CARBONATOAPATITE FORMATION IN ENAMEL MINERALIZATION

牙釉质矿物质在牙齿发育和萌出中的描述最为充分。 作为碳酸盐磷灰石。本提案的目的是：a)确定 碳磷灰石的化学计量和溶度积常数 不同发育阶段的釉质组织；b)评估驱动力 釉质形成过程中牙釉质矿物的沉淀力； 一个长期目标，c)研究可能的进化变化 硬组织中碳磷灰石的形成机制。这项工作将 需要结合化学分析、电子显微镜、FTIR和 傅立叶变换红外显微镜、X射线衍射仪和蛋白质分析。这样的一个 程序的组合将适用于以下具体情况 目的：(1)测定牙釉质矿物的溶解度 控制二氧化碳的分压。每个样本的平衡将是 在离子组成类似于 釉质液体。(Ii)牙釉质矿物化学计量比的测定 并开发了新的溶解度模型，考虑了大多数 晶格组成：Ca2+、PO43-、HPO42-、CO32-、Mg2+、Na+、OH-和F-。 为此，这些物种的总含量和可交换的 晶体表面上的碳酸盐、HPO42-、Mg2+和Na+池将是 单独评估。最后，计算了化合物的溶度积常数 在猪牙釉质发生的不同阶段，釉质矿物将 根据化学计量比和溶解度模型确定的 对实验数据进行最好的拟合。(Iii)达利石的制备-和 含HPO42-、Mg2+、Na+As的方沸石型碳磷灰石 晶格成分。镁、钠和氟离子的影响 在CO32-和HPO42-掺入晶格上，CO32-的位置。 取代，并对微晶的形态进行评估。这个 合成产品，更好的搪瓷晶体原型 羟基磷灰石，将用于溶解、蛋白质吸附和结晶 成长研究。(四)调查氟对人体健康的影响 体内和体外碳磷灰石的形成。鱼牙釉质提供 一个独特的模型，因为矿物中的氟化物是 与鱼类的系统发育有关。人们的注意力将集中在物种上- 碳酸盐在晶格中的特定取代及其形态 鱼类不同发育阶段的釉质晶体。合成介质 将被用来确定存在临界浓度的 溶液中的氟化物，这会导致降水的显著变化 过程(即前体的参与或磷灰石的从头形成 晶体)和形成的碳化磷灰石的性质，例如 形态和溶解度。(V)阐明可能的监管 牙釉质蛋白晶体形成碳磷灰石的机理 互动。合成碳磷灰石以产生一系列化学物质 物理性质将被用来研究矿物的影响 釉质组成和晶面性质对牙釉质吸附的影响 蛋白质及其在磷灰石表面的吸附抑制活性 晶体生长。 总体建议旨在对这一机制有一个新的见解 生物碳磷灰石的形成及其调控 成釉作用。所获得的信息对预测 牙釉质在正常和龋齿环境及以下环境中的稳定性 氟化物政权。

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.