Influence of Different Build Directions on the Fracture Load and Surface Roughness of Additively Manufactured Three-Unit Provisional Restorations: An In Vitro Study.

Purpose: To compare the influence of 0-, 45-, and 90-degree build directions on the fracture load and surface roughness of additively manufactured three-unit fixed provisional restorations and to compare the additively manufactured provisionals to provisionals fabricated using conventional methods.

Materials and methods: Mandibular typodont right second molars and premolars were prepared for a missing mandibular first molar to receive a three-unit fixed partial denture. For six groups of 10 samples each, three-unit provisionals were fabricated using additive manufacturing at 0, 45, and 90 degrees; heat polymerized PMMA; autopolymerizing resin; and bis-acryl composites resins-and tested for fracture load and surface roughness. One-way ANOVA and Tukey tests were used to analyze the data.

Results: For fracture load, the lowest mean value was for autopolymerizing bis-acryl resin (464.9 N), and the highest value was for additive manufacturing at 0 degrees (596 N). Surface roughness values were lowest for heat-polymerized PMMA (0.132 µm), and the highest value was for autopolymerizing PMMA (0.836 µm). Significant differences were found between the three build directions for fracture load and surface roughness (P = .001); in all pairwise comparisons except between 0 and 90 degrees (P = .502) for fracture load; and between all three build directions for surface roughness (P = .01). Compared to other provisional materials, a significant difference (P = .001) was observed between all groups.

Conclusions: Build direction affected the mechanical properties of additively manufactured three-unit provisionals, with provisionals printed at 0 degrees showing the highest fracture load and lowest surface roughness. Compared to other provisional materials, additively manufactured three-unit provisionals printed at 0 degrees also showed the highest fracture load, with surface roughness similar to heat-polymerized provisionals.