Comparative analysis of experimental torque behavior and physicochemical properties of commercial and in‑house orthodontic aligners.

Authors

Gustavo Holderbaum, Anderson Beatrici, Esther Rieko Takamori, José Mauro Granjeiro

Published in

Journal of the World federation of orthodontists. Sep 15, 2026. Epub Sep 15, 2026.

Abstract

Clear aligner performance depends on the magnitude and time-dependent behavior of experimentally generated moments. This study compared polymer identity, local post-thermoforming thickness, and experimental torque behavior of a commercial multilayer aligner (Invisalign) and two in-house thermoformed PETG aligners.
Ethical approval and consent were obtained. A digital scan from one patient was used to fabricate a standardized 3D-printed maxillary model. Three systems were evaluated: Invisalign (thermoplastic polyurethane [TPU]-based) and two vacuum-formed PETG systems (BioArt and Forestadent). Polymer identity was determined by ATR-FTIR. SEM assessed local thickness and morphology after thermoforming. Experimental torque, defined as mechanical moment (N·mm), was quantified using a setup programmed to produce a 0.3 mm displacement of the maxillary right central incisor. Short-term torque was recorded from 0 to 3 minutes (n = 5 per group) and analyzed using two-way repeated-measures ANOVA. Seven-day torque decay was monitored under dry, room-temperature conditions (n = 2 per group) and interpreted descriptively.
ATR-FTIR confirmed PETG signatures for BioArt and Forestadent and TPU signatures for Invisalign. Thermoforming reduced local PETG thickness at tooth 11 by 58.6% for BioArt and 45.8% for Forestadent. At baseline and 3 minutes, Invisalign and Forestadent generated higher experimental torque than BioArt. Significant short-term torque reduction occurred for Invisalign and Forestadent, but not for BioArt. In the exploratory 7-day assessment, torque loss was 12.3%, 13.6%, and 20.2%, respectively.
Material chemistry and local geometry influenced experimental torque magnitude and relaxation under in vitro conditions. Long-term findings were exploratory and require confirmation under clinically relevant conditions.

PMID:
42744724
Bibliographic data and abstract were imported from PubMed on 16 Sep 2026.

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