Oral hygiene agents at work: effects on Streptococcus mutans and caries risk

Dental caries remains one of the most prevalent chronic polymicrobial diseases worldwide, driven by acidogenic and aciduric bacteria, most notably <i>Streptococcus mutans</i>, that thrive within oral biofilms. Conventional strategies for caries prevention rely on mechanical plaque removal combined with agents that inhibit bacterial growth, disrupt biofilm formation, or enhance enamel remineralization. Here, we synthesize current evidence regarding a range of key agents that are incorporated into modern oral hygiene products. In addition to describing the mechanisms and efficacy of these agents, we describe their distinct biochemical and ecological effects on <i>S. mutans</i> metabolism, acid tolerance, and biofilm development. The agents that are relevant in the present day include fluoride, hydrogen peroxide, chlorhexidine, zinc, prebiotics (such as arginine and xylitol), and probiotics. Fluoride remains the cornerstone of caries prevention through its dual effects on enamel fluorapatite formation and inhibition of bacterial glycolysis, while chlorhexidine and hydrogen peroxide provide broad-spectrum antimicrobial activity. Zinc exhibits multifaceted roles in metabolic inhibition and plaque reduction, whereas pre- and probiotics aim to restore ecological balance by favoring health-associated commensal species. Finally, the review highlights evidence supporting combinatorial and synergistic use of these agents, particularly fluoride pairings, which may yield additive or enhanced protective effects. Understanding the molecular mechanisms that drive the efficacy of these compounds and gaining insight into cumulative influence on oral microbial ecology will drive the development of future treatment strategies.