Effect of varying intraoral scanner tip size, tooth location and preparation design on the marginal and internal fit of 3D-printed zirconia crowns.

The aim of this research was to evaluate the effect of different size of intraoral scanner tips, tooth location, and preparation design on the marginal and internal fit of 3D-printed zirconia crowns. A total of 120 zirconia crowns were designed and fabricated using a stereolithography-based additive manufacturing workflow; according to standard tessellation language (STL) data obtained with three tip sizes of an intraoral scanner, 2 tooth locations (maxillary central incisor and canine), and 2 preparation designs (standard and rounded) (n = 10). Marginal and internal fit of the crowns were evaluated using a three-dimensional digital measurement approach. STL files were analyzed in 3D analysis software (Geomagic Control X; 3D Systems, Rock Hill, SC, USA) to calculate root-mean-square (RMS) values within the selected marginal and internal regions following superimposition. Data were analyzed using three-way ANOVA and post hoc Tukey tests (α = 0.05). Scanner tip size had a significant effect across all regions (P = 0.013), with the small tip producing significantly higher discrepancies. Canines showed larger marginal, axial, and incisal gaps than central incisors (P = 0.025). Rounded preparation designs demonstrated significantly lower marginal gap values compared with standard preparations (P = 0.001). The marginal and internal fit of additively manufactured zirconia crowns is affected by intraoral scanner tip size, tooth location, and preparation design. Careful selection of scanner tip size and preparation geometry may improve the accuracy of digitally fabricated zirconia restorations.