Quantitative study of fluoride transport during subsurface dissolution of dental enamel

Galla Chinensis, a Traditional Chinese Medicine: Comprehensive review of botany, traditional uses, chemical composition, pharmacology and toxicology

ETHNOPHARMACOLOGICAL RELEVANCE

Galla chinensis (GC), a traditional Chinese medicine (TCM), has a wide range of pharmacological properties which have been widely used for more than 1400 years. Based on shape, GC is divided into two groups: jiaobei and dubei. It is a bitter, sour, cold and astringent substance which is usually used for treating diarrhea, constipation, bleeding, cough, vomiting, sweating, hemorrhoids, and anal and uterine prolapse. It is distributed in Japan, North Korea, and all parts of China.

AIM OF STUDY

This study was aimed at carrying out a comprehensive overview of the current status of research on Galla chinensis (GC) for better understanding of it characteristics, while providing a clear direction for future studies. It has aroused the interest of researchers, leading to development of medicinal value, expansion of its application, and provision of wider and more effective drug choices. This study was focused on the traditional uses, botany, chemical composition, pharmacology and toxicology of GC. Finally, the study focused on possible future research directions for GC.

MATERIALS AND METHODS

A comprehensive analysis was done based on academic papers, pharmaceutical monographs, ancient medicinal works, and drug standards of China. This review used Galla and Galla chinensis as keywords for retrieval of information on GC from online databases such as PubMed, Elsevier, CNKI, Web of Science, Google Scholar, SCI hub, and Baidu academic.

RESULTS

It was found that the chemical constituents of GC included tannins, phenolic acid, amino acids and fatty acid, with polyphenol compounds (especially tannins and gallic acid) as the distinct components. In vitro and in vivo studies revealed that GC exerted numerous biological effects such as anti-caries, antibacterial, antiviral, anticancer, and antioxidant effects. The therapeutic effect of GC was attributed mainly to the biological properties of its bioactive components.

CONCLUSIONS

GC is an important TCM which has potential benefit in the treatment of a variety of diseases. However, the relationship amongst the structure and biological activity of GC and its components, mechanism of action, toxicity, pharmacokinetics and target organs need to be further studied. Quality control and quality assurance programs for GC need to be further developed. There is need to study the dynamics associated with the accumulation of chemical compounds in GC as well as the original plants and aphid that form GC.

Mineral loss from bovine enamel by a 30% hydrogen peroxide solution

This study investigated the effect of a 30% hydrogen peroxide bleaching agent on bovine enamel in terms of mineral loss. Contents of mineral elements both in the teeth and bleaching agent were evaluated to estimate the effect of hydrogen peroxide on teeth. Finely polished non-carious bovine incisors (n = 5) were immersed in a 30% hydrogen peroxide solution for 120 h. The amounts of concentrated elements in the bleaching agent (5 mL) were measured using inductively coupled plasma-atomic emission spectrometer and ion chromatograph. The contents of mineral elements in the teeth were measured using an electron probe microanalyzer. The Ca/P ratio in the bleaching agent was approximately 1.99. The amount of Zn in the bleaching agent was below the detection limit. The total content of mineral elements of the unbleached enamel (90.75 +/- 1.58) was slightly greater than that of the bleached enamel (87.44 +/- 0.77). The Ca/P ratio of the bleached enamel was 2.06. The amount of Ca loss from the bleached enamels after 120 h was similar to the amount of Ca loss from teeth exposed to a soft drink or juice for a few minutes. Therefore, mineral loss caused by the bleaching process may not be a threatening factor to teeth.

Electron probe microanalysis and transverse microradiography studies of artificial lesions in enamel and dentin: a comparative study

In cardiology and research involving the interactions between restorative materials and dental hard tissues, it is important for small changes in tooth mineral content to be measurable. Currently, transverse microradiography (TMR) is the most accepted tool for the above purpose. Electron Probe Microanalysis (EPMA) can yield both qualitative identification of elements and quantitative compositional information. The purpose of this study was to compare the mineral distribution in well-defined artificial lesions, in dentin and enamel, by the use of both TMR and EPMA on the same sample. The good correlation between the two sets of data validates EPMA as a technique and helps in the interpretation of its results. The data from TMR analysis are expressed as vol% of mineral, while EPMA gives the levels of Ca and phosphate in wt%. The conversion between the two sets of data is complicated by the fact that local density is, as yet, unknown.

