Digital assessment of subtractive and additive CAD/CAM fabrication methods on the fit and accuracy of lithium disilicate veneers

Abstract

This study compared subtractive and additive fabrication methods regarding their impact on the marginal/internal fit, trueness, and precision of lithium disilicate ceramic veneers. Laminate veneer preparations on an acrylic tooth were duplicated into twenty-four additively manufactured resin dies. Veneers were digitally designed and fabricated via milling (subtractive) or 3D-printing (additive) (n=12/group). All veneers were scanned. For trueness, the final design served as the reference; for precision, pairwise comparisons were made within each group. For adaptation, the scanned die was the reference. Post-cementation and thermal cycling (10,000 cycles, 5–55°C), marginal adaptation was measured using a digital microscope (×100). Data were analyzed using an independent t-test (p < 0.05). Milled veneers exhibited significantly superior trueness (52.86 ± 5.54 μm vs. 55.51 ± 3.54 μm) and precision (31.90 ± 5.90 μm vs. 81.87 ± 27.39 μm). However, pre-cementation fit showed no significant differences in internal (27.28 ± 3.49 μm vs. 28.53 ± 1.56 μm) or marginal adaptation (35.79 ± 0.47 μm vs. 36.27 ± 0.82 μm). Post-cementation marginal adaptation remained comparable (31.97 ± 1.21 μm vs. 32.57 ± 0.69 μm). Milled veneers showed superior manufacturing accuracy. However, lithium disilicate veneers fabricated with both subtractive and additive methods demonstrated clinically equivalent and acceptable marginal and internal fit, both before and after cementation. Despite greater production variability, the 3D-printed veneers achieved a final fit comparable to milled veneers within clinically acceptable limits. This establishes additive manufacturing as a viable alternative that reduces material waste and increases production efficiency without compromising marginal integrity.