Surface roughness and biofilm formation on tooth-colored restorative materials immersed in food-simulating liquids

This study aimed to evaluate the surface roughness and biofilm formation of different restorative materials immersed in food-simulating liquids (FSLs), and to investigate the relationship between these parameters.

A total of 220 disc-shaped specimens (8 mm diameter × 2 mm depth) were prepared using five restorative materials: alkasite [Cention N], giomer [Beautifil II], ormocer [Admira Fusion], direct composite [G-ænial A'Chord], and indirect composite [Gradia Plus] (n = 44 per material). Each material group was divided into four subgroups (n = 11), immersed in one of four solutions-heptane, ethanol, citric acid, or artificial saliva (control)-for 7 days, resulting in a total of 20 experimental subgroups. In each subgroup of 11 specimens, 10 were used for both surface roughness measurements (before and after immersion) and bacterial adhesion assessment using the colony-forming unit (CFU) method, while one was reserved for scanning electron microscopy (SEM) analysis. Additionally, data were tested for normality using the Shapiro-Wilk test, and statistical analyses were performed using robust ANOVA and Bonferroni post hoc tests (p < 0.05).

Alkasite and giomer exhibited significantly higher surface roughness values, whereas indirect composite presented the lowest (p < 0.001). Regarding the immersion solutions, citric acid led to the most pronounced increase in surface roughness compared to the other solutions, while heptane had the least impact (p < 0.001). Consistent with these findings, alkasite and giomer demonstrated the highest levels of bacterial adhesion, in contrast to direct and indirect composite, which showed the lowest (p = 0.008). Furthermore, citric acid resulted in the greatest microbial retention among the solutions, and heptane the least (p < 0.001).

The restorative materials exhibited varying degrees of susceptibility to the tested solutions. Alkasite and giomer showed the most pronounced surface changes, whereas the indirect composite group was the least affected. Among the solutions, citric acid caused the greatest surface alterations, while heptane had the least impact. Surface roughness emerged as a key factor influencing microbial retention on restorative materials.