Reduction of salivary mutans streptococci in orthodontic patients during daily consumption of yoghurt containing probiotic bacteria

A double-blind, randomized crossover study was performed and 24 healthy adolescents (12-16 years) undergoing orthodontic treatment were followed over four periods. During periods 2 and 4 (2 weeks each), the subjects ingested 200 g fruit yogurt containing Bifidobacterium animalis subsp. lactis DN-173010 (2 x 10(8) colony forming units/g) once daily or a control yogurt without viable bacteria. Periods 1 and 3 were run-in and wash-out periods of 1 and 6 weeks, respectively. Salivary mutans streptococci and lactobacilli were enumerated with chair-side kits before and after the yogurt consumption periods. Pre- and post-treatment values within each regimen were compared with a two-tailed marginal homogeneity test for categorical data. A statistically significant reduction of salivary mutans streptococci was recorded after probiotic yogurt consumption (P < 0.05), which was in contrast to the control yogurt. No significant alterations of the salivary lactobacilli counts were observed. Short-term daily consumption of fruit yogurt containing Bifidobacterium animalis subsp. lactis DN-173010 may reduce the levels of mutans streptococci in saliva during orthodontic treatment with fixed appliances.