Self-Healing, Fracture Resistant Restorative Ceramics

牙科陶瓷作为修复材料因其美观的外观和内在的耐磨性、绝热性和生物相容性而日益广泛。不幸的是，与牙科合金相比，目前可用的牙科陶瓷是脆性的。这种抗裂性的缺乏降低了它们的强度和可靠性，导致寿命缩短。以往提高牙科陶瓷使用寿命的策略都集中在提高陶瓷的初始强度和对未来损伤的耐受性上；然而，如果没有修复机制，损伤就会累积，失败是不可避免的。相比之下，天然材料对机械损伤的抵抗力相对较低，但随着时间的推移，它们的有用性可以通过在损伤累积之前进行修复来保持。这个项目的总体目标是研究牙科陶瓷的自我修复机制，通过这种机制，牙科陶瓷可以表现出抗机械疲劳和延长寿命。这一目标将通过在水热玻璃中加入蒙脱石粘土颗粒来形成陶瓷基复合材料来实现，该复合材料将通过增强颗粒的膨胀来闭合裂缝。这些实验材料将被设计用于美观的全陶瓷牙科修复。一种商用的低熔点陶瓷(Duceram LFC)将被用作研究下列假设的对照材料：1)L)粘土颗粒的湿润膨胀是提高抗折性能的一个原因，2)增强颗粒之间的最大平均自由程为45微米，作为提高抗折性能的门槛，3)平均增强颗粒尺寸小于0.39微米，将使材料具有比目前可用的陶瓷核材料更高的半透明性，4)蒙脱石粘土增强陶瓷将表现出与未增强的牙科陶瓷相似或更好的生物相容性，以及5)蒙脱石粘土增强陶瓷将呈现出比未经改性的牙科I瓷更低的硬度和磨损电位。这些努力可能会阐明疲劳失效的机制，并可能产生满足公众对持久、美观的牙科修复需求的材料。

Dental ceramics are increasingly prolific as restorative materials because of their esthetic appearance and their intrinsic wear resistance, thermal insulation, and biocompatibility. Unfortunately, the currently available dental ceramics are brittle in comparison to dental alloys. This lack of fracture resistance compromises their strength and reliability, resulting in decreased lifetime expectancy. Previous strategies for increasing the lifetimes of dental ceramics have focused on improving the initial strength and tolerance to future damage; however, without a mechanism for repair, damage accumulates, and failure is inevitable. In contrast, natural materials have relatively low resistance to mechanical damage, but their usefulness is maintained over time by healing any damage that is sustained before it accumulates. The overall objective of this project is study self-healing mechanisms by which dental ceramics may exhibit mechanical fatigue resistance and increased longevity. This objective will be accomplished through incorporation of smectite clay particles in hydrothermal glass to form ceramic matrix composites, which will close cracks through the swelling of reinforcing particles. The experimental materials will be designed for use in esthetic, all-ceramic dental restorations. A commercially available low fusing ceramic (Duceram LFC) will be used as the control material for investigation of the following hypotheses: l) moisture- activated swelling of clay particles is a source of increased fracture resistance, 2) a maximum mean free path of 45 mum between reinforcing particles acts as a threshold for increased fracture resistance, 3) a mean reinforcing particle size smaller than 0.39 mum will result in materials with greater translucency than currently available ceramic core materials, 4) smectite clay-reinforced porcelains will exhibit similar or superior biocompatibility compared to unreinforced dental porcelain, and 5) smectite clay-reinforced porcelains will exhibit hardness and abrasive potential lower than those of unmodified dental I porcelain. These efforts may elucidate the mechanisms of fatigue failure and may result in materials that will fill the public demand for long-lasting, esthetic dental restorations.