Improving the visibility of tooth cementum annulations by adjustment of the cutting angle of microscopic sections

Age at death assessments by counting tooth cementum annulations (TCAs) in unstained undecalcified microscopic ground sections of (single rooted) teeth is, amongst others, problematic because of the unclear distinction between the bright and darker annulations. Counting is hampered by optical superimposition of the tangentially positioned layers of cementum in the section since 'regular transverse sections' run perpendicular to the axis of a cone-shaped root with its yearly deposited cone-shaped layers of cementum. This study demonstrates that to improve the visibility of the annulations, the cutting angle should be perpendicular to the exterior of a root, not perpendicular to its axis. The site where the cut hits the root perpendicular should show the best possible distinction between the TCAs. Here, superimposition of the now vertical positioned layers within the section will result in increased contrast between bright and darker layers. A procedure for such preparation is given.