Mineral densities and elemental content in different layers of healthy human enamel with varying teeth age

ObjectivesThis study aims to evaluate the mineral density, calcium (Ca), and phosphorus (P) weight percent of healthy human enamel of varying human teeth age and enamel layers.MethodsTwenty human teeth were divided into “young” (18-24 years) and “old” (55≤ years) age groups. From each tooth, one enamel slab (approximately 8 mm × 2 mm × 1.5 mm) was obtained. All enamel slabs were embedded and scanned by micro-computed tomography. The scanned slices were reconstructed into a 3D image and regions of interest (ROIs) were defined. Then, the mineral density for each ROI was calculated. The Ca and P weight percent in the outer, middle, and inner enamel layers were quantified by scanning electron microscopy with energy dispersive spectroscopy. Finally, the data were analysed using one-way ANOVA and Student's t-test.ResultsIn the two age groups, the mineral density, Ca and P weight percent decreased from outer to the inner enamel layer. The mineral density, Ca and P weight percent in the outer enamel layer in the old age group were significantly higher than those in the young age group (P < 0.05); however, no age-dependent differences were observed for these properties in the middle and inner enamel layers (P > 0.05).ConclusionsThe mineral density, Ca and P weight percent decreased from the outer to the inner enamel layers in the two age groups. In the outer enamel layer, the differences in these properties between the two age groups were significantly different; however, no region-dependent differences were observed in the middle and inner enamel layers.