The aim of this two-arm randomized clinical trial was to compare the effect of 7-day and 14-day orthodontic clear aligner wear protocols on external apical root resorption (EARR) and pain perception

Fifty adult patients (21 Male and 29 female with a mean age of 23.7 ± 1.8) presented at the postgraduate orthodontic clinics at Jordan University of Science and Technology (JUST) were randomly allocated into a 7-day or 14-day aligner change protocol. Each patient underwent a standardized series of digital periapical radiographs (three upper and three lower). Baseline radiographs (T0) were taken before the initiation of treatment, and follow-up radiographs (T1) were collected after six months of aligner therapy.

EARR was measured from a line drawn at the cemento-enamel junction (CEJ) to the tooth's apex before treatment (T₀), and after treatment (T1), the difference in length was calculated and graded using the Malmgren Index. Pain perception was assessed using a verbal rating scale (VRS) at six-time intervals (24 hours, first week, second week, first month, third month and sixth month). Statistical analyses were used to compare pre- and post-treatment changes within and between the groups. Multiple linear regression was used to identify predictors of EARR.

Inclusion Criteria:

• Participants with complete permanent dentition except wisdom teeth
• Participants presented with mild to moderate malocclusion (Average degree of crowding).
• Participants with good oral hygiene and absence of periodontal disease.
• No history of trauma or prior orthodontic treatment.

Exclusion Criteria:

• Participants with thin or petite roots.
• Participants with pre-existing root resorption
• Participants with endodontically treated incisors or canines.
• Participants with history of trauma to incisors teeth
• Participants with previous orthodontic treatment.
• Participants with periapical pathology, ankylosisor cystic lesions.
• Participants with medical conditions that may affecting pain or inflammatory responses.