Background: The objective of the study was to investigate the effect of tablets containing probiotic lactobacilli on early caries lesions in adolescents with quantitative light-induced fluorescence (QLF).

Methods: 36 healthy adolescents of both sexes (12-17 years of age) were enrolled and randomly allocated to a placebo-controlled trial with two parallel groups. The test group received two tablets daily containing two strains of Lactobacillus reuteri (DSM 17938 and ATCC PTA 5289) for a period of three months, while the control group got identical placebo tablets without live bacteria.

Results: The primary outcome was QLF-readings (change in fluorescence, ΔF and lesion area, mm2) at baseline and after 3 months, conducted at two buccal sites of each individual, pre-selected with clearly visible clinical signs of enamel demineralisation (white spots). Significantly more premolars were allocated to the placebo group, while the test group had more incisors (P<0.05). There were no statistically significant differences in fluorescence values between the groups, neither at baseline, nor at the follow-up. There was however a significant decrease in fluorescence over time in the test group, but not in the placebo group (P<0.05). No alterations of the lesion area (ΔA) were found in any group. The inter-examiner intra-class correlation coefficient-value for QLF-readings was excellent. No side- or adverse effects were reported during the intervention period.

Conslusion: This pilot study found a significant decrease over time in the test group. However, no statistically significant differences in fluorescence values between the groups were found. Hence, the null hypothesis could not be rejected.