Evaluation of Fracture Resistance of Indirect Ceramic Overlay Used with Different Fiber-incorporated Base Materials

Background and Objectives: Adhesive ceramic overlay restorations have become a popular, conservative alternative to full-coverage crowns, with Computer-aided design and Computer-aided Manufacture technology improving fabrication efficiency. Advances in 3D- printing show promise in replacing milled restorations. In addition to the overlay material, the base material plays a critical role in restoration performance. Current study investigates the fracture resistance of fiber-reinforced core materials with various indirect restorations and examines their correlation in failure modes and fracture behavior. Methodology: This in vitro study was conducted at Hawler Medical University / Erbil in November 2024. 100 freshly extracted maxillary premolars were included in the study. Following Mesio-Occlusal-Distal cavity preparations, teeth were restored using a range of fiber-reinforced base and overlay restorative materials. Fracture resistance was evaluated using a universal testing machine at a rate of 1 mm/min, and failure mode were examined using a stereomicroscope. Statistical analysis was conducted using one-way ANOVA and the Tukey test. Results: The study showed that zirconium and Emax overlays had significantly higher fracture resistance than indirect composite overlays, with no notable difference in resistance between the various base materials (Short fiber-reinforced composite, Polyethylene fiber core, Particulate filled composite) within the zirconium and Emax groups. While indirect composite overlay demonstrated low fracture resistance values, it exhibited the lowest tooth fracture rate compared to other restorative groups. From all of the analyzed groups, Emax+ Polyethylene ribbond core, Zirconium+ Polyethylene fiber core, Emax+ Particulate filled composite) groups showed the most promising fracture behavior and improved fracture resistance. Conclusion: Materials with higher fracture resistance often exhibit unfavorable or catastrophic fracture patterns, whereas materials with lower fracture resistance present more favorable and repairable failure modes. Keywords: 3D printed overlay, Fiber-reinforced restoration, Zirconia overlay, Fracture resistance