Black stain and dental caries in primary dentition of preschool children in Qingdao, China

Black stain (BS) and caries are common oral issues in children worldwide. This study aimed to reveal the prevalence of BS and caries in primary dentition of children in Qingdao, China and evaluate the potential association between them. A total of 672 preschool children aged 3-5 years old from 12 kindergartens in Qingdao, northern China were enrolled in the study. The prevalences of BS and caries were counted, and their distributions across different ages and genders were analyzed. The potential protective role of BS (independent variable) on caries (dependent variable) was analyzed via binary logistic regression analysis. BS was observed in 103 children (15.33%), including 3 severe- (0.45%), 28 moderate- (4.17%), and 72 mild (10.71%) forms. Caries was observed in 374 children (55.65%) and it was positively associated with age. Notably, the prevalence of caries was lower in children with BS than in those without BS (42.72% vs. 58.00%, respectively). Children with BS were less likely to suffer from caries than those without BS. BS in mild or moderate/severe forms was associated with a low risk of caries. In summary, the prevalence of BS in primary dentition in Qingdao, China is at a relatively high level worldwide. BS is a protective factor for caries in primary dentition.