Calculation of intercrystalline solution composition during in vitro subsurface lesion formation in dental minerals

Applications of a novel technique to calculate intercrystalline solution composition during enamel demineralization are presented. Bovine tooth enamel blocks and carbonated apatite (CAP) compressed disks were demineralized in an in vitro subsurface lesion system. The demineralization medium was a 0.1 M acetate buffer at pH 4.5, containing calcium, phosphate, and fluoride (0.5 ppm). Mineral samples were demineralized for various times, and fluoride profiles and mineral density profiles of these samples were determined by electron microprobe and X-ray microradiography, respectively. A model independent data analysis (MIDA) technique uses these data along with the differential equations for mass transfer and permits calculation of the local intercrystalline solution composition profiles inside the porous mineral matrix as functions of time and position. The invariance in diffusivity with time as calculated in the analysis was taken as an indicator of the physical reasonableness of the method. Current outcomes suggest that it is the sharp gradient of fluoride concentration in the intercrystalline solution which causes the formation of subsurface lesions. Since the driving force for mineral dissolution is a function of solution composition, a gradient of this driving force is consequently formed. Using a compressed disk of carbonated apatite powder as a model for block enamel excluded the possibility of the existence of a gradient of mineral composition which could also cause a gradient of the driving force for mineral dissolution. An FAP surface complex hypothesis is consistent with the current view that fluoride in the intercrystalline solution has a stronger inhibition effect on the dissolution of mineral than does fluoride in the mineral phase. With the help of the MIDA technique, calculated results indicate that the mechanism of the formation of subsurface lesions is dynamically controlled by the intercrystalline solution composition.

The application of in vitro models to research on demineralization and remineralization of the teeth

Progress in in vivo and in situ experimentation has led many researchers to speculate as to the relevance and importance of in vitro testing protocols in caries research. A Medline/Biosis search for the present review revealed well over 300 citations (since 1989) documenting in vitro tests associated with caries research on mineralization and fluoride reactivity. The present survey documents these recent applications of in vitro test methods in both mechanistic and 'profile' caries research. In mechanistic studies, in vitro protocols over the past five years have made possible detailed studies of dynamics occurring in mineral loss and gain from dental tissues and the reaction dynamics associated with fluoride anticaries activity. Similarly, in profile applications, in vitro protocols make possible the inexpensive and rapid--yet sensitive--assessment of F anticaries efficacy within fluoride-active systems, and these tests represent a key component of product activity confirmation. The ability to carry out single variable experiments under highly controlled conditions remains a key advantage in in vitro experimentation, and will likely drive even further utilization, as advances continue in physical-chemical and analytical techniques for substrate analysis in these protocols. Despite their advantages in vitro testing protocols have significant limitations, most particularly related to their inability to simulate the complex biological processes involved in caries.

Physical model for lesion formation in the presence of low levels of solution fluoride

A quantitative physical model is presented for the formation of subsurface carious lesions in the presence of low levels of solution fluoride. Calculations using independently determined model parameters are in agreement with mineral density profiles measured in bovine enamel lesions. The proposed mechanism is controlled by fluoride in the following way: as fluoride diffuses into enamel, it is rapidly adsorbed to enamel crystallites, resulting in very low microenvironmental fluoride concentrations, so long as the crystals are not saturated with respect to fluoride adsorption. The result of this saturable adsorption is a widening band of fluoride-saturated crystals near the surface, beneath which the microenvironmental fluoride concentrations are negligible. In the saturated band, the microenvironmental fluoride concentration in the pore solution is high enough to suppress dissolution, while in the deeper, relatively fluoride free region, dissolution can occur. In addition to predicting observed mineral density profiles, the model also predicts the demarcation in solution conditions between the regime where subsurface lesion formation occurs and that where the dissolution pattern is that of surface erosion; and the lack of insensitivity of dissolution rate to hydrodynamics in the presence of low levels of fluoride, as contrasted to the square root of stirring rate dependency observed in the absence of fluoride.