The Significance of Gap and Overextension Measurement of Crowns

Objectives: An important criterion for the success of a crown is marginal fit. However, in patient's mouth, fit can only be evaluated by subjective methods. This study describes the correlation between objective marginal fit and its subjective evaluation by dentists and dental technicians. Methods: 30 human premolars and molars were prepared and randomly divided into 6 groups. For each of the groups complete crowns were made of different alloys and technologies (casting: AuAgCu, AuPdPt, PdAgAu, CoCrMo, Ti, milling: Ti). The crowns were provisional cemented. 10 dentists and 10 technicians were asked to evaluate the fit of the crowns with a new dental explorer. The crowns were cemented with a zinc-oxide-phosphate-cement. The marginal gap (MG) and a possible overextended margin (OM) were examined under a special 4X-light-microscope. The means of MGs and OMs were calculated for each group. Significances were detected by ANOVA and post-hoc-test (Bonferroni, pResults: Crowns made from different alloys and technologies showed partly significantly (pConclusion: Crowns from different alloys and technologies showed differences in marginal fit. MGs and OMs of crowns significantly correlated with the subjective evaluation of their fit by dentists and dental technicians. For the decision of the clinicians, whether a crown is acceptable, overextension was more important than marginal gap. Schlagwörter: crowns, marginal gap, overextension, correlation, marginal fit