无托槽隐形矫治用热压膜材料性能的研究

As a result of increased interest in adult orthodontic treatment, esthetic alternatives to conventional fixed appliances are often requested. Align Technology has addressed this demand by developing an "invisible" method of orthodontic treatment that uses a series of computer-generated, clear, removable appliances. These clear thermoplastic appliances have attracted a great deal of attention as esthetically more acceptable alternatives to traditional ?xed appliances.But many orthodontists reported that 70% to 80% of their patients require midcourse correction, case refinement, or conversion to fixed appliances before the end of treatment and the efficacy of tooth movement with Invisalign is lower than fixed appliances..The clear aligner is made of various thermoplastic materials, different from traditional orthodontic techniques, the mechanical properties of thermoplastic materials are closely related to the quality of orthodontic force exerted by the aligner. Therefore, if good result is desired through orthodontic practice, thorough study of the mechanical properties of various thermoplastic materials is essential and inevitable. However, only a few studies have been published on this topic. And, these studies used the different commercialized thermoplastic products and there are many different thermoplastic materials brand in the market, which have been widely used for orthodontic retainers, temporomandibular joint splints, night guards, bleaching trays. The mechanical properties of these materials are differ from eath other according to their application. Desirable properties for orthodontic materials are large spring back, low stiffness, good formability, high stored energy, biocompatibility, and environmental stability. As thermoplastic polymers are highly viscoelastic materials, both structural factors, such as molecular and crystal structures, and environmental factors, such as temperature, humidity, time after elastic deformation, and forming procedures have marked effects on their mechanical properties. The application of thermoplastic materials for tooth movement requires suf?cient understanding of the material characteristics. However, the comparison of the mechanical properties of dental thermoplastic materials have still not been systematically investigated. At present, materials are selected for use based on the manufacturer's recommendations, feel, or operator's experience. Therefore, the purpose of this study was to provide a complete characterization of contemporary commercialized dental thermoplastic materials' mechanical and physical properties, and investigate changes in material performance that may occur under different test conditions, to improve the properties of thermoplastic materials by blending modification and provide the suggestion of optimal material selection for invisible orthodontics.

无托槽隐形矫治技术已在临床上广泛应用，但其矫治效果并不理想，多数病例不能达到预期的治疗目标。该技术的矫治力主要来源于热压膜材料变形后的回弹力，因此对这种材料性能的研究有利于提高矫治效能。目前有关材料性能的研究并不多见，而且并没有隐形矫治专用的材料，原料组成及加工制作工艺对材料性能的影响机制尚不清楚。本研究对临床常用的几种热压膜材料的相关性能进行比较，为研究隐形矫治用热压膜材料提供一定的参考；在此基础上以聚酯（PETG）和聚氨酯（TPU）为主要原料，应用共混改性的方法，通过添加不同辅料，调整组成比例和加工制作工艺，从而改善原料的相关性能，以满足隐形矫治技术的要求；同时测试并比较不同材料制作的隐形矫治器，在模拟口腔环境下作用在牙齿上的实际矫治力和矫治效能。本研究将系统深入的对隐形矫治用热压膜材料的性能进行研究，并揭示其与原料组成和加工制作工艺之间的关系，为临床合理的设计和应用提供可靠的依据。

无托槽隐形矫治技术已在临床上广泛应用，但其矫治效果并不理想，多数病例不能达到预期的治疗目标。该技术的矫治力主要来源于热压膜材料变形后的回弹力，因此对这种材料性能的研究有利于提高矫治效能。目前有关材料性能的研究并不多见，而且并没有隐形矫治专用的材料，原料组成及加工制作工艺对材料性能的影响机制尚不清楚。本研究对临床常用的几种热压膜材料的相关性能进行比较，为研究隐形矫治用热压膜材料提供一定的参考；在此基础上应用共混改性的方法，通过添加不同辅料，调整组成比例和加工制作工艺，从而改善原料的相关性能，以满足隐形矫治技术的要求；同时测试并比较不同材料制作的隐形矫治器，在模拟口腔环境下作用在牙齿上的实际矫治力和矫治效能。本课题与北京市新型高分子材料加工与改性重点实验室（北京化工大学）合作开展，以聚酯（PETG）和聚氨酯弹性体（TPU）为主要原料，筛选聚碳酸酯（PC）等为辅料进行共混。结果发现PETG/PC/TPU三元共混物在70：10：20的比例时综合力学性能较好，但加工性能稍差。后又以PETG为主料，混合PC2858，在比例为70：30时具有良好的力学性能和加工性能，并加工成型1.0mm厚度的PETG/PC2858热压膜膜片。本研究为探索隐形矫治材料的性能，揭示隐形矫治的材料力学机制提供了一个科学、可靠的研究平台，并为今后进一步研究打下良好的基础。