Three-dimensional evaluation of marginal, internal adaptation and occlusal wear loss of 3d-printed permanent restorations produced with different finish line designs

. ABSTRACT THREE-DIMENSIONAL EVALUATION OF MARGINAL, INTERNAL ADAPTATION AND OCCLUSAL WEAR LOSS OF 3D-PRINTED PERMANENT RESTORATIONS PRODUCED WITH DIFFERENT FINISH LINE DESIGNS This study aimed to evaluate the marginal fit, internal adaptation, and occlusal wear loss of permanent 3D-printed resin crowns with chamfer and shoulder finish line designs using three-dimensional digital analyses. Eighty crowns were fabricated from four different permanent resins and divided into chamfer and shoulder subgroups. All crowns were designed in Exocad, printed with brand-specific 3D printers, and post-processed according to manufacturers' protocols. Marginal fit was assessed by generating margin curves on the die and crown and comparing them in Geomagic Control X using the "Compare → Curve Deviation" function. Sampling was performed every 10 µm along the margin, and RMS, minimum, maximum, and mean values were calculated. The clinical threshold was set at ≤120 µm. For internal adaptation, after triple-scan alignment, "2D Dimension" measurements were taken on X and Y sectional planes at five regions (mesial, distal, buccal, lingual, occlusal). For occlusal wear, all specimens underwent 240,000 chewing cycles, and volumetric loss was determined. The results demonstrated that the Formlabs and Saremco groups consistently remained within the clinically acceptable thresholds for both marginal and internal fit. Although the marginal fit values of the NextDent and Bego groups approached the upper clinical threshold, they were still considered acceptable. Nevertheless, internal fit analysis revealed deviations beyond the predefined limit, particularly in the axial and occlusal regions. The wear evaluation further indicated that the Saremco group exhibited the lowest volumetric loss, comparable to that of ceramic crowns, while the Formlabs group demonstrated wear performance within clinically tolerable levels. By contrast, the Bego and NextDent groups presented volumetric wear values that were close to the upper limit of clinical acceptability. The clinical performance of 3D-printed permanent resin crowns varies according to the resin material and finish line design. Saremco and Formlabs demonstrated superior results in terms of marginal/internal fit and occlusal wear resistance. Keywords: 3D printing, permanent resin, marginal fit, internal adaptation, occlusal wear, triple-scan, geomagic control x