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Objective: To study the effect of orally administered Bifidobacterium animalis subsp. lactis BB-12 and Lactobacillus rhamnosus GG on the salivary levels of Matrix Metalloproteinases (MMP)-8, MMP-9 and of Tissue Inhibitor of Metalloproteinases (TIMP)-1 in healthy adults. Furthermore, the correlations between MMP-8, MMP-9 and TIMP-1 and plaque and gingival indices, salivary mutans streptococci and lactobacilli counts, and stimulated saliva secretion rate were analysed., Design: The salivary samples originated from a randomized controlled trial where healthy student volunteers consumed probiotic or placebo lozenges twice a day for four weeks. The saliva samples were collected and clinical parameters measured at the baseline and at the end of the original study. For this study, the salivary levels of MMP-8, MMP-9 and TIMP-1 were analysed with immunofluorometric assay (IFMA) and enzyme-linked immunosorbent assay (ELISA)., Results: In the probiotic group (n=29), salivary MMP-9 levels increased (p<0.01) and TIMP-1 levels decreased (p<0.01) significantly during the intervention. Furthermore, MMP-9/TIMP-1 ratio differed significantly from the baseline level (p<0.01). These changes were not observed in the control group (n=31). In the whole data, salivary MMP-9 and gingival index correlated (r=0.260, p<0.05 at baseline and r=0.354, p<0.01 at the end of the study). Intergroup differences or correlations with other clinical parameters were not found. Probiotic consumption did not affect the saliva flow rate., Conclusions: Increased MMP-9 and decreased TIMP-1 levels in saliva may indicate that probiotics have immunomodulatory effects in the oral cavity. Furthermore, increased salivary MMP-9 levels may be an indication of the defensive potential of matrix metalloproteinases., (Copyright © 2017 Elsevier Ltd. All rights reserved.)