Clinical trials in children and adults have suggested that daily consumption of probiotic lactic acid bacteria can reduce caries risk and caries development in primary teeth in preschool and stop root caries in the elderly. However, it is not known whether probiotic bacteria can affect the increased porosity in young permanent teeth in children and adolescents with many cavities.

It can be difficult to measure the increased porosity of the enamel by tooth decay, but this can be done using quantitative laser fluorescence (QLF). The method is based on visible light with a wavelength of 370 nm, addressing enamel. This produces an image consisting of red and green color tones and the dominant color of the enamel is green. Increased porosity of the enamel, resulting in a reduction of the auto-fluorescence and the loss (or gain) of the mineral can be quantified by means of a corresponding software.

The purpose of this study is to investigate the effect of a daily supplement of probiotic lactic acid bacteria on the loss of mineral in enamel assessed with QLF. The null hypothesis is that the mineral content will not differ from baseline in either the test group or the placebo group.

Inclusion Criteria:

• two sites with white spot lesions in anterior teeth

Exclusion Criteria:

• antibiotic treatment within 2 months