In vitro fatigue and fracture testing of temporary materials from different manufacturing processes in implant-supported anterior crowns

Objectives The aim of this study was to investigate the in vitro fatigue and fracture force of temporary implant-supported anterior crowns made of different materials with different abutment total occlusal convergence (TOC), with/without a screw channel, and with different types of fabrication. Materials and methods One hundred ninety-two implant-supported crowns were manufactured (4° or 8° TOC; with/without screw channel) form 6 materials ( n = 8; 2 × additive, 3 × subtractive, 1 × automix; reference). Crowns were temporarily cemented, screw channels were closed (polytetrafluoroethylene, resin composite), and crowns were stored in water (37 °C; 10 days) before thermal cycling and mechanical loading (TCML). Fracture force was determined. Statistics: Kolmogorov–Smirnov, ANOVA; Bonferroni; Kaplan–Meier; log-rank; α = 0.05. Results Failure during TCML varied between 0 failures and total failure. Mean survival was between 1.8 × 10 5 and 4.8 × 10 5 cycles. The highest impact on survival presented the material ( η 2 = 0.072, p < .001). Fracture forces varied between 265.7 and 628.6 N. The highest impact on force was found for the material ( η 2 = 0.084, p < .001). Conclusion Additively and subtractively manufactured crowns provided similar or higher survival rates and fracture forces compared to automix crowns. The choice of material is decisive for the survival and fracture force. The fabrication is not crucial. A smaller TOC led to higher fracture force. Manually inserted screw channels had negative effects on fatigue testing. Clinical relevance The highest stability has been shown for crowns with a low TOC, which are manufactured additively and subtractively. In automix-fabricated crowns, manually inserted screw channels have negative effects.