Herbal and Alcohol-Free Mouthwashes as Chlorhexidine Alternatives for Preventing Enamel Demineralization in Orthodontic Patients: An In Vitro Study

Background/Objectives: Chlorhexidine (CHX) and alcoholic (A+) mouthwashes are associated with adverse oral effects. Therefore, this study compared the efficacies of non-alcoholic mouthwashes, including fluoride (A−) and herbal (Hr) rinses, for preventing bacterial accumulation and enamel demineralization around metal brackets (MBs), ceramic brackets (CBs), and resin composite attachments (RCAs). Methods: Following the exposure to CHX, A+, A−, and Hr rinses for 1 min, the growth of Streptococcus mutans on MB, CB, and RCA was assessed using colony-forming units and scanning electron microscopy (SEM). Controls included attachments without intervention. In another setting, enamel with bonded attachments was exposed to mouthwashes for 1 min and subjected to cariogenic demineralization for 24 h. Enamel’s Vickers microhardness was measured before and after the demineralization challenge. Data were analyzed using paired t-tests and one-/two-way ANOVA with Tukey’s tests. Results: CHX mouthwash demonstrated superior antimicrobial efficacy against S. mutans biofilms across all orthodontic attachments (p < 0.05). On metallic brackets, CHX (0 ± 0 log₁₀) and A− (1.7 ± 0.4 log₁₀) significantly (p < 0.001) outperformed controls (6.9 ± 0.1 log₁₀), Hr (6.08 ± 0.2 log₁₀), and A+ (6.2 ± 0.6 log₁₀). Similar patterns emerged for ceramic brackets, with CHX (0 ± 0 log10) and A− (1.4 ± 0 log10) superior to controls (6.6 ± 0.4 log₁₀). On resin composite attachments, CHX (2.9 ± 0.05 log₁₀) and Hr (3.4 ± 0.08 log₁₀) exceeded controls (5.4 ± 0.09 log₁₀) in inhibiting the biofilm growth (p < 0.05). Enamel microhardness reduction was significantly influenced by attachment type (p < 0.0001) and mouthwash type (p = 0.0063), with significant interaction between variables (p = 0.0052). Conclusions: CHX and A− mouthwashes effectively inhibited S. mutans biofilms on orthodontic attachments, while attachment type and mouthwash significantly influenced enamel microhardness reduction.