Materials Science & Engineering, University of Washington, Seattle, WA, USA.
Arch Oral Biol. 2009 Jun;54(6):570-6. doi: 10.1016/j.archoralbio.2009.02.011. Epub 2009 Mar 31.
Enamel, dentine and cementum are dental tissues with distinct functional properties associated with their unique hierarchical structures. Some potential ways to repair or regenerate lost tooth structures have been revealed in our studies focused on examining teeth obtained from mice with mutations at the mouse progressive ankylosis (ank) locus. Previous studies have shown that mice with such mutations have decreased levels of extracellular inorganic pyrophosphate (PP(i)) at local sites resulting in ectopic calcification in joint areas and in formation of a significantly thicker cementum layer when compared with age-matched wild-type (WT) tissue [Ho AM, Johnson MD, Kingsley DM. Role of the mouse ank gene in control of tissue calcification and arthritis. Science 2000;289:265-70; Nociti Jr FH, Berry JE, Foster BL, Gurley KA, Kingsley DM, Takata T, et al. Cementum: a phosphate-sensitive tissue. J Dent Res 2002;81:817-21]. As a next step, to determine the quality of the cementum tissue formed in mice with a mutation in the ank gene (ank/ank), we compared the microstructure and mechanical properties of cementum and other dental tissues in mature ank/ank vs. age-matched WT mice. Backscattered scanning electron microscopy (SEM) imaging and transmission electron microscopy (TEM) analyses on mineralized tissues revealed no decrease in the extent of mineralization between ank/ank cementum vs. WT controls. Atomic-force-microscopy-based nanoindentation performed on enamel, dentine or cementum of ank/ank vs. age-matched WT molars revealed no significant difference in any of the tested tissues in terms of hardness and elastic modulus. These results indicate that the tissue quality was not compromised in ank/ank mice despite faster rate of formation and more abundant cementum when compared with age-matched WT mice. In conclusion, these data suggest that this animal model can be utilized for studies focused on defining mechanisms to promote cementum formation without loss of mechanical integrity.
牙釉质、牙本质和牙骨质是具有独特功能特性的牙齿组织，与其独特的层次结构相关。在我们研究从渐进性骨化（ank）基因位点突变的小鼠获得的牙齿时，发现了一些修复或再生丢失的牙齿结构的潜在方法。以前的研究表明，与年龄匹配的野生型（WT）组织相比，具有这种突变的小鼠局部部位细胞外无机焦磷酸盐（PP（i））水平降低，导致关节区域异位钙化和形成明显较厚的牙骨质层[Ho AM，Johnson MD，Kingsley DM。小鼠 ank 基因在控制组织钙化和关节炎中的作用。科学 2000；289：265-70；Nociti Jr FH，Berry JE，Foster BL，Gurley KA，Kingsley DM，Takata T，等人。牙骨质：一种对磷酸盐敏感的组织。J Dent Res 2002；81：817-21]。下一步，为了确定 ank 基因突变（ank/ank）小鼠形成的牙骨质组织的质量，我们比较了成熟 ank/ank 与年龄匹配的 WT 小鼠的牙骨质与其他牙齿组织的微观结构和力学性能。矿化组织的背散射扫描电子显微镜（SEM）成像和透射电子显微镜（TEM）分析表明，ank/ank 牙骨质与 WT 对照组之间的矿化程度没有降低。基于原子力显微镜的纳米压痕在 ank/ank 与年龄匹配的 WT 磨牙的釉质、牙本质或牙骨质上进行，结果表明在硬度和弹性模量方面，测试的组织中没有任何显著差异。这些结果表明，尽管与年龄匹配的 WT 小鼠相比，ank/ank 小鼠的牙骨质形成速度更快，牙骨质更丰富，但组织质量并未受到影响。总之，这些数据表明，尽管与年龄匹配的 WT 小鼠相比，ank/ank 小鼠的牙骨质形成速度更快且更丰富，但该动物模型可用于研究在不丧失机械完整性的情况下促进牙骨质形成的机制。
