The effects of different surface treatments on the surface properties and microstructure of restorative materials: an in vitro study

Introduction This study aims to systematically evaluate the differential effects of ultrasonic treatment, erythritol sandblasting, sodium bicarbonate sandblasting, and polishing on the surface roughness (Ra), volume loss, and surface microtopography of four dental restorative materials: composite resin, glass ionomer, ceramic, and titanium. Methods Specimens of each material were randomly assigned to the following treatment groups ( n = 16, for each group): Group A (ultrasonic treatment), Group B (erythritol sandblasting), Group C (sodium bicarbonate sandblasting), Group D (polishing), and Group E (non-surface treated control group). Ra was measured before and after treatment using a surface profilometer. Volume loss was quantified with an electronic micrometer, and surface morphology was examined by scanning electron microscopy (SEM). Data were analyzed using paired t-tests, one-way ANOVA, and two-way ANOVA to examine the main effects and interactions. Results Two-way ANOVA revealed a significant interaction between material type and treatment method for both volume loss and Ra ( p < 0.001), indicating that the treatment efficacy was material-dependent. Both sandblasting methods resulted in significantly greater surface improvement, when compared to ultrasonic treatment and polishing ( p < 0.05). Sodium bicarbonate sandblasting yielded the greatest improvement for titanium (ΔRa = −0.295) and glass ionomer (ΔRa = −0.211). Erythritol sandblasting provided effective surface leveling with more uniform and milder morphological changes. SEM confirmed the uniform abrasion after sandblasting versus scratches or residual debris after polishing or ultrasonic treatment, respectively. Glass ionomer had the highest volume loss (139–153 μm), while ceramic had the lowest volume loss (14–17 μm). Conclusion Sandblasting was overall superior to ultrasonic and polishing treatments, as evidenced by the improved Ra, controlled volume loss, and supporting micro-topographical observations. Sodium bicarbonate sandblasting is suitable for reducing aggressive roughness, while erythritol sandblasting is preferable for minimal and uniform surface treatment. Among the tested materials, ceramic had the best wear resistance and surface stability across all surface treatments.