# Molecular Biocompatibility Assessment of PETG Aligners After Processing by Laser or Milling

## TL;DR

This study confirms that PETG, a biomedical material, remains safe after laser or milling processing, with minimal immune or hormonal effects.

## Contribution

The study introduces a comprehensive molecular and immunological assessment of PETG biocompatibility after laser and milling processing.

## Key findings

- PETG processing via laser or milling did not produce cytotoxic effects, with cell viability above 90%.
- Only modest gene expression changes were observed, below thresholds for biological activity.
- PETG remains functionally inert, with no significant immune or hormonal stimulation.

## Abstract

Polyethylene terephthalate glycol-modified (PETG) is a transparent, stable copolymer commonly used in biomedical devices such as surgical guides, clear aligners, and anatomical models. Its biocompatibility must be assessed not only for cytotoxicity, but also for subtle molecular and immunological responses, especially when in contact with mucosal or hormone-sensitive tissues. This study evaluated the biological safety of PETG processed via CNC milling and CO2 laser cutting, two methods that preserve bulk chemistry but may alter surface properties. PETG diskettes were analyzed by FT-IR, 1H-NMR, and GC–MS to confirm chemical integrity and absence of degradation products. Biocompatibility was tested using MCF-7 epithelial cells and THP-1 monocytes. Cell viability remained above 90% over seven days. Inflammatory (COX-2, TNFα, IL-8, IL-1α, IL-4, IL-10, IFNγ) and hormone-related (ERα, ERβ) gene expression was analyzed by qRT-PCR. Gene profiling revealed only modest, non-significant changes: COX-2 was upregulated 1.8-fold after laser processing, and ERα increased 1.6-fold following milling—both below thresholds considered biologically active. These findings indicate that mechanical surface treatments induce minimal bioactivity, with no meaningful immune or hormonal stimulation. PETG remains functionally inert under the tested conditions, supporting its continued safe use in intraoral and hormone-sensitive biomedical applications.