This experimental study will evaluate the effect of corticision on accelerating the leveling and alignment of lower crowded incisors compared with the control untreated group using cone beam computed tomography.

The study sample will consist of 26 patients with less than 6 mm crowding. The sample will be allocated randomly into two experimental groups.

The brackets and passive SS wire will be applied with radiographic metal guides between each tooth to allow for accurate corticision site 2 mm below the gingival papilla and to prevent tooth roots injury. The dentoalveolar changes occurring after leveling and alignment of lower anterior teeth will be evaluated using CBCT radiographs, Frequency, degree of root resorption, and the incidence of bone dehiscence will be assessed in relation to initial situation.

Crowding is the most common form of malocclusion. Different methods have been used to resolve crowding, including extraction and nonextraction. Corticision is an important methods to accelerate tooth movement in crowded cases. Cortical bone incision without flap elevation enhances turnover rate of surrounding structures and decreases the time for leveling and alignment. In orthodontics, CBCT imaging has been applied to evaluate impacted teeth and root resorption. But the data are very rare regarding the application of CBCT in tooth movement. So CBCT will be used in this research to evaluate the amount of external apical root resorption (EARR) and presence of dehiscence in the lower anterior teeth in the crowded cases. Furthermore, the duration of alignment will be compared between corticision group and non-corticision group.

Inclusion Criteria:

• patients age 18 years or more
• complete permanent dentition with second molars
• crowding of less than 6 mm
• good healthy patients without systematic diseases
• absence of spaces in the lower dental arch
• orthodontic treatment protocol does not required extraoral appliances, intraoral elastics, and expansion during leveling and alignment in the lower arch
• good oral hygiene
• absence of periodontal lesion

Exclusion Criteria:

• patients with syndromes, clefts, or craniofacial abnormalities or systematic diseases
• poor oral hygiene or periodontal lesion
• previous orthodontic treatment.
• Inability for brackets bonding in lower anterior teeth
• presence of extreme skeletal discrepancy in vertical , transverse and anteroposterior relations
• Delay rebonding of any loosing brackets for more than one week in the lower anterior teeth

The Individual participant data will be only available for the researchers in the department of Orthodontics, Damascus University