title: Structure and compositional characteristics of caniniform dental enamel in the tuatara Sphenodon punctatus (Lepidosauria: Rhynchocephalia).
abstract: OBJECTIVE
  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.
  
  
  METHODS
  We examined 6 anterior maxillary caniniform teeth from adult Sphenodon by scanning electron microscopy, nano-indentation and Raman spectroscopy.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors: Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin, New Zealand. jules.kieser@stonebow.otago.ac.nz
authors: J A
authors: JA
authors: Kieser
authors: L-H
authors: LH
authors: He
authors: M C
authors: MC
authors: Dean
authors: M E H
authors: ME
authors: Jones
authors: W J
authors: WJ
authors: Duncan
authors: M V
authors: MV
authors: Swain
authors: N J
authors: NJ
authors: Nelson
mesh_terms: D000818:Animals; D003743:Dental Enamel / Q000033:anatomy & histology* / Q000737:chemistry* / Q000648:ultrastructure; D055119:Elastic Modulus; D006244:Hardness; D008855:Microscopy, Electron, Scanning; D012104:Reptiles; D013059:Spectrum Analysis, Raman