Comparison of marginal adaptation and internal fit of monolithic lithium disilicate crowns produced by 4 different CAD/CAM systems

Objectives To evaluate the marginal adaptation and internal space of crowns produced by 4 CAD/CAM systems using microcomputed tomography (mu CT) and replica technique (RT). Materials and methods Monolithic lithium disilicate crowns were milled (Ceramill, Cerec, EDG, and Zirkonzahn) (n= 10). The cement film obtained with low viscosity silicone was scanned by the mu CT system and captured by a stereomicroscope, according to RT. Two-way ANOVA followed by Tukey's test were used for statistical analysis (alpha= 0.05). A uniformity index (UI) was idealized to describe the distribution of crowns' internal space and submitted to the Kruskal-Wallis and Tukey's test (alpha= 0.05). The correlation between mu CT and RT was performed by Pearson's Correlation Coeficient (alpha = 0.05). Results Marginal adaptation and internal space were statistically significant different between the experimental groups for the mu CT and RT (p< 0.05). The medians of the 4 systems tested were within clinically acceptable range and the mean (+/- SD) highest marginal discrepancy was recorded in the Ceramill group at 133.0 +/- 71.5 mu m (mu CT) and 90.6 +/- 38.5 mu m (RT). For internal fit, the UI disclosed a better distribution of the internal space for the Zirkonzahn group (p< 0.001). There was a strong correlation between the methods (p= 0.01 andr= 0.69).