Development of quantitative evaluation method for occlusal morphology and occlusal tooth contacts

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Overall object of this research is to develop objective method for the evaluation of dental occlusion. Followings are outcomes of this research project.1. New workstation computer that was purchased with this budget improved data processing speed of stomatognathic diagnostic system.2. Occlusal facets on molar region were classified into six different types (AM, AD, BM, BD, CM, CD) according to the direction of its normal vector and its position. A, B and C represents medio-lateral position of each facet and direction of the normal vector of it, and M and D represents antero-posterior direction of the normal vector.3. Three-dimensional shape of occlusal surface and six degrees of freedom jaw movement data were combined to analyze dynamic transition of occlusal contacts '' during mastication. Distance between opposite occlusal surfaces and incident angle of the jaw closing f movement pathway were calculated with this method. These numerical parameters were utilized for the evaluation of … More occlusal contact during mastication. The results are as follows1) During fourth phase of chewing stroke, distance between opposing occlusal surfaces were shorter at AM and CM type occlusal facets. This tendency was remarkable at AM type facet on functional cusp of lower molar.2) During fourth phase of chewing stroke, angle between the jaw movement pathway and AM and CM type occlusal facets were relatively small (about 10 degrees). These angles of AD and CD type facets were ranged from 20 to 30 degrees.3) Incident angle of the terminal jaw closing movement was 30 degrees at BD type occlusal facet, and 40 degrees at BM type facet.4) During fifth phase of chewing stroke, distance between opposing occlusal surfaces was shortest at BD type occlusal facet. During fourth phase of chewing stroke, AM type occlusal facet on functional cusp of lower molar and opposing upper molar work as the functional guidance of masticatory movement. This finding suggest that functional property of these facets are mortaring and grinding. On the other hand, BD type occlusal facet works for squeezing, crushing and functional guidance for fifth phase of chewing stroke. The results of this study exhibit rational classification method for occlusal facet and functional properties of each occlusal facet were revealed. These findings provide valuable data to develop objective evaluation method for occlusal tooth contact. Less