6 - Recent Advances on Acellular Cementum Increments Composition Using Synchrotron X-Radiation

Summary

Acellular cementum anchors the root to the alveolar socket via the periodontal ligament and grows in layers continuously throughout life, unlike enamel and dentin. Increments are deposited in a biannual light-dark pattern correlated to age and season at death in transmitted light microscopy. This study investigates the still debated structure of individual acellular increments using x-ray fluorescence and x-ray diffraction mapping with synchrotron radiation microbeams on reindeer, red deer, cattle, and human samples. Results show that Ca or Zn x-ray fluorescent intensities and cAp diffracted intensity reveal cementum band structure. Average crystallographic texture (of cAp nanoplatelets’ orientation and collagen fibril orientations) is constant for each specimen. Microtextural variation is also present across individual bands, demonstrating that the overall collagen fibril orientation undergoes subtle changes with season. Patterns of “feast or famine” and concomitant changes in amount and intensity of PDL loading might produce altered collagen (and cAp) orientations between the “good” and the “bad” seasons for ungulates but maybe not for modern human populations.