W0280
Maturation Effects on the Chemical and Crystallographic
Changes in the Mammalian Teeth Enamel. Joseph D. Ferrara1,
Felicitas B. Bidlack2 and Przemyslaw Dera3,
1Rigaku/MSC, Inc, 9009 New Trails Dr., The Woodlands, TX 77381,
2Dept. of Anthropology, The George Washington Univ., G St NW,
Washington DC 20052., 3Geophysical Laboratory, Carnegie Institution
of Washington, 5251 Broad Branch Rd. NW, Washington, DC 20015.
Dental development begins in humans and many other mammals in
utero, and can extend for years after birth. Tooth enamel, dentin, and cementum
are variations of mineralized organic-matrix structures. Carbonato-apatite
((Ca5(PO4)3(OH)x), the major mineral
component of tooth enamel (~96 wt %), is largely responsible for the mechanical
properties of the tooth. The initial enamel mineralization and subsequent
maturation occur through a series of complex interactions between proteins and
ions. These processes, resulting in a highly organized and complicated
arrangements of enamel prisms, are not well understood. Although in histology
the incremental nature of tooth formation is well visible, it is not clear
whether and how it correlates with the pattern of enamel maturation. A better
understanding of this relationship is vital for a wide array of analyses, where
modern or fossil enamel is sampled to obtain information about an organisms
diet. Previously published crystallographic studies of tooth enamel were
performed with ground samples. We studied thin sections of equid teeth by means
of powder X-ray diffraction. The use of a Rigaku R-AXIS RAPID diffractometer
enabled us to obtain high-quality diffraction data, allowing Rietveld refinement
of the structure of enamel apatite as a function of the location of the sampling
point. It has been suggested that the chemical changes accompanying tooth
maturation include mainly incorporation of hydroxyl and carbonate anions, as
well as substitution of Ca, by Na, Sr and Ba. Full Rietveld refinements,
involving modeling of substitutional disorder, have allowed the determination of
these variations. The movement of matrix secreting cells during the initial
phase of crown formation results in distinct spatial arrangement of enamel
prisms. We found that the size, shape and orientational preferences in the
distribution of apatite crystal change with enamel maturation. Pole-figure
analysis of our diffraction data revealed clear trends in these
properties.