This randomized split-mouth clinical trial aims to compare two different composite materials used for bonding attachments in clear aligner orthodontic therapy. Twenty adult participants with Class I malocclusion and mild crowding will receive flowable nanocomposite attachments on one side of the dental arch and packable microhybrid composite attachments on the opposite side. The primary outcome is the color change (ΔE) of the enamel surface after attachment removal, measured by a spectrophotometer (VITA Easyshade). Secondary outcomes include bonding and debonding time and changes in enamel surface roughness before and after treatment. The study will be conducted at the Orthodontic Department, College of Dentistry, University of Sulaimani. The goal is to determine which composite material provides better color stability, easier handling, and minimal impact on enamel surface characteristics during clear aligner therapy.

Clear aligner therapy has become a popular alternative to conventional fixed orthodontic appliances due to its superior esthetics and comfort. However, the efficiency of aligner treatment often depends on the proper use of composite attachments that enhance tooth movement and retention. Different composite resins are used for this purpose, but their optical stability and effect on enamel integrity after removal remain concerns.

This prospective, split-mouth randomized clinical trial compares a flowable nanocomposite and a packable microhybrid composite used for clear aligner attachments. Each participant will receive both materials in opposite quadrants to minimize inter-individual variability. Outcomes will include enamel color change (ΔE CIE Lab* values), bonding/debonding time, and surface roughness assessment using digital and optical analysis methods.

The study hypothesis is that the flowable nanocomposite will exhibit superior color stability and faster handling time, with comparable enamel surface effects to the packable composite. Results from this trial may help establish standardized protocols for attachment material selection in clinical orthodontic practice.

Inclusion Criteria:

• Adults 18-40 years.
• patients with class l malocclusion with in which there treatment will be completed in 6 month .
• Completed clear aligner therapy and scheduled for attachment debonding at the study clinic.
• Permanent teeth with intact buccal enamel at assessment sites.
• No caries, restorations, cracks, fluorosis, or hypoplasia on assessed surfaces.
• No bleaching within 6 months prior to baseline.
• Good general health (ASA I-II) and able to provide written informed consent.
• Satisfactory oral hygiene and gingival health (e.g., GI ≤ 1).
• Willing and able to complete measurements: spectrophotometric shade (CIE L*, a*, b*), photographs/scans, and VAS for pain/discomfort.
• Available for all visits and follow-up assessment.

Exclusion Criteria:

• Patients younger than 18 or older than 40 years.
• Patients presenting with severe or very severe anterior crowding (LII > 6 mm) or spacing will exclude from the study. Cases with posterior crossbites, open bites, or skeletal discrepancies
• Presence of systemic diseases (ASA > II) that may affect healing, pain perception, or enamel quality.
• Teeth with caries, restorations, fractures, enamel cracks, fluorosis, hypoplasia, or discolorations on the buccal surfaces at assessment sites.
• Patients who have undergone tooth bleaching within the last 6 months.
• History of major dental surgery or trauma in the study region.
• Patients with poor oral hygiene or gingival inflammation (GI > 1).
• Pregnant or lactating women.
• Patients with allergy or hypersensitivity to composite resins or dental adhesives.
• Individuals unable to provide informed consent or not willing to comply with study visits.

ot applicable. Individual participant data will not be shared. Only summarized results will be published.

Single-blind design: the outcome assessor will be blinded to the type of composite used on each quadrant.