Effects Of Ultrasonic Scaling On The Marginal Microleakage And Surface Roughness Of Cast Ceramic Restorations

[Objective]The aim of this study is to analyze the effects of ultrasonic scaling on the marginal microleakage and surface morphology of cast ceramic restorations by simulation of ultrasonic scaling in vitro,dyeing experiments,roughness experiments and scanning electron microscopy,and provide some clinical relevant guidance.[Methods]100 pieces of complete third molar were collected and made into 96 tooth bond models.IPS e.max Press cast ceramic was made into specimens with 6mm long,5mm wide and 1.1mm thick.The specimens were randomly divided into 12 groups of 8 specimens each.Each group was submitted to different luting agents:group 1-6:RelyX U200(U;self-bonding);group 7?8:RelyX Ultimate(LS;self-etching);group 9?10:RelyX Ultimate(LT;total-etching);group 11?12:Variolink N(V;total-etching).Each group was submitted to ultrasonic instrumentation for different scaler tips and different power:group 1,7,9,11-control of U,LS,LT,V;group 2-carbon composite micro-tips at very low power(PH1,0.2w),group 3-conventional metal tips at very low power(1#,0.2w),group 4-conventional metal tips at low power(1#,4.4w),group 5-conventional metal tips at middle power(1#,5.5w),group 6,8,10,12-conventional metal tips at high power(1#,6.6w).After dyeing experiments,specimens should be cutting by Low speed cutting machine.The length of methylene blue infiltration was observed and measured under stereo microscope.IPS e.max Press cast ceramic was made into specimens with 6mm long,5mm wide and 1.1mm thick.The specimens were divided into 3 groups of 10 specimens each,and polished by 400#,600#,800#abrasive paper.Each group was submitted to ultrasonic instrumentation for different scaler tips and different power:group 1-carbon composite micro-tips at low power(CL,PH1,0.2w),group 2-conventional metal tips at low power(ML,1#,0.2w),and group 3-conventional metal tips at high power(MH,1#,5.5w).The surface roughness value(Ra value)of the specimen before and after the measurement was measured.One specimen was selected randomly from each group,and observed by scanning electron microscope.SPSS22.0 was used to analyze the data of each group.P<0.05 was statistically significant.[Results]1.The marginal microleakage values of 1-6 groups were 0.182±0.116mm,0.352±0.157mm,0.296±0.185mm,0.669±0.173mm,0.713±0.263mm and 0.794±0.191mm.There were no significant differences(P>0.05)in the marginal microleakage of the adhesive interface when using same cement(RelyX U200)and simulating ultrasonic scaling by carbon composite micro-tips and conventional metal tips at very low power(0.2w).When using the same cement(RelyX U200)and ultrasonic scaling by conventional metal tips at low power(4.4w),medium power(5.5w)and high power(6.6w),there were no significant differences(P>0.05)in the marginal microleakage of the adhesive interface,but there were significant differences(P<0.05)between these groups and the the control group/the group treated at low power(0.2w).2.Under the same ultrasonic treatment,the microleakage values of 7?12 groups bonded by RelyX U200(U;self-bonding)?RelyX Ultimate(LS;self-etching)?RelyX Ultimate(LT;total-etching)?Variolink N(V;total-etching)were 0.182±0.116mm,0.794±0.191mm,0.098± 0.008 mm,0.168±0.087mm,0.120±0.028 mm,0.387±0.179mm,0.089±0.014 mm,0.089±0.024mm.In the control groups of U,LS,LT and V,no significant differences in microleakage were found(P>0.05).Under the same ultrasonic treatment,there were significant differences between the U/LT group and the control group(P<0.05),but there were no significant differences between the LS/V group and the control group(P>0.05).3.The roughness values before and after ultrasonic treatment were as follows:carbon composite micro-tips at low power(CL,PHI,0.2w):0.099±0.015?m,0.144±0.026?m;conventional metal tips at low power(ML,1#,0.2w):0.090±0.012?m,0.120±0.009?m;conventional metal tips at high power(MH,1#,5.5w):0.096±0.011?m,0.401±0.045?m.There were significant differences(P<0.05)in the roughness values in all the three groups before and after ultrasonic scaling.After treatment,no significant difference(P>0.05)was found between the CL group and the ML group.There were significant differences(P<0.05)between the MH group and the other two groups and the MH group had the highest surface roughness value.SEM observation:CL showed more uniform and intensive scratches and no obvious defect;ML showed unevenly distributed scratches and a small amount of punctate defects;MH showed large pores and defects,with seriously damaged surface.[Conclusions]1.Under the experimental conditions,at the very low power,no matter what kind of ultrasonic tips,the marginal microleakage of cast ceramic restorations were not affected.At the power which suited to supragingival scaling,the marginal microleakage of cast ceramic restorations were affected when ultrasonic scaling by conventional metal tips.2.When using RelyX U200(self-bonding),RelyX Ultimate(self-etching),RelyX Ultimate(total-etching)and Variolink N(total-etching)with no ultrasonic treatment,there were no significant differences in the marginal microleakage of the adhesive interface.Ultrasonic scaling by conventional metal tips at high power will affect the marginal microleakage of the adhesive interface when using RelyX U200(self-bonding)and RelyX Ultimate(total-etching).And no impacts were found when RelyX Ultimate(self-etching)and Variolink N(total-etching)were used.3.Ultrasonic scaling with conventional metal tip and carbon composite micro-tip will affect the surface roughness of cast ceramic restorations.The influence was greater when the higher power was used.At the same low power,there was no significant difference in surface roughness between treating with conventional metal tip and carbon composite micro-tip.Microscopically,conventional metal tip caused greater damage than carbon composite micro-tip.