Association between miR-21 polymorphism and the risk of primary dental caries in preschool children.

Genetic factors play an important role in dental caries, but research on microRNA polymorphisms related to caries susceptibility is still emerging. This study investigated the association between miR-21 polymorphisms (rs1292037, rs13137) and primary tooth caries risk in Chinese Han preschool children. This case-control study included 148 preschool children with primary dental caries and 146 caries-free controls. Oral hygiene habits, dietary habits and clinical caries indices were collected. Rs1292037 and rs13137 polymorphisms were genotyped using TaqMan assays, and salivary miR-21 expression was measured by RT-qPCR. Hardy-Weinberg equilibrium tests the group genetic balance. Logistic regression identified independent factors for primary dental caries. A markedly higher proportion of preschool children in the caries group exhibited poor oral hygiene, did not use fluoride toothpaste, and regularly ate sugary food consumption before bedtime. In codominant and recessive models, the C allele and CC genotype of rs1292037 significantly increased the risk of primary dental caries, while no such association was observed for rs13137. In the primary dental caries group, miR-21 expression was upregulated, positively correlated with caries severity, and significantly higher in CC genotype carriers than T-allele carriers. Multivariate analysis confirmed rs1292037 CC genotype, elevated miR-21 expression and sugary food consumption before bedtime as independent risk factors, while fluoride toothpaste use was protective. The miR-21 rs1292037 polymorphism, particularly the CC genotype, was associated with increased primary dental caries risk in preschool children and elevated miR-21 expression correlated with caries severity.