Intra-subject variability of microbial diversity in caries lesions

The microbial populations of dental caries are highly complex and variable. The representativeness of the bacterial sample taken from one caries lesion as the estimate of microbial diversity has been a concern.

Objectives: To explore the intra-subject variability of microbial diversity in infected and affected dentin of caries lesions and the effects of "starvation" (after the caries lesion was sealed with composite resin restoration) on microbial diversity.

Methods: Standardized dentin biopsies were collected from infected dentin (subjects N=10) and affected dentin (subjects N=3) within established dentinal caries lesions at the time of adhesive restoration and 6-months post-treatment. Two to five tooth sites of the samples were obtained from each subject. Total bacterial DNA was extracted. PCR-based denaturing gradient gel electrophoresis (DGGE) was used to estimate the total microbial diversity for each individual biopsy. The similarity index (C_s) of the microbial profiles within and among the subjects, and before and after the treatment were evaluated using Fingerprinting II Informatix program (BioRad) and analyzed using paired t-test.

Results: The mean similarity indexes (C_s) were 72.2% for infected dentin and 67.9% for affected dentin among different lesions within the same subjects, respectively. C_s of intra-subjects was significantly higher than that of inter-subjects (p <0.01). The diversity of bacterial population in the infected and affected dentins were significantly reduced after 6-month adhesive restoration of the lesion (p <0.05). Conclusions: This study provided initial evidence of intra-subject correlation in microbial diversity in carious lesions. The microbial diversity was significantly reduced after the adhesive restoration of the caries lesion. The outcome also suggested that, for future studies, a microbial sample from one lesion might be used as a representative of the microbial diversity in all carious lesions in the same subject.

Supported by NIDCR/NIH DE-016499 and OVPR U016834 (University of Michigan).