Influence of endodontic access cavity shape and direct restoration protocol on the fracture load of molars with mesio-occlusal class II preparation

Aims: To evaluate whether the configuration of the endodontic access cavity influences the fracture strength of endodontically treated molars with class II mesio-occlusal (MO) preparation. Materials and Methods: Seventy human mandibular third molars were selected and randomly assigned to seven groups (n = 10). MO cavity preparation and endodontic treatment were standardized, except for the positive control group (GC+: sound teeth). The other groups were classified as GV- = conventional endodontic access and no restoration (negative control); GP- = “bridge” endodontic access and no restoration (negative control); GX- = conventional endodontic access and transfixed fiberglass post without restoration (negative control); GV = conventional endodontic access and restoration; GP = “bridge” endodontic access and restoration; and GX = conventional endodontic access and transfixed fiberglass post with restoration. The specimens were subjected to fracture strength testing on a universal testing machine. The fracture site – either pulp chamber floor or cusp – was inspected. Statistical analysis was performed using ANOVA and Tukey’s multiple comparison test (? = 5%). Results: Means followed by the same letter did not show statistical difference in Tukey’s test (P> 0.05): GC+: 3748A ± 326.7; GV-: 874.6D ± 74.88; GP-: 1378C ± 39.24; GX-: 1593C ± 55.28; GV: 1380C ± 78.84; GP: 1709C ± 154.4; and GX: 2403B ± 385. Conclusions: The combined use of transfixing posts and direct restoration with composite resin increased the fracture resistance of endodontically treated teeth. On the other hand, it was observed that preserving the dental structure in the vestibule-lingual direction during endodontic access did not contribute to an increase in fracture resistance.