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 (μCT) 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 μCT system and captured by a stereomicroscope, according to RT. Two-way ANOVA followed by Tukey’s test were used for statistical analysis ( α = 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 ( α = 0.05). The correlation between μCT and RT was performed by Pearson’s Correlation Coeficient (α = 0.05). Results Marginal adaptation and internal space were statistically significant different between the experimental groups for the μCT 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 μm (μCT) and 90.6 ± 38.5 μm (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 and r = 0.69). Clinical relevance Because of the variability of the CAD/CAM systems available, evaluating their accuracy is of clinical interest. The 4 systems are capable to produce restorations adaptated within clinically appropriate levels. The μCT and RT are efficient adaptation methodologies.