Comparison of convergence angle of prepared teeth for full veneer metal ceramic crowns
OBJECTIVE: To compare clinically practiced convergence angle values of tooth preparation with recommended values, and also the effect of tooth position and operator experience on convergence angle.
STUDY DESIGN: Analytical study.
PLACE AND DURATION OF STUDY: The study was carried out at the Dental clinic, The Aga Khan University Hospital, Karachi, from January to June 2007.
METHODOLOGY: A minimum of 75 crown preparation dies including 25 dies in each group of teeth (anterior, premolars and molars) were collected retrospectively which were prepared by residents and specialists of operative dentistry. AutoCAD 2007 software was used for measurement of convergence angle. One sample t-test was applied to compare the mean practiced convergence angle values with its recommended values. Two way ANOVA was applied to measure difference in convergence angle values with respect to operator experience and tooth type with the level of significance being alpha=0.050.
RESULTS: Mean reported convergence angle value was 22.72degrees, which was significantly greater (p < 0.001) than the recommended values. Statistically significant difference in convergence angle was found between anterior vs. molar teeth and between premolars vs. molar teeth (p=0.0001 and p=0.002, respectively).
CONCLUSION: There was a considerable disparity between the convergent angles values recorded in this study and the recommended guidelines. Measured convergence angle values were greater for posterior teeth as compared to the anterior teeth.