Evaluation of fracture resistance of class V premolar restorations reinforced with Ribbond and InFibra fibers using two placement techniques: an in vitro study

Abstract Aim The study aim was to evaluate the fracture resistance of premolar teeth with class V cavities restored with two types of polyethylene fibers using two different techniques of fiber placement in comparison to traditional composite restoration. Method Seventy-five intact maxillary premolar teeth were randomly divided into five groups ( n = 15). Group 1 (control): class V cavities were filled with flowable resin composite, Beautifil flow plus F03; Group2 (Ribbond MD): Ribbond fiber placed horizontally in a mesiodistal orientation on the axial wall of the cavity; Group 3 (Ribbond OG): Ribbond fiber placed on the axial wall of the cavity in an occlusogingival orientation; Group 4 (InFibra MD): InFibra fiber placed horizontally in a mesiodistal orientation on the axial wall of the cavity; Group 5 (InFibra OG): InFibra fiber placed on the axial wall of the cavity in an occlusogingival orientation. After fiber placement, all cavities were filled with the same flowable resin composite, Beautifil flow plus F03 and cured for 10 s. Fracture resistance was assessed using a universal testing machine. Failure mode was also analyzed using magnification loupes. Results A one-way ANOVA that was performed to assess fracture resistance across the five groups, showed no statistically meaningful differences among groups (F = 0.3034, p = 0.8722), with an extremely small effect size (η² = 0.0572). Post hoc analyses with Tukey’s HSD revealed that no pairwise differences were significant ( p > 0.05). Failure mode results revealed 60% favorable fractures in the control group, Ribbond MD and Ribbond OG each demonstrated 20% favorable fractures, whereas InFibra MD and InFibra OG recorded no favorable fractures. Conclusion The incorporation of polyethylene fibers (Ribbond or InFibra) into moderately deep Class V cavities did not significantly enhance the fracture resistance of the teeth. Furthermore, the addition of these fibers was associated with a higher frequency of unfavorable fractures.