Evaluation of Marginal and Internal Fit of a CAD/CAM Monolithic Zirconia-Reinforced Lithium Silicate Porcelain Laminate Veneer System

Purpose To evaluate the marginal and internal fit of monolithic computer-aided design/computer-aided manufacturing (CAD/CAM) ZLS (Vita Suprinity) glass ceramic porcelain laminate veneers (PLVs), in terms of marginal and internal gap widths, in comparison to monolithic lithium disilicate (LDS) [IPS e.max CAD] CAD/CAM veneers, and, also, to analyze the effect of incisal preparation designs (butt joint and chamfer), on the marginal and internal fit accuracy. Materials and Methods Forty dental stone dies poured from impressions made of two master metal dies with different incisal preparation designs were scanned to produce digital models. Forty ceramic veneers were designed and milled using the virtual models-10 ZLS butt joint, 10 ZLS chamfer, 10 LDS butt joint, and 10 LDS chamfer. The monolithic ceramic veneers produced were then subjected to marginal and internal gap width evaluation using X-ray nano-computed tomography and computerized digital analysis (n = 10). Descriptive analyses of data were performed and the influence of "material" and "preparation design" on the marginal and internal fit of veneers was assessed using 2-way ANOVA (alpha = 0.05). Bonferroni post-hoc multiple comparison tests were used to further analyze the interactions between the material and preparation design after adjusting the alpha value by Holm-Bonferroni method (alpha = 0.01). Results Mean marginal and internal gaps for ZLS PLVs were 65 +/- 11 mu m and 112 +/- 14 mu m for butt joint, and 100 +/- 24 mu m and 100 +/- 21 mu m for chamfer, respectively. Corresponding values for LDS PLVs were 78 +/- 25 mu m and 114 +/- 17 mu m for butt joint, and 104 +/- 18 mu m and 106 +/- 7 mu m for chamfer. Marginal gap and internal gap differences between ZLS and LDS PLVs were not significant (marginal gap: F = 1.786, p = 0.190; internal gap: F = 0.807, p = 0.375). However, the preparation designs (butt joint and chamfer) differed significantly in terms of marginal gaps (F = 23.797, p = 0.000), but not internal gaps (F = 3.703; p = 0.059). Conclusions Butt joint margins produced better marginal accuracy in terms of marginal gap, compared to chamfers, for ZLS CAD/CAM laminate veneers.