Fracture Resistance of Glass-Fiber-Reinforced Direct Restorations on Endodontically Treated Molar Teeth with Furcal Perforation

This in vitro study evaluated short-fiber-reinforced composite materials and fiber-reinforced restorations of endodontically treated molars with furcal perforation. The endodontic treatment and mesio-occlusal–distal cavity preparation of 126 two-rooted mandibular third molars were performed. Eighteen non-perforated teeth were restored with resin composite as the control group. Furcal perforations and repair were performed on 108 teeth that were divided into six experimental groups: resin composite (RC), everX Flow (EXF), everX Posterior (EXP), Bioblock (BB), modified transfixed (MT), and horizontal glass-fiber (HGF) groups (n = 18). Fracture resistance tests were performed at an angle of 30◦ using a universal testing machine under static loading, and fracture patterns were classified. Welch’s analysis of variance, Pearson chi-square, and Tamhane post hoc tests (p = 0.05) were used to analyze the data (p = 0.05). The highest fracture resistance values were seen with the HGF (596.305 N), followed by MT (540.365 N), BB (477.906 N), EXP (476.647 N), EXF (414.462 N), control (413.811 N), and RC (335.325 N) groups (p < 0.001). There was no significant difference between the BB and EXP groups or between the EXF and control groups (p > 0.05). In terms of the dominant fracture pattern, the HGF and MT groups were repairable and possibly repairable, whereas the control, RC, and EXP groups were unrepairable. The EXF and BB groups were almost equally divided between possibly repairable and unrepairable. Restorations using horizontal fiber techniques and short-fiber-reinforced materials increased the fracture resistance of endodontically treated teeth with furcal perforation.