Introduction & Objective: The aim of this study was todeterminetheamount of external apical root resorption(EARR)within two orthodontic appliances (standard edgewise and MBT).

Material & Methods In this retrospective study, panoramic radiographs of 83 orthodontic patients (27 male and 56 female) were evaluated. 46 patients had been treated with standard edgewise appliance (29 patients with extraction and 17 patients without extraction) and 37 patients had been treated with MBT appliance (27 patients with extraction and 10 patients without extraction).EARR were evaluated in 24 teeth (anterior teeth, premolars and first molars) in each patient. SPSS software and ordinal regression test were used for statistical analysis.

Result: In this study the most EARR was seen in upper lateral incisors, then lower lateral incisors.EARR in upper canines and lower second premolars was significantly related to extraction of first premolarin MBT appliance. In non extraction cases, EARR was not related to the orthodontic appliance.

Conclusion: Incisors teeth are the most disposed teeth to EARR. Orthodontic treatment with extraction increased EARR in canines and second premolars. MBT appliance may increase EARR.