Purpose: To evaluate the bonding receptiveness of zirconia treated with nano-silica surface infiltration and the bond strength of composite cement after aging.
Materials and methods: Zirconia ceramic green bodies (Ceramill zolid, Amann Girbach) with dimensions of 10 x 10 x 4 mm were divided into three groups (n = 4): group C (control: no treatment after sintering), group S (sandblasted: 50-μm alumina airborne particle abrasion after sintering) and group N (nanosintered: infiltrated with nano-silica colloid, sintered, and then etched with hydrofluoric acid). Phase transformations were examined through X-ray diffraction (XRD). Composite resin (Filtek Z250, 3M Oral Care) was bonded to zirconia using the 10-MDP-containing composite cement Panavia F (Kuraray Noritake). The composite-cement/zirconia bond strength was immediately measured using the microtensile bond strength test (µTBS) as well as after three months of artificial aging in water (n = 20 microstick specimens/group). Failure mode patterns were examined using SEM.
Results: The specimens of groups C and S, as tested by XRD, exhibited almost full tetragonal phases, while a small extent of tetragonal-monoclinic phase transformation (t→m) was observed for group N. Group N achieved the highest bond strengths (41.5 ± 8.6 MPa), which was significantly higher than that measured for groups C and S (p < 0.05). There was a significant drop in µTBS after 90 days of water storage for groups C and S. SEM revealed a decrease in the percentage of cohesive failure in groups N and S after water storage.
Conclusions: Infiltrating zirconia with nano-silica is a reliable method to establish a strong and stable bond to zirconia. The combination of surface infiltration with nano-silica and application of a phosphate monomer-containing composite cement can significantly improve the composite-cement/zirconia bond strength.
Keywords: adhesion; bond strength; nano-silica; zirconia.