A STUDY ON RECONSTRUCTION OF THE FOUR-DIMENSIONAL MOVEMENT MODEL AND ENVELOPE SURFACE OF CONDYLE IN NORMAL ADULTS

Abstract Objective To reconstruct the envelope surface of the condyle and the four-dimensional trajectory model in mandibular border movement in normal adults. Methods Eleven healthy subjects were selected as volunteers. Cone beam CT scanning was performed on the volunteers. The 3D movement path of the mandible was recorded using a virtual articulator PN300 which was based on a 3D model of the mandible. We used Proplan CMF 3.0 software to perform this from the DICOM data generated by CBCT scans. The condylar movement distance was measured in this model during volunteers’ mouth opening, protrusion and lateral excursions. The envelope surface of the condyle was reconstructed by merging functional condylar surface at each recording moment during the whole border movement. Results In the mandibular digital models, the condyle moved downward firstly, and moved upward closed to the position of maximum mouth opening. The condyle moved forward and downward during protrusion. The working condyle rotated slightly and the non-working condyle moved forward, downward and inward during lateral excursions. The means of movement distance of 11 subjects was 19.04±4.37mm during mouth opening (including downward and upward), 9.75±2.38mm during protrusion. During lateral excursions the means of movement distance of working condyle was 2.87±1.13mm, the means of movement distance of non-working condyle was 10.85±3.25mm. The envelope surface of healthy volunteers showed a double-peak pattern. Conclusions The envelope surface of the condyle and four-dimensional movement model can be reconstructed by merging trajectory of mandible recorded from the novel virtual articulator PN300 and 3-dimensional image of mandible.