ORIGINAL RESEARCH article
Front. Mater.
Sec. Ceramics and Glass
Enhancement of Zirconia–Veneering Porcelain Bond Strength via Thermal Phosphoric Acid Etching Combined with Lithium Silicate Coating and the Influence of Multiple Sintering Cycles
Provisionally accepted
- School and Hospital of Stomatology, Wenzhou Medical University, Wenzhou, China
Select one of your emails
You have multiple emails registered with Frontiers:
Notify me on publication
Please enter your email address:
If you already have an account, please login
You don't have a Frontiers account ? You can register here
Objective: To evaluate the effect of thermal phosphoric acid etching combined with a lithium silicate (SiLi) coating on the interfacial bond strength between zirconia and veneering porcelain, and to investigate the influence of multiple sintering cycles on veneering porcelain surface properties and zirconia core mechanical performance. Methods: Zirconia specimens were allocated into four groups: untreated control, acid etching, SiLi coating, and acid etching + SiLi coating. Each group was subjected to 1, 3, 5, or 7 low-temperature sintering cycles. Shear bond strength, three-point flexural strength, water contact angle (WCA), and Vickers hardness were measured. Microstructural and compositional changes were analyzed via scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Results: XRD confirmed the formation of zirconium hydrogen phosphate after acid etching and a SiLi layer after coating. The acid etching + SiLi group showed the highest shear bond strength and a significant reduction in WCA compared with the untreated (p < 0.05). Multiple sintering cycles produced a parabolic trend in bond strength and veneering porcelain hardness, with peak values after three cycles in the acid etching + SiLi group. No significant differences in three-point flexural strength were observed among groups (p > 0.05). Conclusion: Thermal phosphoric acid etching combined with SiLi coating significantly improves the zirconia–veneering porcelain bond without compromising the flexural strength of zirconia. Clinically, the number of sintering cycles should be limited to three or fewer to preserve optimal interfacial adhesion and veneering porcelain hardness.
Keywords: Lithium silicate coating, Sintering Cycles, Thermal Phosphoric Acid Etching, Veneering porcelain, Zirconia
Received: 17 Dec 2025; Accepted: 26 Jan 2026.
Copyright: © 2026 Chen, Yang, Zou, Lin and Hu. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Xiaohui Hu
Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.