Studies on quantification of evaluation of dental occlusion

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The aim of this research was to investigate a quantitative evaluating method of dental occlusion. Methods: Subjects were healthy volunteers (males, female 3, avenged age 22±2.27). Occlusal surface of each subject were digitized with the 3D lazier scanner (Model LPX-1200, Roland DC cooperation) and dental casts. Jaw movements during mastication were recorded with a newly developed 6-degree-of freedom Jaw tracking device, which consisted of a pair of biaxial mils- Those data were linked to analyze occlusal area during mastication with a newly developed custom software. At the same time, masticatory efficiency was measured with a hydrocolloid impression material method, that was one of applications of the sieving test The test food was hydrocolloid impression material (Aromaloid, GC Corporation, Japan), the size of it was l0mm (height) xl3mm (diameter)- Spearman rank correlation was used to evaluate the relationship between masticatory efficiency and an area of occlusion. (SPSS 15.0J, SPSS Inc). Result and discussion: The cumulative area of occlusion during mastication was correlated with the number of pieces of chewed impression material, although the occlusal area at the intercuspal position was not correlated with the masticatory efficiency clearly. At 10 times chewing, occlusal area of 1000 to 1250 μm distance section was correlated with the number of pieces positively, while that of under 250 μm distance section was correlated with the number of pieces negatively. On the contrary, at 20 times chewing, occlusal area under 250 μm distance section was correlated with the number of pieces positively. Those results suggested that the occlusion could not be evaluated without functional movements, and cumulative area of occlusion during mastication could be one of quantitative parameters for evaluating occlusion in functional aspect But it also suggested that chewing phases are very important to formulate a definition of parameters.