【作者】 王珂；

【导师】 李毅； 赵旭；

【作者基本信息】 吉林大学 ， 口腔临床医学（儿童口腔科）， 2016， 硕士

【摘要】 牙髓组织是一种具有修复再生能力的结缔组织,当其受到炎症刺激或机械损伤后,若能发挥其修复再生的能力,对于保存活髓具有重要意义。直接盖髓术或活髓切断术是将药物或材料覆盖在暴露的牙髓处,使牙髓免受外界新的损伤刺激并促进其愈合,以保存牙髓活力。从根本上来说,促进暴露的牙髓组织愈合的目的是促进牙髓细胞向成牙本质细胞分化。这一结果的获得与牙髓暴露的时间、大小、是否感染及盖髓剂的性能有关。良好的盖髓剂应能够促进牙髓组织修复再生,并能够诱导牙髓细胞向成牙本质细胞分化。因此,恰当的盖髓材料是保证这一治疗方法成功的重要条件。辛伐他汀为羟甲基辅酶A还原酶抑制剂,其在临床上为常用的降胆固醇药。近年来研究表明,辛伐他汀在低浓度情况（10-7¹0-9 mol/L）下可以促进牙髓细胞增殖,促进其分泌血管内皮生长因子,且促进其分化为矿化组织的能力。这一发现为辛伐他汀作为盖髓剂进行保髓治疗提供了初步的实验依据。然而,辛伐他汀在高浓度情况下会抑制牙髓细胞增殖,导致牙髓细胞死亡。单纯把药物放在牙髓断面处只能导致局部高浓度。因此,这就需要寻找一种合适的载体,将辛伐他汀载入其中构成缓释体系,使药物保持局部低浓度、持续释放,达到最佳保护牙髓的效果。羟基磷灰石(Ca₁₀（PO₄）₆（OH）₂,HAp)是人体骨骼和牙齿的主要无机成分,由于其良好的生物相容性、骨传导性、生物活性、无毒性反应被广泛应用于生物医学材料、环境工程和化工领域。除此之外,羟基磷灰石还可以吸附多种化学药物在其表面。中空球形羟基磷灰石由于其特殊的内部中空结构和纳米多孔外壳,使其在作为药物载体时,能有效提高药物的存储量,延长缓释作用时间。本文受到生物矿化思想的启发,利用有机分子的调控合成了具有特殊形貌的无机矿物。这一过程称为仿生合成技术。由于有机大分子在人体内作用时多降解为小分子,而与人体生命密切相关的大分子主要是蛋白质,蛋白质在人体内随时间迁移逐渐降解为氨基酸。与牙釉质矿化相关的蛋白（如釉原蛋白、牙本质涎磷蛋白等）片段经检测后发现高度重复的天冬氨酸和磷酸化的丝氨酸序列,且这些氨基酸与钙离子具有强相互作用。本研究通过采用氨基酸（天冬氨酸）和十二烷基磺酸钠组成的“核-壳”式复合物为模板,合成了具有中空结构的羟基磷灰石微球,实现了制备方法简单化和中空微球表面形貌的可控性。根据仿生合成的原理,本实验以氨基酸（天冬氨酸）和十二烷基磺酸钠组成的“核-壳”式复合物为模板,一步法合成了中空羟基磷灰石微球。将辛伐他汀载入中空羟基磷灰石微球构成体外缓释系统,计算载药率、包封率和药物体外缓释时间。建立大鼠上颌第一磨牙直接盖髓模型,用含有不同浓度辛伐他汀的羟基磷灰石中空微球、未载药的中空羟基磷灰石微球和氢氧化钙盖髓,并设空白对照组。结果表明,制备的羟基磷灰石为由短针状的纳米粒子组成的壁厚为0.5-1μm,直径为3-5μm的中空微球,该中空微球表现出良好的载药性和体外药物缓释性能,释放曲线接近线性,几乎看不到突释现象,累积释放率达87.4%。将含有一定浓度辛伐他汀的羟基磷灰石中空微球作为盖髓剂进行盖髓,其生物相容性好且具有促进牙髓损伤后修复性牙本质形成的潜能。更多还原

