Sclerotic Age Changes in Root Dentin of Human Teeth as Observed by Optical, Electron, and X-Ray Microscopy

¹ Harvard School of Dental Medicine, Boston, Massachusetts

1. An investigation of the microstructural differences between opaque and transparent (sclerotic) root dentin was carried out by light microscopy, microradiography, and electron microscopy.

2. By light microscopy and microradiography root dentin from young individuals has the same appearance as opaque root dentin from mature adults. The tubules have a large radiolucent center (odontoblastic process) surrounded by a translucent and highly radiopaque zone (peritubular matrix).

3. In apical sclerotic dentin, the transparency of which increases and spreads crownward as a tooth matures, the tubules are generally difficult to visualize when viewed in the light microscope, most of them being very narrow, with inconspicuous odontoblastic processes. In microradiographs the tubules appear to become virtually completely obliterated by a highly radiopaque substance.

4. Electron micrographs correlate well with the microradiographic findings. The opaque dentin, cut in sections transverse to the tubules, shows an electron-dense material interrupted by circular areas of low electron density corresponding to the patent tubules. In contrast, transparent dentin contains no such circular areas but is of relatively homogeneous electron density throughout. Sclerosed tubules appear to have a different texture and consistency from that of the intertubular dentin.

5. Electron diffraction patterns of areas within the obliterated tubules were identical with those of intertubular dentin, indicating that crystals deposited within sclerotic tubules in the root are of the same type as those found in the intertubular dentin.

6. Sections decalcified by treatment in versine showed a relatively homogeneous organic matrix remaining within mineralized tubules.