distance from these rotation centers to condyle centers was about 8.83 +/- 5.65 mm.