Different Defensin Polymorphisms Associated With Proximal Versus Occlusal Caries

Objectives: Recent studies suggest that susceptibility to proximal and occlusal caries may be under distinct genetic influences. Defensins form a family of microbiocidal and cytotoxic peptides made by neutrophils. The DEFB1 gene encodes Beta-defensin 1, an antimicrobial peptide implicated in resistance of epithelial surfaces to microbial colonization. In the present study, we examine genetic polymorphisms within coding regions of the DEFB1 gene for associations with proximal and occlusal caries in children.

Methods: Ninety five school-aged children aged 6 to 11 years participated in the study. Dietary and demographic information was collected using a questionnaire. Carious lesions on proximal, occlusal and proximal and/or occlusal surfaces on primary molars were evaluated using the WHO+IL caries detection criteria. In most cases, radiographs supplemented the clinical examination. DNA was extracted from whole saliva. Two SNPs in the DEFB1 gene were tested for association with presence of proximal and/or occlusal caries. Genetic association statistical analyses assuming an additive model were used to evaluate association of caries on proximal or occlusal surfaces. The effects of race and ethnicity were adjusted using Principal Components Analysis (PCA). Significance for this exploratory analysis was set at a threshold value of 0.05.

Results: A SNP from DEFB1 was associated with Proximal Caries in the primary molars (rs2738047 (missense VAL/ILE) P=0.011). A second SNP rs149319759 (missense PHE/CYS) showed no association with proximal lesions (P= 0.175 ns). Neither SNP showed an association with only occlusal caries. Combining both Occlusal and Proximal Caries in the primary molars, both SNPs showed statistical significance (rs2738047, P=0.022; rs149319759, P= 0.015).

Conclusions: Different polymorphisms in the DEFB1 gene may be associated with susceptibility to proximal versus occlusal caries. This indicates the importance of considering decay at different types of surfaces when studying caries’ etiological mechanisms.