诱导牙本质再矿化的有机/无机复合纳米粒子

The significance of inducing remineralization of demineralized dentin was not only for improving the existing bonding restoration techniques, but also for the development of new therapies. Various biomimetic analogs and calcium phosphate sources were used in previous studies to remineralize dentin in vitro. This study intends to integrate these two kinds of components, improve the mineralization efficiency and reduce the amount of mineralization fluid, hoping to provide a theoretical basis for the application in vivo. By using the controlled-release technique, modified polyamidoamine (PAMAM) / amorphous calcium phosphate (ACP) composite nanoparticles were synthesized and stabilized by polyacrylic acid. The nanoparticles were designed to rapidly release PAMAM at the beginning to bind collagen fibrils and guide calcium and phosphorus ions to their nucleation sites; then, followed by a prolonged release of calcium and phosphate ions as the mineralization materials. The polyacrylic acid could stabilize the newly formed ACP nanoparticles to allow them diffuse into the intrafibrillar compartments and initiate mineralization. The surface modification of PAMAM could reduce its toxicity and improve the binding ability. Systematic observation would be taken to study the mineralization process in self-assemble collagen fibril model and demineralized dentine and discover the mechanism of PAMAM and PAA; the physicochemical properties of remineralized dentin layer would also be tested to further understand biomineralization theory. The interdisciplinary involved in this study could also provide a new way for dental material research.

诱导脱矿牙本质再矿化，不仅对提高现有粘接修复技术意义重大，更为发展治疗牙体硬组织疾病的新方法提供途径。以往研究应用多种仿生类似物及钙磷源实现了脱矿牙本质的体外矿化。本项目拟将两类组分集成，以提高矿化时效，减小矿化液量，为更接近体内应用提供理论依据。本研究通过纳米控释技术，设计制备聚丙烯酸稳定的无定形磷酸钙（ACP）纳米粒子并复合改性聚酰胺-胺（PAMAM）。在应用初期快速释放PAMAM与胶原纤维结合引导钙磷离子至成核位点，随后持续释放钙磷离子作为矿化原料，聚丙烯酸可稳定新生ACP颗粒的无定形态及纳米粒径，使其作为流动性前驱相进入脱矿胶原纤维内发生矿化。通过对PAMAM的表面改性，降低毒性、提高结合力。通过系统观察胶原纤维模型、脱矿牙本质的矿化过程及再矿化修复层的理化性质，深入研究PAMAM和PAA的作用机理，阐释矿化理论。本项目所涉及的学科交叉也将为相关的口腔医学研究提供新途径。

为了提高粘接耐久性，诱导混合层脱矿牙本质再矿化，本研究开发了一种实验用粘接系统，利用纳米控释技术将氯己定包载入聚酰胺-胺树枝状大分子作为预处理剂，将纳米ACP作为填料加入粘接剂。通过微拉伸粘接强度可以证实该系统能在热机械循环老化后维持粘接强度。通过双荧光原位明胶酶谱分析，可以证实预处理剂中释放氯己定抑制混合层内源性酶，减缓混合层降解，在短期内可以延缓粘接老化，并为再矿化保留完整胶原纤维模板。用实验系统对脱矿牙本质盘进行再矿化后扫描电镜观察，发现聚酰胺胺树枝状大分子与粘接剂中释放的钙磷离子能够促进牙本质再矿化，进一步稳定混合层，利于长期粘接界面的稳定。该粘接系统材料制备易于批量生产，便于临床应用，本研究可为将来的应用提供理论基础。