Self-Healing, Fracture Resistant Restorative Ceramics

牙科陶瓷由于其美观的外观和内在的耐磨性、绝热性和生物相容性，越来越多地被用作修复材料。不幸的是，与牙科合金相比，目前可用的牙科陶瓷很脆。这种抗断裂性的缺乏降低了它们的强度和可靠性，导致预期寿命缩短。以前提高牙科陶瓷寿命的策略集中在提高初始强度和对未来损伤的容忍度；然而，如果没有修复机制，损伤就会累积，故障是不可避免的。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，它们的用途可以在损伤累积之前修复任何持续的损伤。该项目的总体目标是研究牙科陶瓷的自修复机制，使其具有抗机械疲劳和延长寿命的能力。这一目标将通过在水热玻璃中掺入蒙脱石粘土颗粒形成陶瓷基复合材料来实现，这种复合材料将通过增强颗粒的膨胀来关闭裂缝。实验材料将被设计用于美观的全陶瓷牙齿修复。一种市售的低熔点陶瓷（Duceram LFC）将被用作对照材料，用于研究以下假设：1)粘土颗粒的水分激活膨胀是增加抗断裂能力的来源，2)增强颗粒之间的最大平均自由径为45 μ m，是增加抗断裂能力的阈值，3)平均增强颗粒尺寸小于0.39 μ m，将导致材料比目前可用的陶瓷芯材具有更大的半透明性。4)蒙脱石粘土增强瓷的生物相容性与未改性的牙用瓷相似或更好；5)蒙脱石粘土增强瓷的硬度和磨蚀潜力低于未改性的牙用瓷。这些努力可能阐明疲劳失效的机制，并可能导致材料将满足公众对持久，美观的牙科修复体的需求。

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.