The Effect of Polyethylene Fiber and Flowable Resin Composite on Fracture Resistance in the Restoration of Large MOD Cavities.

Objective: This in vitro study aims to evaluate the effect of placing polyethylene fibers used in large Class II MOD (mesio-occlusion-distal) cavities into different flowable resin composites and in different positions on the fracture resistance of the restoration.

Materials and methods: Ninety healthy human molars were used in the study. No treatment was performed on 10 of these teeth and they were used as the control group. The other 80 teeth were divided into 8 groups by opening large MOD cavities (n = 10). The groups were divided into 4 main groups according to the use of fiber strips; no fiber, placed in the buccolingual direction, placed in the mesiodistal direction, and placed in an "O" shape on all walls. Each main group was divided into two subgroups according to the use of the nanofill flowable composite or flowable short fiber resin composite (SFRC) as the base material. All teeth were aged with a thermal cycler and then fractured with a universal testing machine. Fracture types were recorded in terms of fracture strength and repairability. Kruskal-Wallis, one-way ANOVA, and Tukey post hoc tests were used to compare fracture strength values (p < 0.05).

Results: The highest fracture resistance was observed in the control group (2888.67 ± 395.43 N). The control group was significantly higher than all groups except the 7th and 8th groups (p < 0.05). Among the restored groups, the highest mean fracture resistance values were observed in the 8th group (2463.92 ± 332.37 N). The 8th group was statistically significantly higher than the 1st and 2nd groups (p < 0.05). There was no statistically significant difference between any of the other restored groups (p > 0.05).

Conclusions: The application of polyethylene fiber in the treatment of teeth with large MOD cavities in different positions did not result in a significant difference in fracture resistance.