Minnesota Dental Research Center for Biomaterials and Biomechanics (MDRCBB), School of Dentistry, University of Minnesota, MN 55455, USA.
Acta Biomater. 2014 Jan;10(1):375-83. doi: 10.1016/j.actbio.2013.08.034. Epub 2013 Sep 3.
Oral biofilms can degrade the components in dental resin-based composite restorations, thus compromising marginal integrity and leading to secondary caries. This study investigates the mechanical integrity of the dentin-composite interface challenged with multi-species oral biofilms. While most studies used single-species biofilms, the present study used a more realistic, diverse biofilm model produced directly from plaques collected from donors with a history of early childhood caries. Dentin-composite disks were made using bovine incisor roots filled with Z100(TM) or Filtek(TM) LS (3M ESPE). The disks were incubated for 72 h in paired CDC biofilm reactors, using a previously published protocol. One reactor was pulsed with sucrose, and the other was not. A sterile saliva-only control group was run with sucrose pulsing. The disks were fractured under diametral compression to evaluate their interfacial bond strength. The surface deformation of the disks was mapped using digital image correlation to ascertain the fracture origin. Fracture surfaces were examined using scanning electron microscopy/energy-dispersive X-ray spectroscopy to assess demineralization and interfacial degradation. Dentin demineralization was greater under sucrose-pulsed biofilms, as the pH dropped <5.5 during pulsing, with LS and Z100 specimens suffering similar degrees of surface mineral loss. Biofilm growth with sucrose pulsing also caused preferential degradation of the composite-dentin interface, depending on the composite/adhesive system used. Specifically, Z100 specimens showed greater bond strength reduction and more frequent cohesive failure in the adhesive layer. This was attributed to the inferior dentin coverage by Z100 adhesive, which possibly led to a higher level of chemical and enzymatic degradation. The results suggested that factors other than dentin demineralization were also responsible for interfacial degradation. A clinically relevant in vitro biofilm model was therefore developed, which would effectively allow assessment of the degradation of the dentin-composite interface subjected to multi-species biofilm challenge.
口腔生物膜可降解牙本质树脂基复合材料修复体中的成分，从而降低边缘完整性，并导致继发龋。本研究调查了经多物种口腔生物膜挑战后的牙本质-复合材料界面的机械完整性。虽然大多数研究使用单物种生物膜，但本研究使用了一种更现实、更具多样性的生物膜模型，该模型直接来自于有早期儿童龋病史的供体斑块中培养。使用牛切牙根填充 Z100(TM)或 Filtek(TM) LS（3M ESPE）制成牙本质-复合材料圆盘。使用先前发表的方案，将圆盘在配对的 CDC 生物膜反应器中孵育 72 小时。一个反应器用蔗糖脉冲，另一个则不用。用蔗糖脉冲运行无菌唾液对照。将圆盘在直径压缩下断裂，以评估其界面结合强度。使用数字图像相关技术对圆盘的表面变形进行映射，以确定断裂起源。使用扫描电子显微镜/能量色散 X 射线光谱法检查断裂表面，以评估脱矿质和界面降解。在蔗糖脉冲生物膜下，牙本质脱矿化更大，因为脉冲过程中 pH 值降至 <5.5，LS 和 Z100 标本的表面矿物质损失相似。用蔗糖脉冲进行生物膜生长还导致了复合材料-牙本质界面的优先降解，具体取决于使用的复合材料/胶粘剂系统。具体而言，Z100 标本显示出更大的结合强度降低和更频繁的胶粘剂层内聚性失效。这归因于 Z100 胶粘剂对牙本质的覆盖不足，这可能导致更高水平的化学和酶降解。结果表明，界面降解的原因除了牙本质脱矿化之外还有其他因素。因此，开发了一种临床相关的体外生物膜模型，该模型可有效地评估多物种生物膜挑战下牙本质-复合材料界面的降解情况。
