# 3D volumetric changes and force delivery at the attachment region of different aligner materials

## TL;DR

This study compares how two aligner materials change in volume and force delivery under simulated mouth conditions and repeated use.

## Contribution

The study introduces a novel in vitro model to assess aligner material deformation and force resistance under simulated intraoral aging.

## Key findings

- Exposure to simulated intraoral environment increased disinsertion force by 56.2% in aligners.
- PET-G polymer showed greater volumetric changes compared to Polyutherane-based polymer.
- Volumetric changes were not significantly affected by crowding severity or SIE exposure.

## Abstract

The aim of this in vitro study was to compare the volumetric changes in the attachment regions of two aligner materials subjected to a cyclic insertion-disinsertion model, as well as the influence of a simulated intraoral environment (SIE) on the disinsertion force of the aligners.

Passive aligners of each material were obtained from two patients with different intraoral conditions (mild and severe crowding). Half of these aligners were immersed in SIE. Three study times were established at 35, 50, and 75 insertion disinsertion cycles. At each study time, the aligners were scanned with a Trios 3 intraoral scanner, and the STL models obtained were superimposed for comparative analysis of the volumetric change. The mean and maximum disinsertion forces were also quantified.

An increase in the mean force of disinsertion was observed for both aligner materials after exposure to SIE, with a statistically significant increase observed for material 1 (p < 0.05). Following exposure to SIE, the aligners exhibited a mean rise in maximum disinsertion force of 56.2% in contrast to their performance under ideal conditions. However, there were no statistically significant differences in volumetric changes regardless of the magnitude of crowding and exposure to SIE.

Exposure to SIE adversely affects aligner deformation and disinsertion resistance. The PET-G based polymer demonstrated a consistently greater tendency toward volumetric change than the Polyutherane-based polymer.

Intraoral aging can significantly affect aligner force and volumetric changes, reducing the predictability of planned tooth movements.

The online version contains supplementary material available at 10.1007/s00784-025-06733-3.