Clinical convergence angle and rounding radius on tooth preparation for zirconia all-ceramic crown / 대한치과보철학회지

ABSTRACT

PURPOSE: This article attempted to examine how teeth for restoration is made in a clinical practice and utilize it as future educational material of teeth formation and basic data for additional research. MATERIALS AND METHODS: This experiment investigated the models sent to milling center for production of zirconia crowns. After scanned with Lava CAD/CAM System (3M ESPE, Seefeld, Germany), they are measured on 'ImageJ (version 1.32j, National Institutes of Health, USA)' program and compared and analyzed. Convergence angle from mesio-distal surfaces and bucco-lingual surfaces of each teeth are measured. Also, bucco-lingual diameter of the region lowered as much as 0.4 mm from incisal edge in anterior teeth except canines.(This measure is defined as the Peak 0.4) The analysis of data between each group was conducted by Windows SPSS statistic program, and was proved significant on 95% confidence level by independent t-test, one-way ANOVA and multiple analysis (Sheffe test). RESULTS: The mean value of convergence angle was 18.67degrees. It is ranked as molar (26.70degrees) > premolar (16.87degrees) > anterior teeth (14.81degrees) in the order of mesio-distal convergence angle; anterior teeth (22.32degrees) > molar (20.93degrees) > premolar (15.41degrees) in the order of bucco-lingual convergence angle. The mean value of Peak 0.4 was 1.18 mm. CONCLUSION: Convergence angle of abutment of zirconia all ceramic crown has difference depending on the location in the arch. Due to the nature of production of zirconia all ceramic crown, convergence angle of abutment and line angle finishing degree can have an effect on internal suitability of restoration.