Primary Evaluation of Shape Recovery of Orthodontic Aligners Fabricated from Shape Memory Polymer (A Typodont Study)

Abstract

As an innovative approach to overcome the rate-limiting staging of conventional aligners, using shape memory polymers (SMPs) as aligners’ materials was investigated in this in vitro study. The ability of SMPs to shape recover and consequently move tooth, upon appropriate stimuli, was evaluated on a typodont model before clinical application. The study design was to achieve 1.9 mm correction movement of an upper central incisor by one aligner after multiple steps/activation. A custom-made aligned typodont model with a movable upper central incisor was scanned. Using an orthodontic software and a 3D printer, resin-models were generated. Seven aligners of ClearX sheets (SMPs) were fabricated by thermoforming on the resin aligned model. Each aligner was tested for repositioning of the central incisor in the typodont model. The model was scanned after each step and the corrective movement was measured through the superimposition of scans. Results showed that the total correction efficiency of the SMPs’ aligner was ≈93% (1.76 mm). The corrective movement was 0.94 ± 0.04 mm after the reforming step, 0.66 ± 0.07 mm after the first activation step, and 0.15 ± 0.10 mm after the second activation step. It was concluded that aligners made of SMPs could have a promising future-use in orthodontic aesthetic treatment.

Potential Application of 4D Technology in Fabrication of Orthodontic Aligners

“…Aesthetics is one of the major demands of patients who seek dental treatment. Major problems facing patients of orthodontic treatment are the bad appearance of metallic orthodontic braces, keeping good oral hygiene, and the long treatment time (Elshazly et al, 2021). In the last decade, treatment by orthodontic aligners has shown growing interest (Ercoli et al, 2014;Ojima and Kau, 2017).…”

“…In most of the popular aligner systems in the market, each aligner is designed to move a tooth within the restriction of 0.2 to 0.3 mm for translations and 1 °to 3 °for rotations, for that it is worn approximately 14 days, and then it should be changed with its successor (Kwon et al, 2008;Thukral and Gupta, 2015;Elkholy et al, 2016). This stepwise staging of conventional aligners leads to time and material consumption and consequently high cost of the treatment (Martorelli et al, 2013;Ercoli et al, 2014;Elshazly et al, 2021).…”

“…Nonetheless, investigators are continuously working on improving the efficiency of the treatment. Many optimizations, innovations, and advances are aiming to facilitate the process and to reduce the time and the cost (Phan and Ling, 2007;Morton et al, 2017;Elshazly et al, 2021). Several researchers are focusing on two main drawbacks: the shortcomings of conventional materials and the biological consideration of tooth movement.…”

“…Numerous methods have been introduced to biologically accelerate tooth movement (Ojima and Kau, 2017). On the other side, introduction of new aligner material also draws attention (Silverman and Cohen, 1969;Choi and Kim, 2005;Lai and Rule, 2020;Elshazly et al, 2021).…”

“…Shape memory polymers (SMPs) are one of the novel materials to be recently introduced into the field of dentistry, particularly for orthodontic applications (Mahmood et al, 2019;Elshazly et al, 2021). They provide great potential for applications in medical materials (Lendlein and Langer, 2002;Zhang et al, 2009;Meng and Li, 2013).…”