Effect of Bacteria and Mechanical Loading on Degradation of the Composite-Tooth I

描述（由申请人提供）：本申请代表了对RFA-DE-10-004：延长牙科树脂复合材料的使用寿命（R 01）的多学科、多机构响应。更换牙科复合材料的主要原因是龋齿和骨折。虽然两者的机制都不明确，但大多数失效前的时间进程表明，材料/牙齿界面和/或材料的某些降解过程发生在口腔环境中。我们的总体目标是进一步阐明牙齿结构的经常性脱矿作用的机制，由周围的牙科复合材料fixations的细菌，并开发解决方案，以抑制it. To做到这一点，我们将确定条件下，细菌定植在牙科复合材料fixatives和牙齿结构之间的界面，通过改变初始尺寸的界面间隙以及固化的树脂复合材料的程度。我们还打算评估在循环载荷下暴露于细菌对边缘界面的影响。在这项研究中要测试的一个中心假设是，有一个有限的界面间隙的大小，易受细菌和广泛的脱矿质的复合材料修复界面的殖民化，这个接口可能会进一步降解的细菌的影响。我们还打算将一种新型的生物活性玻璃（BAG）加入到树脂复合材料中，以开发一种新的牙科修复材料。我们的假设是，与BAG材料，这些材料和牙齿结构之间的界面，将经历较少的化学和机械降解比那些没有抗菌生物活性玻璃时，暴露于疲劳负荷和口腔型生物膜形成的组合延长的时间。为了进一步探索失效机制，将通过生产具有不同固化程度的树脂来改变材料的抗微生物行为，这可能反映了牙科复合材料在临床实践中产生的高度可变的结果。材料将被放置到牙齿的准备和生物膜将生长在他们的表面之前和期间的界面的间歇疲劳加载。将通过光学和扫描电子显微镜评估界面失效和细菌存在。将通过能量色散光谱（EDS）x射线分析确定脱矿证据。生物膜对含和不含BAG复合材料的影响的证据将通过表面分析进行评估，包括光泽度、表面粗糙度和显微硬度。本申请特别响应RFA的限定范围的三个方面，包括开发新材料以赋予龋齿抗性，确定边缘间隙大小是否对细菌定植和进一步脱矿作用有影响，以及阐明临床相关环境中修复材料失效的机制。这项工作的潜在有益成果是，由于牙科树脂复合材料的持久性更好，在美国（和全球）的口腔保健和减少口腔疼痛方面节省了大量成本。 公共卫生相关性：更换牙科复合材料的主要原因是牙齿的进一步腐烂。我们的总体目标是更好地了解牙科复合材料修复的牙齿在暴露于口腔细菌和机械应力时复发性龋洞形成的机制。此外，我们打算表明，含有新型生物活性玻璃的新型牙科复合材料配方可以使修复体在模拟口腔环境中对细菌的负面影响更具抵抗力。这项工作的结果可能会增加牙科复合材料的寿命和使用寿命，从而节省患者进一步的痛苦，金钱和牙科治疗。

DESCRIPTION (provided by applicant): This application represents a multidisciplinary, multi-institution response to RFA-DE-10-004: Increasing the Service Life of Dental Resin Composites (R01). The primary reasons for replacement of dental composites are caries and fracture. Whereas the mechanisms underlying both are ill-defined, the time course of years preceding most failures suggests that some process of degradation of the material/tooth interface and/or material occurs within the oral environment. Our overall goal is to further elucidate the mechanism of recurrent demineralization of tooth structure by bacteria around dental composite restorations, and to develop solutions for inhibiting it. To do this, we will identify conditions under which bacteria colonize interfaces between dental composite restoratives and tooth structure, by varying the starting size of the interfacial gap as well as the extent of cure of the resin composite. We further intend to evaluate the effect of the exposure to bacteria under cyclic loading on the marginal interface. A central hypothesis to be tested in this study is that there is a finite interfacial gap size that predisposes the composite restorative interface to colonization by bacteria and extensive demineralization, and that this interface may be further degraded by the effects of the bacteria. We also intend to incorporate a novel bioactive glass (BAG) into the resin composite to develop a new dental restorative material. Our hypothesis is that materials with BAG, and the interface between these materials and tooth structure, will undergo less chemical and mechanical degradation than those without an antibacterial bioactive glass when exposed to a combination of fatigue loading and oral-type biofilm formation for extended periods of time. To further probe the mechanism of failure, the anti-microbial behavior of the materials will be varied by producing resins with different extents of cure, which likely reflects the highly variable outcomes produced for dental composites in clinical practice. Materials will be placed into preparations in teeth and biofilms will be grown on their surface before and during intermittent fatigue loading of the interface. Interfacial failure and bacterial presence will be assessed by optical and scanning electron microscopy. Evidence of demineralization will be determined by energy dispersive spectroscopic (EDS) x-ray analysis. Evidence for biofilm effects on composites with and without BAG will be assessed by surface analysis, including gloss, surface roughness and microhardness. This application is particularly responsive to three aspects of the defined scope of the RFA, including development of new materials to confer caries resistance, determining whether the marginal gap size has an effect on bacterial colonization and further demineralization, and elucidating mechanisms of restorative material failure in a clinically relevant environment. The potential beneficial outcome of this work is extensive cost savings in oral health care and reduced oral pain in the US (and globally) due to longer lasting dental resin composite restorations. PUBLIC HEALTH RELEVANCE: The primary reason for replacement of dental composites is further decay of the tooth. Our overall goal is to better understand the mechanism of recurring cavity formation in teeth restored with dental composites when they are exposed to oral bacteria and mechanical stress. Further, we intend to show that new dental composite formulations containing novel bioactive glasses can render the restoration more resistant to the negative effects of bacteria in a simulated oral environment. The outcome of this work may be increased longevity and service life of dental composite restorations, thus saving the patient further pain, money and dental treatment.