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CARBONATOAPATITE FORMATION IN ENAMEL MINERALIZATION

牙釉质矿化过程中碳磷灰石的形成

基本信息

批准号：
2130134
负责人：
TAKAAKI AOBA
金额：
$ 23.34万
依托单位：
ADA FORSYTH INSTITUTE, INC.
依托单位国家：
美国
项目类别：
财政年份：
1988
资助国家：
美国
起止时间：
1988-09-01 至 1994-12-31
项目状态：
已结题

项目摘要

Enamel mineral in developing and erupted teeth is most adequately described as a carbonatoapatite. The present proposal aims at: a) determining the stoichiometry and solubility product constants of the carbonatoapatite in the enamel tissue at various developmental stages; b) assessing the driving force for precipitation of the enamel mineral during amelogenesis; and, as a long-term objective, c) investigating possible evolutionary changes in the mechanism of carbonatoapatite formation in hard tissues. The work will entail a combination of chemical analyses, electron microscopy, FTIR and FTIR microscopy, x-ray diffraction and protein analyses. Such a combination of procedures will be applied toward the following specific goals: (i) Determination of the solubility of enamel mineral under controlled partial pressures of CO2. Equilibration of each sample will be conducted in solutions having ionic composition similar to that of the enamel fluid. (ii) Determination of the stoichiometry of enamel mineral and development of new solubility models taking into account most of the lattice constituents: Ca2+, PO43-, HPO42-, CO32-, Mg2+, Na+, OH-, and F-. For this purpose, the total contents of these species and the exchangeable pools of carbonate, HPO42-, Mg2+, and Na+ on the crystal surfaces will be assessed separately. At the end, solubility product constants of the enamel mineral at the various stages of porcine amelogenesis will be determined on the basis of the stoichiometry and the solubility model that fit the best the experimental data. (iii) Preparation of dahllite- and francolite-type carbonatoapatites containing HPO42-, Mg2+ and Na+ as lattice constituents. The effects of magnesium, sodium, and fluoride ions on the CO32- and HPO42- incorporation into the lattice, the sites of CO32- substitution, and the morphology of the crystallites will be assessed. The synthetic products, better prototypes for enamel crystals than hydroxyapatite, will be used in solubility, protein adsorption, and crystal growth studies. (iv) Investigation of the effects of fluoride on carbonatoapatite formation in vivo and in vitro. Fish enameloid provides a unique model, since the fluoride incorporation into the mineral is related to the phylogeny of fishes. Attention will be focused on species- specific carbonate substitution in the crystal lattice and morphology of fish enameloid crystals at various stages of development. Synthetic media will be used to ascertain the existence of a critical concentration of fluoride in solution, which causes significant changes in the precipitation process (i.e., involvement of precursors or de novo formation of apatite crystals) and in the properties of formed carbonated apatites, such as morphology and solubility. (v) Elucidation of a possible regulatory mechanism of carbonatoapatite formation through the enamel proteins-crystal interaction. Carbonatoapatites synthesized to yield a range of chemical and physical properties will be used to study the effects of mineral composition and crystal-surface properties on the adsorption of enamel proteins and inhibitory activity of the adsorbed proteins on apatite crystal growth. The overall proposal is designed to gain a new insight into the mechanism of biological carbonatoapatite formation and its regulation during amelogenesis. The information obtained is valuable to predict the stability of dental enamel in normal and cariogenic environments or under fluoride regimes.

牙釉质矿物质在发展和爆发的牙齿是最充分的描述碳磷灰石本建议旨在：a）确定化学计量和溶解度积常数的碳磷灰石在 B）评估驱动在釉质形成过程中釉质矿物质沉淀的力;以及，一个长期目标，c）调查可能的进化变化，硬组织中碳磷灰石形成的机制。这项工作将需要化学分析、电子显微镜、FTIR和 FTIR显微镜、X射线衍射和蛋白质分析。这样的将对以下具体项目实施一系列程序目的：（i）测定釉质矿物质的溶解度，控制二氧化碳分压。各样品的平衡将在离子组成类似于釉质液 (ii)搪瓷矿物化学计量的测定并开发新的溶解度模型，同时考虑到大多数晶格组成：Ca 2+、PO 43-、HPO 42-、CO 32-、Mg 2+、Na+、OH-、F-。为此，这些物种的总含量和可交换的晶体表面的碳酸盐、HPO 42-、Mg 2+和Na+池将被单独评估。在最后，溶解度积常数的在猪牙釉质形成的各个阶段，基于化学计量和溶解度模型确定，最好的实验数据。 (iii)制备dahlite-和含HPO_（42-）、Mg ~（2+）和Na ~+的钙钛矿型碳磷灰石晶格成分镁、钠和氟离子的影响 CO_3 ~（2-）和HPO_4 ~（2-）的晶格结合，取代，并将评估微晶的形态。的合成产品，更好的搪瓷晶体的原型，羟基磷灰石，将用于溶解，蛋白质吸附，和晶体成长研究。 (iv)氟对人的影响在体内和体外的碳磷灰石形成。鱼珐琅提供了一个独特的模型，因为氟化物掺入矿物是与鱼类的生殖有关。注意力将集中在物种上- 晶体晶格中的特定碳酸盐取代和鱼的釉质晶体在不同的发展阶段。合成培养基将被用来确定存在的临界浓度溶液中的氟化物，这会导致沉淀的显着变化过程（即，前体的参与或磷灰石的从头形成晶体）和形成的碳酸磷灰石的性质，如形态和溶解度。 (v)阐明可能的监管牙釉质蛋白晶体形成碳酸磷灰石的机制互动合成的碳磷灰石可以产生一系列化学物质和物理性质将被用来研究矿物的影响组成和晶体表面性质对牙釉质吸附的影响蛋白质及其在磷灰石上的吸附抑制活性晶体生长总体建议旨在对该机制有一个新的认识生物碳磷灰石的形成及其调控釉质形成所获得的信息对于预测牙釉质在正常和致龋环境中的稳定性氟化物制度。