Biomaterials Science Research Unit, Faculty of Dentistry, University of Sydney, Sydney Dental Hospital, Surry Hills, NSW, 2010 Sydney, Australia.
J Biomech. 2012 Jun 1;45(9):1679-83. doi: 10.1016/j.jbiomech.2012.03.021. Epub 2012 Apr 25.
Improved understanding of the effects of hydration and drying in mineralized tissues is highly desirable, particularly for physiologically hydrated biological materials such as dentin. We investigated the influence of hydration on the nanomechanical properties of healthy dentin and hypothesized that drying leads to an increase in indentation induced energy expenditure and hardness. Hydrated and dry dentin were tested with a UMIS set up with a Berkovich indenter at a maximum load of 50 mN. Values representative of the energy expenditure behavior were presented as dissipated energy, U(d), recovered energy, U(e), normalized energy expenditure index, ψ, and hardness, H. Energy expenditure index results, which normalize the energy expenditure for each test and describe the relative energy dissipation-recovery behavior of a material, suggested that, for the relatively severe contact strains about a sharp Berkovich indenter, dissipation dominates the mechanical response of both the hydrated and dry dentin. In support of our initial hypothesis, dry dentin presented a significantly higher energy expenditure index than hydrated dentin (p<0.0001). These results were primarily associated with a lower U(e) that was found upon drying. Hydration also decreased H significantly (p<0.0001). In summary, this study presents the first direct measurements of the energy expenditure behavior of hydrated and dry dentin using instrumented nanoindentation.
提高对矿化组织水合和干燥影响的理解是非常需要的，特别是对于生理水合的生物材料，如牙本质。我们研究了水合作用对健康牙本质纳米力学性能的影响，并假设干燥会导致压痕诱导能量消耗和硬度增加。使用带有 Berkovich 压头的 UMIS 在最大负载为 50 mN 的情况下对水合和干燥牙本质进行测试。以耗散能量 U(d)、恢复能量 U(e)、归一化能量消耗指数 ψ 和硬度 H 表示代表能量消耗行为的值。能量消耗指数结果对每个测试的能量消耗进行归一化，并描述了材料的相对能量耗散-恢复行为，表明对于尖锐的 Berkovich 压头的相对严重的接触应变，耗散主导了水合和干燥牙本质的机械响应。支持我们的初始假设，干燥牙本质的能量消耗指数明显高于水合牙本质（p<0.0001）。这些结果主要与干燥时发现的较低的 U(e)有关。水合作用还显著降低了 H（p<0.0001）。总之，本研究首次使用仪器化纳米压痕直接测量了水合和干燥牙本质的能量消耗行为。
