【作者】 廖颖敏；

【导师】 冯祖德；

【作者基本信息】 厦门大学 ， 无机化学， 2007， 博士

【摘要】 龋损的早期是施行龋病防治的有效阶段,因而本研究建立了电诱导体系,利用电化学的方法在有人工早期龋损的牙釉质表面制备羟基磷灰石(HA)涂层。此涂层与牙釉质基底结合紧密,且具有与健康牙釉质相近的维氏显微硬度和较高的抗菌性能,从而实现对早期釉质龋进行快速、有效的修复。本文综合分析了电诱导体系中影响牙釉质表面所形成涂层的表面形貌、物相以及表面物理性能的各种因素,如电解液的初始pH值、钙磷物种的浓度、体系的温度、时间和电流密度等;并从热力学理论计算出发,提出了相应的电诱导牙釉质表面HA涂层形成过程的模型,建立了受扩散过程控制的动力学方程,并设计了相应的实验进行验证;进而在热力学和动力学分析的基础上,探讨了电诱导牙釉质表面HA涂层的形成机理。实验结果显示应用交流阻抗法可有效判定离体牙釉质的龋坏程度。酸性预处理可获得人工早期釉质龋,并提高牙釉质样品表面的亲水性,从而有利于诱导HA涂层的形成。当电解液初始pH为6、温度为328K、电流密度为0.5mA/cm~2时,涂层中HA晶体在(002)上的择优取向度接近于天然牙釉质中的。升高温度和降低钙磷物种的浓度可使HA晶粒尺寸单调减小,样品表面致密化。通过动力学分析证实HA涂层的形成速率主要由溶液中的离子向阴极表面扩散所控制,存在的诱导期随着温度的升高而缩短。阐明电诱导牙釉质表面HA涂层形成需要的两个重要步骤分别为阴极近表面的析氢反应和HA晶体的形成。本研究表明,电诱导HA涂层在牙釉质表面的形成是修复早期牙釉质龋的一种比较新颖的方法,对于在临床上快速、有效地防治早期釉质龋具有重要的意义。更多还原

【Abstract】 The early stage of caries was the effective stage for preventing and treating the caries. In this study, an electrochemical system was founded. Electrichemical technique was adopted to prepare hydroxyapatite coatings on human enamel that had artificial initial enamel lesions. The hydroxyapatite coatings could tightly combine to the enamel surfaces and exhibited a strong resemblance to the sound human enamel in Vickers micro-hardness. Also, the antibacterial activities of the enamel surfaces were improved. Then the initial enamel lesions were prevented and restored rapidly and effectively.Effects of process prameters (such as the initial pH value of electrolyte, concentration of calcium and phosphorus species, temperature of the system, time, current density, etc.) on morphology, compositon and physicalchemical character of hydroxyapatite coatings were analyzed synthetically in this study. Thermodynamic calculations were carried out, and a model that was corresponding to the formation of hydroxyapatite coatings on enamel surface by electrochemical technique was proposed. Then the kinetic equations governed by the diffusion process were presented and confirmed by the relative studies that were carried out. Eventually, the possible mechanism was proposed based on the thermodynamic and kinetic analysis.The results showed that the degree of caries could be judged effectively using electrochemical impedance spectroscopy techniques. After acid treatment, initial enamel lesions could be gained and the hydrophilicity of the samples was improved. These were helpful for the preparation of coatings. In addition, the preferential (002) orientation showed a similar value in the comparison between the sound enamel and hydroxyapatite coatings that were prepared with the current density of 0.5mA/cm~2 at 328K when the initial pH value was 6. The dimension of hydroxyapatite crystal decrease significantly upon the increasing temperature and the decreasing concentrations of calcium and phosphorus species, then the surface became smooth. It was indicated that the growth rate of hydroxyapatite coating was mainly controlled by the diffusion of ions towards to the cathode. An induction period was exised during the hydroxyapatite precipitation, which showed a decrease upon increasing temperature. Two important steps, hydrogen evolution reaction and formation of hydroxyapatite precipitation, were contained in the formations of the hydroxyapatite coatings on human enamel surface by electrochemical tschnique.In conclusion, it was a novel method to restore the initial enamel lesions by preparing hydroxyapatite coatings on human enamel using electrochemical technique. And it was significant to prevent and restore the initial enamel lesions rapidly and effectively in clinic.更多还原