Biology Reference
In-Depth Information
from stress-induced cessation of ameloblast activity (
Duray, 1996
). Enamel hypoplasias
consist of deficiencies in enamel thickness, and this ranges from a single pit to entirely
missing enamel (
Goodman and Rose, 1991
). These defects are easily detected in teeth, with
linear enamel hypoplasia (LEH), represented by one or more transverse lines or grooves in
the enamel surface, being the most common type seen.
While LEH is nonspecific
7
(meaning that the actual source of stress is unknown), it is
recognized that it represents a serious and prolonged stress episode usually due to metabolic
stress of some sort (
Rose et al., 1985
). For example, animal research has shown that anything
disrupting growth such as disease or hormonal imbalance could lead to defects (
Goodman
and Rose, 1991
). Further, the actual location of defects on the crown reflects how complete
the crown was at the time of the stress episode (
Lukacs, 1989
). Therefore this allows the esti-
mation of the age at which the insult occurred, given knowledge of dental development.
There also appears to be a general trend towards an increase in the development of defects
around the time of weaning
8
according to studies of both contemporary and prehistoric
populations (e.g.,
Cassidy, 1980; Schultz et al., 1998
). In addition, it is clear that enamel
hypoplasia frequency increased with the advent of agriculture, suggesting that stress
episodes were not uncommon for these populations (e.g., see papers in
Cohen and
Armelagos, 1984
).
Because of the relationship with metabolic stress episodes, enamel hypoplasia is an espe-
cially useful tool when examining population histories. Combining this indicator with other
nonspecific indicators of stress (see Smith [Chapter 7], this volume) has the potential to reveal
information specific to individual and population health in the past. Further, LEH (as well as
caries) may be a clue in modern contexts with identifying skeletal remains in terms of indi-
cating a possible population for the decedent, given that LEH would not be expected in indi-
viduals who had sufficient access to resources as children (good nutrition, medical care, etc.)
(e.g., see
Birkby et al., 2008
).
TEETH AND GENETIC MATERIAL
DNA analysis involving the teeth is most often associated with forensic investigations to
identify human remains. As with other parts of the body, genetic material is present in teeth.
Fortunately, due to the strength of enamel and dentin capsule, and the location of the teeth
within the oral cavity in a relatively protected space, DNA sampling from teeth has the
potential to produce results when other areas of the skeleton cannot. As with other skeletal
elements, degradation of the DNA in teeth can be accelerated due to exposure to high
temperatures, extreme pH, water, and radiation. Fortunately, teeth are less susceptible to
these elements than is the rest of the skeleton and therefore represent a great place to look
for reliable DNA samples.
7
See Smith (Chapter 7), this volume, for discussion of other nonspecific stress markers affecting the
skeleton.
8
See Smith (Chapter 7), this volume, for a discussion of the risks to health associated with weaning.
