| Objective To study the effects of three different rapid sintering procedures on the shear strength of zirconia and veneer ceramics,the infiltration of chemical elements at the interface between zirconia and veneer ceramics,and the change of crystal structure of zirconia substrates,so as to provide data support for clinical selection of ideal sintering procedures.Methods Eighty-four zirconia cuboid specimens were prepared.They were randomly divided into three groups:control group,experimental group one and experimental group two,twenty-eight pieces in each group.All specimens were sanded and then sintered in sintering furnace.The control group sintered for one hundred and nineteen minutes(P-One program),the experimental group one sintered for one hundred and sixty-nine minutes(P-Two program),and the experimental group two sintered for one hundred and ninety-nine minutes(P-Three program).After conventional pre-oxidation,a thin layer of decorative porcelain was coated on the surface of the ceramic block for pre-sintering.After natural cooling,the samples were sandblasted,polished and stacked with cylindrical decorative ceramic slurry for sintering.The shear strength of the bonding interface between base and veneer ceramics was tested by an electronic universal material testing machine,and the experimental data were analyzed by SPSS 17.0 software.The crystal phase composition,grain diameter and density of zirconia-based ceramics were analyzed by X-ray diffraction.Scanning electron microscopy(SEM)and energy dispersive spectrometry(EDS)were used to observe the interface and determine the elements.Scanning electron microscopy(SEM)was used to observe and analyze the surface morphology of the broken end.ResultsOne Point Shear bond strengthThe shear strength of the control group was forty two point four six(±six point two eight MPa/mm~2),that of the experimental group one was tirty seven point four nine(±five point five tree MPa/mm~2),and that of the experimental group two was thirty six point nine five(±five point eight seven MPa/mm~2).There was a significant difference in the shear strength of the three groups.There was statistical difference between the control group and the experimental group one,and between the control group and the experimental group two.There was no statistical difference between the experimental group and the experimental group two.Two Point Scanning Electron Microscope ObservationTwo Point One In control group,the bonding interface between zirconia and decorative ceramics was uniform and dense,showing"mosaic bonding",and the bonding interface between zirconia and decorative ceramics was close;in experimental group one,the bonding interface between zirconia and decorative ceramics was uniform and dense,and a few"mosaic bonding"sites were observed,and the bonding depth was shallow,and the bonding between zirconia and decorative ceramics was not close enough;in experimental group two,the bonding interface between zirconia and Decorati Poor.Two point two In the control group,there were more bubbles at the broken ends of zirconia-based ceramics and no"ridge"structure,suggesting that the middle layer decorative ceramics had not been completely exfoliated,suggesting that the middle layer decorative ceramics were closely bound to zirconia;in the experimental group one,the number of bubbles at the broken ends of zirconia-based ceramics decreased,and some"ridge"structures were visible,with shallower depth,suggesting that a few of the middle layer decorative ceramics had exfoliated In the experimental group two,there were a few bubbles at the broken ends of zirconia basement porcelain,and the"ridge"structure of the cross section was obvious,suggesting that most of the intermediate layer decorative porcelain exfoliated,which suggested that the bonding between the intermediate layer decorative porcelain and zirconia was poor.Three Energy Spectrum AnalysisZr element was not detected on the side of three groups of intermediate layer decorative porcelain,and Si and Al elements were not detected on the side of zirconia base porcelain.There was no element penetration between the three groups of zirconia base ceramics and intermediate decorative ceramics,suggesting that there was no chemical bonding between zirconia and intermediate decorative ceramics.Four X-ray Diffraction AnalysisThe three groups consist of tetragonal and monoclinic phases,without cubic phase.In the control group,tetragonal phase content was the largest,monoclinic phase content was the least,grain diameter was the smallest and density was the largest.With the increase of sintering time,the tetragonal phase transforms to monoclinic phase in group one.With the increase of sintering time,the phase transformation hardly occurs in group two,but the grain diameter increases with the increase of sintering time and the density decreases.ConclusionFirst The three sintering modes(the highest temperature is one thousand and five hundred?,and they are all kept for thirty minutes)are used to sinter zirconia crystals.When the sintering time is one hundred and nineteen minutes,the bonding strength between zirconia and decorative ceramics is the tightest,and the bonding strength between zirconia and decorative ceramics is the highest.The bonding strength between zirconia and decorative ceramics in the sintering process is one hundred and nineteen minutes later than that in the process of one hundred and sixty-nine minutes and one hundred and ninety-nine minutes.Therefore,when zirconia needs decorative ceramic modification,it is suggested that short-time sintering mode be used in the crystallization process of zirconia.Second Under the experimental conditions,there is no element penetration between the intermediate layer decorative porcelain and the zirconia substrate.Therefore,it is considered that increasing the intermediate layer decorative porcelain does not increase the chemical bonding force between the two,but it is not excluded that the change of thermal expansion coefficient has an effect on the physical bonding force between the two. |
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