Silica Surface Modification Enhances the Mechanical Reliability of Zirconia-Porcelain Bilayer Systems

Abstract

Introduction and aims Zirconia-porcelain bilayer restorations commonly suffer from veneer chipping due to insufficient interfacial bonding and mechanical reliability. This study systematically compared alumina sandblasting with sol-gel-based silica surface modification in terms of the mechanical and interfacial performance of yttria-stabilised tetragonal zirconia polycrystal (Y-TZP)-porcelain systems. Methods We treated zirconia specimens by alumina sandblasting or sol-gel silica surface modification and characterised them using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and contact angle measurements before porcelain veneering. After veneering, flexural strength and bonding strength were evaluated in accordance with ISO 9693:2019. We assessed mechanical reliability using Weibull analysis. We examined fracture surfaces by SEM and qualitatively evaluated surface topography using confocal laser microscopy. Results Sol-gel-treated groups exhibited significantly higher flexural strength and bonding strength than the control or sandblasted groups and showed higher Weibull moduli. Representative SEM and EDS observations showed relatively uniform surface morphologies in the sol-gel-treated groups, with silicon remaining detectable after final polishing. The sol-gel-treated groups also exhibited significantly improved surface wettability. Representative fractographic observations further suggested distinct fracture characteristics between the surface treatment groups, with increased residual porcelain and mixed/cohesive fracture features observed in the sol-gel-treated groups. Conclusion Sol-gel-based silica surface modification improved the mechanical performance of zirconia-porcelain bilayer systems under the present in vitro testing conditions and was associated with higher Weibull reliability than conventional alumina sandblasting. Clinical relevance This study indicates that sol-gel-based silica surface modification may improve the mechanical performance and predictability of zirconia-porcelain bilayer systems. Further studies incorporating cyclic fatigue, thermocycling and hydrothermal aging are required to determine its long-term clinical relevance.

The authors' abstract, as published at the source. International Dental Journal, 2026 · DOI ↗