Plaque accumulates around the rough surfaces of retainers, and enamel demineralization may follow. According to research from the Hamadan University of Medical Sciences in Iran, adding silver nanoparticles to retainers can reduce the bacteria causing this demineralization.
The study comprised 36 orthodontic patients at the debonding stage of orthodontic treatment. One group of patients received conventional removable retainers. The other group received removable retainers that contained silver nanoparticles that measured about 40 nm in size and 500 PPM in concentration.
Next, the researchers took swab samples from the maxillary palatal side of each patient at retainer placement one week after debonding and again 7 weeks later. The researchers then measured the number of Streptococcus mutans colony-forming units in these samples.
The patients with the silver retainers had higher S mutans colony counts than the control group at the first measurement. Yet 7 weeks later, they showed a significant reduction in the number of colonies. The mean difference of colony counts between the groups was 40.31.
The researchers concluded that adding silver nanoparticles to the acrylic plate of retainers had a strong antimicrobial effect against S mutans under clinical conditions. The study was published by the American Journal of Orthodontics & Dentofacial Orthopedics.