Journal of Dental Research, Vol 69, 1287-1292, Copyright © 1990 by International & American Associations for Dental Research Online Journals
The inorganic components of cementum- and enamel-related dentin in the rat incisor
J. Steinfort, B. M. Deblauwe and W. Beertsen
Department of Periodontology, Academic Centre for Dentistry Amsterdam, The Netherlands.
Recently, we have shown that, in rodent incisors, the crown- and
root-analogue dentin (enamel- and cementum-related dentin) show differences
in mineralization rates (Beertsen and Niehof, 1986) and composition of the
organic matrices (Steinfort et al., 1989). It was the aim of the present
study to determine whether these differences were accompanied by
differences in the inorganic components. Rat incisors were analyzed by
means of hardness measurements, microradiography, and the determination of
Ca, Mg, and PO4 content. The outer circumpulpal dentin layer of the
enamel-related dentin (ERD) was considerably harder and denser than the
comparable layer of the cementum-related dentin (CRD). Concomitantly, a
higher Ca and PO4 content was found for the ERD than for the CRD, while the
reverse occurred with respect to Mg. From the apical end of the incisor
toward the incisal edge, the Ca/PO4 ratio tended to decrease for both ERD
and CRD, while the Mg/PO4 ratio increased. All differences appeared to be
statistically significant. It is concluded that differences in the
non-collagenous organic matrix were accompanied by differences in the
inorganic components. More specifically, a relatively high content of
highly phosphorylated phosphoproteins (ERD) was associated with a higher Ca
and a lower Mg content.
