牙体修复中聚氨酯弹性层的构建

The two main reasons for treatment failure using light-cured composite resins to restore posterior teeth are restoration fracture and secondary caries, which are closely related to the stresses caused by polymerization shrinkage of direct restorative light-cured composite resin filling, and produced due to the large differences in the coefficient of thermal expansion of the resins and that of dental hard tissues. How to effectively improve the quality of filling composite resins is and will continue to be a clinical problem to be solved for the foreseeable future. In this study, we designed and synthesized a light-curing polyurethane elastic layer, suitable for tooth tissue defect repair, sandwiched between the tooth tissues and cured composite resins, acting as an elastic buffer layer, absorbing the stresses resulted from polymerization shrinkage of resins and the temperature changes. We screened for and selected the best formulation by experimenting with synthesis, evaluating features and biological properties of the materials, and assessing the anti-aging adhesive capability of the polyurethane elastic layer. Our approach is highly innovative because the selected elastically stretchable polyurethane sheet material has high adhesive strength, is resistant to aging, and acts as a buffer layer to reduce the stresses and the occurrence of marginal leakage between teeth hard tissues and the composite resins. Thus the elastic layer can effectively decrease the risks of fracture and secondary caries following composite resin restoration, and improve the clinical effect and durability of teeth composite resin restorations.

断裂及继发龋是导致后牙光固化复合树脂修复治疗失败的两个主要原因，这与光固化复合树脂直接充填固化产生的聚合收缩、树脂和牙体硬组织之间的热膨胀系数差异较大而产生的应力密切相关。如何采取有效措施提高复合树脂修复质量是目前及今后相当长时间内临床亟待解决的问题。本研究设计合成适用于牙体组织缺损修复的光固化聚氨酯弹性层材料，将其固化在牙体硬组织和复合树脂之间，形成一个弹性缓冲层，以吸收树脂固化产生的收缩应力及温度变化而导致的应力。通过材料的合成与表征及生物性能评价，聚氨酯弹性层粘接体系耐老化评价，筛选确定最佳的配方。研究的创新性在于通过设计粘接强度高，耐老化，能够弹性伸缩的聚氨酯薄层材料，真正降低牙体硬组织与复合树脂之间的各种应力，减少两者间边缘渗漏的发生，从而有效降低复合树脂修复后继发龋和断裂的发生几率，提高复合树脂修复的临床治疗效果和耐久性。

研究背景：牙本质粘接界面的稳定性和耐久性是预防继发龋发生的关键。牙本质粘接界面的质量受多种因素影响，如界面应力、细菌及菌斑生物膜的聚集、牙本质粘接界面的降解等，且各因素间相互关联。为降低各因素对牙本质粘接的不利影响，本项目设计不同功能的光固化聚氨酯（Polyurethane，PU），构建新型牙本质粘接修复体系，并进行实验评估，最终达到封闭牙本质小管、缓冲界面应力、耐水解、长期有效抗菌的目的，形成良好的牙本质粘接界面，为提高牙本质粘接质量提供有价值的思路和参考依据。.主要研究内容：（1）光固化PU弹性层的合成、表征及应用；（2）疏水性抗菌性PU弹性层的合成、表征及应用；（3）亲水性PU预处理剂的合成、表征及应用。.重要结果及科学意义：.（1）调节PTMEG 2000 型 PU 预聚物（Pre-PU-A）和1,6-己二醇型PU预聚物（Pre-PU-B）的比例（Pre-PU-A/B 按照 1:0, 6:1, 4:1, 3:1 和 2:1 的体积比）混合均匀后，加入过量HEMA封端。通过实验评估，筛选出最佳配方比例。其中Pre-PU-A/B为3:1组，拉伸强度和断裂伸长率均较大，说明PU弹性层具有一定弹性；应用于光固化复合树脂修复体系，冷热循环老化后微拉伸强度增高，微渗漏0或1级。.（2）合成可光固化抗菌单体（TCS-IH），调整TCS-IH掺入比例，最终获得抗菌性PU弹性层。通过实验检测，加入3wt% TCS-IH的PU弹性层具有较高双键转化率，较低吸水值/溶解值，最大拉伸强度和断裂伸长率，且可发挥较强抗菌作用，应用于牙本质粘接修复体系，且微拉伸强度具有良好的耐老化性，微渗漏0级。.（3）设计含-COOH的PU，加入吸水剂、nHAp等成分，获得亲水性PU预处理剂。材料固化后充分浸水1.5 h，吸水率和直径增大率达到最大且持续，分别为0.8g/g、20%；应用于牙本质后可封闭绝大部分牙本质小管口，并形成50-100 nm长的树脂突形成，且微拉伸强度具有良好的耐老化性。.研究结果显示，应用不同功能的PU，可提高牙本质粘接界面的耐久性和稳定性，为提高牙本质粘接质量提供有价值的思路和参考依据。