Comparison of the Fracture Strength and Fracture Mode of Endodontically Treated Maxillary Incisors Restored with Cast Metal and Glass Fiber Post

Background: Restoration of endodontically treated teeth with post and core systems is integral to restorative dental practice. Endodontically treated teeth are more susceptible to biological and mechanical failure and exhibit a higher fracture risk than vital teeth. The purpose of this study was to compare the fracture strength (FS) of endodontically treated maxillary incisors restored with cast metal post (CMP) and glass fiber post (GFP) with composite core using a Universal Testing Machine (UTM) and evaluate their fracture mode (FM). Methods and Results: Sixty human maxillary incisors were extracted for periodontal reasons and selected based on their similar root canal morphology. All study teeth were randomly divided into two groups. Group 1 (n=30) was restored with CMP, and Group 2 was restored with GFP. The posts were luted with the adhesive resin cement Speedcem Plus. Prepared samples were subjected to a compressive load using a UTM (H001B:1000kN, Matest, Italy). Loads were applied at an angle of 135° in the middle of the lingual surfaces of the samples at a crosshead speed of 0.5 mm/min. Fracture loads and modes were recorded. The maximum load necessary to fracture for each specimen was measured in Newtons (N). Fractures were classified as restorable in the incisal third of the root and catastrophic if located apical to that point. The median FS of Groups 1 and 2 were 161.87±1.36N and 1220.83±2.04N. A comparative analysis of the FS values between CMP and GFP groups showed that the influence of post type on FS was significant (P=0.000). Group 2 exhibited higher strength values. All catastrophic fractures (n=5) belonged to Group 1. In Group 1, 40% of fractures were in the apical third and middle of roots. In Group 2, all fractures occurred in the incisal third of the roots. Conclusion: The results have clinical implications for the selection of materials in dental practices, particularly in contexts where the material's mechanical strength is a critical factor in clinical outcomes.