Fracture Resistance and Failure Mode of Endocrown Restorations with Different Remaining Walls and Finish Lines

Abstract

Objective: Endocrown is a conservative treatment plan for endodontically treated teeth. The aim of this study was to evaluate the fracture resistance of four different preparation designs of endocrown restorations in mandibular molars. Methods: Thirty-six endodontically treated molars were divided into two groups (L, MD). In group L, the lingual wall and in group MD, mesial and distal walls were removed up to 1 mm above the CEJ. For each group, 2 subgroups (n=9) were considered: B) 2mm occlusal reduction with but joint finish line, S) axial reduction with radial shoulder finish line, in addition to 2mm occlusal reduction. Digital impression was performed, followed by designing and milling the lithium disilicate blocks. After cementation of the restorations and thermocycling, fracture resistance and failure mode were investigated. Results: Groups LB and LS, showed significantly higher fracture resistance compared to groups MDB and MDS (P=0.02). However, the type of finish line did not have a significant effect on the fracture resistance in the experimented groups (P=0.232). Conclusion: Unlike the finish line type, the number of remaining axial walls had a significant effect on fracture resistance. Although most of the fractures were catastrophic, they occurred due to forces much greater than usual.