Forensic Dentistry, Second Edition

age estimation from oral and dental structures 289

There was significant dimorphism between the sexes, with third molars
developing earlier in males than in females. This is opposite from the pattern
observed in the other, earlier-forming teeth.
Table 13.12 shows the empirical probability of an individual being at least
age eighteen—that is, legally an adult—based on stage of third molar forma-
tion. As with the computation of chronological age, the relationship between
third molar development and attainment of legal adulthood is quite variable.
However, a forensically useful observation was made. It was found that if
third molar root formation was complete with closed apices and uniform

Table 13.11 Mean Ages at Attainment of Stages of

Third Molar Crown-Root Formation in U.S./Canadian

Caucasians

Grouping Statistic

Grade of Formation

D E F G H

Maxilla

Males Mean 16.0 16.6 17.7 18.2 20.2

SD 1.97 2.38 2.28 1.91 2.09

Females Mean 16.0 16.9 18.0 18.8 20.6

SD 1.55 1.85 1.95 2.27 2.09

Mandible

Males Mean 15.5 17.3 17.5 18.3 20.5

SD 1.59 2.47 2.14 1.93 1.97

Females Mean 16.0 16.9 17.7 19.1 20.9

SD 1.64 1.75 1.80 2.18 2.01

Table 13.12 Empirical Probabilities (%) of an

Individual Being at Least 18 Years of Age Based on the

Grade of Third Molar Formationa

Group

Grade of Formation

D E F G H

Maxilla

Males 15.9 27.8 44.0 46.8 85.3

Females 9.7 28.4 50.4 63.3 89.6

Mandible

Males 6.1 69.4 40.5 56.0 90.1

Females 11.3 27.4 43.2 69.8 92.2

a Values are based just on whites from the United States and

Canada. Probabilities for the terminal grade (H) presume that,

based on other criteria, the subject is less than twenty-five years

of age.