RESUMO
OBJECTIVE: External apical root resorption (EARR) is a frequent iatrogenic effect of orthodontic treatment. Patients with genetic variants in the interleukin 1 gene have been related to an increased risk of suffering EARR. The objective of this study is to determine whether variants in the interleukin 1 receptor antagonist gene are positively/negatively associated with interleukin 1 gene polymorphisms, particularly in relation to the clinical features of EARR patients. MATERIALS AND METHODS: Genetic screening of 54 orthodontic patients was performed for three polymorphisms (rs1800587, rs1143634 and rs419598) in the IL1 gene cluster. Subjects were divided according to the presence or absence of EARR of more than 2 mm. The genotype distributions and allelic frequencies were calculated by the chi-square-test. Odds ratios (OR) and 95% confidence intervals were also calculated. RESULTS: A highly significant association was found in the comparative analysis of homozygous subjects [1/1(CC)] for the IL1B gene, resulting in an increased risk of suffering postorthodontic EARR (OR: 3.47; P = 0.027; CI: 95%). While no association was found for the IL1A gene (P = 0.097), subjects who were homozygous [1/1(TT)] for the IL1RN gene were more likely to be affected with EARR (OR: 6.75; P = 0.001; CI: 95%). CONCLUSION: Variations in the interleukin 1 receptor antagonist gene (rs419598) - and not only in the IL1B gene (rs1800587) - are determinants of a predisposition to postorthodontic EARR.