Evaluation of fit and fracture strength of three-dimensional provisional crowns printed with different orientations and different layer thicknesses: an in-vitro study

AIM: The effect of 3D printing parameters on the marginal fit and fracture resistance of 3D printed provisional crowns is not clear. The objective of this research was to use different printing orientations and layer thicknesses to build 3D printed provisional crowns and to evaluate the marginal fit and fracture resistance of it. MATERIALS AND METHODS: A maxillary first premolar resin tooth was reduced for all-ceramic tooth preparation then was scanned using intraoral scanner. 60 dies were printed using Digital Light Processing (DLP) 3D printer. One of the printed dies was scanned. The design of the crown was made then the design was exported to 3D printing software. 60 provisional resin crowns were printed using DLP 3D printer. 36 Provisional crowns were divided into 3 groups(n = 12) according to the printing orientation used: group A (0°), group B (90°) and group C (30°)0.24 Provisional crowns were divided into 2 groups (n = 12) according to the layer thickness used: group D (50 μm) and group E (100 μm). Absolute marginal discrepancies (AMD) were measured using stereomicroscope. Fracture resistance was measured using a universal testing machine. Data analysis was performed using one way-ANOVA, independent T- test and paired t-test at 0.05 using IBM SPSS version 26.0. RESULTS: One-way ANOVA revealed a significant effect of printing orientation and layer thickness on the marginal fit and fracture strength of 3D printed crowns (p < 0.001). One-way ANOVA showed that group C (60.76 [± 6.96]μm) showed significantly lower mean [± SD] absolute marginal discrepancy (AMD) in µm than group A (72.26 [± 6.07] μm) and there was no statistically significant difference between group B and group C. One-way ANOVA revealed that there was a statistically significant difference in the mean value of fracture resistance between group B and each of two other groups: group A and group C. The highest mean value [± SD] was reported with the samples of group A (977.97 [±10.69]), while the lowest mean value was reported with the samples of group B (785.10 [± 20.43]) (p < 0.001). CONCLUSION: Printing orientation and layer thickness influenced marginal fit and fracture resistance of 3D printed provisional crowns.