An investigation of the lamellae in human acellular cementum as a possible means of determining biological age

Hodych, Carolyn Ellen (1976) An investigation of the lamellae in human acellular cementum as a possible means of determining biological age. Masters thesis, Memorial University of Newfoundland.

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Abstract

In many species of non-human mammals the number of growth lines in the dentin and cementum reliably reflects the animal's biological age. In humans only cementum continues to be formed throughout life and usually does not undergo extensive resorption. It also has a laminated appearance. Therefore, it is possible that the growth lines in human cementum may reflect a person's biological age. -- The sample investigated includes 25 teeth removed for pathological reasons, 2 teeth removed from one cadaver and 2 teeth from an ancient burial site. The teeth, embedded in Bioplastic, were sectioned at mid-root; then ground and polished, and etched in a solution of detergent and water (0.6 cc Ivory liquid detergent to 250 cc tap water) for 8-24 hours. The prepared specimens were then observed in reflected light and interference contrast. Composite photographs were made of the entire cementum thickness at one location on the tooth's circumference. Lamellae seen in each composite photograph were plotted on a graph where one axis represents the number of visible lamellae and the other axis represents the cumulative thickness of the lamellae. -- Observations (x63 objective) of the etched surface revealed the presence of thin (1/3 - 3 microns) lamellae in all samples (excepting the two archeological specimens). There was no noticeable difference between the size and appearance of lamellae in pathological and cadaver teeth. Lamellae formed during the first 20 years of cementum deposition are generally more clearly defined than those formed later in life. Older teeth usually have large gaps in the sequence of lamellae seen in the outer half of the cementum thickness. No simple one to one relationship was found between the number of lamellae present and the number of years of cementum deposition. However, teeth with 20 years cementum deposition or less have approximately 4 times as many lamellae as years of deposition. -- Cementum thickness data obtained in this study was compared with that provided by Zander and Hürzeller (1958). A simple straight-line relationship does not seem to describe adequately the relationship between cementum deposition and age. For the sample examined here, cementum thickness seems to increase at a fairly constant and even rate during the first 20 years of deposition and then level off. -- Teeth from the same mouth were compared for similarities in their acellular cemental lamellae patterns. None were found. Local conditions seem to have a more direct influence on the cementum than any biological rhythm which might be present. -- Cementum from young female teeth was compared with that from young male teeth. No differences were found in the size and appearance of the lamellae. However, female teeth showed visible lamellae throughout the entire cementum thickness more often. Male teeth usually showed noticeable discontinuities in the sequence of visible lamellae throughout the cementum thickness.

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