Forensic Dentistry, Second Edition

264 Forensic dentistry

For age estimation, the investigator is concerned with the person’s degree
of maturity: How far along the pathway from wholly immature to wholly
mature has the person traveled? Investigators depend on useful landmarks
along this pathway, like emergence of the first baby tooth or mineralization
of the third molar. Commonly the attainment of specific biological events,
such as crown completion of a particular tooth, is used to compare against
the person’s chronological age to gauge his or her tempo of development.
Unfortunately, there are a number of confounding issues, like the person’s
sex (males develop slower for many traits), socioeconomic status (well-off
kids tend to develop faster), health history (illness and poor nutrition both
slow development), and race (some combinations of genes promote the tempo
of growth; others slow it down). It is unusual that the investigator would
know most, let alone all, of these important modifying factors. We also com-
monly need to assume that the person is (or was) growing near the average
for his group and that we can apply appropriate norms for “his group” since
the range of population growth patterns far exceeds the available published
standards for any method.
A key issue not comprehensively covered here is that investigators should
use as much information—and as many methods—as practical. Composite
age estimates based on multiple kinds of data typically are more accurate
than any one alone.5–8 Similarly, while our expertise is with the dentition,
some questions are better answered using other sorts of information. For
example, craniometrics is much more informative about racial affiliation.9,10

13.2 Tooth Eruption/Tooth Emergence

The timing and pattern of tooth eruption are fairly well buffered from the
external environment, and recording tooth eruption status can be a rapid,
useful, and convenient way to estimate a person’s age if the subject is in the
primary or mixed dentition. There is a diversity of applications here. A person’s
age may be undocumented or, in preliterate settings, simply unknown, or the
person may wish to falsify his age.11–14 It may be of interest to ask whether
groups of people differ in their tempos of growth or whether normative stan-
dards can accurately be applied to another group.15–19 Most commonly for the
forensic odontologist, the issue is to establish or estimate age (or age at death)
in a contemporary, recent, or archaeological setting.2,4
In fact, tooth eruption is the process of a tooth’s migration from its initial
position in its bony crypt into occlusion. The proper term to be used here
is tooth emergence,^20 and there are at least three operational definitions
of emergence in the literature: In one, emergence commonly is defined as
the appearance of some portion of the tooth’s crown piercing the gingival
mucosa (gingival eruption). This is the conventional clinical definition. But