AbstractIn this study, the effect of bacterial multispecies communities on the adhesion of Streptococcus mutans and Streptococcus sanguinis to dental restorative material was investigated. The saliva‐coated specimens of zirconia and composite were incubated with the following combinations: single species, S. mutans or S. sanguinis; two species, single species combined with other oral streptococci; multiple species, combination of Actinomyces naeslundii, Fusobacterium nucleatum, and Prevotella ssp.; and the two‐species combinations. The adherent bacteria were counted after plating of serial dilutions. Effects of material and bacteria on adhesion of S. mutans and S. sanguinis were evaluated with multiple linear regression analyses. No significant differences between the materials regarding the adhesion of S. mutans and S. sanguinis were observed. The adhesion of S. mutans was negatively influenced by the presence of other streptococci. Enhancing effects (610.6%) were seen in the presence of Prevotella intermedia. The adhesion of S. sanguinis decreased in the presence of other bacteria, except F. nucleatum (increase of 717.4%). Significant inhibitory effects were detected in the presence of S. mutans and A. naeslundii (reduction of 95.9% and 78.5%, respectively). The results of this study suggest that adhesion of both types of streptococci to restorative materials is influenced by various bacterial interactions.