Introduction: Fixed orthodontic appliances include a wide variety of archwires used as a means of delivering forces on teeth. As there are a variety of available archwires, it is important to know which is the most efficient during the initial aligning stage of the treatment. During the initial phase of orthodontic treatment, the use of rectangular arch wires has been reported to result in decreased incisor inclination compared to the traditional round NiTi arch wires. Debates still exist regarding the effect of SLB on the alveolar bone and the root length. Aim of the study: The aim of this clinical study is to evaluate the changes in the alveolar bone and the root resorption during initial leveling and alignment with rectangular NiTi arch wires. Materials and methods: The current randomized clinical prospective study was conducted on a total sample of 20 patients, divided into two groups of ten. Group I consisted of 10 patients treated with active self-ligating stainless-steel brackets and round Cu NiTi wires using the conventional sequence for leveling and alignment. Group II consisted of 10 patients treated with active self-ligating stainless-steel brackets and rectangular Cu NiTi archwires for leveling and alignment. CBCTs were taken after achieving the study objectives (post leveling and alignment) to be used for analyzing the study measurements and comparison with the pretreatment CBCT data. Both groups were compared regarding alveolar bone length, alveolar bone thickness and root length. Conclusion: We concluded that there was no significant difference between the two groups concerning alveolar bone length and thickness. However, group II (treated with rectangular Cu NiTi archwires) showed a significant decrease in root length.