Effect of zirconia nanopowders as functional fillers in dental adhesives on bonding durability and wear resistance to zirconia substrates

A major cause of long-term failure in zirconia-based restorations is the degradation at the adhesive interface, often accelerated by hydrolytic and mechanical stress. This study investigated the effect of incorporating zirconia nanoparticles into a light-curable adhesive system to enhance interfacial durability and bonding performance to zirconia. Forty zirconia discs were treated with adhesive formulations containing zirconia nanoparticles at different weight ratios (0:10, 2:8, 5:5 and 8:2, labeled Pure, 2Z8A, 5Z5A and 8Z2A respectively). Following photopolymerization, solubility tests in deionized water and wear resistance assessments under cyclic abrasion were conducted up to 24 weeks and 48,000 cycles respectively. Shear bond strength (SBS) was also tested using 20 sintered zirconia specimens. Surface morphology, roughness and elemental composition were characterized via optical microscope, surface profilometry, scanning electron microscope. Immersion testing revealed that the weight loss of the Pure group slightly increased, whereas the 2Z8A group exhibited the least weight loss and superior stability during the long-term period after four weeks while further exhibiting minimal thickness change after the abrasion test. In SBS testing, although the 2Z8A group exhibited the highest mean bond strength, the difference was not statistically significant compared with that of the Pure group ( P > 0.05). 2Z8A exhibited stable performance in abrasion, solubility, and bond strength, suggesting potential for oral applications in the future. The enhanced performance of the zirconia nanopowder-containing adhesive, especially 2Z8A, demonstrated improved hydrolytic and mechanical stability at the zirconia crown–abutment interface, addressing a key challenge in long-term clinical success.