Silica coating of zirconia by silicon nitride hydrolysis on adhesion promotion of resin to zirconia

In this study, the effect of silica coating on zirconia by silicon nitride hydrolysis in resin zirconia bonding was investigated. The silica coated zirconia samples were prepared in silicon nitride dispersion at 90 °C under different immersion times followed by a thermal treatment at 1400 °C. Four test groups were prepared: 1) zirconia samples treated by sandblasting, 2) zirconia samples treated by immersion in silicon nitride dispersion for 6 h, 3) zirconia samples treated by immersion in silicon nitride dispersion for 24 h and 4) zirconia samples treated by immersion in silicon nitride dispersion for 48 h. The coatings were characterized by SEM, EDX, XRD and Raman. The resin zirconia bond strengths of the four test groups were evaluated under three storage conditions: dry storage, water storage in deionized water at 37 °C for 30 days and thermo-cycling for 6000 cycles between 5.0 and 55.0 °C. Surface morphology and composition of zirconia were changed after surface treatments. Phase transformation was observed for zirconia surface by sandblasting treatment but was not observed for zirconia surface treated with silicon nitride hydrolysis. Significant differences in bond strengths were found under different surface treatments (p < 0.001) and under three storage conditions (p < 0.005). The highest bond strength values were obtained by sandblasting treatment.