Kieser J A, He L-H, Dean M C, Jones M E H, Duncan W J, Swain M V, Nelson N J
Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin, New Zealand.
N Z Dent J. 2011 Jun;107(2):44-50.
The evolution of dental tissues in relation to tooth function is poorly understood in non-mammalian vertebrates. We studied the dentition of Sphenodon punctatus, the sole remaining member of the order Rhynchocephalia in this light.
We examined 6 anterior maxillary caniniform teeth from adult Sphenodon by scanning electron microscopy, nano-indentation and Raman spectroscopy.
The elastic modulus (E) for tuatara enamel was 73.17 (sd, 3.25) GPa and 19.52 +/- 0.76 Gpa for dentine. Hardness (H) values for enamel and dentine were 4.00 (sd, 0.22) and 0.63 +/- 0.02 Gpa respectively. The enamel was thin (100 gm or less), prismless and consisted of grouped parallel crystallites. Incremental lines occurred at intervals of about 0.5 to 1 rm. There were tubular structures along the enamel dentine junction running from the dentine into the inner enamel, at different angles. These were widened at their base with a smooth, possibly inorganic lining. Enamel elastic modulus and hardness were lower than those for mammals.
The presence of enamel tubules in the basal part of the enamel along the EDJ remains speculative, with possible functions being added enamel/dentinal adhesion or a role in mechanosensation.
在非哺乳动物脊椎动物中，牙齿组织与牙齿功能的进化关系尚不清楚。鉴于此，我们研究了喙头目现存的唯一成员——斑点楔齿蜥的牙列。
我们通过扫描电子显微镜、纳米压痕和拉曼光谱对成年斑点楔齿蜥的6颗上颌前犬齿状牙齿进行了检查。
楔齿蜥牙釉质的弹性模量（E）为73.17（标准差，3.25）吉帕，牙本质的弹性模量为19.52±0.76吉帕。牙釉质和牙本质的硬度（H）值分别为4.00（标准差，0.22）和0.63±0.02吉帕。牙釉质很薄（100微米或更薄），无棱柱结构，由成组的平行微晶组成。生长线每隔约0.5至1微米出现一次。沿着牙釉质牙本质界有管状结构，从牙本质以不同角度延伸到牙釉质内部。这些管状结构在底部变宽，有光滑的、可能是无机的衬里。牙釉质的弹性模量和硬度低于哺乳动物。
沿牙釉质牙本质界的牙釉质基部存在釉质小管仍属推测，其可能的功能是增强牙釉质/牙本质的附着力或在机械感觉中起作用。
