Influences of environmental temperature on the UV-C colour printing performance

Bai X, Xu M, Wang A, Chen Y, Pow EH, Lohbauer U, Fan Z, Tsoi JK (2026)

Publication Type: Journal article

Publication year: 2026

Journal

Journal of Dentistry Elsevier

Book Volume: 165

Article Number: 106304

DOI: 10.1016/j.jdent.2025.106304

Abstract

Objectives: To explore the effects of environmental temperature during 222 nm UV-C colour printing on the change of optical properties of 3Y-TZP. Methods: 3Y-TZP discs were irradiated with a 222 nm UV-C light (irradiance: 1.870 mW/cm²) for 15 minutes to 24 hours. Environmental temperatures were controlled by a coldplate or hotplate, forming four groups: Heating group 1 (HG1, 360.15 K), HG2 (340.15 K), reference group (RG, 310.15 K), and cooling group (CG, 280.15 K). CIE^⁎L^⁎a^⁎b values were recorded before and at multiple time points (0, 1, 3, 7, 10, and 14 days) post-irradiation to calculate ΔE^⁎, ΔE^⁎00 and TP. SPSS 28.0 was used for statistical analysis (α=0.05). Results: Lower environmental temperatures enhanced immediate ΔE^⁎ and reduced TP, with quadratic relationships observed. For 24-hour group, immediate ΔE^⁎ ranked CG (15.30) > RG (9.43) > HG2 (6.94) > HG1 (5.75), and TP ranked HG1 (10.11) > HG2 (10.16) > RG (8.56) > CG (6.71). Except in HG1, ΔE^⁎ and TP showed logarithmic relationships with irradiation time. Lower temperatures accelerated recovery for both ΔE^⁎ (Recovery speeds were 3.520, 3.656, 5.694 and 12.308 for HG1, HG2, RG and CG, respectively) and TP. RG showed the highest stabilised ΔE^⁎ for t ≥ 4h, while TP recovery was incomplete in CG groups with longer irradiation times. ΔE^⁎00 has similar trends with ΔE^⁎. Conclusions: 222 nm UV-C direct colour printing on zirconia was significantly influenced by environmental temperature. Lower environmental temperatures yield higher immediate ΔE^⁎, greater TP reduction, and faster recovery. This technique offers aesthetic colouration of dental zirconia restorations, UV-C detection, and reusable short-term information storage. Clinical Significance: 222 nm UV-C colour printing enables colour customisation, and the colour printing outcomes can be controlled through irradiation time and environmental temperature.

Authors with CRIS profile

Ulrich Lohbauer Medizinische Fakultät

Involved external institutions

The University of Hong Kong (HKU) / 香港大學

Hong Kong (HK) Columbia University Irving Medical Center (CUIMC)

United States (USA) (US) Hong Kong University of Science and Technology (HKUST) / 香港科技大學

China (CN)

How to cite

APA:

Bai, X., Xu, M., Wang, A., Chen, Y., Pow, E.H., Lohbauer, U.,... Tsoi, J.K. (2026). Influences of environmental temperature on the UV-C colour printing performance. Journal of Dentistry, 165. https://doi.org/10.1016/j.jdent.2025.106304

MLA:

Bai, Xuedong, et al. "Influences of environmental temperature on the UV-C colour printing performance." Journal of Dentistry 165 (2026).

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