Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin 9054, New Zealand.
Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin 9054, New Zealand.
Arch Oral Biol. 2022 Feb;134:105318. doi: 10.1016/j.archoralbio.2021.105318. Epub 2021 Nov 20.
To investigate the microstructure, elemental composition and mechanical properties of polar bear teeth.
Incisors, canines and fourth premolar teeth of two subadult male museum specimens were analysed. Teeth were measured, photographed, embedded in Epoxy resin, sectioned, polished and etched for scanning electron microscope (SEM) imaging, elemental composition and nanomechanical testing analyses.
The thickness of enamel ranged from 350-430 µm in canines, 220-330 µm in incisors and 320-510 µm in premolars. SEM images showed distinct transversely-oriented undulating Hunter Schreger bands from the enamel-dentine junction (EDJ) to the outer enamel surface. Enamel prisms had a hexagonal shape, with open prism sheaths. Prisms measured 6-8 µm in diameter. The EDJ was straight with no evidence of scalloping. Larger tubules adjacent to the EDJ were observed in the mantle dentine zone. Enamel Hardness and Elastic modulus values were higher in premolars (6.9 GPa and 269 GPa), followed by canines (6.5 GPa and 230 GPa) and incisors (4.9 GPa and 187 GPa). Dentine Hardness and Elastic modulus values were higher in canines. CaO and PO were the components with higher oxide weight percentage in both enamel and dentine.
Understanding the microstructure, elemental composition and mechanical properties of polar bear teeth can help elucidate the biology and functional morphology of this globally threatened species and could be used as a proxy for studies with fossil ursids.
研究北极熊牙齿的微观结构、元素组成和力学性能。
分析了两只亚成体雄性博物馆标本的门齿、犬齿和第四前臼齿。对牙齿进行测量、拍照、包埋在环氧树脂中、切片、抛光和蚀刻，进行扫描电子显微镜（SEM）成像、元素组成和纳米力学测试分析。
犬齿的釉质厚度为 350-430μm，门齿为 220-330μm，前臼齿为 320-510μm。SEM 图像显示，从釉牙骨质界（EDJ）到釉质表面有明显的横向波浪形亨特·施雷格带。釉质棱柱呈六方形状，有开放的棱柱鞘。棱柱直径为 6-8μm。EDJ 是直的，没有扇贝状的迹象。在牙本质鞘区附近观察到更大的管腔。前臼齿的釉质硬度和弹性模量值较高（6.9GPa 和 269GPa），其次是犬齿（6.5GPa 和 230GPa）和门齿（4.9GPa 和 187GPa）。牙本质硬度和弹性模量值在犬齿中较高。CaO 和 PO 是釉质和牙本质中氧化重量百分比较高的成分。
了解北极熊牙齿的微观结构、元素组成和力学性能有助于阐明这种全球受威胁物种的生物学和功能形态学，并且可以作为研究化石熊类的替代物。
