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

描述（由申请人提供）：超过70%的龋损（现在每年超过1.25亿）使用丙烯酸酯基树脂复合材料修复，其使用寿命中位数不到6年（而汞合金为15年）。替换这些牙本质的主要原因是继发龋，但这些病变在树脂基复合材料上发展更快的原因尚不清楚。由于相互作用变量的复杂性和无法准确监测间隙尺寸，先前关于边缘间隙与继发性龋发展关系的临床研究导致了模棱两可的结果。更多的受控体外实验集中在汞合金而不是树脂基复合材料上。本研究将研究商业丙烯酸酯基树脂牙科复合材料和相关聚合物系统，具体目的如下：（1）确定微间隙在人类牙齿继发性龋齿发展中的作用，（2）确定间隙尺寸如何控制差距内的闭塞化学，以及（3）确定闭塞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新的测量工具和技术的4年研究工作中完成。具有天然形成的微间隙的修复体和具有精确控制的微间隙尺寸的模型修复体将暴露于由人工唾液中与龋齿相关的口腔细菌的聚生体组成的真实的受控体外环境。微生物生物膜对牙齿和复合材料表面附近的cavosurface边缘和微间隙尺寸的影响将进行非破坏性监测与亚微米分辨率与一种新的干涉测量技术，超分辨率垂直扫描干涉。将确定间隙尺寸、不同细菌菌株的活性以及继发性龋的频率和严重程度之间的关系。此外，pH值和Ca2+浓度内的微间隙将测量作为深度和时间的函数与微传感器技术，是新的牙科研究。最后，将使用动态力学测试、疲劳测量和新开发的微束技术以及FTIR检查闭塞微间隙化学对树脂复合材料性能和化学的直接影响，以确定是否存在水解导致主链断裂的直接证据。这项研究的成功完成将最终测试树脂基复合材料中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。 公共卫生相关性：树脂基牙科复合材料是美国每年用于修复超过1.2亿个牙洞的主要材料，但其使用寿命非常有限，仅为汞合金的40%。该计划将使用新的可用工具和实验方法来严格评估这些材料在牙科中的有效性。新的，更精确的方法将被开发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.