A clinical simulation was developed for the evaluation of amalgam restorations with defective margins. These restorations were defined as exhibiting marginal breakdown of various dimensions but having no clinically or radiographically detectable caries. Twenty-six restorations with marginal defects were evaluated by 124 dentists. A standardized patient description was presented, and the participant were requested to state their recommended treatment: no treatment, smooth or polish, or replace. Replacement decisions for amalgam restorations with marginal defects were highly variable. Treatment cost implications were significant, with a 625% difference between the high and low respondents. The appropriateness of most of the prescribed treatment needs to be evaluated in light of the Criteria developed as the recent International Symposium on Criteria for Placement and Replacement of Dental Restorations.