Armitage, GC, Christie, TM. Structural Changes in Exposed Human Cementum II. Electron Microscopic Observations. J. Periodont. Res., 8:356, 1973.

Aim

To determine if the granules seen in the exposed cementum with the light microscope can be seen with the transmission electron microscope (TEM).

Methods and materials

1. 7 teeth from 4 individuals were used in the study.
2. The teeth were decalcified, and the specimens were prepared and sectioned.
3. Areas with granules were examined under TEM.
4. Unexposed cementum was selected from the same areas and were compared to the exposed cementum.

Results

1. In all exposed specimens, dental calculus and microorganisms were associated with the surface.
2. In the unexposed cementum, collagen fibers were observed.
3. In the exposed, vacuole-like formations 15-25 microns under cemental surface were observed, and 5-15 microns into the dentin. Vacuoles were not seen in the unexposed cementum (except 1).
4. The exception specimen of the unexposed cementum was the only one showing granules under the light microscope.
5. Vacuoles were seen in four basic morphologic patterns:
   • racemose or grape-like clusters.
   • long chain like aggregates
   • small isolates vacuoles
   • very long fissure-like areas
6. The morphology of the vacuoles in the exposed cementum closely follows the pattern, orientation and configuration of the collagen.
7. No differences were observed between the vacuoles seen in cementum versus dentin.

Discussion

1. Granules and vacuoles have similar distribution
2. Similar size
3. Same basic shape
4. Are found in the same specimens

It is speculated that the vacuoles are areas where collagen fibrils have degenerated (due to close relation/location between vacuoles and collagen fibers). Vacuoles occurred where collagen fibers were not fully mineralized.

Conclusion

The granules seen by the light microscope are vacuoles (corroborated by TEM). It is speculated that vacuoles are areas where collagen is not fully mineralized.

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