Introduction and objective:
The aim of the study is to evaluate the effect of short-term, oral supplementation of non-viable Lactobacillus salivarius (HM6 Paradens) on the number of caries-related microorganisms in the supragingival plaque biofilm of pre-school children.

Material and methods:
The study is prospective, randomized and observational in design performed on 2 parallel groups (test and control) of 72 childrenaged between 3 – 6 years, with or without early childhood caries (ECC). The primary outcomes measured are changes in S. mutans counts (number of colony-forming units – CFU) and the percent of the total viable counts) in dental plaque biofilm within the groups between baseline and 2-weeks follow-up, while secondary outcomes are changes in Lactobacilli spp. and C. albicans counts.

Results:
For analysis performed only on the children with detectable bacterial counts at baseline, the reduction in the level of S. mutans increased in the control group, and decreased in the probiotic group, Lactobacillus spp. increased in the probiotic group and decreased in the control group, and for C. albicans, the level decreased in both the control and probiotic groups after 2 weeks.

Conclusions:
The presence of L.salivarius (HM6 Paradens) may modify the interactions between S. mutans and Lactobacillus spp., which could support microbiological homeostasis and have a beneficial impact on ECC prevention.