Comparative Studies Of CPP-ACP And Fluoride Products In Inhibiting Enamel Demineralization

Objective:To evaluate and study CPP-ACP and several fluoride products which are often used inclinic comparatively in inhibiting enamel demineralization, using Atomic Force Microscopy(AFM).It is expected to provide the experiment result for clinical practice.Methods:Seventy premolars extracted before orthodontic treatment which were sound．A4mmX4mm windowing area was formed by nail vanish at the clinical centre of the labialsurfaces of the premolars. The70samples were randomly divided into seven groups：A：CPP-ACP，B：CPP-ACP＋fluoride mouth rinses，C：fluoride mouth rinses，D：FujiVII，E：fluoride resin binder，F：fluoride varnish and G：the control, applied separately withCPP-ACP、CPP-ACP＋fluoride mouth rinses、fluoride mouth rinses、FujiVII、fluoride resinbinder、fluoride varnish and distilled water on labial enamel.7groups were dipped into anartificial caries solution and an artificial saliva solution alternately with a frequency of3times a day, and5minutes every time. Then all samples were detected by atomic forcemicroscope(AFM) and hardness tester on the first month、the second month and the thirdmonth. Atomic Force Microscopy was used to observe enamel surface morphology of everysample at every point in time. One-way ANOVA analysis was used to compare enamelsurface roughness and hardness whether there was statistical significance(Test P=0.05).Thedata were statistically analyzed using SPSS software.Results:①Macroscopic observation results: as the time had passed, the enamel surface of thecontrol group among the seven groups was empty of luster which was chalky.The other6groups had not seen chalky change and the intimacy of enamel surface was normal.Glossiness and surface smooth degree in windowing area of the samples in B group is betterthan other groups.②Atomic force microscope observe results: when the first month of the experiment,the small hollow of the enamel surface could be seen in every group. The hollow of the control group was obvious; when the second month of the experiment, it could be seen thatmineral substance in the form of a small pellet from A to F group and the demineralizationholes changed smaller. By contraries, the demineralization holes of the control groupchanged bigger; when the third month of the experiment, there were no obviousdemineralization holes in the enamel surface of CPP-ACP＋fluoride mouth rinses group, andenamel fiber arranged regularly. A lot of mineral matters deposited on the enamel surface tofill up the circumscribed small pits, the enamel of the control group present alveolar changeshowed evident demineralization holes. The other groups could not be seen evidentdemineralization holes, and several mineral matter in the form of a small pellet deposited.③One-way ANOVA analysis used to compare enamel surface roughness showed thatin the first month of the experiment, surface roughness was lower evidently compared thegroup of D with G,there was significant difference in enamel surface roughness（P<0.05）.The second month and the third month, there was a statistically significant difference (P <0.05) in enamel surface roughness between the group of G and the other groups； Betweenthe group of B and the other6groups a statistically significant difference (P <0.05) inenamel surface roughness was registered； Amongst treatment specimens of groups D，E，F and C a statistically significant difference (P <0.05) in enamel surface roughness wasregistered.④One-way ANOVA analysis used to compare enamel surface hardness showed that inthe first month of the experiment, there was no a statistically significant difference (P>0.05)in enamel surface hardness between the group of G and the other groups；in the secondmonth between the group of G and the other6groups a statistically significant difference(P <0.05) in enamel surface hardness was registered except the group C；in the third month,there was a statistically significant difference (P <0.05) in enamel surface hardnessbetween the group of G and the other groups；The second month and the third month,between the group of B and the other6groups a statistically significant difference (P <0.05) was registered, amongst treatment specimens of groups D，E，F and C astatistically significant difference (P <0.05) in enamel surface hardness was registered.Conclusions:①Atomic force microscope imaged the enamel surface, samples preparation wassimple, it can acquire enamel surface pictures which were high resolution ratio, discretioncan reach nanometer level. Three-dimensional images rebuild can know microstructure of enamel surface more intuitionisticly.②CPP-ACP can inhibit enamel demineralization in vitro,the effect is evident.③Joining fluoride in CPP-ACP in inhibiting enamel demineralization was better.④The effect of FujiVII in inhibiting enamel demineralization was earliest.⑤The group of solid fluoride had better results in inhibiting enamel demineralizationthan the group of liquid fluoride.⑥Enamel surface roughness and hardness were used to token demineralization andremineralization of enamel surface, which results were consistent.