Meeting Abstract
Cementum is a continuously growing tissue that anchors the periodontal ligament to the root surface. It is deposited annually and aside from age of the individual, has the potential to record life history parameters such as age at sexual maturity and nursing cycles. The fine increments of cementum are usually visualized through destructive histological sectioning. Here we explore the utility of micro-CT scanning in detecting cementum in fossils and compare it to traditional histologically thin sections. We sampled 7 teeth (1 incisor, 5 canines, and 1 premolar) of 6 individuals of the 55-million-year old mammal Coryphodon from the Bighorn Basin of Wyoming. Histological thin sections were sampled around the apical one third of the root and standard petrographic techniques were used to create ground thin sections. Specimens were micro-CT scanned either before or after thin sectioning on a Bruker SkyScan 1173 at 0.015-0.020 mm voxel resolution. Cementum lines were traced in Adobe illustrator (histological thin sections) or Amira (micro-CT data). Our results indicate that micro-CT is capable of detecting cementum growth lines in fossils. Preliminary data reveal one specimen with consistent cementum line numbers using both methodologies, while the remaining samples varied in clarity and number. This indicates that there may be a preservation bias in cases in which histology out performs micro-CT scans and vice versa. Sub-micron level resolution may be necessary to provide detail regarding the organization of cementum. Exploring the use of micro-CT technology is of great value due to its non-destructive nature and allowance for visualization in multiple planes.