【Abstract】 Dental pulp is a kind of connective tissue which possess repair and regeneration capacity. When it is subjected to inflammatory stimulation or mechanical damage, the reparative regeneration ability has great significance for preservation of vital pulp. Direct pulp capping or partial pulpotomy is a method of treatment in which the exposed dental pulp is covered with a material protecting the pulp from additional injury and stimulating healing and repair. Ultimately, the goal of treating the exposed pulp with an appropriate pulp-capping material is to promote the odontoblastic differentiation of the pulp cells. The result is related to time, size and infection extent of exposed pulp as well as property of pulp capping agent. In this respect, appropriate pulp capping agent is the key to ensure success of the therapeutic method.Simvastatin, a hydroxymethylglutaryl-coenzyme Areductase inhibitor, is known to be used clinically to reduce blood cholesterol levels. Recently, it has been reported that simvastatin in low concentration（10-7¹0-9mol/L） can accelerate proliferation, secreting vascular endothelial growth factor（VEGF） as well as mineralizating of dental pulp cells.This found suggested simvastatin as a potential supplemental pulp-capping agent. Simvastatin in high concentration can suppess proliferation, leading to apoptosis of dental pulp cells. However, local high concentration can be formed if we simply put simvastatin on the exposed dental pulp. Therefore, it needs to find a suitable carrier to constitute local drug delivery system, the sustained low concentration of simvastatin can achieve the best effect of protecting dental pulp.Hydroxyapatite(Ca₁₀（PO₄）₆（OH）₂, HAp) is the main inorganic constituent of bones and teeth, which possess excellent biocompatibility, osteoconductivity, bioactivity and nontoxicity. It has been widely used in biomedical materials, environmental engineering, chemical and technological fields.Morever, hydroxyapatite can absorb a variety of chemicals. Hollow hydroxyapatite microsphere could provide an excellent device for sustained local delivery of drugs because of its hollow interior and nanoporous shell.In this paper, inspired by the idea of biological mineralization, we prepared inorganic minerals with specific morphology utilizing organic molecules. This process is called biomimetic synthesis. Since the organic macromolecule are usually degraded intomicromolecules, the main macromolecule closely with human life protein can be degreded into amino acids gradually migrating over time. Protein fragments associated with enamel mineralization such as amelogenin and dentin sialophosphoproteins contain highly repeated sequences of aspartic acid and phosphorylated serine. These amino acids are known to have strong interactions with Ca2+. In this study, hollow hydroxyapatite microspheres were synthesized utilizing amino acids（ aspartic acid） and sodium dodecyl sulfonate（SDS） “core-shell” complex serving as templates. This method implements simplification for preparation and controllability of hollow microspheres surface morphology.Based on the principles of biomimetic synthesis, hollow hydroxyapatite microspheres were fabricated with one step strategy utilizing amino acids（ aspartic acid） and sodium dodecyl sulfonate（SDS） “core-shell” complex serving as templates. The as-prepared hollow hydroxyapatite microspheres were loaded with simvastatin following drug loading and encapsulation efficiency and in vitro sustained-release time calculated.The model of direct dental pulp capping of maxillary first molars of Wistar rats were established, the drug loaded microspheres containing different concentration of simvastatin,hollow hydroxyapatite microspheres without simvastatin and calcium hydroxide were applied on the exposed dental pulp, the dental pulp without treatment worked as control group. The results showed that the prepared hollow hydroxyapatite microspheres were 3⁵μm with thickness for the shell 0.5¹μm and constructed by short needle nanoparticles. The microspheres exhibit excellent drug-loading capacity and sustained release property, the release behavior followed nearly linear release profile. The drug loaded microspheres containing certain concentration of simvastatin show its excellent biocompatibility and potency in promoting the formation of reparative dentin after pulp capping.更多还原