| Objectives Penetrating resin and nano hydroxyapatite(n HA)were used in combination to verify their synergistic effect on treatment of white spot lesions(WSL)induced by orthodontic treatment.Furthermore,their effect on WSL was compared with that of fluoride(Na F)to provide experimental data for their clinical application in the future.Methods 1)Selection and preservation of samples: Collect 75 premolars extracted due to orthodontics at Tangshan Bochuang Stomatological Hospital,and remove calculus and tissue debris by using dental cleaning equipment from the tooth surface,and store them in saline in a refrigerator at 4°C for using.2)Preparation of samples:(1)Establish the orthodontic models: bonding of metal brackets in the center of the clinical crown on the buccal side of all teeth.Apply antacid nail polish to all dental tissues except the labial surface of the teeth.(2)Establish demineralization model: place orthodontic model in artificial demineralization solution at 37℃for 72 hours.3)Experimental grouping and processing: 75 teeth were divided into 5 groups randomly with each group of 15.Group A is a control group,and the demineralised samples are put into 37°C artificial saliva which is replaced regularly;group B is 5% Na F,and the demineralised samples are treated with fluor protector once;Group C is 10% n HA group,and the samples after demineralization are treated with 10% n HA,5 mins each,3 times a day;Group D was the penetrating resin group,and the samples after demineralization are treated by penetrating resin and placed into 37°C artificial saliva;Group E is a penetrating resin combined with 10% n HA group,and the demineralised samples were treated with penetrating resin and then treated with 10%n HA for 5 min each and 3 times a day.4)General specimen observation,Micro-hardness test,scanning electron microscope observation and X-ray energy spectroscopy analysis,surface roughness measurement.Results 1)General specimen observation: the normal tooth enamel surface before demineralised is smooth and shiny,translucent,and the tooth surface color is basically the same without color difference;Group A: The tooth enamel after demineralised treatment is chalky,the color of the surrounding tooth enamel is sharply contrasted;Group B and group C: The chalky plaque on the surface of the tooth enamel basically disappears,but there is still a small color difference with the surrounding normal tooth enamel;Group D and Group E: the chalky plaque on the surface of the tooth enamel disappears,and there is basically no color difference with the surrounding normal tooth enamel;It can be concluded that 5% Na F,10% n HA,penetrating resin and penetrating combined with 10% n HA can all improve the chalky patches,and the penetrating resin group and the combined group have better covering effect on WSL.2)Micro-hardness test: In each group,the microhardness of group A is the smallest,followed by group D(P<0.05),and the difference is statistically significant;the microhardness of group E is slightly higher than that of groups B and C,which is no statistical difference(P>0.05).It is concluded that the microhardness of enamel can be improved to a certain extent by penetrating resin treatment alone,but the effect is not good.When combined with 10% n HA,the microhardness increases significantly and is slightly higher than that of traditional fluoride.3)Scanning electron microscopy observation: Group A: Enamel surface is rough with a large number of pit-like demineralization pores;Group B and group C: The enamel surface is relatively flat,the pit-like demineralization pores are significantly reduced and smaller,and there are obvious mineral deposits on the surface with a small number of smaller cracks;Group D:The enamel surface is flat,and the demineralization pores are basically disappeared,but a small number of smaller pits are still visible,and the surface is basically invisible to mineral deposition.Group E: The surface of the enamel is flat,the pit-like demineralization pores disappear,and there is a large amount of irregular mineral deposition on the surface.It can be seen that there is almost no mineral deposition on the surface of penetrating resin treatment alone,but there is obvious mineral deposition on the surface of enamel after combined with 10% n HA.4)X-ray energy spectrometry analysis:there is no statistical difference in the molar ratio and mass ratio of calcium and phosphorus in group A and group D(P>0.05);there was no statistical difference in the molar ratio and mass ratio of calcium and phosphorus in B,C and E groups(P>0.05),and the mass ratio and molar ratio of calcium and phosphorus in groups A and D were smaller than those in groups B,C and E(P<0.05),the difference is statistically significant.The experimental results also show that there is no mineral addition in the treatment of penetrating resin alone,but there is obvious mineral deposition after the combination of 10%n HA,and the Ca/P ratio is basically equal to that of traditional fluoride.5)Roughness measurement: each group has the largest roughness in group A and followed by group D(P<0.05),and the difference is statistically significant;the roughness in group E isslightly smaller than that in group B,but there is no statistical difference(P>0.05);the roughness of the B and E groups is the smallest,and there is statistical differences with the other three groups(P<0.05).It can be concluded that the surface roughness of enamel can be improved to a certain extent by penetrating resin treatment alone,but it is limited.When combined with 10% n HA,the surface roughness can be greatly improved and is slightly lower than that of traditional fluoride.Conclusions 1)The results shows that fluor protector,penetrating resin and n HA can promote enamel remineralization.2)The combination of n HA and penetrating resin improves the remineralization effect,which is basically the same as that of fluor protector.Furthermore,both materials do not contain fluorine,and the covering effect of WSL is better.Figure 7;Table 4;Reference 102. |
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