Fit of crowns and clinical evaluation by dentists and technicians

Introduction: An important criterion for the success of a crown is marginal fit. However, in the 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. Materials and methods: 30 human premolars and molars were randomly divided into 6 groups and prepared with a shoulder. For each of the 6 groups complete crowns were made of different alloys and technologies (casting: AuAgCu, AuPdPt, PdAgAu, CoCrMo, Ti and milling: Ti). The crowns were cemented with provisional cement. 10 dentists and 10 technicians were asked to evaluate the fit of the crowns with a new dental explorer. The crowns were then cleaned and cemented with a zincoxide phosphate cement. The marginal gaps of the crowns were examined under a computerized light microscope (x560). The means of the gaps were calculated for each group. Means of the gaps were calculated for each alloy and statistically compared using H-Test and U-Tests (pResults: Crowns made from different alloys and technologies showed partly significantly (pConclusion: Crowns from different alloys and technologies showed differences in marginal fit. The number of crowns with a satisfactory estimated marginal gap was decreasing with an increasing width of the marginal gap. It is suggested that within crowns with a small ( 90 µm) clinicians may use other criteria rather than marginal gaps to evaluate the fit of crowns. In this case over- or under contouring of crowns has possibly more importance in the clinical decision. Keywords: cast crowns, marginal gap, cement width, marginal fit