The Effect of a Green Smoothie on Microhardness, Profile Roughness and Color Change of Dental Restorative Materials

Acidic drinks are known to exert negative effects on surface properties of dental restorative materials. However, the effect of increasingly popular green smoothie drinks has not been addressed so far. The present study investigated the effect of cyclic immersions (5 min daily over 30 days) in a green smoothie drink on the surface properties of contemporary dental restorative materials, including resin composites, an alkasite, and a glass ionomer. Continuous immersion in distilled water was used as a negative control. Vickers microhardness, surface roughness, and perceptible color change in the CIE L* a* b* color space were evaluated as clinically relevant properties of the material surface. Statistically significant effects of green smoothie drink were identified for all surface properties, resulting in material-dependent changes in microhardness, as well as significantly higher surface roughness and higher color change compared to the negative control. After 30-day green smoothie immersion, microhardness values either decreased for 8–28% (for resin composites) or increased for up to 91% (for glass ionomer). The increase in surface roughness (Ra parameter) of smoothie-immersed specimens was 7–26 times higher compared to the control group. The perceptible color change (Δ E) in the smoothie group was 3–8 times higher compared to the control group. The Δ E values of the smoothie-immersed specimens ranged from 3.2 to 14.2, indicating visually notable color differences. Overall, this study demonstrated that daily exposure of dental restorations to a green smoothie drink can significantly accelerate material degradation, which is reflected as surface softening, as well as higher roughness and higher perceptible color change.