The aim of this study is to investigate the amount of the apical root resorption in the upper and lower incisors due to the direction and amount of tooth movement during the orthodontic treatment. The material consisted of pre- and post-treatment periapical and lateral profile cephalograms of 50 (33 girls,17 boys, mean starting age: 13,91 years, mean treatment time: 1.95 years) treated cases by using Edgewise (34 cases) and Straight wire (16 cases) techniques. 34 cases treated by extraction, 16 cases treated by nonextraction methods and the root resorptions were caused by the treatment. 28 subjects (22 girls, 6 boys) had Class 1,19 subjects (10 girls, 9 boys) had Class II and 3 subjects (1 girl, 2 boys ) had Class III malocclusions skeletally and dentally. In 28 girls and 7 boys the apical root resorption was observed on the upper and lower incisors, in 2 girls and 3 boys, on the lower incisors, in 3 girls and 7 boys on the upper incisors.The total dimension between the incisal edges and root tips of the central teeth were measured on pre- and post-treatment lateral cephalograms and the percentage of the root resorptions were calculated.For each parameter.the mean values and the standard deviations were found. Mann Whitney U-Test and Simple Regression Analysis were used for statistical evaluations. The results showed that;(1) There was a correlation between the amount of overjet and the amount of the apical root resorption ,(2) The amount of the resorption was significantly greater in Class II cases than in Class I subjects, (3) Root resorption was found significantly greater in subjects trated by using Edgewise technique than in cases treated by using Straight wire technique, (4) The amount of the resorption was found greater in subjects treated with using rectangular stainless steel wire than in subjects treated with using rectangular nitinol or rounded stainless steel wires, (5) The amount of the resorption increased by the amount of retrusion, (6) One degree of protrusion of upper central teeth caused 1 % of resorption .while two degrees of retrusion caused 1 % of resorption, (7) On average, one degree of retrusion of the lower central teeth caused resorption of 1.37 , while one degree of retrusion of the upper central teeth caused resorption of 0.54 percentage.

Keywords: Orthodontic treatment, root resorption