An In Vitro Study Of CariesRisk On Resin Infiltration In Orthodontic Interproximal Enamel Reduction

Abstract:Objective:the aim of this study was to observe the effect of caries prevention for the resin infiltration afer interproximal enamel reduction (IER) methods of extraced teeth by PH-cycling in vitro experiment, and applying the evidence for clinical application of resin infiltraion after inerproximal enamel reducion.Methods:24healthy human premolars extracted for orthodontic reasons were collected for the experiment. The Gown was split vertically into two halves with hard tissue cutter. Then the48specimens were divided into3groups as group A,B,C randomly,16specimens for each group.Every group was reduced enamel with IER mothods to clinical routine,included the polishing treatment.After that,processed by the following methods:group A,control;group B, With infiltration resin penetration.group C, with fluor protector(contain FO.1%).After specimens preparation,all groups of specimens were put in37℃constant temperature water bath. Then caries Was created by pH-cycling for30days in-vitro. The enamel surface of microstructure Was examined by scanning electron microscopy(SEM),the Microhardness of enamel surface of all specimens was detected by microhardness testing machine before and after pH-cycling. The Microhardness value of each group was analyzed by SPSS19. O.Paired t-test was used to compare microhardness value before and after the PH-cycling of each group;The differences among mean values were compared by multiple analysis of variance,as statistical analysis.Results: Before PH-cycling, the microhardness value of the similar between the groups A&C has no statistical significance; Group B surface microhardness value is greater than the two groups above, and the difference is highly statistically significant; The group B surface enamel structure has been strengthened.After PH-cycling the value of groupB was still greater than the groupA.The decrease of microhardness in group B was smaller than that of groupA(p<0.05),which means that the risk of demineralization of groupB is statistically lower than that in groupA;but there were no statistcal difference between groupB and groupC,which indicates that both the infiltration resin and fluoride protector could lower the risk of demineraliazition of enamel after IER,and the difference of caries risk in the two groups is similar.②The scanning electrical microscope(SEM)images shows a relaticely rough surface left by IER.The scrapes can’t be completely polished.There were some Resin protrusions penetration into the surface after IER observed. After PH-cycling, serious demineraliazation was happend on the almost whole enamel surface in group A,which showed the’etching-like’appearence;Parts of demineralization could be noticed on the enamel surface in groupB&C, by less than Group A.Conclusion:1. Resin infiltration can inhibit the demineralization of enamel surface after IER,which may benefit to anti-caries in clinical operation.2. Resin infiltration and flour protector both are both capable of Inhibition of demineralization after IER,and both effects are consistent.3.Resin infiltration can strengthen the structure of enamel surface before and after PH-cycling.