Elsevier

HOMO

Volume 57, Issue 1, 24 February 2006, Pages 29-50
HOMO

Incremental lines in root cementum of human teeth —A reliable age marker?

https://doi.org/10.1016/j.jchb.2005.09.002Get rights and content

Abstract

In root cementum of teeth, alternating dark and light lines become visible in cross-sections under the light microscope. These lines bear an apparent resemblance to the annual rings of trees. Numerous studies have been done to correlate the number of cementum lines with the dental age by examining a great number of teeth of known age. Our study used a different approach. If lines in root cementum develop in an annual rhythm and are thus comparable to annual rings of trees, the same or at least a very similar number of these structures should be found in all areas of the root cementum of the same tooth. We counted cementum lines in the buccal, lingual, distal and mesial region of different sections, all from the middle third of the same root. This was repeated in eight teeth. To our surprise, we had immense difficulty in counting reproducible line numbers in the same cementum area at repeated counts. Nevertheless, the same tooth was found to differ markedly in the number of lines in different sections as well as in different regions of the same sections. These differences cannot be ascribed to variations caused by difficulties with reproducible line counting. Therefore, we are more than skeptical about the reliability of counting lines in root cementum as a method for determining the age of human teeth.

Introduction

Teeth are the most durable structures in human and animal bodies, and they are sometimes the only and often the best-preserved remains of corpses. Therefore, forensic medicine and paleoanthropology evidently have a great interest in deducing from these remains as much information as possible about the individual.

When slices are cut from the roots of human teeth and ground to a thickness of about 80–100 μm, thin alternating dark and light lines become visible in the band of cementum under the light microscope. Their sometimes nearly concentric appearance is reminiscent of the annual rings of trees. Since there is also a life-long apposition of root cementum in teeth (Zander and Hürzeler, 1958), it seemed likely that the number of these lines might be age-dependent (Stott et al., 1982). This would be of particular interest, because counting lines in root cementum would be the first method to determine the real chronological age without being influenced by the maturation state of the individual. Numerous investigators obtained different results when using teeth of known age to check the reliability of this method for age determination. Some were not able to find any connection between the age and the number of lines (Lipsinic et al., 1986; Lucas and Loh, 1986; Miller et al., 1988), while others found only a moderate correlation between the two parameters and remained skeptical (Jankauskas et al., 2001; Kvaal and Solheim, 1995; Stein and Corcoran, 1994). However, many of the investigators found a good correlation between the number of lines in cementum and the age of the tooth (Charles et al., 1986; Condon et al., 1986; Großkopf, 1990; Stott et al., 1982). Moreover, very recent publications have proposed cementum line counting as a feasible method for determining the age-at-death of an individual (Kagerer and Grupe, 2001; Rao and Rao, 1998; Wittwer-Backofen et al., 2004). But an increasing divergence between predicted and actual age was found with increasing age (Kvaal and Solheim, 1995; Stein and Corcoran, 1994). Pilloud (2004) found a correlation (r=0.85) between counted lines and known age in a group of individuals aged from 21 to 45 yrs but no correlation (r=0.029) in a group of individuals aged from 57 to 90 yrs.

Some critical questions still remain unanswered. The ultra-structural nature of these lines in human root cementum is still unclear (Renz et al., 1997) e.g., and the underlying biological rhythm is not understood.

In our study, we counted cementum lines in different sections from the middle third of the root of the same tooth. Since annually recurring external factors leaving their imprint in dental root cementum should be visible in every part of it, the same number of cementum lines should be found in different sections of the same root and, of course, in each region of these sections. This alone would justify the terms “cementum rings” or “cemental annulations”. If the numbers of lines varied in different regions of root cementum of the same tooth, there would be no way to determine which line number is the “correct” one, and counting lines in root cementum as a method for age determination would be at least dubious.

Section snippets

Preparation of sections

Eight premolars P1 and P2 (T1=14; T2=15; T3=44; T4=45; T5=34; T6=35; T7=45; T8=14), extracted for clinical reasons from patients of known age (T1=90 yrs; T2=48 yrs; T3=50 yrs; T4=71 yrs; T5=50 yrs; T6=32 yrs; T7=69 yrs; T8=65 yrs), were collected and stored in 5% formaldehyde in water. Attention was paid to the integrity of root cementum after extraction. Premolars from patients with obvious periodontal problems were not used in this study, and this was the only criterion for excluding teeth; no other

Difficulties in preparation and evaluation

Publications on age determination by counting cementum lines suggest this method would be technically most simple and unproblematic. We could not in the least confirm this view. We would therefore like to direct some attention to the description of specimen preparation and, particularly, to the appearance of the lines in dental root cementum and the difficulties involved in counting these lines.

During sectioning or grinding, some of the sections broke completely or parts of the cementum broke

Discussion

If we assume that root cementum of teeth is formed in an annual rhythm and that the microscopically visible lines in tooth sections reflect this annual rhythm, we would expect to find a comparable number of lines in all regions of the root of the same tooth or at least in a definable region where such regular cementum formation would occur. All studies on age determination using cementum lines are based on this assumption and, with the aid of statistics, conclude from the number of counted

Acknowledgements

We thank Kurt W. Alt and Werner Götz for helpful discussions, Vanessa Schaefer for collecting the teeth and preparing the sections, Anne Kähler for counting (observer 2) and Joanne Weirowski for her help with the English manuscript.

References (23)

  • D. Lieberman

    Life history variables preserved in dental cementum microstructure

    Science

    (1993)
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