In vitro Evaluation of the Accuracy of Seating Cast Metal Fixed Partial Denture on the Abutment Teeth with Varying Degree of Convergence Angle

摘要

Background: The prime goal of a diligent prosthodontist is to obtain adequate marginal fit while restoring lost tooth structure. The marginal fit of the restoration, in turn depends upon the geometrical morphology of the tooth preparation. Objective: To determine the effect of varying degree of convergence angle on the marginal seating of the single crown, three-unit fixed partial denture and multiple-unit fixed partial denture with pier abutment. Materials and Methods: Three dies, of same convergence angle, were placed in an arch form on a base. In this way, four arch forms were prepared for four different convergence angles i.e. 00, 60, 120, and 200. Five castings each were made for single crown, 3-unit fixed partial denture and multiple-unit fixed partial denture (FPD) with pier abutment for each convergence angle. The castings were seated on their respective dies and vertical marginal discrepancy was measured at four points for each casting with the help of an optical microscope. Results: The results showed that 200 convergence angle showed better marginal seating of the single crown, 3-unit FPD as well as for the multiple unit FPD. Conclusion: There was a possibility that the retention and resistance may be compromised with 200 taper. Hence 120 taper is suggested for crowns and fixed partial denture retainers as the marginal discrepancy is reasonable and retention and resistance is optimum. There was a high statistical significant difference in the values obtained for the different convergence angles.