It was the aim of this study to investigate the scanning electron microscopy (SEM) features and the
element content of
calcium (Ca)
phosphorus (P),
magnesium (Mg),
oxygen (O), and
carbon (C) of sound dentin, demineralized
dentin, secondary dentin, intratubular and peritubular de novo dentin formation due to caries progression and to compare the
element content with chemically pure
hydroxyapatite. Eighteen extracted teeth with deep
dentin carious lesions were embedded in Technovit 9100 (Kulzer), and serial sections of 80 microm thickness were made. These sections were then investigated with polarized light microscopy to identify the lesions. Two sections of each lesion were then coated with
carbon and studied with a scanning electron microscope. Of the 18 teeth, 8 showed intratubular dentin formation. The
element content was measured using energy dispersive X-ray analysis (EDX). About 75% of all involved dentin tubules showed intratubular de novo dentin formation. The Ca/P ratio in sound dentin, demineralized dentin, peritubular dentin, and
secondary dentin was within the range of
hydroxyapatite, whereas in intratubular dentin the Ca/P ratio was different than that of
hydroxyapatite. The
element content for Ca was statistically highly significantly different (P < 0.01) among sound dentin/intratubular dentin, sound dentin/peritubular dentin, and sound
dentin/ secondary dentin, but not between sound dentin/ demineralized dentin and sound dentin/
hydroxyapatite. For the other measured elements varying statistical differences were found. Our results indicate that intratubular dentin does not occlude the dentin tubules completely and mineralizes different than that of sound dentin and may therefore not be true
hydroxyapatite.