Objectives: The aim of this study was to determine the effects of MDPB on the growth characteristics of the predominant acidogenic and aciduric microflora associated with active root caries lesions. Methods: Five independent isolates of each of the following species, S. mutans, S. oralis, S. salivarius, A. naeslundii, A. israelii, A. gerensceriae, A. odontolyticus, Lactobacillus spp. and C. albicans were studied. The MIC and MBC values for MDPB of each species were determined according to NCCLS guidelines using a microtiter plate methodology. The effect of sub-MIC concentrations of MDPB on the lag time (h), doubling time (h) and maximum A₆₂₀ were also determined by growing each organism in microtiter plates. In some experiments we determined the effect of pH on the activity of MDPB. The means of duplicate results were analysed using appropriate non-parametric tests. Results: MICs for all the tested species ranged from 3.1 to 18.0 mg/ml with A. gerensceriae and Lactobacillus spp. being the most sensitive and A.naeslundii the most resistant species. Sub-MICs of MDPB had significant effects on the growth of each of the species tested. In every case the lag time and doubling time increased with increasing MDPB while the maximum A₆₂₀ decreased. Thus for S. mutans the lag time, doubling time and maximum A₆₂₀ were 356%, 182% and 60% of the control values with 5mg/ml MDPB while with C. albicans the values were 282%, 190% and 69%, respectively. Using Lactobacillus spp. and C. albicans we found that low pH (<5.5) had a significant antagonistic effect on MDPB with higher concentrations required to inhibit growth. Conclusion: This study has demonstrated that MDPB has strong antimicrobial properties, which were pH-dependant, and that sub-MICs significantly inhibited the growth characteristics of caries-associated microflora.

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Back to the 81st General Session of the International Association for Dental Research (June 25-28, 2003)

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