Effects of multispecies biofilm dentin caries-like lesion in artificial mouth

Abstract

OBJECTIVES: To characterise the mineral and organic content of the dentin caries-like lesions developed in an artificial mouth and the interaction of multi-species cariogenic biofilm. METHODS: Caries-like lesions were created by demineralizing human dentin blocks prepared from extracted sound third molars (IRB-UW08-052). Multi-species cariogenic biofilm was formed on caries-like lesions using common cariogenic bacterial species, namely Streptococcus mutans, Streptococcus sobrinus, Lactobacillus acidophilus, Lactobacillus rhamnosus, and Actinomyces naeslundii in artificial mouth for 21 days with internal controls. The mineral content of the dentin caries-like lesion was evaluated with Microhardness Testing, Energy Dispersive Spectroscopy and Fourier Transform Infra-Red Spectroscopy. Microbial kinetics was evaluated at weekly intervals using colony forming units. RESULTS: The microhardness of dentin, which reflected the mineral content, was significantly reduced (p<0.05) on the outer 125 µm after 21 days. The SEM-EDS results showed Ca and P weight percent decreased significantly on outer 75 µm. The collagens (collagen I) in dentin were progressively destroyed with time, as reflected by an increase in ratio of amide I :HPO42-.The predominant bacteria were Lactobacilli and A.naeslundii at 7, 14 and 21 days. Log CFU of the bacteria were 9.28 ± 0.39 (total), 4.59 ± 0.42 (Streptococci), 8.62 ± 0.23 (Lactobacilli) and 8.80 ± 0.30 (A.naeslundii) respectively at day 21. CONCLUSION: There is a progressive loss in mineral and organic content of caries-like dentin lesion with time. The five cariogenic bacteria modulate the properties of each other in the multi-species consortia augmenting the cariogenic properties.