Effect of protein supplements on the surface roughness of three nanohybrid composite resins: in vitro study

Introduction: protein supplements are viscous and acidic in nature, posing a potential risk for increasing the surface roughness of composite resins. Objective: to compare the effect of immersion in protein supplements on the surface roughness of three nanohybrid composite resins in an in-vitro study. Methods: one hundred eighty discs (6 mm x 2 mm) were fabricated from Filtek Z250XT, Tetric N-Ceram, and Forma Zirconia resins. Each resin was divided into three groups (n= 20) according to the immersion medium: artificial saliva (control), whey-based supplement (pH 6,4), and plant-based supplement (pH 5,9). Specimens were immersed for one hour daily over 21 days. Surface roughness (Ra, µm) was measured with a profilometer at baseline and after 7, 14, and 21 days. Repeated-measures ANOVA and post-hoc tests were applied (p < 0,05). Results: surface roughness increased significantly over time in all three resins (p < 0,001). At 21 days, the whey-based supplement produced the highest roughness values in Filtek Z250XT (0,57 µm), Tetric N-Ceram (0,58 µm), and Forma Zirconia (0,67 µm). The greatest overall roughness (0,69 µm) was observed in Forma Zirconia immersed in the plant-based supplement. Minimal changes were recorded in the artificial saliva control. Conclusions: daily exposure to protein supplements increases the surface roughness of nanohybrid composite resins. The whey-based supplement was the most aggressive medium, and Forma Zirconia was the most affected resin. The acidic pH and high viscosity of the supplements appear to contribute to surface degradation, suggesting that prolonged contact with composite restorations should be avoided.