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histological methods used to estimate the age of an individual, as well as form conclusions
regarding their overall state of health ( Skinner and Anderson, 1991 ). As you can see, there
is a wide spectrum of research opportunities in the field of dental anthropology, including
but not limited to forensic anthropology, human evolution, morphology, and population
health ( Scott and Turner, 1988 ). However, the scope of this section will be limited to the
aspect of dental research concerning histology. Refer to Hammerl (Chapter 10), this
volume, for a complete overview of research in dental anthropology.
Definitions and Basic Principles of Dental Histology
The main components of dentition that are examined during histological analysis are
enamel and dentin, and to a lesser degree cementum and the pulp chamber of the tooth.
These structures develop from different embryological origins, have different functions
during the life of the individual, and thus have different appearances in histological thin
sections.
Enamel
Enamel is the heavily mineralized layer that covers the crowns of the dentition. Enamel is
the hardest material in the human body, which is what makes it such a durable tissue, and
therefore so important in the field of skeletal biology. Unlike all of the other tissues that
make up the dentition, enamel has an embryonic ectodermal origin ( Junqueira and Carneiro,
2003 ). Enamel is a noncellular structure that is formed by cells referred to as ameloblasts,
which differentiate out of epithelial cells located in the internal enamel epithelium ( Sadler,
2006 ). Enamel formation by the ameloblasts starts at the apex of the tooth and works down-
wards to form the crown of the tooth.
The enamel is secreted by ameloblast cells in two different stages. The first stage involves
the secretion of a matrix that will be the framework for the structure of the enamel. This matrix
has both an organic component and an inorganic component. The matrix is secreted out of the
end of the ameloblast, from a protuberant area referred to as the Tome's process. Any disruption
of the ameloblast, from either mechanical or metabolic causes, can lead to a constriction of the
Tome's process ( Hillson, 1996 ). This constriction of the Tome's process leaves a permanent line
in the formation of the enamel matrix. This line is a permanent mark in the enamel, and is
visible on histological section. These lines of discontinuity are commonly referred to striae
of Retzius. These striae of Retzius have an implication in the anthropological world as
well. For example, a case report by Skinner and Anderson (1991) investigates whether striae
of Retzius can be used to correlate with specific times of stress in an individual's life in an
attempt to provide a basis for presumptive identification of unknown remains. If the stress
to which an individual is exposed continues for a prolonged period of time, these lines of
discontinuity can become visible macroscopically as linear enamel hypoplasias.
The second stage of enamel formation is the mineralization or maturation stage. Once the
matrix has been secreted by the ameloblasts, they undergo a transformation and start to
break down the organic component of the matrix ( Hillson, 1996 ). While the ameloblasts
are taking away the organic component of the enamel, crystals are also forming in the nonor-
ganic component. Once maturation is complete, only the nonorganic material remains.
However, any incongruities left from the enamel formation, such as the striae of Retzius,
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