Fracture Resistance and Failure Modes of Cuspal-coverage Restorations Using Fiber-reinforced and Non-fiber-reinforced Materials: An In Vitro Study.

Background: The purpose of this in vitro study was to determine the fracture resistance and failure mode of direct cuspal-coverage restorations utilizing fiber-reinforced and non-fiber-reinforced materials.

Materials and methods: Fifty extracted human mandibular third molars were prepared for mesio-occlusal-facial single cuspal-coverage restorations. Ten cuspal-coverage restorations were constructed per group using the following restorative material types: nanofill composite (NC), nanometer-scale, short-fiber-reinforced composite (NS-SFRC), micrometer-scale, short-fiber-reinforced composite (MS-SFRC) dentin base covered with a nanofill composite (MS-SFRC + NC), polyethylene fiber-based leno-weave covered with nanofill composite (PF + NC), and bonded amalgam (AM). After thermocycling and cyclic fatiguing, fracture load testing was performed on the specimens utilizing a universal testing machine. Then, each specimen was examined to determine failure mode. Data were analyzed with a one-way analysis of variance and Tukey's post hoc tests (α = 0.05).

Results: The highest fracture load was found in MS-SFRC + NC group (1112.9 ± 249.3 N), which was significantly greater than all other groups (p < 0.011). The NC group had the lowest fracture load (651.7 ± 228.3 N), but it was not significantly different from NS-SFRC (701.6 ± 209.4 N, p = 0.989), PF + NC (754.7 ± 267.7 N, p = 0.862), or AM (749.3 ± 213.7 N, p = 0.884). The MS-SFRC + NC group had the greatest percentage of adhesive failures (70%), and the AM group had the greatest percentage of cohesive failures (80%). The NS-SFRC group had the greatest percentage of failures of the tooth/restoration complex with periodontal involvement (40%) and both the NC and PF + NC had the greatest percentage of failures of the tooth/restoration complex without periodontal involvement (20%).

Conclusions: The MS-SFRC + NC group had the highest fracture load and was significantly greater than all other groups-which were not significantly different from each other: MS-SFRC + NC > PF + NC = AM = NS-SFRC = NC. The observed fracture mode for the MS-SFRC + NC group was predominantly adhesive, resulting in an overall repairable failure mode.

Clinical significance: Limited research is available evaluating the fracture resistance and failure mode of single cuspal-coverage restorations using fiber-reinforced materials. For enhanced strength in cuspal-coverage composite restorations, a micrometer-scale, short-fiber-reinforced composite dentin base combined with an overlay of an NC may be advantageous. How to cite this article: Pierce AL, Kosaraju A, Gedge JL, et al. Fracture Resistance and Failure Modes of Cuspal-coverage Restorations Using Fiber-reinforced and Non-fiber-reinforced Materials: An In Vitro Study. J Contemp Dent Pract 2025;26(1):4-9.