Effect of Salivary Ph Fluctuations and Dietary Acid Exposure on the Surface Stability, Color Stability, and Mechanical Performance of Next-Generation Universal Restorative Materials

Abstract

Background: Next-generation universal restorative materials are increasingly used in contemporary dentistry, but their stability under fluctuating salivary pH and dietary acid exposure remains an important concern. Objective: To evaluate the effects of salivary pH fluctuations and dietary acid exposure on the surface stability, color stability, and mechanical performance of next-generation universal restorative materials. Methodology: A laboratory-based experimental study was conducted at the Department of Dental Materials, from January to December 2025. A total of 160 specimens from four next-generation universal restorative materials were prepared and randomly allocated to four groups: control, acidic exposure, salivary pH fluctuation, and dietary acid exposure, with 40 specimens (25.00%) in each group. Surface hardness, surface roughness, color stability, and mechanical performance were assessed before and after experimental exposure. Data were analyzed using appropriate comparative statistical tests, with p<0.05 considered statistically significant. Results: Acidic and dietary acid exposure produced reductions in surface hardness and mechanical performance, while surface roughness and color change increased across the restorative materials. Overall, surface hardness decreased from 77.8±5.1 VHN in the control condition to 64.1±5.6 VHN after acidic exposure, while surface roughness increased from 0.19±0.04 to 0.40±0.08 µm following dietary acid exposure. Color change increased from 1.32±0.35 to 4.06±0.77 ΔE, whereas mechanical performance decreased from 122.6±9.1 to 98.3±9.5 MPa (all p<0.001). Conclusion: Acidic environmental challenges adversely affected the surface, optical, and mechanical properties of next-generation universal restorative materials, with variable responses among materials.