Association of polymorphisms in TNF‐α, IL‐1β, GSTM and GSTT genes with apical periodontitis: is there a link with herpesviral infection?

Aim To investigate the possible association between TNFα (−308 G/A) and IL‐1β (−511 C/T) single nucleotide polymorphisms (SNPs) and GSTT and GSTM deletion polymorphisms and risk of apical periodontitis (AP) development, and determine the association of different genotypes with the presence of herpesviral infection in AP. Methodology The study included 120 periapical lesions and 200 control samples. Gene polymorphism analysis was performed using either polymerase chain reaction (PCR) or PCR/ restriction fragment length polymorphism (RFLP). Relative gene expression of TNF‐α and IL‐1β was analysed using reverse transcriptase – real‐time PCR. The presence of Epstein–Barr virus (EBV) and human cytomegalovirus (HCMV) was assessed by nested PCR. Chi‐square and Fisher’s exact tests and logistic regression analyses were done for polymorphisms, whilst Mann–Whitney U‐test was performed for the expression analysis. The expected frequency of variants was analysed by the Hardy–Weinberg equilibrium test. Results TNF‐α (−308 G/A) SNP increased AP susceptibility for heterozygous (odds ratio (OR) = 1.72, 95% confidence interval (CI) = 1.06–2.80, P = 0.027) and homozygous (OR = 8.55, 95% CI = 1.77–41.36, P