Effectiveness of Adjunctive Mouthwash Use in Patients Undergoing Fixed Orthodontic Treatment: A Systematic Review

Background Fixed orthodontic appliances create significant challenges for oral hygiene, increasing the risk of demineralized lesions (white spots) and gingival inflammation. Mouthwashes are commonly recommended as adjunctive measures, but evidence-based guidance on optimal selection is needed. Objective To systematically evaluate current evidence regarding the effectiveness of various mouthwash formulations as adjuncts to oral hygiene in patients undergoing fixed orthodontic treatment. Methods A systematic literature search was conducted in PubMed (MEDLINE) and the Cochrane Library for publications from January 2018 to February 2026. The search strategy combined terms for population, intervention, and outcomes. In PubMed, filters were applied for article type (Meta-Analysis, Randomized Controlled Trial, Systematic Review), publication date, and language. Due to access considerations, the "Free Full Text" filter was applied; this represents a limitation. In the Cochrane Library, the same search was applied to the Title Abstract Keyword field. Two independent reviewers performed study selection, data extraction, and quality assessment using AMSTAR 2 for systematic reviews and the Cochrane Risk of Bias tool (RoB 2) for RCTs. Due to heterogeneity of interventions and outcomes, a narrative synthesis was conducted. A total of 3,181 records were screened, and 6 studies met inclusion criteria. Results Six studies were included (3 systematic reviews with meta-analysis, 2 RCTs, 1 systematic review). The 2019 Cochrane Review (AMSTAR 2: high quality) provided evidence that high-concentration fluoride toothpaste (5000 ppm) may reduce demineralized lesions (RR 0.68, 95% CI 0.46-1.00) and that professional fluoride foam (12,300 ppm) may be beneficial (RR 0.26, 95% CI 0.11–0.57). A 2025 meta-analysis (AMSTAR 2: moderate quality) confirmed daily sodium fluoride mouthrinses (0.05% F) are effective for caries prevention (pooled RR 0.72, 95% CI 0.58–0.89). For gingivitis control, a 2022 meta-analysis (AMSTAR 2: moderate quality) confirmed CHX efficacy (plaque SMD − 1.24, 95% CI -1.89 to -0.59) but with significant tooth staining (reported in 83% of included studies); a 2018 RCT (RoB 2: low risk) demonstrated CPC effectiveness with significant plaque reduction (32% vs. 12%, p < 0.01) and no staining. A 2023 systematic review found insufficient evidence for whitening mouthwashes during active treatment due to biological implausibility. Conclusions Current evidence supports a stratified approach: high-fluoride toothpaste plus daily fluoride rinse for caries prevention; CPC for long-term gingival health; CHX reserved for short-term professional indications. Whitening products should be deferred until after brace removal. These findings should be interpreted cautiously due to the access-related limitation and heterogeneity among studies. PROSPERO Registration: Due to the preprint nature and timeline of this review, PROSPERO registration was not completed; future updates will aim for registration to increase transparency.