Innovation Glass-Ceramic Spray Deposition Technology Improving the Adhesive Performance for Zirconium-Based Dental...

Dental restorations require strong and durable bonding between zirconia and resin cement. Lithium disilicate (LD) glass-ceramics are known for their favorable bonding properties. However, applying LD to zirconia remains challenging. Glass-ceramic spray deposition (GCSD) has emerged as a promising technique for coating zirconia surfaces with LD. While GCSD has shown potential in improving resin cement adhesion, the impact of etching duration on bond strength and long-term durability remains unclear. Existing studies have not fully explored how etching time affects the microstructure and wettability of the LD layer. This uncertainty motivates further investigation into optimizing GCSD protocols for zirconia-based dental restorations.

This study aimed to evaluate how different etching times after GCSD affect the resin cement–zirconia bond strength and durability. Researchers focused on comparing air abrasion and hydrogen fluoride (HF) etching methods with varying durations. The goal was to determine whether specific etching conditions could produce bond strengths comparable to those of pure LD. By analyzing surface characteristics such as roughness, wettability, and phase changes, the study sought to identify optimal post-GCSD treatments for zirconia. The research also aimed to assess how thermocycling impacts bond durability over time. This work addresses a gap in understanding how surface modification influences long-term bonding performance in dental restorations.

The study used zirconia samples coated with lithium disilicate via glass-ceramic spray deposition (GCSD). Samples were treated with either air abrasion using aluminum particles (ABB) or air abrasion (GAB), or etched with 5.0% hydrogen fluoride (HF) for 20, 60, 90, or 120 seconds (G20, G60, G90, G120). Lithium disilicate (LD) served as a control group (LDG). Researchers analyzed surface microstructure, sub-micron roughness, wettability, and phase changes using appropriate characterization techniques. Resin cement was applied to the treated zirconia surfaces, and half of the samples underwent thermocycling (5000 cycles at 5–55°C) to simulate long-term use. Shear bond strength (SBS) was measured for each group, with 10 samples per condition. The study compared bond strength values pre- and post-thermocycling to assess durability.

GCSD combined with hydrogen fluoride etching significantly improved resin cement–zirconia bond strength. Etching for 90 or 120 seconds (G90, G120) produced shear bond strength (SBS) values comparable to those of the LD control group (p > 0.760). These samples maintained high bond strength even after thermocycling. Surface roughness and hydrophilicity increased with longer etching times, which likely contributed to stronger bonding. Shorter etching times (20–60 seconds) resulted in lower SBS values, suggesting insufficient surface modification. The study found no significant differences in SBS between pre- and post-thermocycling for G90 and G120 groups. This indicates that HF etching for 90–120 seconds after GCSD provides durable bonding performance. The results suggest that etching time is a critical factor in achieving optimal bond strength and durability.

The study demonstrates that hydrogen fluoride etching for 90–120 seconds after GCSD can produce resin cement–zirconia bond strengths comparable to those of pure lithium disilicate. This finding suggests that GCSD combined with appropriate etching protocols can effectively enhance bonding performance. The authors propose that increased surface roughness and hydrophilicity from longer etching times contribute to stronger and more durable bonds. The results indicate that etching time significantly influences the microstructure and wettability of the LD layer. The study supports the use of GCSD with HF etching as a viable method for improving zirconia bonding. No prior work had resolved how etching duration affects bond durability in this context. The findings suggest that optimizing etching time can help achieve bonding performance similar to traditional LD materials. These conclusions are based on the observed SBS values and surface characteristics reported in the study.