The thermoplastic retainers indicated a rising incidence of cariogenic bacteria such as Streptococcus mutans. A report suggested the case of a patient with severe gingival inflammation and dental caries as a result of inadequate appliance cleaning. This study aims to compare the various antimicrobial agents for thermoplastic polymeric retainers. A minimum bactericidal concentration (MBC) of acetic acid was determined. Streptococcus mutans biofilm was formed on punched 4-mm copolyester (Essix ACE®) and polyurethane (Vivera®) retainers after they were submerged in 0.12% chlorhexidine (CHX group), acetic acid (AA group), Polident Denture Cleanser® (PD group), and Polident Pro Guard & Retainer® (PR group). A crystal violet (CV) test was performed. The biofilm imaging was assessed by confocal laser scanning microscopy (CLSM). The results showed that all chemical disinfectants exhibited statistically significant differences (p < 0.05) compared to the positive control. This novel finding elucidated that 0.625% acetic acid is effective for antimicrobial in both copolyester and polyurethane retainers. However, only the CHX, PD, and PR groups could reduce biofilm mass. In addition, the CV assay cannot provide information about the actual number of living and dead bacteria. Furthermore, the LIVE/DEAD BacLight assay was able to show the bacterial viability.
Keywords: Essix; Vivera; cleaning; clear retainer; disinfection; thermoplastic.