| ObjectiveHydrofluoric(HF)acid etching is the most common method of surface treatment before bonding with machinable ceramic restorations,however,HF acid is highly corrosive and toxic to humans.The aim of this experiment was to study the effect of Er:YAG laser irradiation with different pulses energy on the micro-morphology of a machinable lithium-silicate reinforced glass ceramic called IPS e.max CAD ceramic.The practicability of Er:YAG laser used for surface treatment of IPS e.max CAD ceramic was discussed,and the effect of Er:YAG laser on the bonding properties of IPS e.max CAD ceramic was evaluated.The research was intended to provide an efficient and safe surface treatment technique for the clinical bonding of this kind of ceramics.Materials and MethodsReagent and instrument:Ivoclar IPS e.max CAD for CEREC and in lab,Er:YAG laser,hard tissue slicer-E300CP,scanning electron microscope(SEM),atomic force microscope(AFM),stereoscopic microscope,universal testing machine,ultrasonic cleaning machine,tell turbine about 37? thermostat box,VarioLink N bonding kit,4.5%HF hydrofluoric acid,methylene blue.MethodsDesigned six different Er:YAG laser parameters of pulse energy(100 mJ,200 mJ,300 mJ,400 mJ,500 mJ,600 mJ),choose the best parameter as a selection of the remaining experiments by observing micro-structures with SEM and AFM.Designed three different specimens(ceramic-resin,ceramic-enamel and ceramic-dentin),tested the shear bond strength(SBS)by an universal testing machine and analyzed the failure types of each specimen after different surface treatments,which included control group,HF acid etching group and Er:YAG laser group.And then,measured the microleakage by stereo-microscope with 2%methylene blue stainings.The data were analyzed by SPSS 19.0 software,the measurement data was described in x±s and analyzed with one-way ANOVA to perform group comparisons at 5%significance level.The LSD-t test were used for multiple comparisons of mean values at ?=0.05.Enumeration data was analyzed with chi square test at 5%significance level.Results1.By observing micro-structures with SEM and AFM,it found that different pulse energy parameters had different effects on the surface morphology of IPS e.max CAD ceramic.Er:YAG laser irradiation with a pulse energy of 400 mJ could provide a large number of uniform micro-mechanical interlocking structures and offer a suitable roughness values,which could be used as a parameter selection for the remaining experiments.2.The SBS of Er:YAG laser group in ceramic-resin specimen was 24.12±1.91 MPa,which was higher than that of control group and HF group and the the differences were statistically significant(P<0.05).The SBS of Er:YAG laser group in ceramic-enamel was 30.33 ±2.06 MPa and in ceramic-dentin was 27.98 ± 1.96 MPa,which were higher than that of the control group and the the differences were statistically significant(P<0.05),but there was no statistical differences between laser group and their own HF group(P>0.05).There was a significant difference in the failure types of each group in this three different specimens(P<0.05).3.The microleakage of Er:YAG laser group in ceramic-resin specimen was 0.37 + 0.03 mm,which was less than that of the control group and HF group,and the the differences were statistically significant(P<0.05).The microleakage of Er:YAG laser group in ceramic-enamel was 0.56 + 0.03 mm and in the ceramic-dentin was 0.50 + 0.03 mm,which were higher than that of the control group and the the differences were statistically significant(P<0.05),but there was no statistical differences between laser group and their own HF group(P>0.05).ConclusionThe results showed that Er:YAG laser irradiation with a pulse energy of 400 mJ could be used as a substitute surface treatment of HF acid etching for IPS e.max CAD ceramic. |
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