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

描述（由申请人提供）：该申请代表了对RFA-DE-10-004：增加牙科树脂复合材料的使用寿命（R01）的多学科，多机构的响应。更换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，但在大多数失败之前的时间过程表明，在口腔环境中发生了材料/牙齿界面和/或材料的降解过程。我们的总体目标是进一步阐明牙齿复合修复体周围细菌对牙齿结构复发性脱矿的机制，并开发抑制它的解决方案。为了做到这一点，我们将通过改变界面间隙的起始尺寸以及树脂复合材料的固化程度来确定细菌在牙齿复合材料和牙齿结构之间的界面上定植的条件。我们打算进一步评估细菌在循环载荷下对边缘界面的影响。本研究需要验证的一个中心假设是，存在一个有限的界面间隙大小，使复合恢复性界面容易被细菌定植和广泛脱矿，并且该界面可能在细菌的作用下进一步降解。我们还打算在树脂复合材料中加入一种新的生物活性玻璃（BAG），以开发一种新的牙科修复材料。我们的假设是，当长时间暴露于疲劳载荷和口腔型生物膜形成的组合中时，具有BAG的材料以及这些材料与牙齿结构之间的界面将比没有抗菌生物活性玻璃的材料经历更少的化学和机械降解。为了进一步探索失败的机制，材料的抗微生物行为将因生产不同固化程度的树脂而变化，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。在界面间歇性疲劳加载之前和期间，将材料放入牙齿的准备物中，并在其表面生长生物膜。界面失效和细菌的存在将通过光学和扫描电子显微镜进行评估。脱矿的证据将由能量色散光谱（EDS） x射线分析确定。生物膜对复合材料的影响将通过表面分析来评估，包括光泽度、表面粗糙度和显微硬度。该应用对RFA定义范围的三个方面特别敏感，包括开发新材料以赋予耐龋性，确定边缘间隙大小是否对细菌定植和进一步脱矿有影响，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结果是在美国（以及全球）由于更持久的牙科树脂复合修复体，在口腔保健方面节省了大量的成本，减少了口腔疼痛。

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.