Predominant obligate anaerobes in secondary carious lesions around restorative materials

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In this study, we attempted to isolate and identify the predominant cultivable flora in secondary caries around restorative materials by strict anaerobic procedures.The samples of dental plaque were taken from the surfaces on secondary caries around composite resin and amalgam. The range of CFU counts for all cultivable bacteria taken from each of 3 plaque samples on composite resin and amalgam was respectively 2.73*10^8 to 8.72*10^9 and 7.92*10^5 to 8.02*10^8. The number of Streptococci and Lactobacilli accounted for 1/100 to 1/3 of all cultivable bacteria. However, there was no significant difference in Streptococci and Lactobacilli counts of total bacterial counts between composite resin group and amalgam group.The samples were taken from secondary carious dentin around 3 teeth restored with composite resin and 2 teeth restored with amalgam. The rates of predominant obligate anaerobes were 73.4% to 100% of total isolates in 4 cases, except that the rate of obligate anaerobes was 22.7% in one case.Of 48 isolates of composite resin group, the facultative anaerobes were 4 strains of Streptococcus and 1 strain of Actinomyces, while the obligate anaerobes were 13 strains of Peptostreptococcus, 21 strains of Actionomyces, 6 strains of Arachnia and 1 strain each of Eubacterium, Bifidobacterium and Propionibacterium. Of 139 isolates of amalgam group, the facultative anaerobes were 64 strains of Streptococcus, 9 strains of Actinomyces and 2 strains of Lactobacillus, while the obligate anaerobes were 27 strains of Peptostreptococcus, 4 strains of Streptococcus, 17 strains of Actinomyces, 2 strains of Eubacterium, 1 strain each of Lactobacillus and Propionibacterium, and 12 strains of Veillonella.The results suggested that the predominant cultivable flora in secondary carious lesions had characterization intermediate between dental plaque and primary carious dentin. However, the bacteria around composite resin were not substantially different from those around amalgam.