Fracture resistance and failure patterns of MOD composite restorations reinforced with InFibra versus ribbond polyethylene fibers: an in vitro comparative study

Abstract Recent advancements in restorative materials, particularly fiber-reinforced composites, have enhanced the reinforcement of weakened teeth and improved their ability to withstand masticatory forces. The aim of this in vitro study was to evaluate the biomechanical performance of InFibra and Ribbond in MOD cavity restorations by assessing fracture resistance under simulated masticatory loading and analyzing failure patterns. A total of 90 extracted, caries-free human mandibular molars were utilized. Standardized mesio-occluso-distal (MOD) cavities were prepared. The teeth were randomly allocated into three groups ( n = 30). Group 1 (control, restored with a bulk-fill composite Jen-Radiance Molar), Group 2 (restored with INFIBRA polyethylene fibers followed by same bulk-fill composite), and Group 3 (restored with RIBBOND polyethylene fibers followed by the same bulk-fill composite. Specimens were thermocycled for a total of 1000 cycles for a 20s. Fracture resistance testing was performed. Fracture patterns were examined under stereomicroscope. Data was analyzed using one-way ANOVA test followed by Tukey’s post hoc test to detect the significance difference between groups ( p = 0.05). Statistically significant differences in fracture resistance were observed among the three groups ( p < 0.001), with a moderate effect size. The Control group exhibited predominantly unfavorable failures (73.33%). In contrast, both the InFibra and Ribbond groups showed significantly higher percentages of favorable failures (80.00% each) compared to the Control group ( p < 0.001 for both). Adhesive failures occurred significantly more frequently in the InFibra and Ribbond (60.00%) groups. Cohesive restoration & substrate failures were significantly more common in the Control group (33.33%). Polyethylene fiber reinforcement did not improve the fracture resistance of mesio-occluso-distal (MOD) composite restorations; however, both systems significantly promoted more favorable, repairable failure patterns.