Synchrotron imaging and Markov Chain Monte Carlo reveal tooth mineralization patterns

PLoS One. 2017 Oct 19;12(10):e0186391. doi: 10.1371/journal.pone.0186391. eCollection 2017.

Abstract

The progressive character of tooth formation records aspects of mammalian life history, diet, seasonal behavior and climate. Tooth mineralization occurs in two stages: secretion and maturation, which overlap to some degree. Despite decades of study, the spatial and temporal pattern of elemental incorporation during enamel mineralization remains poorly characterized. Here we use synchrotron X-ray microtomography and Markov Chain Monte Carlo sampling to estimate mineralization patterns from an ontogenetic series of sheep molars (n = 45 M1s, 18 M2s). We adopt a Bayesian approach that posits a general pattern of maturation estimated from individual- and population-level mineral density variation over time. This approach converts static images of mineral density into a dynamic model of mineralization, and demonstrates that enamel secretion and maturation waves advance at nonlinear rates with distinct geometries. While enamel secretion is ordered, maturation geometry varies within a population and appears to be driven by diffusive processes. Our model yields concrete expectations for the integration of physiological and environmental signals, which is of particular significance for paleoseasonality research. This study also provides an avenue for characterizing mineralization patterns in other taxa. Our synchrotron imaging data and model are available for application to multiple disciplines, including health, material science, and paleontological research.

MeSH terms

  • Animals
  • Markov Chains*
  • Models, Biological
  • Monte Carlo Method*
  • Sheep
  • Synchrotrons*
  • Tooth Calcification*
  • X-Ray Microtomography

Grants and funding

This work was supported by National Science Foundation Grants 1247426 to DRG and 0923831 to ASC, the Wenner-Gren Foundation, the Leakey Foundation, Harvard University, and the European Synchrotron Radiation Facility award EC 1018 all to DRG.