Variations among operators in the performance of tunnel preparations in vitro.

A study was performed to assess the variations among dentists in the performance of tunnel preparations for "caries" removal and cavity design, and to evaluate how these variations are affected by instruction and training. Twenty-seven dentists with limited clinical experience in performing tunnel preparations participated in the study. They did three partial tunnel preparations each in extracted premolars with standardized, artificial, approximal "carious lesions". The first preparation was made without instruction, the second after instruction and under supervision, and the last without supervision. After information/supervision, 26% did not manage to do a tunnel preparation without residual caries, indicating that this is not an easy procedure for beginners. The occlusal opening was significantly larger and the width of the remaining approximal wall was significantly smaller in preparations without "residual caries" than in those exhibiting "residual caries". Visibility appears to be improved by extending the occlusal opening toward the marginal ridge.