Derotational movement generated by 3D directprinted aligner without attachment: A pilot study / Lee Geng Lim

Lee , Geng Lim (2024) Derotational movement generated by 3D directprinted aligner without attachment: A pilot study / Lee Geng Lim. Masters thesis, Universiti Malaya.

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Abstract

A three-dimensional (3D) direct-printed aligner is a new form of aligner which is directly printed from the designed file. Unlike the conventional thermoformed clear aligner, it omits the need to first print out a working model and subsequently thermoform a thermoplastic material on the model. It is claimed that 3D direct-printed aligner, printed using Tera Harz TC-85 (Graphy Inc, Seoul, Korea), exhibits shape memory and superior fitting accuracy while minimising or even omitting the need for attachment. The elimination of attachment in clear aligner therapy is desirable for patients and clinicians if predictable orthodontic tooth movement can be achieved without attachment. Nonetheless, clinical evidence is lacking on whether the 3D direct-printed aligner can achieve the planned orthodontic movement without attachment, particularly for challenging movements such as the derotation of round-shaped teeth. This study aimed to pilot test the effectiveness of 3D direct-printed aligner in derotating round-shaped teeth without using attachment. A prospective, pilot study was conducted on four patients who presented with five rotated premolars (4 maxillary first premolars, 1 mandibular second premolar) of more than ten degrees at the Postgraduate Orthodontic Clinic, Faculty of Dentistry, Universiti Malaya, from 25th January 2024 to 22nd July 2024. Each aligner was designed with a three-degree rotation specifically for the studied premolar and was worn full-time for ten days, except during meals and tooth brushing. The study involved wearing five aligners for a total of fifty days. The effectiveness of 3D direct-printed aligner in derotating the premolars without using attachment was explored by determining the percentage change in the rotation angle of the studied premolars based on the planned derotational movement (a total of 15 degrees using 5 aligners). Three participants developed temporary allergic reactions to the aligner halfway through the study, manifesting as symptoms such as inflammation, a burning sensation, or dry mouth. The fourth participant experienced no undesirable events throughout. Three out of four participants completed the study, while one participant dropped out after having the first aligner due to an allergic reaction; this participant also presented with a rotated mandibular second premolar. The percentage change in the rotation angle of the studied premolars based on the planned derotational movement was 6.7% (2 premolars), 20.0% (1 premolar), and 66.7% (1 premolar), respectively. The highest percentage change was observed in the only participant who did not experience any allergic reaction. Within the limitations of this pilot study, the effectiveness of 3D direct-printed aligners to derotate round-shaped teeth without attachment was found to be inconsistent, with percentage changes in premolar rotation angle varying from 6.7% to 66.7%. This variability may be due to inconsistent and/or non-compliant wear of the aligners, secondary to allergic reactions.

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