Galla Chinensis Compounds Remineralize Enamel Caries Lesions On Animal Experiment And The Exploration Of The Action Mechanism

As a unique hard tissue disease, caries lesions cannot get restored through cellular mechanism, for the absence of blood vessels and cells in mature enamel. A process both physical and chemical, mineralization, is essential to repair it. And we have found that Galla chinensis（G. chinensis） has the potential to remineralize initial enamel caries lesions.Objectives: This study was based on previous findings, and the new idea that emphasize both the effective component research and total pharmacological effect was applied throughout the study. A classical rat caries model, which was famous in the international evaluation system for newly found anti-caries agents, was built to evaluate the effects of G. chinensis chemical compounds on the remineralization of enamel caries in oral environment; and the hypothesis of the remineralization mechanism was explored. We aimed to research anti-caries Chinese medicine with independent intellectual property rights, for the prevention and treatment of this popular human oral disease. The work was of great significance.Methods: 1. G. chinensis compounds remineralize enamel caries lesions on an animal experiment: To develop the classical caries model in rats, 40 SPF Sprague-Dawley rats aged 17 d with equal sex ratio were adopted, inoculated with Streptococcus sobrinus（S. sobrinus 6715） after an antibacterial treatment. The rats were weighed weekly, fed a cariogenic diet（Keyes 2000#） and deionized water containing 10% w/v sucrose ad libitum. They were randomly divided into four groups and treated topically twice a day with each of the extracts（or control） for 5weeks: distilled and deionized water（DDW, negative control）; 1000 ppm NaF（positive control）; 4000 ppm G. chinensis crude aqueous extract（GCE）; or 4000 ppm gallic acid（GA）. After the experimental period, the rats were sacrificed, and the mandibles and maxillae were dissected. Keyes’ caries diagnosis and scoring technique was applied as a preliminary evaluation on the molar teeth. For more accurate remineralization data, the molar areas were scanned by micro CT, and theresidual enamel volume of the first molar and the mineral density（MD） of the enamel were further computed. Finally, the differences between groups were analyzed.2. Complexation of G. chinensis compounds with calcium ion: G. chinensis compounds（GCE, GA） were mixed with CaCl₂ solution respectively, and the ultraviolet-visible spectrophotometry was implemented to detect the complex compounds formed. The equilibrium constants were calculated respectively.Results: 1. The Keyes scores indicated that the severity of molar enamel caries in G. Chinensis compounds treated groups were decreased compared with DDW treated group. The severity of enamel caries decreased in the following order of treatment groups: NaF < GCE < GA < DDW（p < 0.05）. According to micro CT data,the residual first molar enamel volume and MD values increased in the order of DDW, GA, GCE, and NaF treatment group（p < 0.05）. Besides, in most molars,remineralization layers were observed on the surface of lesions under the stereoscopic microscopy.2. The indications of the newly generated complex compounds were observed through the ultraviolet-visible spectrophotometer, when CaCl₂ solution was mixed with G. chinensis compounds. In addition, no obvious change on the absorption spectra was observed during the reaction time of 10 minutes to 1 hour. However, the equilibrium constants of the reactions were quite small, moreover, the GA involved reaction got a relatively smaller equilibrium constant when compared with that of GCE.Conclusion: 1. G. chinensis compounds（GCE, GA） remineralized enamel caries lesions in a rat model.2. GCE and GA formed complexes with Ca²⁺respectively, which might provide an evidence for their roles of “calcium ion carriers” to promote calcium ion deposition.