Ultrastructural and microbiological analysis of the dentin layers affected by caries lesions in primary molars treated by minimal intervention

PURPOSE: The purpose of this in vivo study of primary teeth was to analyze the ultrastructure and microbiology of dentin layers affected by caries lesions before and after restorations with resin-modified glass ionomer. METHODS: Samples of carious dentin from primary teeth removed prior to restoration placement (baseline-0 day) were compared with samples taken after 30 and 60 days. Dentin from 8 primary molars was analyzed by scanning electron microscopy (SEM) and dentin from 22 primary molars was examined microbiologically to compare bacteria (total of viable counts, Streptococcus spp, Streptococcus mutans, Lactobacillus spp, and Actinomyces spp) before and after treatment (30 and 60 days). RESULTS: Baseline caries samples had enlarged dentinal tubules with bacteriol invasion. SEM samples after treatment suggest better tissue organization, with more compact collagen fibers arrangement and narrower dentinal tubules. The number of bacteria decreased in all samples at both 30 (98%) and 60 (96%) days, with all bacteria species showing similar trends. CONCLUSIONS: The minimal intervention approach is very effective to promote beneficial changes in the lesion environment and favorable conditions for the healing process in primary teeth.