Accuracy and retention of laminate veneers made from zirconia, resin composite, and lithium disilicate using additive and subtractive techniques: An in vitro study.

Objectives To evaluate and compare the trueness and retention of laminate veneers (LVs) fabricated using four different CAD-CAM material-process combinations, including both additive (AM) and subtractive (SM) manufacturing techniques. Materials And Methods An in vitro study was conducted using a standardized maxillary central incisor preparation. Eighty LVs were fabricated (n=20/group) from: AM resin composite (AM-RC), AM zirconia (AM-Z), SM advanced lithium disilicate (SM-LDS), and SM zirconia (SM-Z). Trueness was assessed using root mean square (RMS) deviation values and color map visualization. Retention was tested after thermomechanical aging. One-way ANOVA and Tukey's HSD test were used for statistical analysis (α=0.05). Results There were significant differences in trueness and retention among groups (p<0.005). AM-RC showed the highest RMS values (e.g., internal: 38.32 ±2.2 µm) and the lowest retention (689.85 ±30.81 N). No significant differences in trueness or retention were found between SM-Z (internal: 30.12 ±2.4 µm; 782.10 ±34.12 N), SM-LDS (internal: 31.85 ±2.3 µm; 801.90 ±39.43 N), and AM-Z (internal: 32.45 ±2.5 µm; 799.45 ±33.83 N). Conclusions The material type and manufacturing method significantly influenced the adaptation and retention of LVs. AM-Z, SM-Z, and SM-LDS demonstrated comparable and clinically acceptable outcomes, while AM-RC showed inferior trueness and retention. Clinical Relevance Subtractive lithium disilicate and zirconia, as well as high-performance additive zirconia, exhibited clinically acceptable adaptation and retention, supporting their use in definitive laminate veneers. In contrast, printed resin composite showed inferior performance and should be limited to provisional applications.