Influence of finish line quality and axial surface location on marginal adaptation of selective laser melting fabricated copings.

BACKGROUND/PURPOSE: The digital transition in dentistry necessitates reexamining traditional preparation standards, particularly finish-line quality for 3D-printed restorations. This study investigated how finish-line characteristics affect the marginal adaptation of selective laser melting (SLM) fabricated copings. MATERIALS AND METHODS: Forty typodont maxillary central incisors prepared for porcelain-fused- to-metal crowns were scanned. Margin width, margin curvature, and finish-line curvature were measured at four axial surfaces. Finish lines were graded on a 1-4 scale based on distinctness and continuity. The maximum marginal gap at each surface of every SLM-printed coping on its respective abutment was recorded and categorized as excellent (120 μm). Friedman and Wilcoxon signed-rank tests assessed marginal gaps; repeated-measures ANOVA and McNemar-Bowker tests evaluated categorical outcomes. Generalized estimating equations (GEE) estimated odds ratios for poor adaptation (α=0.05). RESULTS: Marginal gaps on mesial (79.75±42.39 μm) and distal (86.48±32.49 μm) surfaces were significantly larger than labial (25.35±39.76μm) and palatal (39.83±52.17 μm) surfaces (P0.05). CONCLUSION: Finish-line distinctness and axial surface location were the important determinants of SLM coping adaptation. Even in digital workflows, meticulous tooth preparation remains essential, while evaluation rubrics may recalibrate the weighting of finish-line continuity and smoothness.