Two- and three-body wear of BPA-free resin composites

OBJECTIVES: This study evaluated wear resistance, surface hardness, and wear-induced roughness and morphology of nine BPA-free resin composites and one conventional Bis-GMA-based composite with high wear resistance (Clearfil AP-X, control). METHODS: Two- and three-body wear tests were performed using the ACTA wear machine (ISO/TS 14569-2). Wear depth and surface roughness (Ra) were measured via profilometry, and surface morphology was analyzed using scanning electron microscopy (SEM) after each wear experiment. Vickers hardness was assessed on separate specimens at the same time points as the wear measurements. Data were analyzed using ANOVA with post-hoc tests and linear regression to explore relationships between wear, hardness, and filler content. RESULTS: Clearfil AP-X showed the lowest three-body wear (28.2-36.0 µm) and highest hardness (109 HV). Among BPA-free composites, Clearfil Majesty Flow (37.9-42.2 µm) and Venus Diamond (36.9-42.9 µm) demonstrated the highest wear resistance. Three-body wear moderately correlated with filler volume (R² = 0.51) and hardness (R² = 0.50), while two-body wear showed weak correlation. Surface roughness increased significantly after three-body wear, especially in micro-hybrid composites. SEM revealed matrix degradation, filler exposure, and crack formation. SIGNIFICANCE: BPA-free composites showed variable wear performance. Clearfil Majesty Flow and Venus Diamond performed similarly to the Bis-GMA-based control. While filler volume ratio and hardness are among key determinants of wear behavior, it is evident that other factors also play a role. Further in vivo studies are needed to confirm long-term clinical performance and safety of BPA-free materials.