The Effect Of Anti-caries On CPP-nHA Solution After Interproximal Enamel Reduction

Objectives To make casein phosphate polypeptide and nano-Hydroxyapatite(CPPnHA)solution and carry out its structure analysis.To observe the anti-caries effect of different concentrations of CPP-nHA solution on enamel after interproximal enamel reduction(IER)by caries experiment in vitro.To compare the anti-caries effect of dorafur,resin infiltration,casein phosphopeptide-orphous calcium phosphate(CPP-ACP),nanohydroxyapatite(nHA)and CPP-nHA on enamel after IER,and provide experimental basis for the prevention of clinical application.Methods Experiment 1,CPP-nHA was made from nHA with diameter of 20 nm and a concentration of 1%,3% and 5% of casein phosphopeptide(CPP)under alkaline conditions.Observing the solution properties by naked eye,and analysing the structure of CPP-nHA by X-ray diffraction(XRD)and fourier transform infrared spectroscopy(FTIR).Experiment 2,36 healthy premolars were selected to model of IER,which were randomly divided into blank group,1% CPP-nHAP group,3% CPP-nHAP group and 5% CPP-nHAP group(18 samples per group).Each group was treated with corresponding solution,5min/times,twice a day,the caries was created by PH-cycling for 30 days in vitro.Experiment 3,54 healthy premolars were selected to model of IER,which were randomly divided into 6 groups(18 samples per group),blank control group enamel was treated with deionized water,for 5 min/times,twice a day.Dorafur group was treated with Dolafur once.resin infiltration group was treated with resin infiltration for once.CPP-ACP group enamel was treated with tooth mousse,for 5 min/times,twice a day.nHA group was treated with nHA solutionfor 5 min/times,twice a day.CPP-nHA group was treated with 3% CPP-nHA solution,for 5 min/times,twice a day.the caries was created by PH-cycling for 30 days in vitro.Both experiment 2 and experiment 3 were to measure the surface microhardness(MH)of enamel by microhardness detector,The histomorphologic changes of enamel surface was compared by scanning electron microscope(SEM)and the elements of enamel was analyzed by X-ray energy spectrometer(EDX).Thickness of fluorescence beneath the surface of early enamel caries,which was observed by fluorescence microscopy(FM).Results Experiment 1,By naked eye observations the CPP-nHA solution was the viscous milky flow suspension.The characteristic peaks of nHA and CPP appeared in three groups of CPP-nHA with FT-IR results,with varying degrees of deviation,It showed that nHA and CPP had chemical action occurred.XRD results showed that the increase of nHA characteristic peak strength in CPP-nHA,in which 3% CPP-nHA up the most.Experiment 2,The MH of enamel before caries experiment was significantly higher than that after experiment,and the difference was statistically significant(P<0.05);The MH of the 3%CPP-nHA group was the largest,and the hardness difference was the lowest after the experiment,with statistically significant difference compared with other groups(P<0.05).The SEM showed that the surface roughness of the blank glaze was uneven,and there was many low density pores left by ore removal.A large number of particles or clumps of mineralized sediments were observed in the enamel surfaces of the experimental group.In which the enamel surface of 3%CPP-nHA group was the most flat,and the porosity was the least.The results of EDX showed the molar ratio of Ca and P in 5%CPP-nHA group was no significant difference from 3%CPP-nHA group(P>0.05),higher than that of other groups,and the difference was statistically significant(P<0.05).FM results showed that the fluorescence band was the narrowest in 3%cpp-nHA group,and the difference was statistically significant compared with other groups(P<0.05).Experiment 3,The MH of enamel before caries test was significantly higher than that after experiment,and the difference was statistically significant(P<0.05).The MH of CPP-nHA group showed that the MH was highest,the blank group was the lowest,and the difference was statistically significant(P<0.05).SEM showed a large number of demineralization pits in the blank glaze surface.There were lamellar mineralized sediments in the glaze of the dolafur group,and there were more ore removal holes.The resin infiltration group had less porosity and was more flat.there are more ore removal holes on the enamel surface of the CPP-ACP group.A large number of granular and short rod crystals were deposited on the enamel surface of the nHA group,and the ore removal pores were relatively few.The surface of CPP-nHA group was smooth,and there were a large number of small needle-like ore-forming pores visible in granular crystals.The results of EDX showed that the main elements of the dolafur group were Ca,P,O and F elements,and main elements of other groups are Ca,P,O elements.No significant difference of the molar ratio of Ca and P between resin infiltration group and CPP-nHA group(P>0.05),and higher than other groups significantly(P<0.05);FM results showed no difference between the group of resin infiltration group and CPP-nHA group(P>0.05),compared with other groups,there were significant differences in the depth of demineralization(P<0.05).Conclusions 1 The CPP-nHA compound was made by nHA and CPP under alkaline conditions,the solution is milky white suspension,stable characters.2 CPP-nHA solution can effectively inhibit the enamel surface demineralization after the IER,in which the 3%CPP-nHA solution has the best effect.3 Dolafur,resin infiltration,CPP-ACP,nHA,CPP-nHA the function to the caries after IER,in which the resin infiltration and the CPPnHA have the most outstanding effect.