Park Saejin, Wang Duck H, Zhang Dongsheng, Romberg Elaine, Arola Dwayne
Department of Mechanical Engineering, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA.
J Mater Sci Mater Med. 2008 Jun;19(6):2317-24. doi: 10.1007/s10856-007-3340-y. Epub 2007 Dec 23.
Aging and the related changes in mechanical behavior of hard tissues of the human body are becoming increasingly important. In this study the influence of aging on the mechanical behavior of human enamel was evaluated using 3rd molars from young (18 < or = age < or = 30 years) and old (55 < or = age) patients. The hardness and elastic modulus were quantified using nanoindentation as a function of distance from the Dentin-Enamel Junction (DEJ) and within three different regions of the crown (i.e. cervical, cuspal and inter-cuspal enamel). Results of the evaluation showed that the elastic modulus and hardness increased with distance from the DEJ in all three regions examined, regardless of patient age. The largest increases with distance from the DEJ occurred within the cervical region of the old enamel. Overall, the results showed that there were no age-dependent differences in properties of enamel near the DEJ. However, near the tooth's surface, both the hardness (p < 0.025) and elastic modulus (p < 0.0001) were significantly greater in the old enamel. At the surface of the tooth the average elastic modulus of "old" enamel was nearly 20% greater than that of enamel from the young patients.
衰老以及人体硬组织力学行为的相关变化正变得越来越重要。在本研究中，使用年轻患者（18≤年龄≤30岁）和老年患者（年龄≥55岁）的第三磨牙评估了衰老对人牙釉质力学行为的影响。使用纳米压痕法，根据距牙本质-牙釉质界（DEJ）的距离以及在牙冠的三个不同区域（即颈部、牙尖和牙尖间牙釉质）内对硬度和弹性模量进行了量化。评估结果表明，在所检查的所有三个区域中，弹性模量和硬度均随距DEJ的距离增加而增加，与患者年龄无关。距DEJ距离增加时，老年牙釉质颈部区域的增加幅度最大。总体而言，结果表明在DEJ附近牙釉质的性能不存在年龄依赖性差异。然而，在牙齿表面附近，老年牙釉质的硬度（p<0.025）和弹性模量（p<0.0001）均显著更高。在牙齿表面，“老年”牙釉质的平均弹性模量比年轻患者牙釉质的平均弹性模量高近20%。
