Maximum Fracture Load of Interim Crowns Fabricated by Additive and Subtractive Techniques

Abstract

To evaluate fracture load values of five types of interim CAD/CAM crowns with and without thermocycling. Materials and Methods: A complete coverage crown was designed on a mandibular first molar with a uniform 1.5-mm axial and occlusal reduction, and the STL file was exported to manufacture 100 crowns using five materials (20 crowns per material): ZCAD Temp Esthetic (SM-ZCAD; Harvest Dental); Telio CAD (SM-TCAD); P pro Crown and Bridge (AM-PPRO); E-Dent 400 C&B MHF (AM-EDENT); and DENTCA Crown & Bridge (AM-DENTCA). Each group was then divided into two subgroups: before and after thermocycling (10 cornws per subgroup). The STL file of the mandibular first molar die was used to manufacture 100 resin dies. Each die was assigned to one interim crown. Interim crowns were then luted to their assigned die using a temporary luting agent. The fracture strength of crowns was then assessed using a universal testing machine at a crosshead speed of 2 mm/minute. Two-way ANOVA followed by Tukey multiple comparations post-hoc tests were used to assess the effect of material choice and thermocycling process on the fracture strength of interim crowns (α = .05). Results: Material choice and the thermocycling process exerted a significant (P < .001) impact on the fracture strength of interim crowns. However, the interaction between these two factors did not yield a statistically significant effect (P = .176). Conclusions: Within the limitations of this study, the type of interim materials and thermocycling process have a significant impact on the fracture strength of interim crowns.