Effect of different artificial aging conditions on ceramic-composite bond strength

Current knowledge about how storage conditions affect resin-ceramic bonding remains incomplete. While prior research has shown that water exposure can reduce bond strength, the specific effects of thermocycling versus prolonged water storage are less clear. Established methods include sandblasting and ultrasonic cleansing as standard preparation steps. However, the durability of these bonds under simulated oral conditions is still debated. No prior work had resolved whether thermocycling or water storage alone has a greater impact on bond strength. This uncertainty limits the ability to predict long-term performance of dental restorations. The need for clearer comparisons between aging conditions is evident. This gap motivated the current investigation into different artificial aging protocols.

This study aimed to assess how different artificial aging conditions affect the bond strength between composite resin and zirconia ceramic. The specific problem addressed is the lack of clarity regarding which aging method—thermocycling or water storage—has a stronger influence on bond durability. The motivation comes from the need to improve the longevity of dental restorations. Understanding the effects of simulated oral conditions is essential for clinical application. The study focused on comparing five distinct storage conditions. These included varying durations of water exposure and thermocycling cycles. The goal was to identify which conditions most significantly impact bond strength. This information could help guide clinical bonding protocols.

The experiment involved bonding composite resin to zirconia ceramic disks after sandblasting and ultrasonic cleansing. Five bonding methods were tested, each with distinct surface preparation and adhesive application. Ceramic samples were stored under five different conditions. These included 3 days, 31 days, and 150 days in distilled water at 37 degrees Celsius. Additional conditions involved thermocycling between 5 and 55 degrees Celsius. Thermocycling was applied either alone or in combination with water storage. Tensile bond strength was measured after each condition. Statistical analysis used the Kruskal-Wallis and Wilcoxon rank sum tests. These methods allowed comparison of bond strength across groups.

The highest mean bond strength was 41.9 MPa, while the lowest was 7.7 MPa. These values varied significantly across the five storage conditions tested. The Kruskal-Wallis test confirmed statistically significant differences among groups. The Wilcoxon rank sum test further identified specific condition pairs with significant differences. Thermocycling had a greater impact on bond strength than water storage alone. Prolonged water storage at 37 degrees Celsius reduced bond strength over time. The most extreme condition—150 days in water plus thermocycling—showed the lowest bond strength. These findings suggest that thermocycling is a more severe aging condition for resin-ceramic bonds.

The authors found that thermocycling significantly affects resin bond strength to zirconia ceramic. Their results suggest that thermocycling is a more severe aging condition than prolonged water storage. The study does not propose new bonding methods but highlights the importance of considering thermocycling in durability assessments. These findings may influence how bonding protocols are evaluated in clinical settings. The authors do not claim that water storage alone is sufficient for predicting bond strength. They emphasize the need to include thermocycling in aging protocols. No new materials or techniques are introduced in this work. The conclusions are based solely on the observed data from the five storage conditions.