Assessment of convergence angle of full veneer preparations carried out by practitioners with different levels of experience

OBJECTIVES: To investigate the convergence angle (CA) of dies achieved by clinicians with different levels of experience and to study the effect of the number and location of abutments on the CA. MATERIALS AND METHODS: Two hundred and ninety one dies were obtained and mounted with the occlusal plane of the prepared teeth parallel to the floor. Photographs of facial and proximal aspects were taken for each die. The photographs were transferred into a personal computer and an AutoCAD software program was used to measure the bucco-lingual and mesio-distal CA of each preparation. Analysis of Variance (ANOVA) was used to test the significance at 95% confidence level. RESULTS:The greatest mean CA was in the teeth prepared by general practitioners (25.7°) while the smallest was in teeth prepared by prosthodontists (16.9°). Statistically significant difference was found among CA values of the three groups (P .0001). Statistical significant difference was also found between the CA of the preparation for single crown and for fixed partial denture abutments. No statistically significant differences were found between the CA of the anterior and posterior tooth preparations. CONCLUSIONS: The prosthodontists produced a lower convergence angle of prepared teeth compared to students and general practitioners. There is a need for all groups to exert extra effort to reduce the CA during tooth preparation. The recommended 6° taper is difficult to be achieved clinically.