Evaluation of the Effect of Aligner Seaters on the Predictability of Tooth Movement in Clear Aligner Therapy.

A single-operator, multi-center randomized controlled trial (RCT) with a 1:1 allocation ratio will be conducted among patients seeking orthodontic treatment with clear aligner therapy. The study will take place at the Postgraduate Orthodontic Clinic, College of Dentistry, University of Baghdad, Baghdad, Iraq. Eligible participants will be randomly assigned to one of two aligner seater (chewy) use protocols. To minimize inter-operator variability, all participants will be treated by the same orthodontist.

A standardized clinical protocol will be followed. Each participant will undergo extraoral and intraoral photography, intraoral scanning using the Medit i700 scanner (Medit Corp., Seoul, South Korea), and radiographic assessment including cone-beam computed tomography (CBCT) and lateral cephalometric radiography.

On the day of aligner insertion, gingival index and plaque index will be recorded. The teeth will be isolated and cleaned with a water-pumice slurry using a rubber polishing cup mounted on a low-speed handpiece. The enamel surfaces will be rinsed and dried with oil-free compressed air, followed by conventional acid etching with 37% phosphoric acid for 30 seconds. The etched surfaces will then be rinsed for 10 seconds according to the manufacturer's instructions and air-dried until a frosty white appearance is observed.

A universal adhesive (BISCO All-BOND UNIVERSAL, USA) will be applied to the etched enamel surfaces using a nylon brush, followed by gentle air thinning for 2 seconds with the air stream directed perpendicular to the enamel surface. Attachment templates will be filled with Neo Spectra™ ST Universal Composite (Dentsply Sirona), a nanohybrid composite material, and attachments will be bonded according to the aligner manufacturer's prescribed attachment positions. The composite will then be light-cured for 20 seconds.

Group A (Regular-use group): Participants will use the aligner seater during the initial insertion of each new aligner for one to two days, or until the aligner is fully seated without visible gaps. Participants will be instructed to bite on the aligner seater for a few seconds while the aligner is in place.

Group B (Customized-use group): In addition to the regular-use protocol described for Group A, participants will be instructed to bite on the aligner seater for a few seconds each night at bedtime throughout the study period.

All participants will receive standardized written instructions regarding clear aligner care and the manufacturer's recommendations. A study-specific questionnaire will be completed to assess pain during treatment. Participants will attend follow-up visits every 30 days (after every three aligners), during which gingival index, plaque index, intraoral photographs, digital intraoral scans, and questionnaire data will be collected. Participants will also be instructed to contact the treating orthodontist immediately if attachment loss occurs.

Participants will be followed for four months.