Biocompatibility and Safety of 3D Printing Resins for Orthodontic Aligners: A Critical Review of Current Evidence
Cecilia Goracci, Utkarsh Mangal, Stevan M. Čokić, Annalisa Mazzoni, Alessandro Vichi, Uroš Josić · 2025 · 9 citationsRead the paper
Orthodontic aligners 3D-printed in resin currently provide a viable alternative to thermoformed ones. However, concerns have been raised regarding their biocompatibility. This review addressed the available scientific evidence on the biological properties of marketed resins for 3D printing of orthodontic aligners, encompassing cytotoxicity, estrogenicity, biofilm formation, and oral soft tissues reactions. A comprehensive literature search of several databases was conducted and PRISMA guidelines were followed to summarize the retrieval. Eleven studies were included in the review. They provided information on only three marketed resins: Tera Harz TC-85 DAC and Tera Harz TA-28 (Graphy) and Clear-A (Senertek). For the last two materials, only one investigation has been performed. Despite the large variability in experimental protocols, the lack of cytotoxicity of Tera Harz TC-85 DAC was a consistent finding. Also, no estrogenic effect was detected for this resin, in line with the lack of any bis-phenol A precursor in its chemical composition. In two clinical studies, oral soft tissue reactions were reported as rare and non-serious occurrences. Biofilm adhesion was regarded as critical for the clinical safety of 3D-printed aligners. Standardization of in vitro protocols, also including more clinically relevant settings, chemical characterization of the resins' eluates, and collection of additional in vivo data are advised to improve the quality of the evidence.
What the full text shows
Working prototype- Tera Harz TC-85 DAC resin demonstrated a consistent lack of cytotoxicity across various tested cell lines. (In vitro tests using various cell lines and extraction media)
- No estrogenic effect or BPA elution was detected for Tera Harz TC-85 DAC. — 0 μg/L BPA (Eluates stored in distilled water at 37 °C for 1 week)
- UDMA monomer release was detected from TC-85 aligners. — 29 to 96 μg/L (Centrifuged and post-polymerized for 24 min (non-nitrogen environment), stored in distilled water for 1 week)
- Post-curing in an oxygen-depleted (nitrogen-rich) environment significantly improves biocompatibility compared to curing in the presence of oxygen. — Moderate cytotoxicity in oxygen-present vs. high biocompatibility in nitrogen-rich (TC-85 resin tested on mouse calvaria pre-osteoblasts (MC3T3E-1) over 14 days)
- TC-85 aligners exhibit higher biofilm formation compared to thermoformed aligners. — Significantly more biofilm at 7 days vs. Smartee or Invisalign (Tested with Streptococcus mutans and Lactobacillus acidophilus)
- Clinical reactions to TC-85 aligners were rare and non-serious. — 1 case of lip swelling (n=17); 3 cases of moderate burning and 2 minor tissue reactions (n=54) (In vivo clinical use of TC-85 aligners)
- Setup
- Review of 11 studies focusing on three resins: Tera Harz TC-85 DAC, Tera Harz TA-28, and Clear-A.
- How
- A systematic review following PRISMA guidelines was conducted across Medline, Scopus, Web of Science, and Cochrane library. The authors analyzed 11 studies evaluating cytotoxicity, estrogenicity, biofilm formation, and clinical soft tissue reactions of 3D-printed resins.
- Limitations
- Large variability in in vitro experimental protocols (extraction media, incubation times, and ratios). · Limited chemical composition disclosure from manufacturers (only TC-85 disclosed). · Small sample sizes in available clinical studies. · Lack of standardized protocols for biocompatibility testing of 3D-printed aligners.
Summarized by Gemma 4 from the open-access full text · 8 Oct 2026. Read it