CBCT AND SEM EVALUATION OF MARGINAL AND INTERNAL FIT OF LITHIUM DISILICATE COPINGS FABRICATED WITH 2 DIFFERENT TECHNIQUES (IN VITRO STUDY)

Statement of the problem. The marginal & internal adaptation of all-ceramic crowns may vary depending on the technique of fabrication and the methodology of measurement.
Purpose. To evaluate the marginal and internal adaptation of lithium disilicate crown copings fabricated with two techniques using two measuring modalities, cone beam computed tomography CBCT and scanning electron microscopy (SEM).
Materials and methods. The materials selected were Emax CAD for CEREC inlab (Group 1) and Emax Press for the lost wax and heat pressing (Group2). 10 copings were designated for each group. The copings were cemented on standardized epoxy resin dies with self-adhesive resin cement RelyX Uncem. A CBCT system was used to obtain measurements from reconstructed slices in two orthogonal planes for each sample, and a scanning electron microscope (SEM) was used for cross-sectioned samples. Mean, SD, median, range and 95% confidence level were calculated using Kolmogrov-Smirnov test and comparison of the ceramic types and methodology of testing were accomplished with Mann-Whitney U test and Spearman correlation tests respectively the significance level being set at P<0.05.
Results. Heat pressing exhibited lower vertical gap margin in SEM 22.7um (±5.3) than Emax CAD 47um (±16.1). The overall values of misfit of Emax CAD were significantly higher than Emax press in SEM & CBCT measurements. There was statistical correlation between the two measuring methods in both the mesial, lingual and total measurements according to Spearman correlation test.
Conclusion. The Emax press has a better overall marginal and internal fit than the Emax CAD, still the values are clinically acceptable for both.