BACKGROUND/OBJECTIVES: The purpose of the study is to evaluate the effect of daily intake of lozenges containing probiotic bacteria on white spot lesion (WSL) formation as well as on salivary lactobacilli (LB) and mutans streptococci (MS) counts, in patients undergoing orthodontic treatment with fixed appliances.

MATERIALS/METHODS: A randomized double-blind placebo-controlled study design with two parallel arms was employed. Patients (n = 85, mean age 15.9 years) with maxillary braces on at least eight anterior teeth and a remaining treatment period of 7-24 months were finally enrolled and randomly allocated to a test or placebo group. Subjects in the test group were instructed to take one probiotic lozenge containing two strains of Lactobacillus reuteri once daily. An identical lozenge without active bacteria was used in the placebo group. Dental plaque, WSL, and salivary MS and LB levels were recorded at baseline and immediately after debonding.

RESULTS: The groups were balanced at baseline. The mean duration of the intervention was 17 months and the total dropout rate was 10 per cent. There were no differences in the incidence of WSL between the groups at debonding. The patients had generally a neglected oral hygiene, both at baseline and at the follow-up. The levels of salivary LB were significantly reduced in both groups (P < 0.05) at the time of debonding compared with baseline, while no alterations of the MS counts were unveiled.

LIMITATIONS: WSL were scored from photos that may not fully mirror the clinical situation. Chair-side tests estimate the counts of selected bacteria in saliva and do not reflect the entire microbiota. The invention was implemented approximately 6 months after the onset of the fixed appliances and some lesions may have been present at bonding.

CONCLUSIONS/CLINICAL IMPLICATIONS: Daily intake of probiotic lozenges did not seem to affect the development of WSL during orthodontic treatment with fixed appliances.