[Effect of SiO(2)-ZrO(2) slurry coating on shear bond strength of zirconia to resin cement].

Objective: To evaluate the effect of shear bond strength between resin cement and zirconia using SiO(2)-ZrO(2) slurry coating. Methods: One hundred and forty pre-sintered zirconia discs were randomly divided into seven groups (n=20) according to the surface treatments: AS (as-sintered), SB (sand blasting with Al(2)O(3)), 2SiO(2)-1ZrO(2) (2ratio1 mole ratio SiO(2)-ZrO(2) coating), 1SiO(2)-1ZrO(2) (mole ratio 1ratio1 SiO(2)-ZrO(2) coating), 1SiO(2)-2ZrO(2) (mole ratio 1ratio2 SiO(2)-ZrO(2) coating), 1SiO(2)-3ZrO(2) (mole ratio 1ratio3 SiO(2)-ZrO(2) coating), 1SiO(2)-4ZrO(2) (mole ratio 1ratio4 SiO(2)-ZrO(2) coating). Each zirconia disc was bonded to composite resin cylinder using resin cement. All specimens were stored in distilled water (37 ℃, 24 h). Each group was divided into two subgroups in which half specimens were tested using universal testing machine and another half specimens accepted artificial aging of 5 000 times thermocycling then tested. Scaning electron microscopy (SEM) was used to observe the micro-morphology of coating surface etched by hydrofluoric acid,then the coating thickness was measured. Results: Before artificial aging, 1SiO(2)-1ZrO(2) showed a higher shear bond strength [(41.69+/-6.28) MPa] than all the other group (P<0.05). 1SiO(2)-2ZrO(2) gained a higher strength than AS, SB, 1SiO(2)-3ZrO(2) and 1SiO(2)-4ZrO(2) (P<0.05). However, 1SiO(2)-2ZrO(2) did not get a significant higher shear bond strength than 2SiO(2)-1ZrO(2) (P>0.05). No significant differences were found among SB, 2SiO(2)-1ZrO(2) and 1SiO(2)-3ZrO(2) (P>0.05). After artificial aging, shear bond strength of all groups were decreased significantly besides 2SiO(2)-1ZrO(2). 2SiO(2)-1ZrO(2), 1SiO(2)-1ZrO(2) and 1SiO(2)-2ZrO(2) [(24.13+/-5.50), (22.28+/-4.40), (23.11+/-4.80) MPa] showed higher shear bond strength than SB and 1SiO(2)-3ZrO(2) (P<0.05),no intergroup differences were observed (P>0.05). Shear bond strength of AS and 1SiO(2)-4ZrO(2) fell to 0 MPa approximately. The SEM images of etched coating surface showed contraction fissure due to different thermal expansion coefficient between SiO(2) and ZrO(2) and intercrystal pores of zirconia. The thickness of coating was measured to be less than 30 mum. Conclusions: Mole ratio 1ratio1 SiO(2)-1ZrO(2) slurry coating showed the highest shear bond strength of resin cement to zirconia.