Forensic Dentistry, Second Edition

288 Forensic dentistry

It does not appear that anyone has yet used the TWI for age estimation,

but the use of simpler systems continues to show that, while attrition is age

progressive in a population, the wide ranges of variability within and among

people make the precision of age estimates poor.149,151

13.4.5 Third Molar Formation

Although the third molar is the most variable tooth in the dentition with
respect to developmental chronology, it is sometimes used to estimate age
during late adolescence and early adulthood.13,92,152 Arguably, there are no
other, more reliable biological indicators available during this period, and
third molar development is readily assessable from dental radiographs.
In most jurisdictions the attainment of a specific calendar age marks
adulthood and legal implications change significantly. In the United States
this is at eighteen years. Recently, the chronology of third molar development
has been used extensively to judge whether an individual is a juvenile or an
adult. Such estimations are often requested by immigration authorities in
cases involving foreign nationals.
Several studies have indicated that although actual age estimation using
third molar development is relatively inaccurate because of large varia-
tion among individuals, a reasonable evaluation as to whether a subject
has reached adulthood can be made by this method.13,153–155 An early proto-
type study was done under the auspices of the American Board of Forensic
Odontolog y.^13 Data submitted by ABFO diplomates from the United States
and Canada were taken from dental radiographs, principally panoramic
radiographs. Subjects (n = 823) were between 14.1 and 24.9 years of age, and
80% were categorized as Caucasians. The contributing dentists scored the
stage of third molar development using the eight-grade scheme developed by
Demirjian and coworkers^62 (Figure 13.4).
Only 54% of cases showed the same stage of crown-root development in
both the maxilla and mandible. Left-right symmetry was present in 78%.
The sex-specific mean age at each formative stage was calculated
(Table 13.11). Only data from white subjects are shown in these computa-
tions because too few from other racial groups were available to yield reliable
estimates. Stages A and B did not occur in the ages under study, and Stage C
was present in only 1%.
As reported by others, staging of third molar development was shown to
be inaccurate for prediction of chronological age. Standard deviation (SD)
for each grade ranged from 1.5 to 3.4 years, with an average of about 2 years.
This means that age predictability within each stage consists of an interval of
about eight years.