Comparison of tooth movement, root resorption and predictability of canine retraction using direct printed clear aligners with versus without attachment: A Cone-beam computed tomography-based study

Title

Comparison of Tooth Movement, Root Resorption, and Predictability of Canine Retraction Using Direct Printed Clear Aligners with Versus Without Attachment: A Cone-Beam Computed Tomography-Based Study

This split-mouth, in-vivo clinical study aims to compare the efficiency, predictability, and biological effects of canine retraction using in-house direct-printed clear aligners with and without attachments. The study will be conducted among orthodontic patients indicated for bilateral maxillary first premolar extractions and aligner therapy.

A total of 7 patients (14 samples) will be recruited following specific inclusion criteria such as age above 18, Class I or II malocclusion, good oral hygiene, and absence of systemic or periodontal disease. Each patient will undergo a split-mouth intervention, where one side of the arch will be randomly assigned to receive aligners with attachments, while the opposite side will receive aligners without attachments. Attachments include vertical rectangular shapes on canines to facilitate retraction and horizontal attachments on premolars and molars for anchorage. All aligners will be fabricated using a 3D printer and biocompatible resin and will be worn for 22 hours/day, with tray changes every 10 days over a 3-month period.

Cone-Beam Computed Tomography (CBCT) will be used at baseline (T0) and after retraction (T2) to obtain 3D models and assess treatment changes. Tooth movement will be measured in sagittal, transverse, and vertical planes, using defined anatomical reference planes and points. Parameters evaluated will include distalisation, tipping, rotation, extrusion, and bodily movement. In addition, root resorption will be measured by comparing root lengths between pre- and post-treatment CBCT scans.

Predictability will be assessed by comparing predicted movement (T1) with actual outcomes (T2) using Geomagic software for 3D superimposition, referencing the palatal vault and rugae. The main outcomes include differences in tooth movement, the extent of root resorption, and overall treatment predictability between the two groups.

This study addresses a critical gap in evidence regarding the role of attachments in improving the biomechanical performance of aligners during canine retraction. Findings from this research may influence clinical decision-making, aligner design, and enhance patient outcomes by supporting safer and more efficient orthodontic treatment protocols.