Effect Of Cyclic Loading On Shear Bond Strength Of Three Kinds Of Resin Cement To Zirconia Ceramics

Purpose:The purpose of this paper was to research the effect of cyclic loading on shear bond strength of three kinds of resin cement to zirconia ceramics.Cyclic loading wich includes compressive cyclic loading and shear cyclic loading was to simulate the oral masticatory force.The bond strength of the three kinds of resin cement was compared.Then it can provide reference for the selection and application of three kinds of resin cement.Materials and methods:1.Zirconia ceramic embryo was cut into the size of 10 mm * 10 mm * 10 mm and 10 mm * 10 mm * 5mm blocks with the low speed cutting machine,the number of each type of zirconia blocks was 36,then the zirconia blocks was sintered at high temperature sintering furnace.After sintering,the surfaces of the zirconia blocks was polished with 600 grit Sic for 5 minutes in the metallographic sample polishing machine,clean and dry,then the zirconia surfaces was blasted with alumina particles?Al2O3?with an average particle size of 110?m under a pressure of 0.2 Mpa for 21 seconds at a perpendicular distance of 10 mm from the holder.finally,the blocks were cleaned in ultrasonic cleaning machine for 6 minutes and dried with compressed air,it is in order to obtain the same surface roughness.2.The bonding and grouping of zirconia blocks: 3 kinds of resin cement were used in this experiment,which include:EMBRACE^TM WetBond^TM?Pulpdent company,USA,hereinafter referred to as EMB adhesive?;RelyX^TM Ultimate?3M company,USA,hereinafter referred to as Rely adhesives?;Multilink N?Ivoclar Vivadent company,Liechtenstein,hereinafter referred to as Mult adhesives?.According to the instructions for the use of three adhesives,Two types ofzirconia blocks are randomly chosen to be bonded,a total of 36 specimens were bonded,the bonded specimens were divided into 6 grops?n=6 per gronp?.All the bonded specimens were soaked in artificial saliva for 24 h,then soaked in artificial saliva for 9h.The bonded specimens are divided into the following groups:Group A: no cyclic loading,group EMB;Group B: no cyclic loading,group Rely;Group C: no cyclic loading,group Mult,Group a: cyclic loading,group EMB;Group b: cyclic loading,group Rely;Group c: cyclic loading,group Mult.Cyclic loading conditions: Firstly,shear cyclic loading of 50,000 cycles at 3 HZ between 0 and 98 N?for approximately 9 hours?was applied on the bonded specimens?group a,b,c?,the load was applied parallel to and at the edge part of the bonding surface in artificial saliva.Secondly,compressive cyclic loading of 50,000 cycles at 3 HZ between 0 and 98 N?for approximately 9 hours?was applied on the bonded specimens?group a,b,c?,the load was applied perpendicular to and at the centeral part of the bonding surface in artificial saliva.3.Experimental determination:?1?Shear bond strength testThe bonded specimens were subjected to the shear bond strength test at a crosshead speed of 0.5 mm/min until fracture occurred with the Instron 8872 fatigue testing machine.The force at separation?N?was divided by the cross-sectional area?100 mm2?to provide results in units of stress?MPa?: the shear bond strength ?b=maximum load shear force Fmax/ cross-sectional area.The experimental data were drawn by Origin software,and the results would be visualized.The shear bond strength??b /MPa?of group A and a,group B and b,group C and c would be compared by paired t test.The shear bond strength??b /MPa?of group A,B,C and group a,b,c were respectively analyzed with single factor analysis of variance?One-factor ANOVA?with spass20.0.P<0.05 is considered to have significant differences.?2?Microscope observation and energy spectrum analysisThe fractured interfaces of the specimens after shear bond test were examined with an ultra-deep-field microscope?OM?.The fracture surface of representative specimens were oberserved under a scanning electron microscopy?SEM?with an acceleration voltage of 5 kV after sputter coating using a gold-palladium alloy conductive layer,at the same time,the electronic scanning electron microscope?SEM-EDS?analysis were used,in order to determine the composition of different parts of the fracture surface.Thus the fracture characterization and analysis of surface will be obtained.Results:1.The shear bond strength??b /MPa?of group A,B,C and group a,b,c were respectively analyzed with single factor analysis of variance?One-factor ANOVA?with spass20.0.the result was that: There was significant differences between group A and group B,group a and group b,group A and group C,group a and group c,P<0.05;There was no significant differences between group B and group C,group b and group c.P> 0.05.2.The results of t test showed that there was no significant differences between group A and group a,group B and group b,group C and group c,P> 0.05.3.Microscope observation and energy spectrum analysis showed that:The failure mode of bonding surface of the all specimens was mainly mixed failure.Conclusion:1.The bond strength of EMB adhesive to zirconia ceramics was significantly less than that of Rely adhesive and Mult adhesive,while the bond strength of Rely adhesive and Mult adhesive had no significant differences.2.The bond strength of EMB adhesive,Rely adhesive and Mult adhesive to zirconia ceramics after 50000 cycles loading were decreased,but it had no significant differences.3.Microscope observation and energy spectrum analysis showed that: The failure mode of bonding surface of the all specimens was mainly mixed failure.