Fatigue-Resistance and Microleakage of CAD/CAM Ceramic and Composite Molar crowns

Purpose: Aim of this study was to determine effect of compressive cyclic-loading on fatigue-resistance and microleakage of monolithic molar ceramic and composite crowns fabricated using CEREC-3D and cemented with two adhesive resin cements. Methods: Thirty two extracted molars were prepared to receive CEREC crowns according to manufacturer's guidelines using special paralleling device (Parallel-A-Prep, Dentatus) for standardized angle of convergence. Sixteen feldspathic all-ceramic crowns (Vita Mark-II, VITA Zahnfabrik) and sixteen resin composite crowns (Paradigm-MZ100 blocks, 3M/ESPE) were made using CEREC-3D machine (Sirona Dental Systems). Eight crowns of each group were cemented to their respective teeth using self-etching resin cement (Panavia F-2.0, Kuraray) and eight crowns were cemented using self-adhesive resin cement (Rely-X Unicem Clicker, 3M/ESPE). Following storage for 1 week in water crowns were subjected to uniaxial compressive cyclic-loading in a universal testing machine (Instron) at 12 Htz for 1,000,000 cycles. Load applied at cental fossa and cycle range was 60-600N. Specimens were then subjected to microleakage testing. Data were statistically-analyzed using factorial ANOVA and Post Hoc (Tukey HSD) tests at a significance level of P<.05. Results: All composite crowns survived the compressive cyclic-loading while three ceramic crowns (37.5%) from the group cemented with Rely-X Unicem Clicker developed surface cracks at center of occlusal surfaces and extended laterally. Microleakage scores of the ceramic crowns cemented with Panavia F-2.0 were significantly lower than those of the other three groups (p<.05). Conclusions: After 1 million cycles of compressive cyclic loading Paradigm MZ100 composite molar crowns were more fatigue-resistant than Vita MarkII ceramic ones with none of 16 crowns undergoing any signs of breakdown. Microleakage scores of ceramic crowns cemented with Panavia F-2.0 were significantly lower than those of ceramic crowns cemented with Rely-X Unicem Clicker and those of all composite crowns. Acknowledgements: Egyptian Ministry of Higher Education, 3M/ESPE, Vita Zahnfabrik, Kuraray, Sirona.