Preliminary Study On Remineralization Of Incipient Enamel Garies Treated By Green Tea Extract Under Scanning Electron Microscope

Objective: To observe the surfaces morphology of enamel by scanning electron microscope(SEM)after the green tea extract acted on the incipient enamel caries,image analyze the micro-pore areas of enamel and evaluate its remineralization effect.Trying to provide a theoretical basis for the research and development of natural products for caries prevention.Methods:(1)Fifteen premolars were selected for orthodontic fresh extraction(which required no caries,no crack,no fillings),ultrasonic cleaning,crown root separation in the neck,removed soft tissue,longitudinal splited crown into two parts along the long axis of teeth,forming thirty tooth enamel specimens,leaving buccal or lingual surface about 4 mm x4 mm fenestration area,the rests were closed with nail polish.Six of them were randomly selected for scanning electron microscope observation of normal enamel surface structure,the remainderar were subjected to demineralization treatment;after demineralization,six enamel pieces were randomly selected as the demineralization group for scanning electron microscope observation;the remainder 18 demineralized enamel pieces were randomly divided into three groups: green tea extract group,2mg/l sodium fluoride group(positive control group)and deionized water group(negative control group),with 6 samples in each group for pH cycle treatment.(2)pH cycle treatment: added 10 ml of test solution,remineralization solution and demineralization solution to each sample.The daily cycle consisted of 4 h treatment in demineralization solution,6h treatment with the same amount of deionized water,sodium fluoride and green tea extract,and overnight immersion in the sameamount of remineralization solution.Rinse with 200 ml deionized water for 5 min before each treatment solution is changed,and circulate continuously for 10 days.After completion of the whole cycle,all specimens were washed with deionized water for 10 min and stored in deionized water containing 0.05mmol/l thymol at 4 degree for detection.(3)The surfaces morphology of enamel before and after demineralization and treatment with different experimental solutions were observed by scanning electron microscope(SEM)and image analyzed the micro-pore areas of enamel.Results:(1)Visual observation showed that the enamel surfaces of each group were intact,and the enamel in the windowing areas were chalky after demineralization,after ph cycle experiment,the windowing areas in the green tea extract group became brownish yellow,but the staining in the deionized water group and sodium fluoride group did not change.(2)The results of scanning electron microscope(SEM)were as follows: before demineralization,the enamel surfaces were smooth and flat,a small amount of fine grinding marks could be seen.After demineralization,the surfaces of enamel were uneven,the outline of enamel column and some grinding marks were visible,and there were obvious micro-pores under low magnification,at high magnification,there were large pits and scattered gaps in the enamel surfaces,which were in the form of uneven honeycomb structure.After ph cycle experiment: under low magnification,the enamel surfaces of the green tea extract group were flat,the sodium fluoride group were flat but rough,in which the micro-pores of the enamel surfaces of the green tea extract group were almost completely covered,the micro-pores of the enamel surfaces of the sodium fluoride group were partially covered and there were still a small amount of micro-pores,the newly formed crystal structure was observed in the green tea extract group under high magnification.In the deionized water group,the enamel surfaces were uneven under low magnification,and there were obvious micro-pores,at high magnification,the structure was loose and a large number of scattered voids still remain.(3)After ph cycle,the surfaces micro-pores area of green tea extract groupand sodium fluoride group were significantly reduced compared with that of demineralization group(P<0.01),the micro-pores area of enamel surfaces in the green tea extract group were smaller than that in sodium fluoride group(P<0.05),there was no significant difference in the area of enamel micro-pores between deionized water group and demineralized group(P>0.05).Conclusion:(1)The surfaces of demineralized enamel Can be promoted remineralization after treated with green tea extract and sodium fluoride,and the effect is superior obviously than that of pure artificial remineralization liquid.(2)After demineralized enamels are treated with green tea extract,the surface sediments are denser and more uniform than those of sodium fluoride group,and the crystal structure is typical,which suggest that there are other components in tea except fluoride participating in the remineralization of enamel.(3)The green tea extracts are rich in components and have a positive effect on remineralization,which can be fully used to carry out caries prevention of local natural medicines.