The impact of restoration protocols on the fracture resistance of root canal treated anterior teeth: an in vitro study

This study aimed to evaluate the fracture resistance of endodontically treated maxillary central incisors restored with various post-and-core configurations and computer-aided design/computer-aided manufacturing (CAD/CAM) resin composite crowns. Additionally, it assessed whether restoration design influences mechanical performance. Twenty-one maxillary central incisors underwent endodontic treatment and were allocated into three groups (n = 7). The FRCP group received a fiber-reinforced composite (FRC) post with a composite core; the NRCC group received a nanoparticle zirconia-reinforced composite core alone; and the FRCC group received an FRC core alone. Following fabrication of CAD/CAM resin-composite crowns, the specimens underwent 10,000 thermal cycles. Specimens were loaded to failure in a universal testing machine, and fracture patterns were examined under a stereomicroscope. Restoration type significantly influenced fracture resistance (p = 0.014). Mean fracture loads were 612.36 ± 87.80 Newtons (N) for FRCP, 516.98 ± 80.34 N for NRCC, and 465.65 ± 84.95 N for FRCC. The fiber post-composite core configuration exhibited higher fracture resistance compared to composite core materials alone. However, all groups withstand loads exceeding typical anterior biting forces, suggesting that reinforced composite cores may serve as viable alternatives for restoring endodontically treated maxillary central incisors.