Effect Of Glaze Technology Inside The Crown On Adhesive And Mechanical Properties Of Y-TZP Ceramic

ObjectiveZirconia is an inert material with limited glass phase,so zirconia is resistant to hydrofluoric acid（HF）,and there is no reliable bonding between zirconia ceramic and resin cement.Therefore,surface treatments are often used to improve the bonding prop-erty of zirconia.It applies the new surface treatment-glaze technology inside the crown in this study,comprehensively evaluating the effect of glaze technology inside the crown on mechanical behavior of yttrium-stabilized zirconium dioxide（Y-TZP）ce-ramic and its bonding strength with resin cement from two aspects of adhesive and mechanical properties.It is aimed to study whether surface treatments can improve the bonding strength,at the same time minimizing the damage to the mechanical property of zirconia ceramic or effectively improving the strength.MethodsPrecision cutting saw was used to make 64Ⅰclass specimens（8 mm×8 mm×3 mm）（±0.2 mm）and 40Ⅱclass specimens（25 mm×4 mm×1.2 mm）（±0.2 mm）of Y-TZP ceramic,respectively.Ⅰclass specimens were used for scanning electron microscope（SEM）,the surface roughness,energy spectrum analysis（EDS）,X-ray diffraction（XRD）and shear bond strength（SBS）test,whileⅡclass specimens were used for three-point bending strength test.Zirconia specimens were randomly divided into 4groups.Group A:blank control group;Group B:sandblasting treatment group;Group C:glazing+hydrofluoric acid etching treatment group;Group D:glazing+hydroflu-oric acid etching+silanization treatment group.In this paper,the bonding property of Y-TZP ceramic was analyzed by means of bonding property indexes.Firstly,SEM was used to observe the surface microstructure.Form talysurf was used to measure the sur-face roughness.EDS was used to analyze the surface chemical composition.Then,specimens of each group were bonded with Rely X^TM U200 self-adhesive resin cement,and the samples were kept in a constant temperature water bath at 37℃for 24 h.Fi-nally,the SBS between zirconia and resin cement was tested by universal testing ma-chine,and the fracture patterns of all fragments were observed under microscope with20 times magnification.The mechanical property of zirconia was evaluated by mechan-ical property indexes.XRD was used to analyze the surface crystal structure and uni-versal testing machine was used to test the three-point bending strength,respectively.Results1.The surface roughness of treatment groups increased obviously,whose descend-ing order was group C（0.62±0.01）μm>group D（0.55±0.02）μm>group B（0.11±0.02）μm>group A（0.05±0.01）μm（P<0.05）.2.The surface of specimens in the group B contained 2.2%monoclinic zirconia（m-Zr O2）,while the content of other groups was zero.3.In addition to elements of Zr and O,there was 6.49%Al element in the group B specimens,and 18.67%and 25.78%Si element in the groups C and D specimens,re-spectively.4.The SBS in the groups A,B,C and D was（3.11±0.40）,（4.23±0.45）,（6.62±0.60）and（10.46±0.83）MPa,respectively（P<0.05）.5.The three-point flexural strength in the groups A,B,C and D was（961.07±75.53）,（1234.73±114.09）,（1024.28±120.51）,and（1036.09±80.10）MPa,re-spectively,among which the multiple comparisons of groups A,C and D showed no statistical difference（P>0.05）.Conclusions1.Limited surface roughness is formed on the specimen surface of sandblasting treatment group,and the improvement effect on zirconia bonding strength is insuffi-cient.2.Glazing inside the crown+HF acid etching+silanization treatment can signifi-cantly improve the bonding strength between zirconia and the adhesive.This kind of treatment will not cause tetragonal zirconia（t-Zr O₂）→m-Zr O₂transition on the surface of zirconia ceramic,and will not affect the bending strength.3.As a surface treatment method with important clinical application value,the glazing technology inside the crown can obviously improve the bonding strength of zirconia ceramic without affecting the bending strength,simplify the process and re-duce the production cost.