The Role of Biofilm on Margin Stability and the Development of Secondary Caries

描述（由申请人提供）：超过70%的龋齿病变（现在每年超过1.25亿）使用丙烯酸酯基树脂复合材料修复，其平均使用寿命不到6年（相比之下，汞合金为15年）。更换这些修复体的主要原因是继发性龋齿，但这些病变在树脂基复合材料上发展得更快的原因尚不清楚。以往临床对牙缘间隙与继发龋发生关系的研究，由于相互作用变量复杂，且无法准确监测牙缘间隙尺寸，结果模棱两可。更多受控的体外实验集中在汞合金上，而不是树脂基复合材料上。本研究将研究一种商用丙烯酸酯基树脂牙科复合材料和相关聚合物体系，其具体目的如下：(1)确定微间隙在人类牙齿继发龋发育中的作用，(2)确定间隙尺寸如何控制间隙内的封闭化学，(3)确定封闭化学如何影响树脂和复合材料的结构和性能。这将在一个多学科团队和最新可用的测量工具和技术的4年研究努力中完成。具有自然形成的微间隙的修复体和具有精确控制微间隙尺寸的模型修复体将暴露在一个现实的、受控的体外环境中，该环境由人工唾液中与龋齿相关的口腔细菌组成。采用超分辨率垂直扫描干涉技术，以亚微米分辨率无损监测微生物生物膜对牙槽面边缘附近复合表面和微间隙尺寸的影响。将确定间隙尺寸、不同菌株的活性与继发性龋齿的频率和严重程度之间的关系。此外，微间隙内的pH值和Ca2+浓度将被测量为深度和时间的函数，这是牙科研究的新微传感器技术。最后，封闭的微间隙化学对树脂复合材料性能和化学的直接影响将通过动态力学测试、疲劳测量、新开发的微束技术以及FTIR来检查，以确定是否有水解导致骨架断裂的直接证据。这项研究的成功完成将最终验证树脂基复合材料继发性龋齿的领先理论，严格检查这些材料在牙科中的功效，并开发新的，更精确的工具，用于实验室和临床的生物材料研究。

DESCRIPTION (provided by applicant): More than 70% of carious lesions (now over 125 million per year) are restored with acrylate-based resin composites which have a median service-life of less than 6 years (vs. 15 years for amalgam). The major reason for replacing these restorations is because of secondary caries, but the reason these lesion develop more rapidly on resin-based composites is unclear. Previous clinical studies on the relationship of the margin gap to the development of secondary caries have resulted in equivocal results due to the complexity of interacting variable and the inability to accurately monitor gap dimensions. More controlled in vitro experiments have focused on amalgams and not resin-based composites. This research will investigate a commercial acrylate-based resin dental composite and relevant polymer systems with the following specific aims: (1) to determine the role of the microgap in the development of secondary caries in human teeth, (2) to define how gap dimension controls the occluded chemistry within the gap, and (3) to determine how the occluded chemistry impacts the structure and properties of the resin and composite. This will be accomplished in a 4 year research effort with a multidisciplinary team and newly available measurement tools and techniques. Restorations with naturally formed microgaps and model restorations with precisely controlled microgap dimensions will be exposed to a realistic, controlled in vitro environment consisting of a consortium of oral bacteria relevant to caries in artificial saliva. The effects of the microbial biofilm on the tooth and the composite surface near the cavosurface margin and on the microgap dimensions will be monitored non-destructively with submicron resolution with a new interferometric technique, Super Resolution Vertical Scanning Interferometry. The relationship of gap dimensions, the activity of the different bacterial strains, and frequency and severity of secondary caries will be determined. In addition, the pH and Ca2+ concentration within the microgap will be measured as a function of depth and time with micro-sensor techniques that are new to dental research. Finally, the direct effect of the occluded microgap chemistry on the resin composite properties and chemistry will be examined using dynamic mechanical testing, fatigue measurements, and a newly developed minibeam technique, as well as FTIR to determine if there is direct evidence of backbone scission by hydrolysis. The successful completion of this research will conclusively test a leading theory for secondary caries in resin-based composites, critically examine the efficacy of these materials for use in dentistry, and develop new, more precise tools for biomaterial investigations in the laboratory and the clinic. PUBLIC HEALTH RELEVANCE: Resin-based dental composites are the principle material used to restore over 120 million cavities each year in the US, but have a very limited service-life that is 40% of an amalgam. This program will use newly available tools and experimental methods to critically evaluate the efficacy of these materials for use in dentistry. New, more precise methods will be developed for biomaterial investigations in the laboratory and the clinic.