In Vitro Study:The Effect Of Different Surface Treatments On Surface Microstructure And Bond Strength Of Hybrid Ceramics

Objective:To evaluate the effect of different surface treatments on surface microstructure and bond strength of hybrid ceramics.Methods:Two types of hybrid ceramics（Vita Enamic[VE]and Lava Ultimate[LU]）were selected.The ceramics were respectively sectioned into 40 specimens（6 mm×6mm×5 mm）and 32 specimens（16 mm×4 mm×1.5 mm）.Then,the specimens of each size were divided into 5 groups according to the surface treatments.（A）control,no treatment;（B）5%hydrofluoric acid etching for 60s;（C）sandblasted by25μm glass beads;（D）sandblasted by 50μm glass beads;（E）sandblasted by 110μm glass beads;（F）sandblasted by 25μm AL₂O₃ sandblasted;（G）sandblasted by 50μm AL₂O₃;（H）sandblasted by 110μm AL₂O₃ sandblasted.All of the sandblasting were applied for 15 s at a pressure of 2 bar with a distance of 10 mm.For the size of 16 mm×4 mm×1.5 mm,there are four different analysis as follows:Scanning Electron Microscope（SEM）,Laser scanning Confocal Microscopy（LSCM）,Surface roughness value（Ra）,three-point bending strength.Eighty dentin surfaces were bonded to the treated speciments of the size of 6 mm×6 mm×5 mm using a dual-cure resin cement（RelyXTM Ultimate,3M ESPE）according to the manufacturer’s instructions.The bonded specimens were stored in distilled water for 24 h at 37°C.The micro-shear bond strength（μSBS）of each sample was measured by using an universal testing machine at a cross-head speed of 1 mm/min（n=10/group）.The data were analyzed of ANOVA by SPSS 21.0 software（α=0.05）.Result:Comparing with the control group,the surface treatment showed a significant effect on the surface roughness value（Ra）（p<0.05）.The surface treatment with110μmAL₂O₃ showed higher surface roughness value compared with other surface treatments（p<0.05）.The SEM analysis showed that the surfaces of specimens treated by sandblasted showed micro-sized elevated and depressed areas with crevices and pits which possibly resulted from the high impact of blasting particles.110μm AL₂O₃group showed significantly lowest three-point bending strength compared with other group.For the VE system,HF,110μm glass beads,50μm AL₂O₃,110μm AL₂O₃groups showed significantly higher micro-shear bond strength（μSBS）compared with other groups.For the LU system,110μm glass beads,50μm AL₂O₃,110μm AL₂O₃groups showed significantly higher micro-shear bond strength（μSBS）compared with other groups.Conclusion:The surface morphology of hybrid ceramics could be influenced by alumina and glass beads sandblasting significantly.Appropriate sandblasting conditions could increase the bond strength of hybrid ceramics,which is an ideal surface treatment method.