Effects of clinical experience and explorer type on judged crown margin acceptability

This study was undertaken to simultaneously compare instrumentation type and operator characteristics in judgments of clinical acceptability of crowns exhibiting a controlled range of marginal gaps. The research was conducted in a laboratory setting and generalizability analysis was used as a statistical technique to identify the sources contributing to variation in the judgment outcome.

A crown was seated on an ivorine tooth in a device that permitted continuous adjustment in intervals of 25 mum to produce known marginal gaps ranging from zero to 250 microm. Forty-nine students and six faculty members used five types of explorers each to determine, by tactile examination, the point on the controlled increasing marginal gap where they would no longer regard the gap as clinically acceptable.

There were no differences across type of explorer. Operators with clinical experience had a threshold that rejected crowns at a smaller gap than did those operators without clinical experience (p= 0.007). Faculty members maintained a higher individual degree of consistency in their personal judgments than did students (p= 0.02); however, the inter-operator consistency was significantly lower for faculty members than for students (p < 0.05).

Differences among operators in a simulation of the decision regarding gaps in crowns accounted for 63% of the variance; type of explorer used in assisting this decision accounted for about half as much variance. Faculty members making such judgments exhibited high intra-operator consistency but significantly lower inter-operator consistency than did students. The study suggests that the internal standards dentists use for clinical decision making deserves further study as they may be as significant as the equipment used.