LAUSR

INTRODUCTION Microbial biofilm accumulation around orthodontic brackets and composite is a common complication of fixed orth-odontic treatment. This study assessed the antibacterial effects of orthodontic primer containing chitosan nanoparticles (CNPs) against the multispecies biofilm of cariogenic bacteria in а rat model. MATERIALS AND METHODS Transbond XT orthodontic primer containing 0%, 1%, 5%, and 10% CNPs was experimentally prepared. The Wistar rats were randomly divided into four groups (n=7) of control (0% CNPs), 1%, 5% and 10% CNPs. The oral cavities of the rats were infected with cariogenic bacteria. After anesthetizing the rats, 1 drop (10 µL) of primer with different concentrations of CNPs was applied to their central incisor and light-cured for 20 seconds. Transbond XT orthodontic adhesive (2 × 2 mm) was applied on the primer. Another drop (10 µL) of primer was applied and light-cured for 40 seconds. The number of Streptococcus mutans, Streptococcus sanguinis, and Lactobacillus acidophilus colonies in the saliva of rats was quantified at 24 hours, 4 days and 7 days. RESULTS Adding 1% (p=0.005), 5% (p<0.001) and 10% (p<0.001) of CNPs to orthodontic primer significantly reduced the S. mutans colony count at 24 hours compared with the control group. At 24 hours, the mean S. sanguinis colony counts in the 5% (p=0.04) and 10% (p=0.02) CNP groups were significantly lower than that in the control group. Also, at 4 and 7 days, the mean colony counts in the 5% and 10% CNP groups were significantly lower than that in the control group (p<0.05). At 24 hours and 4 days, the mean L. acidophilus colony count in the 10% CNP group was significantly lower than that in the control group (p<0.05). At 7 days, rats with failed adhesive showed a significantly higher count of all three bacteria compared with rats with adhesive (p<0.05). CONCLUSIONS The addition of 5% CNPs to orthodontic primer significantly decreased the colony count of cariogenic bacteria in rats.