Insights into <italic>AQP5</italic> Polymorphism and Genetic Associations in Molar Incisor Hypomineralization and Dental Fluorosis.

INTRODUCTION

While fluoride exposure is a well-established factor in the development of dental fluorosis (DF), individual variability in susceptibility suggests that additional factors may also contribute to its manifestation. The etiology of molar incisor hypomineralization (MIH), in turn, is multifactorial and remains not fully understood. The aim of this study was to investigate the association between MIH, DF, caries, and polymorphisms in the AQP5, MMP2, and COMT genes in children exposed to high fluoride levels in drinking water.

METHODS

A total of 268 schoolchildren aged 6-12 years from an area endemic for fluorosis were included. The EAPD, Thylstrup and Fejerskov, and WHO criteria were used for the diagnosis of MIH, DF, and caries, respectively. Saliva samples from participants were collected for genomic DNA extraction and subsequent genotyping, using the TaqMan method, focusing on markers in AQP5, MMP2, and COMT genes. For statistical analysis, chi-square and Fisher's exact tests, along with binary logistic regression, were used, considering a 5% significance level. Additionally, genetic assessments were conducted using PLINK software.

RESULTS

DF was negatively associated with MIH in both crude (OR = 0.3; p = 0.003) and adjusted analyses (OR = 0.3; p = 0.002). AQP5 rs3736309 was significantly associated with an increased risk of DF under a dominant model, with the G allele being more prevalent in affected individuals, while its association with MIH followed a recessive pattern, requiring two copies of the G allele for increased risk. MMP2 rs9923304 was associated with DF under a recessive model, while rs2287074 and rs9923304 were related to dental caries in individuals with DF or MIH.

CONCLUSIONS

The marker in the AQP5 gene was significantly associated with both DF and MIH, presenting different risk patterns depending on the genetic model analyzed (dominant vs. recessive). DF appears to have a protective effect against MIH, highlighting the complex interplay between genetic and environmental factors in dental conditions.