Thermocycling Effect on the Flexural Strength of Fiber-Reinforced and Conventional Flowable Composite

Abstract Aim: Flowable resin composites are widely used in restorative dentistry but are prone to mechanical degradation under oral conditions. This study evaluated the impact of thermocycling on the flexural strength of a short fiber-reinforced flowable composite compared to two conventional flowable composites. Materials and Methods: Rectangular specimens (25 × 2 × 2 mm) were fabricated using EverX Flow (Group E), Tetric EvoFlow (Group T), and Tokuyama Universal Flow (Group P) ( n = 14 per material). Half the samples were tested immediately; the other half were subjected to thermocycling with 500 cycles (5–55°C, 10 s dwell). Flexural strength was tested using a 3-point bending test. One-way analysis of variance, paired t tests, and post hoc Duncan’s test were used ( α = 0.05). Effect sizes (Cohen’s d) and 95% confidence intervals were calculated. Results: EverX Flow exhibited the highest flexural strength before (30.56 ± 9.55 MPa) and after aging (27.45 ± 4.25 MPa), with no significant reduction post-thermocycling ( P = 0.791, d = 0.30). Tetric EvoFlow showed the lowest strength post-aging (16.38 ± 2.11 MPa) with a significant reduction ( P < 0.001, d = 1.90). Tokuyama Universal Flow also exhibited a notable decrease ( P = 0.001, d = 0.84). Conclusion: The short fiber-reinforced composite demonstrated superior flexural strength and resistance to thermal aging compared to conventional flowable. EverX Flow demonstrated superior flexural strength and thermal stability, indicating its potential suitability for stress-bearing restorations.