Interactions Between Oral Biofilms and Dental Resin Composites

描述（由申请人提供）：该项目的长期目标是通过对继发性龋齿发展的基本了解来增加牙科树脂复合修复体的使用寿命。我们更直接的目标是验证口腔生物膜有助于边缘退化的假设，从而导致继发性龋齿的更频繁发生。这可能是因为复合材料在边缘选择了更容易引起龋齿的菌群，或者因为细菌代谢的产物有助于复合材料本身的分解。这两种机制都不是相互排斥的，所以每个问题都将在补充的临床和实验室研究中得到解决，如具体目标中所述：1。比较健全银汞合金修复体、健全复合修复体、早期继发龋修复体和直接继发龋修复体牙釉质界面生物膜的细菌种类组成。人类口腔微生物鉴定微阵列将用于提供包含272种微生物的生物膜。与汞合金-牙釉质界面相比，我们将测试复合牙釉质界面被独特细菌物种定植的假设。这种生态选择可以解释在牙齿-复合材料界面的生物膜的毒力增加。近红外光学计算机断层扫描（OCT）将作为临床龋齿诊断的重要辅助手段，通过比传统方法更早地发现龋齿，并确认声音界面。2.） 通过优化生物膜反应器系统，在拔牙修复体的复合牙釉质界面生长多物种口腔生物膜，并涂上唾液，从而连接我们的临床和实验室研究。该系统将为验证细菌代谢产物有助于复合分解的假设提供基础。来自临床研究的牙菌斑样本将用于建立与复合牙釉质界面相对应的微观世界，其中没有龋齿，早期龋齿或直接龋齿。HOMIM系统将用于监测微观世界的物种组成，并确定从患者样本中复制生物膜主要物种概况所需的条件。3)。使用明尼苏达人工口将负荷循环纳入生物膜反应器模型。将复合修复体放置在拔牙上，将经历唾液涂层、生物膜在反应器中生长和在人工口腔中加载的反复循环。用复合材料修复的牙齿产生不同程度的收缩应力，将暴露在不同类型的微观世界中，也暴露在无菌唾液培养基中，有或没有加载。OCT和micro-CT成像将用于监测牙齿组织中矿物质的损失，而显微硬度测试和傅里叶变换红外光谱将用于评估复合材料的变化。该体外模型系统将用于验证这样的假设，即细菌微生物和机械载荷对复合修复体的材料特性、牙齿修复边缘的降解和修复失败的时间产生单独和共同的影响。

DESCRIPTION (provided by applicant): The long-term goal of this project is to increase the service life of dental resin composite restorations by obtaining a fundamental understanding of the development of secondary caries. Our more immediate goal is to test the hypothesis that oral biofilms contribute to the degradation of the margin, leading to more frequent instances of secondary caries. That might occur because composite materials select for a more cariogenic flora at the margin, or because products of bacterial metabolism contribute to the breakdown of the composite itself. Neither mechanism is mutually exclusive, so each question will be addressed in complementary clinical and laboratory studies, as described in the Specific Aims: 1.) Compare the bacterial species composition of biofilms collected from the enamel interface of sound amalgam restorations, sound composite restorations, composites with early secondary caries, and composites with frank secondary caries. Human Oral Microbe Identification Microarrays will be used to provide biofilm profiles incorporating 272 species. We will be testing the hypothesis that composite-enamel interfaces are colonized by distinctive bacterial species, compared to amalgam-enamel interfaces. Such ecological selection could account for an increase in virulence of the biofilm at the tooth-composite interface. Near-infrared optical computed tomography (OCT) will be used as an important adjunct to our clinical caries diagnosis, by detecting caries earlier than conventional methods, and confirming sound interfaces. 2.) Bridge our clinical and laboratory studies by optimizing a biofilm reactor system for growing multi-species oral biofilm microcosms at the composite-enamel interface of restorations placed in extracted teeth and coated with saliva. This system will provide the basis for testing the hypothesis that products of bacterial metabolism contribute to composite breakdown. Plaque samples from the clinical study will be used to establish microcosms corresponding to composite-enamel interfaces with no caries, early caries, or frank caries. The HOMIM system will be used to monitor the species composition of microcosms, and determine the conditions needed to reproduce the major species profiles of biofilms from patient samples. 3.) Use the Minnesota Artificial Mouth to incorporate load cycling into the biofilm reactor model. Composite restorations placed in extracted teeth will be subjected to repeated cycles of saliva coating, biofilm growth in the reactor, and loading in the artificial mouth. Teeth restored with composites that generate different levels of shrinkage stress will be exposed to the different types of microcosm, and also to sterile saliva medium alone, with or without loading. Both OCT and micro-CT imaging will be used to monitor the loss of minerals in the tooth tissues, while microhardness testing and Fourier-transform infrared spectrometry will be performed to assess changes in the composites. This in vitro model system will be used to test the hypothesis that defined bacterial microcosms and mechanical loading exert individual and combined effects on the material properties of composite restorations, degradation of the tooth-restoration margin and the time to restoration failure. PUBLIC HEALTH RELEVANCE: Replacing failed dental restorations takes up 70% of a dentist's effort and contributes $5 billion to health care costs in the US. Among the different types of restorations, composite restorations have been shown to have a higher failure rate than amalgam restorations, with the main cause of failure being secondary or recurrent caries. The knowledge gained from this and future projects will help guide the design of the next generation of dental composite materials, which are likely to require reduced shrinkage stress, improved bond strengths, as well as antibacterial and cariostatic capabilities.