Department of Preventive and Restorative Dental Sciences, University of California San Francisco, San Francisco, CA, USA.
J Biomech. 2011 May 17;44(8):1626-9. doi: 10.1016/j.jbiomech.2011.03.004. Epub 2011 Mar 26.
The soft zone in dentine beneath the dentino-enamel junction is thought to play an important role in tooth function, strain distribution and fracture resistance during mastication. Recently reported asymmetry in mechanical properties with tooth side may point at a basic property of tooth function. The aim of our study was to test if this asymmetry was reflected in the nano- and micromechanical properties of dentine. We investigated the mechanical properties of dentine on the buccal and lingual side of nine extracted human teeth using nano- and microindentation. Properties were analysed on the natural log scale, using maximum likelihood to estimate the parameters. Two-sided 0.05-level likelihood ratio tests were used to assess the influences of surface (buccal versus lingual) and dentine depth, measured from the DEJ in crown dentine and from the CDJ in root dentine. Results showed the well known gradual increase in mechanical properties with increasing distance from the DEJ. Coronal dentine showed higher elastic modulus and hardness on the lingual side of teeth for all measurements, while root dentine was harder on the buccal side. Due to the subtlety of these effects and the small number of teeth studied, results failed to reach statistical significance. Results suggest that dentine nano- and micromechanical properties vary with tooth side in agreement with recent literature using macroscopic methods. They also reveal that buccal-lingual ratios of hardness are in opposite directions in crown and root dentine, suggesting compensatory functions.
牙本质在牙釉质牙本质界下方的软区被认为在咀嚼过程中对牙齿功能、应变分布和抗断裂性起着重要作用。最近有报道称，牙齿侧面的机械性能存在不对称性，这可能表明了牙齿功能的一个基本特性。本研究旨在测试这种不对称性是否反映在牙本质的纳米和微观机械性能中。我们使用纳米压痕和微压痕技术研究了 9 个人类离体牙颊侧和舌侧牙本质的机械性能。使用最大似然法对参数进行估计，对自然对数尺度上的特性进行分析。采用双侧 0.05 水平似然比检验来评估表面（颊侧与舌侧）和牙本质深度的影响，牙本质深度从冠部牙本质的 DEJ 处和根部牙本质的 CDJ 处测量。结果表明，随着距 DEJ 距离的增加，机械性能逐渐增加，这是众所周知的。对于所有测量，冠部牙本质的舌侧弹性模量和硬度较高，而根部牙本质的颊侧硬度较高。由于这些影响的细微性和研究牙齿数量较少，结果未达到统计学意义。结果表明，牙本质的纳米和微观机械性能与牙齿侧面有关，与最近使用宏观方法的文献一致。它们还表明，冠部和根部牙本质的硬度颊舌比方向相反，表明具有代偿功能。
