Effect of Combined Use of Reinforcement Materials on the Fracture Resistance of MOD Cavity Restorations in Endodontically Treated Teeth

Abstract

Objective Bucco-lingual/palatinal vertical fractures are among the most common fractures found in mesio-occluso-distal (MOD) cavity restorations of endodontically treated teeth. This study aimed to compare the effects of different new-generation reinforcement materials applied to two cervical and coronal segments of the teeth on the fracture resistance of endodontically treated teeth in their coronal restorations. Materials and methods A total of 84 freshly extracted, intact human mandibular molars were selected and treated endodontically according to standardized protocols. Standard MOD cavities were prepared, and the specimens were then randomly divided into seven groups (n = 12) based on the combinations of reinforcement materials applied to the cervical or coronal segments, and a control group. The control group had intact teeth. The experimental groups included combinations of flowable composite (Flow), posterior composite (PC), EverX flow (Xflow), EverX posterior (XP), PC, and Ribbond (RIB). After thermocycling, fracture resistance was evaluated using a universal testing machine, and failure patterns were examined under a stereomicroscope. Data were analyzed using the Kruskal-Wallis H test, following a Shapiro-Wilk test that indicated the data did not follow a normal distribution (p < .05). Results A statistically significant difference was observed between the groups (p < .05). Group 5, which had RIB flow and XP restoration structure, exhibited the highest fracture resistance (1827.90 N), while Group 1, which had Flow and PC restoration structure, demonstrated the lowest fracture resistance (1121.98 N). Fiber-reinforced structures demonstrate superior fracture resistance compared to the other groups (p < .05). There was no significant difference between conventional restoration and Ribbond in the coronal segment (p > .05). ConclusionUsing fiber-reinforced restoration in the cervical segment increases fracture resistance more than in the coronal segment. Fiber-reinforced composites are easily packable and demonstrate higher fracture resistance than Ribbond. Clinical relevanceResin-reinforced composite combinations used in cervical and coronal applications improve fracture resistance and can be safely applied for MOD cavity restoration of endodontically treated teeth.