Comparison of the Antibacterial Effect of Three Different Methods for Cleaning Hawley and Essix Retainers

Although different methods have been recommended for cleaning orthodontic retainers, a standard method has not yet been introduced. The present study aimed at evaluating the antibacterial effect of three different methods in cleaning Hawley and Essix retainers. A total of 30 patients with orthodontic appliances who were candidates for receiving orthodontic retainers after their treatment were divided into two groups, including Hawley and Essix (n=15 each). Each patient used three home disinfection protocols for cleaning the retainers. Protocol 1: the patients were instructed to clean their retainer using their received toothbrush and toothpaste 3 times a day. Protocol 2: the patients cleaned their retainers the same as in protocol 1. In addition, they were instructed to spray the retainer with 0.12% chlorhexidine for 30 min every night. Protocol 3: the patients were instructed to soak their retainer in distilled white vinegar (50%) for 15 min every night and then clean their retainer in the same way as in protocol 1. Each protocol was applied for 2 weeks, and there was a 2-week wash-out interval between the protocols. At the end of each protocol, samples were taken from each retainer and the number of Streptococcus mutans colonies was counted and compared between the groups. Kruskal-Wallis and Mann-Whitney tests were used for statistical analysis (P≤0.05). Antibacterial effectiveness of the three cleaning protocols did not show a significant difference in the Essix and Hawley groups (P=0.510 and P=0.095, respectively). However, a significant difference between the two types of retainers was observed when the patients used protocol 2 for cleaning the retainers. Spraying chlorhexidine or soaking in vinegar following brushing of the retainers was equally effective as brushing the retainers with toothpaste alone.