Influence of Filler Content and Polishing on <i>Candida</i> and <i>Streptococci</i> Biofilm Formation in Resin‐Based Composites: An In Vitro Evaluation

<b>Aim:</b> The purpose of this study was to investigate the impact of filler content and polishing of resin-based composites on in vitro biofilm formation of <i>Candida</i> and <i>Streptococci</i> species. <b>Materials and Methods:</b> Specimens of four commercially available resin-based composites including Z100, P60, Z250, and Z350, with different filler amounts and volumes, were prepared according to the manufacturer's instructions. Each group was divided into polished and unpolished specimens, which were then placed in a 24-well tissue culture plate with microbial suspension and incubated. The XTT technique was used to evaluate biofilm formation. <b>Results:</b> Z250 resin-based composites, which had the highest percentage of filler (68%), had the highest biofilm metabolic activity. A significantly less microbial biofilm metabolic activity was noted on P60 polished resin-based composites than on unpolished groups (<i>p</i> < 0.001). Polishing procedures reduce biofilm metabolic activity. <i>Streptococcus salivarius</i> produced the least biofilm metabolic activity among the <i>Streptococcal</i> species (<i>p</i> < 0.001). However, there were no statistically significant differences between <i>Candida</i> species in the biofilm metabolic activity. <b>Conclusion:</b> The results revealed that the amount of filler in resin-based composites had a major impact on the biofilm metabolic activity. Therefore, resin-based composites with a minimized excess resin matrix, minimized filler amount, and smoother surfaces might be more useful in reducing biofilm metabolic activity and secondary caries. These findings may be useful for modifying novel resin-based composite formulations to improve oral health and patient wellbeing.