Investigating the role of aligner material and tooth position on orthodontic aligner biomechanics

Abstract

The primary objective of this work was to investigate the effect of material selection and tooth position on orthodontic aligner biomechanics. Additionally, material property changes with thermoforming were studied to elucidate its role in material performance in-vitro. An orthodontic simulator (OSIM) was used to evaluate forces and moments at 0.20 mm of lingual displacement for central incisor, canine and second premolar using Polyethylene terephthalate (PET), Polyurethane (PU) and Glycol-modified polyethylene terephthalate (PET-G) materials. The OSIM was scanned to generate a model used to fabricate aligners using manufacturerspecified thermoforming procedures. Repeated measures of MANOVA was used to analyze the effect of teeth and material on forces/moments. The role of thermoforming was evaluated by flexural modulus estimated by 3-point bend tests. -Pre-thermoformed and post-thermoformed samples were prepared using as-received sheets and those thermoformed over a simplified arch using rectangular geometry, respectively. Groups were compared using Two-way ANOVA. The PET, PU, and PET-G materials exerted maximum buccal force and corresponding moments on the canine. PU exerted more buccal force than PET-G on the canine and second premolar, and more than PET on the second premolar. The impact of thermoforming varied according to the specific polymer: PET-G remained stable, there was a slight change for PET, and a significant increase was noted for PU from pre-thermoformed to post-thermoforming. The results of this study elucidate the influence of material and arch position on the exerted forces and moments. Further, the mechanical properties of thermoplastic materials should be evaluated after thermoforming to characterize their properties for clinical application.

Effectiveness and Biocompatibility of Tooth Aligners Made from Polyethylene Terephthalate Glycol (PeT-G), Polypropylene (PP), Polycarbonate (PC), Thermoplastic Polyurethanes (TPUs), and Ethylene-Vinyl Acetate (EVA): A Systematic Review

“…Clear aligners, regardless of material, can treat a wide range of malocclusions. [ 6 7 8 9 10 ] Aligners are in direct contact with oral tissues during therapy; hence, biocompatibility is important. All aligner materials had low adverse effects and good biocompatibility in most trials.…”

“…Due to their transparency and endurance, patients liked PeT-G aligners. [ 1 10 ] TPU aligners, known for their flexibility and elasticity, were more pleasant than other materials during early treatment. [ 1 4 ] These findings show that aligner materials that improve patient comfort and tissue irritation may improve treatment outcomes and patient compliance.…”

“…PeT-G, PP, PC, TPU, and EVA aligners did not significantly affect malocclusion correction or treatment duration [ Table 1 ]. [ 6 7 8 9 10 ] Biocompatibility: Patient-reported discomfort, tissue reaction, and material-related adverse events assessed aligner biocompatibility. Most investigations found few adverse effects and good biocompatibility for all materials.…”

Advancements in Clear Aligner Fabrication: A Comprehensive Review of Direct-3D Printing Technologies

“…Intrusive forces are particularly concerning, as they commonly lead to root resorption during various tooth movements [87]. Lateral incisors are especially vulnerable due to force concentration on their smaller root surface area [88]. Inadequate forces hinder effective tooth movement [78], necessitating careful consideration of undesirable forces and moments during aligner-based orthodontic treatment planning [88].…”

“…Lateral incisors are especially vulnerable due to force concentration on their smaller root surface area [88]. Inadequate forces hinder effective tooth movement [78], necessitating careful consideration of undesirable forces and moments during aligner-based orthodontic treatment planning [88]. To mitigate these issues, it is crucial to apply mild forces initially to protect teeth and surrounding tissues.…”