Journal of Dental Research, Vol 72, 1285-1290, Copyright © 1993 by International & American Associations for Dental Research Online Journals
Crystallographic morphology of heterogeneous fluoridated carbonate apatites
M. Okazaki
Department of Dental Technology, Osaka University Faculty of Dentistry, Japan.
Carbonate-containing fluoridated apatites were synthesized with two
different modes of fluoride incorporation: by supplying F-free solution
initially, followed by a F-containing solution; and with the order of
supply of these solutions reversed. Both of these heterogeneously
synthesized fluoridated CO3 apatites showed typical apatitic x-ray
diffraction patterns; and both had similar total fluoride contents (0.87
+/- 0.07 and 0.94 +/- 0.03 mmol/g, respectively), i.e., half of the maximum
fluoride content of fluorapatite. However, they differed considerably in
their crystallographic properties. The 300 reflection peaks of both
apatites were split, and their patterns were slightly different. In the
former, SEM observation revealed capsule-like crystals with a rounded
hexagonal shape. However, the latter had many small crystals, similar to
those of homogeneous CO3 apatite, adhering to the larger hexagonal
crystals, which were also similar to homogeneous fluorCO3 apatite.
Wavelength-dispersive spectroscopy attached to the SEM showed a higher
fluoride intensity in the former spectrum than the latter. These results
suggest that two different types of heterogeneous fluoridated CO3 apatites
were formed, CO3 apatite covered with fluorCO3 apatite, and fluorCO3
apatite covered with CO3 apatite. The simple two-step supply system used in
this study is helpful for the study of complicated heterogeneous formation
of apatites.
