Biomaterials Science Research Unit, Faculty of Dentistry, University of Sydney, NSW, Australia.
Acta Biomater. 2010 Dec;6(12):4553-9. doi: 10.1016/j.actbio.2010.06.028. Epub 2010 Jun 30.
Our objectives were to correlate the mineral density (MD) and elastic modulus (E) of natural white spot lesions (WSLs) and compare them with analytical and numerical models. Five natural WSLs from four extracted sound premolar teeth were scanned at a voxel size of 7.6μm using a desktop X-ray microtomography (XRMT) system. Five hydroxyapatite phantoms with densities ranging from 1.52 to 3.14gcm⁻³ were used as calibration standards for each scan. MD throughout the WSLs was quantified using an MD calibration equation derived from hydroxyapatite phantoms. Subsequently, teeth were cross-sectioned and the E modulus was measured systematically across the WSLs at intervals of 25 and 50μm using nanoindentation. The MD and E modulus of WSLs correlated well. The relationship may be expressed as E=E⁰exp(-bP) (R²=0.952) with E⁰ the elastic modulus of the fully dense material, P the porosity and b a constant. The results for sound enamel were compared with Spears model. The limitation of Spears model to the WSLs is discussed and an alternative model developed by Rice for porous materials is proposed. Clinical implications of this work for quantifying de-/remineralization of teeth are pointed out. We conclude that XRMT can be utilized to extrapolate the E modulus of WSLs. This provides a basis for non-destructive, longitudinal analysis of WSLs in de-/remineralization studies of enamel.
我们的目的是将天然白斑（WSL）的矿物质密度（MD）和弹性模量（E）相关联，并将其与分析和数值模型进行比较。使用台式 X 射线微断层扫描（XRMT）系统，对来自四颗拔除的健康前磨牙的五个天然 WSL 进行了体素大小为 7.6μm 的扫描。五个羟磷灰石幻像用于每个扫描的校准标准，密度范围从 1.52 到 3.14gcm⁻³。使用从羟磷灰石幻像得出的 MD 校准方程定量测定 WSL 中的 MD。随后，对牙齿进行了横切，并使用纳米压痕技术系统地测量了 WSL 中每隔 25 和 50μm 的 E 模量。WSL 的 MD 和 E 模量相关性良好。该关系可以表示为 E=E⁰exp(-bP)（R²=0.952），其中 E⁰是完全致密材料的弹性模量，P 是孔隙率，b 是常数。将健康牙釉质的结果与 Spears 模型进行了比较。讨论了 Spears 模型对 WSL 的局限性，并提出了 Rice 为多孔材料开发的替代模型。指出了这项工作对量化牙齿脱矿/再矿化的临床意义。我们得出结论，XRMT 可用于推断 WSL 的 E 模量。这为釉质脱矿/再矿化研究中 WSL 的非破坏性、纵向分析提供了基础。
