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Effect of Endodocrown Materials on fracture strength of Endodontically Treated Teeth; comparative in vitro study

Objective: To assess the effect of different CAD/CAM endocrown materials on fracture strength of endodontically treated mandibular molars. Materials and Methods : Thirty mandibular second molars were selected and randomly divided into three groups (n=10 each). Group 1; the control group was left intact, where neither root canal treatment nor preparation were performed, Group 2 and group 3 were endodontically treated, mounted in epoxy resin blocks and prepared to receive endocrowns using CAD CAM. Groups 2 and 3 were individually scanned; endocrowns were designed and milled in Grandio Bloc with high filler loading (HFL) about 86% filler and e.max CAD blocks respectively. Each endocrown was verified for fit, and adhesively cemented using standard bonding protocol to its respective molar. Then all samples were subject to fracture resistance using universal testing machine by compressive mode under occlusally applied load at a crosshead speed of 0.5 mm/min, fracture loads were recorded in Newtons (N). Statistical analysis of variance (One–Way ANOVA) and Kolmogorov Smirnov and Shapiro- Wilk test was performed and significance level was set at 0.05. Results: there was a significant difference between different groups (f=6.54, p=0.005). The highest value was found in Grandio (2572.67±280.28), followed by the control group (2546.94±103.54), while the lowest value was found in e.max (2186.59±352.92). Post hoc pairwise comparisons showed e.max to have a significantly lower value than other groups (p<0.001). Conclusion: The use of resin composite blocks for fabrication of endocrowns improved the mechanical performance of endodontically treated molars.