| The eventual outcome of dental caries is determined by the dynamic balance between pathological factors that lead to demineralization and protective factors that lead to remineralization. How to regulate all the factors in order to inhibit the demineralization and enhance the remineralization is the key point of caries prevention. Mature dental enamel contains little organic matrix which is approximately 1% by weight. Researches have found that organic matrix can inhibit enamel demineralization, the mechanism is that organic matrix may control the ions diffusion in enamel. Recently, Galla chinensis has been well studied as a new anti-caries agent. It has been demonstrated that Galla chinensis has retardation effect on enamel demineralization, which is equal to the effect of fluoride and is related to enamel organic matrix. However, the mechanism remains unclear. In order to further investigate the mechanism of the retardation effect of Galla chinensis and enamel organic matrix on enamel demineralization, several method were employed in this study to observe the influence of Galla chinensis and enamel organic matrix on enamel porosity and permeability. The study comprised four experiments:1. Screening of the optimal concentration for Galla chinensis inhibiting enamel demineralizationFifty-six enamel samples were made from freshly extracted teeth, then were randomly divided into seven groups. The natural enamel surfaces of all the samples were treated with deionized water and 4,8,16,30,60,120 mg/mL Galla chinensis aqueous extract solutions respectively and then demineralized with artificial demineralization solution. Enamel mineral loss and lesion depth were analyzed by microradiography. The Ca2+ concentrations in the demineralization solution of each group were measured with a titrator. Results revealed that: 16mg/ml Galla chinensis aqueous extract solution had significant retardation effect on enamel demineralization; when the concentration of Galla Chinensis reached 30 mg/ml, it had the most potent retardation effect on enamel demineralization, no statistical difference was seen when compared with groups in which higher concentration solutions were used.2. Analysis of enamel crystal structure before and after being treated with Galla chinensis by XRDThe enamel was cut from ten freshly extracted teeth and ground into powder, then was randomly divided into two groups. One group was remained untreated, the other one was treated with 30mg/ml Galla chinensis aqueous extract solution. The samples from both groups were analyzed by powder crystal XRD. The result indicated that: the enamel crystal size reduced slightly after been treated with Galla chinensis, however, enamel crystal structure did not change. 3. Study on the influence of Galla chinensis and enamel organic matrix on enamel porosityThe enamel was cut from ten freshly extracted teeth and ground into powder at 0℃, then was randomly divided into two groups. One group was remained untreated and marked as Normal, the other one was treated with 10%NaClO and marked as OM Extracted. Half of the enamel powder was taken out from both groups. After been treated with 30mg/ml Galla chinensis aqueous extract solution, the samples were marked as GC Treated and GC Treated+ OM Extracted, respectively. Multipoint BET surface area and pore volume of the samples were obtained from N2 adsorption measurement at﹣196℃with a porosimeter. Results revealed that: after the OM was extracted, surface area of enamel powder increased significantly (P<0.05), however, the pore volume did not change (P>0.05); after been treated with Galla chinensis, the surface area and pore volume of normal enamel powder reduced significantly (P<0.05), however, the surface area and pore volume of OM extracted enamel powder did not change. The result of factor analysis indicated that both GC and OM had significant influences on the surface area and pore volume of enamel, and there was interaction between these two factors.4. Study on the influence of Galla chinensis and enamel organic matrix on enamel permeabilityFive freshly extracted teeth were used and cut into 200μm thick enamel sections with a microtome. Four sections were cut from each tooth, and then randomly divided into 4 groups marked as Normal, OM Extracted, GC Treated and GC Treated + OM Extracted after being treated in different ways, respectively. Enamel permeability was obtained by FRAP method with CLSM. The results are as follows: after the OM was extracted, diffusion coefficient (DC) of enamel sections increased significantly (P<0.05); after been treated with Galla chinensis, the DC of normal enamel sections reduced significantly (P<0.05), however, the DC of OM extracted enamel sections did not change. The result of factor analysis indicated that both GC and OM had significant influences on the permeability of enamel, and there was interaction between these two factors. |
