To compare the degree of external apical root resorption (EARR) in patients using selfligating brackets with conventional brackets in a long run. Methods: Electronic search was made in databases including PubMed, OVID, the Cochrane Library, EMBASE, FMRS, CBM, CNKI, VIP and WanFang Data until November 2019 to retrievalled randomized controlled trials and clinical controlled trials that compared the EARR between patients using selfligating or conventional brackets. What's more, manual search was

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... ade in NLM, SIGLE, Campbell library, WHOLIS, Chinese Journal of Evidence-based Medicine and the Journal of Orthodontics. Literature filtering, data extraction and methodological quality evaluation were finished independently by two researchers and disagreements were solved by a third reviewer. Original outcome data, if possible, were subjected to statistical pooling by Review Manager 5.3 for Meta analysis. Results: Through a predefined search strategy, ten studies were included in the systematic review and nine eligible studies were pooled in meta-analysis. There was a significant difference between self-ligating and conventional brackets in terms of the value of EARR in maxillary central incisors (P=0.01; SMD: -0.42mm; 95%CI: -0.76, -0.09) in a long run. No significant difference in maxillary lateral incisors (P=0.07; SMD: -0.17; 95%CI: −0.35, 0.01), mandibular central incisors (P=0.69; SMD: 0.04; 95%CI: −0.17, 0.26) and mandibular lateral incisors (P=0.38; SMD: −0.10; 95%CI: −0.32, 0.12). Conclusions: Self-ligating brackets have a long-term effect in protecting maxillary central incisors from the EARR compared to conventional brackets. However, self-ligating brackets were not superior to conventional brackets in reducing the EARR of maxillary lateral incisors, mandible central incisors and mandible lateral incisors. Background External apical root resorption (EARR) which could be defined as the blunting and shortening of root apex caused by the pathologic loss of the cementum and dentine is considered as one of the most serious adverse effect during orthodontic treatment. 1 Although EARR has been considered as an iatrogenic problem associated with orthodontic treatment, the relationship between orthodontic treatment and EARR has never been fully answered. EARR and conventional preadjusted brackets. Stomatology. 2017;37:635-7. 17. Blake M, Woodside DG, Pharoah MJ, et al. A radiographic comparison of apical root resorption after orthodontic treatment with the edgewise and Speed appliances.