[MARMAM] New paper on polar bear teeth

Carolina Loch Silva lochcarolina at gmail.com
Tue Nov 30 18:05:36 PST 2021

Dear MARMAM subscribers,

My co-authors and I are pleased to announce the following paper in the
of Oral Biology*:

*Microstructure, elemental composition and mechanical properties of enamel
and dentine in the polar bear Ursus maritimus*

Carolina Loch, Louisa Hemm, Bertie Taylor, Ingrid N. Visser, Øystein Wiig



Objective: To investigate the microstructure, elemental composition and
mechanical properties of polar bear teeth.

Design: 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

Results: The thickness of enamel ranged from 350 to 430µm in canines, 220
to 330µm in incisors and 320 to 510µm in premolars. SEM images showed
distinct transversely-oriented undulating Hunter Schreger bands (HSB) from
the enamel-dentine junction (EDJ) to the outer enamel surface. Enamel
prisms had a hexagonal shape, with open prism sheaths. Prisms measured
6-8µm 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 P2O5 were the components with higher oxide
weight percentage in both enamel and dentine.

Conclusions: 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.

Keywords: Elastic modulus; Hardness; Hunter-Schreger bands; Ursidae; Teeth

Full text is available at:

Or alternatively, a *pdf* can be requested at: carolina.loch at otago.ac.nz

Best regards,


Carolina Loch Silva, PhD

Lecturer in Oral Biology

Department of Oral Sciences

Sir John Walsh Research Institute

Faculty of Dentistry, University of Otago

Dunedin 9054, New Zealand

Phone: +(64) 03 479-9255

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