Method of Objectively Evaluating Tooth Preparation during Clinical Training

Purpose: Evaluation of tooth preparation during clinical training of students and residents is prone to subjective judgments by instructors. The purpose of this study was to develop an objective method of evaluation using numerical criteria.Materials and Methods: As the first step, phantom epoxy resin teeth (PC-23, Nisshin Inc., Japan) from the same lot were subjected to three-dimensional morphometry using a high-speed laser scanner (Surfracer, Unisn, Osaka, Japan). A 3-D reconstruction was then made using the digitized data for each tooth. These data were superimposed with the reference axis at a right angle to the center of the base of the teeth. The taper angle of the preparation surface was evaluated every 45° around the axis, and the position of the margin was evaluated every 5° compared with data obtained from the instructor's standard preparation. Evaluations were made using numerical parameters.Discussion: One tooth was prepared by an instructor (IN) and one by a resident at the beginning of the training (R0) and after three months of training (R3). The mean difference in the taper of the preparation between IN and R0 was +14.8°, while it was +2.7° between IN and R3. The difference in the margin location between IN and R0 at the 72 sites was 118.1mm, while it was 78.8mm between IN and R3. The value of the margin was determined by the differences between IN and R (R0, R3) preparations.Conclusion: Using the difference in the numerical values between the abutment teeth, an objective and longitudinal evaluation is possible for technical assessment of tooth preparation during clinical training.