Water and Liquid Soap Cleaning of Removable Orthodontic Appliances: A Triple‑Blind Randomized Crossover Study of Microbial Load Reduction

Background: To evaluate the effectiveness of water and a liquid soap solution compared with 0.2% chlorhexidine (CHX) mouthwash in reducing microbial load and microbial plaque formation on removable orthodontic appliances. Methods: Forty-two patients aged 9 to 16 years who had newly received acrylic resin removable orthodontic appliances were enrolled and randomized in a triple-blind crossover clinical trial. Thirty participants completed all study phases and were included in the final analysis. Participants were randomly allocated into 3 groups (n=10) according to the initial cleaning protocol: water, water plus liquid soap solution, or 0.2% CHX mouthwash. Each protocol was followed for one week, after which participants crossed over to the remaining protocols until all patients completed all 3 cleaning regimens. At the end of each intervention period, the plaque index (PI) of the removable appliances and the Streptococcus mutans microbial load were assessed. Results: Significant differences were observed among the 3 cleaning protocols in both qualitative and quantitative microbial assessments ( P <0.001). The highest mean microbial load was detected following cleaning with water alone, whereas the lowest microbial load was observed with 0.2% CHX mouthwash. Plaque index measurements were consistent with these findings. In the microbroth dilution assay, the minimum inhibitory concentration (MIC) against S. mutans was 32 μg/mL for 0.2% CHX mouthwash and >500 μg/mL for the liquid soap solution. Conclusions: Although water and liquid soap solution demonstrated lower antimicrobial activity than 0.2% CHX mouthwash, they were still effective in reducing plaque index scores and S. mutans load in patients using removable orthodontic appliances.