External apical Nilotinib mechanism root resorption is an undesirable sequel of orthodontic treatment that results in permanent loss of tooth structure from the root apex. Different types of orthodontic tooth movement may produce different mechanical stresses at varying locations with the root.1 An extensive review concerning root resorption by Brezniak and Wasserstein2,3 indicated that multiple factors are involved in the mechanism. These include such matters as genetics and systemic factors, sex differences, type of tooth movement, magnitude of orthodontic force, duration and type of force.2,3 Some studies4,5 have aimed to elucidate the causal relationship between force application, tooth movement and root resorption by using scanning electron microscopy (SEM) and concluded that root resorption is time- and force-dependent, and the type of tooth movement also seems to play a role.

All human teeth develop resorption lacunae on the pressure side of the root surfaces shortly after application of orthodontic forces1,6�C8 starting at or near the periphery of hyalinized areas.1,6 Owman et al7 reported that the initial resorption lacunae are small and can be identified only by histological methods and orthodontically-induced root resorptions after 7 weeks of treatment, are verified histologically, and are not visible in periapical radiographs. Radiographic examination of orthodontically treated patients showed some loss of root length.9�C11 The maxillary incisors have been regarded as the most susceptible to root resorption, particularly those with blunt or pipette-shaped roots.

9,12�C13 A 3-month radiographic control has been recommended for maxillary incisors with an enhanced risk of root resorption.14 There are different opinions regarding whether a correlation exists between the duration of active treatment and the incidence and degree of root resorption.14�C18 The aims of this study were to determine the prevalence of apical root resorption in maxillary central and lateral incisors during the initial stages of active orthodontic treatment and to test the hypothesis that root resorption increases with the progress of the treatment. MATERIALS AND METHODS The study sample consisted of 20 Turkish Anatolian patients (14 females and 6 males), with a mean age of 14.9��2.8 years (range 11.6 to 22.3 years).

After ethical clearance from Ankara Clinic Researches Ethical Committee No: 3 with record number: HEK 09/243, the patients Brefeldin_A who were referred to Department of Orthodontics for the treatment of their malocclusion were selected randomly. The initial malocclusion of the patients was Angle Class I with anterior crowding. The severity of the crowding (4�C6 mm) was similar among the patients. All the patients were treated with multibonded pre-adjusted appliances (Roth brackets) with .018�� bracket slots. During the treatment edgewise mechanics were used. The initial arch wire was .016�� Nickel-Titanium, then .016x.016�� Ni-Ti, .016x.