One of the major challenges in orthodontic treatment is long-term stability. Because removable retainers are worn for at least one year, bacteria and fungi may accumulate on the retainers in the form of multi-species plaque biofilms. This may result in increased incidence of proximal dental caries or oral candida infection. Thus, incorporation of antimicrobial activity in orthodontic acrylic resin to achieve plaque biofilm reduction is highly desirable. An antimicrobial and antifungal quaternary ammonium methacryloxy silicate molecule (QAMS) has been synthesized by sol-gel reaction and incorporated into orthodontic acrylic resin.
The QAMS-copolymerized acrylic resin demonstrated contact-killing properties against single-species biofilms in previous in vitro studies and has received US FDA 510(K) clearance for marketing. The objective of the present randomized clinical trial is to determine the in vivo antimicrobial efficacy of the QAMS-containing orthodontic acrylic by using removable retainers that are worn by recruited subjects to create 48-hour multi-species plaque biofilms. The null hypothesis tested is that there is no difference in the antimicrobial activities between QAMS-free and QAMS-containing orthodontic acrylic resin on oral biofilms grown in vivo in human subjects.