Investigation of the effect of genetic factors on root resorption i̇n orthodontic treatment

Aim: External apical root resorption is a multifactorial pathological process associated with permanent loss of dental root structure in response to a common mechanical, inflammatory, autoimmune or infectious stimulus of orthodontic treatment. The aim of this study is to examine the effects of genetic factors on external root resorption seen in individuals undergoing orthodontic treatment, to investigate individual predisposition and to establish a genetic database. Material and Method: In our study, individuals who applied to Dicle University Faculty of Dentistry Department of Orthodontics for orthodontic treatment and completed orthodontic treatment with high quality panoramic radiographs at the beginning and end of orthodontic treatment were included as the study group, which consists of 11 individuals who underwent premolar tooth extraction and whose external apical root resorption amount relative crown-root ratio (rRCR) was rRCR˂0,90 (score 3 or 4 according to Levander&Malmgren scoring), 11 individuals who were applied intermaxillary elastics and 10 individuals who were applied rapid maxillary expansion, and were included as the control group, which consists of 10 individuals who underwent premolar tooth extraction and whose root resorption amount relative crown-root ratio (rRCR) was 0.90 ≤ rRCR < 1.00 (score 0, 1 or 2 according to Levander&Malmgren scoring), 10 individuals who were applied intermaxillary elastics and 10 individuals who were applied rapid maxillary expansion. In addition, 23 individuals who applied to our clinic for orthodontic treatment but have not started orthodontic treatment yet were included in our study in order to investigate the frequency of gene polymorphisms in the population and to predict their contribution to individual predisposition. In the blood samples taken from 85 individuals participating in our study, the presence of possible new mutations was tried to be determined by including single nucleotide polymorphisms as rs1800587 for IL-1A gene, rs1143634 for IL-1β, rs419598 for IL-1RN, rs315952, rs1800796 for IL-6, rs1059703 for IRAK 1, rs1718119, rs208294, rs2230912 for P2RX7, rs1805034 for RANK (TNFRSF11A), and all polymorphisms and mutations belonging to the relevant genes in the database of Dicle University Faculty of Medicine, Department of Medical Biology and Genetics and relationship with EARR was evaluated. Results: As a result of the measurements, the teeth with the most external apical root resorption were the left upper lateral tooth and the right lower central tooth. Significantly more single nucleotide polymorphisms were observed in the P2RX7 and RANK genes in the individuals included in the study group compared to the control group (p<0.05). Conclusion: The single nucleotide polymorphism of rs208294 (c.463T>C) in the P2RX7 gene was the most significantly observed polymorphism in our study group (p<0.05). There was no significant difference between the individuals in the study group (extraction, intermaxillary elastic, rapid maxillary expansion) for polymorphisms (p>0.05). Keywords: External Apical Root Resorption, Etiology, Gene Polymorphism, Mutation, Orthodontic Treatment