Evaluation of the effects of temperature and centrifugation time on elimination of uncured resin from 3D-printed dental aligners
Ji-Eun Kim, Utkarsh Mangal, Jae-Hun Yu, Gi-Tae Kim, Hoon Kim, Ji-Young Seo et al. · 2024 · 33 citationsRead the paper
The study investigated the effects of temperature and centrifugation time on the efficacy of removing uncured resin from 3D-printed clear aligners. Using a photo-polymerizable polyurethane resin (Tera Harz TC-85, Graphy Inc., Seoul, Korea), aligners were printed and subjected to cleaning processes using isopropyl alcohol (IPA) or centrifugation (g-force 27.95g) at room temperature (RT, 23 °C) and high temperature (HT, 55 °C) for 2, 4, and 6 min. The control group received no treatment (NT). Cleaning efficiency was assessed through rheological analysis, weight measurement, transparency evaluation, SEM imaging, 3D geometry evaluation, stress relaxation, and cell viability tests. Results showed increased temperature and longer centrifugation times significantly reduced aligner viscosity, weight (P < 0.05), and transmittance. IPA-cleaned aligners exhibited significantly lower transparency and rougher surfaces in SEM images. All groups met ISO biocompatibility standards in cytotoxicity tests. The NT group had higher root mean square (RMS) values, indicating greater deviation from the original design. Stress relaxation tests revealed over 95% recovery in all groups after 60 min. The findings suggest that a 2-min HT centrifugation process effectively removes uncured resin without significantly impacting the aligners' physical and optical properties, making it a clinically viable option.
What the full text shows
Working prototype- Heating resin to 55 °C increases flowability and reduces viscosity. — 2.34-fold increase in flow; viscosity reduced from 0.95 Pa s (RT) to 0.17 Pa s (HT) (Tera Harz TC-85 resin)
- Centrifugation at 55 °C for 2 min effectively removes uncured resin while maintaining optical and physical properties. — Weight reduced to 2.18 ± 0.01 g vs. 2.47 ± 0.04 g (NT) (g-force 27.95 g, 500 rpm)
- IPA cleaning significantly reduces transparency and increases surface roughness compared to centrifugation. — Transmittance 33.99% (IPA) vs. 56.12% (HT-2) (1 min ultrasonic rinse in 99.5% IPA)
- Lack of cleaning (NT) leads to greater dimensional deviation from the original design. — Significantly higher RMS value (P < 0.05) (No treatment group)
- All cleaning methods maintained high shape recovery after stress relaxation. — >95% recovery after 60 min (Immersed in 80 °C water for 1 min, then 37 °C water bath)
- All tested groups met ISO biocompatibility standards. — Cell viability range 82.10% to 97.26% (L929 cells, ISO 10993-5 protocol)
- Setup
- n=3 to 5 per group; Tera Harz TC-85 polyurethane resin; LCD 3D printer (UNIZ NBEE); 0.5 mm aligner thickness.
- How
- 3D-printed aligners were cleaned using either IPA or centrifugation at two temperatures (23 °C and 55 °C) for three durations (2, 4, and 6 min). Efficacy was measured via rheology, weight, UV-vis spectrophotometry, SEM, 3D morphometric analysis, and MTT cytotoxicity assays.
- Limitations
- Small sample size for some tests (n=3) · Limited number of resin types tested (only Tera Harz TC-85)
Summarized by Gemma 4 from the open-access full text · 8 Oct 2026. Read it