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样品制备技术对人牙骨质硬组织结构和纳米力学性能测定的影响。

The effect of sample preparation technique on determination of structure and nanomechanical properties of human cementum hard tissue.

作者信息

Ho Sunita P, Goodis Harold, Balooch Mehdi, Nonomura Grace, Marshall Sally J, Marshall Grayson

机构信息

University of California, San Francisco, USA.

出版信息

Biomaterials. 2004 Aug;25(19):4847-57. doi: 10.1016/j.biomaterials.2003.11.047.

Abstract

The mechanical properties of a tissue can be evaluated by determining the response of the structure to mechanical loading. This can be accomplished only when the tissue has been prepared with minimum to no artifacts, thus preserving its structure. In this study it was hypothesized that the structure of cementum is inhomogeneous, contributing to a significant variation in mechanical properties of cementum. Therefore, the goals of the study were to identify potential artifacts generated by conventional sample preparation techniques such as polishing and ultrasectioning and subsequently characterize the prepared specimens using an atomic force microscope (AFM) and an AFM-nanoindenter. Comparisons between cryofractured, ultrasectioned and polished specimens concluded that ultrasectioned surfaces have significantly lower average surface roughness 'R(a)' (p<0.05). Microstructure of ultrasectioned specimens characterized using an AFM illustrated Sharpey's fibers (SF) and intrinsic fibers (IF) running perpendicular and parallel to the root surface similar to the observed microstructure of cryofractured cementum. In addition, a 10-50 microm wide cementum dentin junction (CDJ) was distinctly observed in the ultrasectioned specimens but not in polished specimens. The SF and CDJ illustrated relatively higher levels of hydrophilicity under wet conditions. The observed inhomogeneous microstructure of the ultrasectioned specimens led to a broader range of nanomechanical properties (modulus: 14.2-25.9 GPa; hardness: 0.48-1.09 GPa). However, masking of the same regions such as SF and CDJ due to smeared cementum in polished specimens resulted in a narrower range of nanomechanical properties (modulus: 18.2-20.8 GPa; hardness: 0.79-0.89 GPa). This effect is most noticeable under wet conditions for ultrasectioned specimens (modulus 2.6-10.9 GPa; hardness 0.05-0.30 GPa) compared to the polished specimens (modulus 12.2-14.5 GPa; hardness 0.33-0.45 GPa). Cementum also was shown to be highly viscoelastic, especially when hydrated. The results suggest ultrasectioning of cementum was superior to polishing preparation technique since it allowed visualization of cementum structures similar to cryofractured specimens while providing a flat surface necessary for AFM-based nanoindentation techniques. Additionally, the structural inhomogeneity observed within ultrasectioned cementum contributed to a broader range of mechanical properties.

摘要

组织的力学性能可通过确定该结构对机械负荷的反应来评估。只有在制备组织时将伪像降至最低或完全消除,从而保留其结构,才能做到这一点。在本研究中,我们假设牙骨质的结构是不均匀的,这导致了牙骨质力学性能的显著差异。因此,本研究的目的是识别由传统样品制备技术(如抛光和超薄切片)产生的潜在伪像,并随后使用原子力显微镜(AFM)和AFM纳米压痕仪对制备的标本进行表征。对冷冻断裂、超薄切片和抛光标本的比较得出结论,超薄切片表面的平均表面粗糙度“R(a)”显著更低(p<0.05)。使用AFM对超薄切片标本的微观结构进行表征,结果显示沙比纤维(SF)和固有纤维(IF)分别垂直和平行于牙根表面,这与冷冻断裂牙骨质观察到的微观结构相似。此外,在超薄切片标本中清晰地观察到了一条宽10 - 50微米的牙骨质牙本质界(CDJ),而在抛光标本中未观察到。SF和CDJ在湿润条件下表现出相对较高的亲水性。观察到的超薄切片标本不均匀的微观结构导致了更广泛的纳米力学性能范围(模量:14.2 - 25.9 GPa;硬度:0.48 - 1.09 GPa)。然而,由于抛光标本中牙骨质涂抹而导致SF和CDJ等相同区域被掩盖,使得纳米力学性能范围变窄(模量:18.2 - 20.8 GPa;硬度:0.79 - 0.89 GPa)。与抛光标本(模量12.2 - 14.5 GPa;硬度0.33 - 0.45 GPa)相比,这种效应在湿润条件下对于超薄切片标本最为明显(模量2.6 - 10.9 GPa;硬度0.05 - 0.30 GPa)。牙骨质还被证明具有高度粘弹性,尤其是在水合状态下。结果表明,牙骨质的超薄切片优于抛光制备技术,因为它能够观察到与冷冻断裂标本相似的牙骨质结构,同时提供基于AFM的纳米压痕技术所需的平坦表面。此外,在超薄切片牙骨质中观察到的结构不均匀性导致了更广泛的力学性能范围。

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