Study On The Caries Prevention Of CPP-CSH After Interproximal Enamel Reduction

Objectives To make casein phosphate polypeptide and hydrated calcium silicate（CPP-CSH）solution with different concentrations and analyze its structural characterization.The effect of different concentrations of CPP-CSH solution on enamel remineralization after interproximal enamel reduction（IER）was studied by using the anti-caries experiment of isolated teeth.The optimal concentration of CPP-CSH was compared with Duraphat,calcium silicate,and CPP-ACP（Casein phosphopeptide-orphous calcium phosphate）,To investigate the ability of four groups of remineralization reagents to promote remineralization in order to provide evidence for preventing caries after orthodontic interproximal enamel reduction.Methods Experiment 1:Calcium silicate hydrate was made by using Ca（OH）₂ and Na₂Si O₃·9H₂O in a calcium to silicon molar ratio of 1:2 at a temperature of 45℃,p H=11and constant stirring for 5 hours.Under alkaline conditions,different concentrations of CPP-CSH solutions were made by using 10%calcium silicate hydrate（CSH）and 1%,3%,5%casein phosohopetide（CPP）solutions.The characterization of calcium silicate hydrate and CPP-CSH were analyzed by X-ray diffraction（XRD）and Fourier Transform Infrared Spectroscopy（FT-IR）,respectively.Experiment 2:96 interproximal enamel reduction models were constructed and randomly divided into blank group,1%CPP-CSH group,3%CPP-CSH group and 5%CPP-CSH group,with 24 samples in each group.Each group was dealt with deionized water and CPP-CSH solution of corresponding concentration,5min/time,twice a day,The extracorporeal p H circulation lasted for 30 days.Experiment 3:96 interproximal enamel reduction models were constructed and randomly divided into 1%CPP-CSH group,Duraphat group,10%CSH group and CPP-ACP group,with 24samples in each group.each group took the following measures:In 1%CPP-CSH group,10%CSH group and CPP-ACP group,the interproximal enamel reduction part of 1%CPP-CSH group,10%CSH group and CPP-ACP group was dealt with 1%CPP-CSH,10%CSH and CPP-ACP reagent,5 min/time,twice a day,respectively;In the Duraphat group,the interproximal enamel reduction site was only dealt once with Duraphat during the p H circulation,The extracorporeal p H circulation lasted for 30 days.In experiment 2 and experiment 3,Energy dispersive X-ray（EDX）and microhardness tester were used for quantitative analysis of the experimental area,and Scanning electron microscope（SEM）was used for qualitative analysis of the experimental area.Results Experiment 1:XRD and FT-IR data showed that the synthesized calcium silicate hydrate had high purity and crystallinity.XRD data showed that in different concentrations of CPP-CSH solution,CSH kept its original crystal structure,and the crystallinity was strengthened,and 1%CPP-CSH crystallinity increased the most.FT-IR data showed that after CPP-CSH solution was made by CSH and CPP under alkaline conditions,The original vibration absorption peak of CPP at 900～1100 cm^-1 disappeared,indicating that CSH chelated with CPP.Experiment 2:1)Energy spectrum analysis data showed that 1%,3%and 5%CPP-CSH groups contained Ca,P and O elements as well as Si elements,and 1%CPP-CSH group had the highest Ca/P ratio,which had statistical significance compared with the other three groups（P<0.05）.The Ca/P ratio of 3%CPP-CSH group and 5%CPP-CSH group had no statistical significance（P>0.05）,but the Ca/P ratio was higher than that of the blank group.2)The microhardness data showed that the microhardness values before the experiment were higher than those after the experiment,and the differences were statistically significant（P<0.05）.The microhardness value of 1%CPP-CSH group after the experiment was higher than that of other groups.3)Scanning electron microscopy（×500）showed that there were still a small number of scratches on interproximal enamel reduction site in each group,but the scratches in 1%CPP-CSH group were the least.Scanning electron microscopy（×5000）showed that the surface of 1%CPP-CSH group was the most smooth,while that of blank group was pitted with rough surface.Experiment 3:1)Energy spectrum analysis data showed that 1%CPP-CSH group and 10%CSH group contained Ca,P,O and Si elements,while Duraphat group contained Ca,P,O and F elements,while CPP-ACP group contained Ca,P and O elements,and Duraphat group had the highest Ca/P ratio,there was no statistical difference compared with 1%CPP-CSH group（P>0.05）.There were no significant difference in Ca/P ratio between the CPP-ACP group and the 10%CSH group（P>0.05）,However,there were statistical differences in Ca/P ratio between the Duraphat group and CPP-ACP group（P<0.05）.2)The microhardness data showed that the microhardness values before the experiment were higher than those after the experiment,and the differences were statistically significant（P<0.05）.After the experiment,There was no statistical significance in microhardness between 1%CPP-CSH and Duraphat group（P>0.05）,but the microhardness of 1%CPP-CSH group was significantly higher than that of 10%CSH and CPP-ACP group.There was no statistical significance in microhardness between 10%CSH group and CPP-ACP group（P>0.05）.3)Scanning electron microscopy（×500）showed that the scratches on interproximal enamel reduction sites of each group did not disappear after treatment with different kinds of remineralization agents,but the scratches were significantly reduced.Scanning electron microscopy（×5000）showed that the surface of 10%CSH group and CPP-ACP group was not as flat as that of 1%CPP-CSH group and Duraphat group,and there were still some pitted structures on the surface.Conclusions 1)CPP-CSH can promote enamel remineralization,and 1%CPP-CSH has the best remineralization ability.2)1%CPP-CSH has a better ability to promote enamel remineralization than 10%CSH,and 1%CPP-CSH has the same remineralization ability as Duraphat.Figure 14;Table 6;Reference 129.