Effect Of Different Surface Treatment Methods On The Flexural Strength Of Zirconia Ceramic

Objective To investigate the effects of four different surface treatment methods on the shear bond strength and flexural strength of zirconia,provide experimental basis for the clinical choice of suitable surface treatment.Methods Preparation of fifty class ?(15mm �3mm �1mm)zirconia specimens and fifty class ?(3mm �3mm �3mm)zirconia specimens.after water sandpaper polishing,Class ? specimens were randomly divided into four groups and received the following treatments(n=10): A: blank control group;B: sandblasting with 110-?m alumina blasting particles;C: sandblasting with 50-?m alumina blasting particles;D: Er:YAG laser etching;D: hot acid etching of HF and HNO3.the changes of three-point bending strength of zirconia and crystal structure were tested after different surface treatment methods.The broken test piece were used for scanning electron microscopy to observe the surface morphology.Class ? specimens received the same treatments with class ?,After testing the surface roughness of the specimen,bonded the processing interface to the enamel(treating agent is Monobond N,and adhesive agent is PULPDENT embrace resin cement).Then stored in distilled water at 37? for 24 hours,the shear bond strength(SBS)was measured.All data were statistically analyzed using SPSS20.0 statistical software.The statistical test was set to P<0.05 with statistical significance.The resulting data is expressed as the mean � standard deviation.Results 1 The three-point bending(TPB)strength for the five groups were as follows: There was no statistically significant difference between Group A and Group C,Group D and Group E(P?0.05),but the difference between other groups were statistically significant(P?0.05).2 Scanning electron microscope results showed that the blank control group had a smooth surface and a compact structure.The surface of the 110 ?m alumina blasting group formed a pronounced bar-shaped depression.The surface of the 50 ?m alumina blasting group also had a bar-shaped depression,which was shallow and slender.The phenomenon of particle embedding is obvious;on the zirconia surface of the Er;YAG laser etched group,there are stripe etched lines and spotted pits after laser etching;a large number of prismatic grain granules are visible on the surface of the zirconia block of the hot acid etching of HF and HNO3 group.3 The XRD patterns show that the volume percentage of monoclinic phase of the five groups is 0.91%,12.50%,12.17%,6.64% and 17.81% respectively.The roughness value(?m)for the five groups were as follows: There was no statistically significant difference between Group B and Group C(P ? 0.05),but the difference between other groups were statistically significant(P ? 0.05).4 Mean SBS(MPa)was 7.00�0.67 in A,11.73�1.31 in B,9.89�0.92 in C,8.75�0.92 in D and 12.05�1.05 in E.There was no statistically significant difference between Group B and Group D(P?0.05),but the difference between other groups were statistically significant(P?0.05).Conclusion 1 50?m alumina sandblasting will not cause the change of zirconia's flexural strength,while 110-?m alumina blasting,Er:YAG laser etching,hot etch of HF/HNO3 mixed solution will cause the reduction of zirconia's flexural strength.The effect of 110?m alumina blasting on the zirconium oxide flexural strength was lower than that of Er:YAG laser etching and hot acid etching of HF and HNO3.2 Four kinds of surface treatment processes can effectively improve the shear bond strength of zirconia and resin cement.Among them,the zirconium oxide of 110-?m alumina sandblasting group and HF/HNO3 mixed solution hot etched zirconia has more obvious bending strength.3 Four kinds of surface treatment methods will lead to the transformation of tetragonal phase to monoclinic phase in zirconia ceramics.