Dental Caries and Microbiota in Children with Black Stain and Non-discoloured Dental Plaque

<b><i>Aim:</i></b> We aimed to assess caries experience and microbiota in systemically healthy children with black stain (BS) and non-discoloured plaque. <b><i>Methods:</i></b> Forty-six children with BS and 47 counterparts with non-discoloured plaque aged 7.9 ± 1.3 years were clinically examined. Dental caries was scored using WHO criteria. Samples of BS and non-discoloured dental plaque were collected from tooth surfaces. The DNA of the samples was extracted and real-time PCR was performed to determine the total number of bacteria and the species <i>Streptococcus mutans</i>,<i> S. sobrinus</i>,<i> Lactobacillus </i>sp.,<i> Actinomyces naeslundii</i>,<i> Aggregatibacter actinomycetemcomitans</i>,<i> Porphyromonas gingivalis</i>,<i> Prevotella intermedia and Fusobacterium nucleatum</i>. <b><i>Results:</i></b> Children with BS had lower DMFT (p = 0.013), lower DT values (p = 0.005) and a tendency to lower caries prevalence (p = 0.061) than children with non-discoloured plaque. Plaque samples of the BS group contained higher numbers of <i>A. naeslundii</i> (p = 0.005) and lower numbers of <i>F. nucleatum</i> (p = 0.001) and <i>Lactobacillus </i>sp. (p = 0.001) compared to the non-discoloured plaque samples of the control group. Comparing the children with BS and non-discoloured plaque, higher counts for<i> A. naeslundii</i> (p = 0.013) were observed in caries-free children with BS while in caries-affected children with BS, lower counts of <i>F. nucleatum</i> (p = 0.007) were found. Counts of <i>Lactobacillus </i>sp. were higher in non-discoloured plaque samples than in BS of caries-free and caries-affected children. <b><i>Conclusion:</i></b> Results suggest that the different microbial composition of BS might be associated with the lower caries experience in affected subjects. The role of black-pigmented bacteria associated with periodontitis needs further studies.