Fracture resistance of CAD CAM endocrowns bonded to teeth with different number of remaining walls :An In-Vitro Study.

Abstract

Objective: The endocrown is suitable for all molars, there is no current recommendation for the minimum number of remaining walls.Materials and methods: Fifty resin specimens were divided into 5 main groups according to the remaining wall number , into; group W0 no missing walls, group W1 1 missing wall, group W2 2 missing walls, group W3 3 missing walls, group W4 4 missing walls. Ten resin dies for each group were fabricated using resin and assigned to each group. Resin dies from all groups were individually scanned using extra oral digital scanner. Monolith generation 2 zirconia endocrowns were milled accordingly using a milling machine. All the endocrowns were sintered according to the manufacturer's recommendation’s exact firing cycle. After trial fitting all endocrowns were cemented to their corresponding resin dies. After thermal cycling, each specimen was fixed to the lower fixed part of a universal testing machine with a load cell of 5 kN. at crosshead speed of 0.5 mm/min. All specimens were loaded to failure which were recorded in Newton using computer software. Data were collected, tabulated and statistically analyzed.Results: Group W1 showed higher mean values (2933±733.61) followed by W0 group (2453.5±492.48), then W4 group (2187±576) and group W2 (2108.17±451.28) and finally W3 group (1992±205.63). At 95% of confidence level One-Way ANOVA revealed significant differences between tested groups. (P= 0.033)Conclusions: There was a significant difference in fracture resistance between groups with different numbers of remaining walls.