age estimation from oral and dental structures 265what if you are dealing with macerated or skeletal material—with no mucosa?
Similarly, what is one to do with radiographs where the gingiva is difficult or
impossible to visualize? In such situations, one needs to find normative data
where emergence is defined as the most occlusal portion of the crown emerg-
ing above the alveolar bone (alveolar emergence). Yet a third, occasional defi-
nition of emergence is when the tooth is fully erupted, so it is in functional
occlusion with its antagonist in the opposing arch.21,22 Obviously these three
definitions yield different ages, with emergence above the alveolar bone pre-
ceding exposure through the gingiva, and eruption into functional occlusion
occurring several weeks later.^23
The twenty teeth of the primary dentition erupt (and emerge) when the
infant is between about six and thirty months of age.24,25 Ta n g u ay a nd c ow o r k-
ers provide some of the more detailed statistics in this regard (Table 13.1). The
modal eruption sequence is i1-i2-m1-c-m2 in both arches, defining a simple
mesial-to-distal gradient, though m1 normally precedes canine emergence,
so the canine is the one primary tooth that emerges into a confined space.
Tanguay et al. document a slight but statistically significant male precedence
of about one month in their sample of French Canadians, which agrees with
the bulk of studies, but they also make the case that the amount, and even the
direction, of sexual dimorphism exhibits ethnic and racial variability.24,25
Few studies have compared deciduous tooth emergence in American
blacks and whites, but there seems to be trivial racial variation in the primary
dentition, especially given the confounding effects of lower socioeconomic
status in most studies of American blacks, which is likely to slow the tempos
of development.25,26
Exfoliation of the primary teeth affords another means of estimating
a child’s age, and Moorrees’ landmark publications are still considered the
most reliable sets of data in this area.2 7, 2 8 Some other publications are avail-
able for more restricted groups.29,30 Moorrees et al. reported on the three
deciduous buccal teeth (c, m1, m2) in the mandible. These teeth exfoliated
between about nine and twelve years of age in their sample of normal, white
children in Ohio. The authors report the median ages of three stages of root
Table 13.1 Mean Ages (in Months) for
Emergence of Primary Teeth (Sexes Combined)
To o t h Maxilla SD Mandible SD
i1 9.03 2.20 7.18 2.46
i2 10.19 3.28 12.13 3.45
c 18.04 3.47 18.34 3.40
m1 15.13 2.69 15.01 2.80
m2 27.48 4.87 26.40 4.73
Source: Data from Tanguay et al., based on a sample of
314 French Canadian children.