The Study Of The Effect Of New-type Glass Lonomer In Promoting Demineralized Enamel Remineralization In Vitro

Objective:This study make the artificial enamel demineralization model invitro, using electron microscope and surface microhardness, to observeand evaluate the effects of the new-type glass Ionomer Clinpro XTVarnish on remineralization to the demineralizated enamel， and tomeasure material acid resistant effect to the surrounding tissue.We hopewe can provide experimental basis for clinical application.Methods:We collect40premolars,incisors or molars extraced because oforthodontic treatment or periodontal disease. The teeth require no cariesdamage, no white spot, no defect and no crack. The teeth are randomlydivided into5groups,.Group A: Clinpro XT varnish group, Group B:GC group;Group C: fluorine protection paint group, Group D:3Mglass ion group and group F: blank control group, each group has eightteeth.The buccal of the teeth set aside about4m m*4m m area to open a window, the windowing area are polished with sandpaper to beflat and level. The rest of the teeth is double closed with different colornail polish which can be resistance to acid corrosion.The5groups teethsuspend in lactic acid gel to be preparated into the model of the artificialdemineralization in vitro. The teeth are remineralizated by coating fivekinds of materials, and after remineralized40days we observe themicrostructure change of enamel surface after demineralization using thescanning electron microscope and measure the microhardness of theenamel after remineralized20days and40days.The result of the5groupsdo the statistical analysis using SPSS19.0software package. After40days we selete some samples and remove the nail polish with acetone,clean water to clean, then using the35%phosphoric acid treatment for60seconds, macroscopic observate the result, and measure themicrohardness outside window area of2mm, the results for statisticalanalysis.Results:①After demineralization macroscopic observation results： Theenamel surface become chalky,the windowing area is smooth, withoutluster. Electron microscope observate that the enamel surface haveobvious corrosion appearance,enamel dissolves seriously and have a lot of pore.After demineralization the enamel surface morphology of5groups have no obvious difference.②With the time passing the chalky surface of A-D groups becomelighter and disappeared, group F change a little and chalky area remainvisible. Electron microscopy show the different appearance, group A,group B and group D can see a large number of mineral deposits, whichare sediment sizes, irregular form. Group C surface enamel pore haveuniform circular sediments. Group F no obviously change.③Variance analysis was carried out on the enamel surfacemicrohardness results show that: as time goes on, the microhardness ofsamples of5groups increase.group A, group B and group Dmicrohardness values increase slowly, group C of20days,themicrohardness value increasesmost, group F microhardness also increase,but change is not obvious.④20days later each enamel surface microhardness value comparedwith the blank control group had significant difference (P <0.05), inwhich the group A, group B and group C compared with the blank controlgroup difference significantly.40days later, each group compared withblank control group were statistically significant (P <0.05), of whichgroup A has the highest microhardness values. But there was no significant difference among5groups (P>0.05),⑤After40days in the ares of acid corrosion, macroscopicobservation show that the area of each groups are visible chalky, groupA chalky area with lighter color, group B second group C are secondly,group D and group F chalky clearly. Microhardness measurements of thesurrounding area after the acid treatment was lower than those ofnormal enamel, the microhardness of group A is higher than the blankcontrol group, and have significant differences (P <0.05) than the othergroups.Conclusions:1). Clinpro XT Varnish have the effects of promoting demineralizedenamel remineralization like the other mineralizing materials.2). Afer20days the microhardness of the Fluoride protection paint ishighest, It shows that Fluoride protection paint group have theearliest time of remineralization.3).Artificial saliva have the effect of remineralization,but theeffect is weak.4).Clinpro XT Varnish not only have the effects of promotingdemineralized enalnel remineralization,but also have the role of forming the acid resistant protective coating to the surrounding area.