Evaluation of Convergence Angles of full Ceramo-Metal Crown Preparations by Dental Students (Preclinical Stage)

Abstract

Bacckground & aim: The angle of convergence of walls for full preparations, which is recommended by many researchers in fixed prosthodontics, is up to 6 degrees, and in the academic work we rely on estimating the angle of convergence without effective methods for accurate calculations. This study aimed at determining the angle of convergence of teeth prepared on artificial acrylic teeth by students of the Faculty of Dentistry of the Syrian Private University at the end of the laboratory stage and comparing the results with similar studies conducted in other universities.

Materials and Methods: 120 sculptures of prepared teeth to receive ceramo-metal crown

(30 Upper central incisors, 30 upper canines, 30 upper premolars, and 30 upper molars) were subjected to the study. A digital camera (Canon eos 600 D sigma®) was used to capture 2 photos for the sculptures; namely bucco-lingual and mesio-distal shots. The camera was vertically positioned upon the sculpture and always was on a constant distance of it. All images were transferred to the computer and analyzed by means of AutoCAD software program to specify all convergence angles for all teeth. T-test was used to examine the differences of means between convergence angles obtained and the standard convergence angle that is usually mentioned in the literature (i.e 6◦).

Results: The mean of mesio-distal and bucco-lingual convergence angle for all teeth was 17.21 and 2.51 degree and the mean of convergence angle for central incisors, canines, premolars, and molars are 17.43, 16.88, 18.93, and 14.38 respectively. The mean of mesio-distal convergence angle for central incisors, canines, premolars, and molars are 19.50 , 19,62 , 21.27,  25.72 respectively. The mean of  bucco-lingual convergence angle for central incisors, canines, premolars, and molars are 15.10, 14.14, 16.60, 23.03. T-test statistically indicated a significant difference in convergence angle values between the results and recommended guideline.

Conclusion: The students in the last preclinical stage could not reach the recommended guideline (convergence angle). However, the results were almost similar to other studies in other universities.