LINEAR ENAMEL HYPOPLASIAS (LEH)
(Photo source: Museum of London via Flickr)
While they are not considered pathological by some anthropologists because they do not present clinical symptoms, enamel hypoplasias are caused by physiological stress early in life. These are deﬁciencies in enamel thickness or the quantity of enamel, which happen during the secretion of the enamel matrix (Goodman and Rose, 1990). They occur when a wider-than-normal band of ameloblasts (enamel-secreting cells) cease matrix production early, resulting in the formation of bands, pits, furrows, or even entire areas of missing enamel (Hillson and Bond, 1997).
The image above shows an example of a bioarchaeological specimen with linear bands of missing enamel. Permanent adult dentition is formed within the alveolar bone of the maxilla and mandible, in pockets known as tooth crypts. Enamel is an extremely hard substance with a much higher mineral content than bone which is deposited on the surface of teeth while the tooth crowns are being formed in the crypts. Enamel is only created once in an individual’s lifetime, and cannot be produced or re-deposited later in life. If a juvenile individual does not receive proper nutrition or suffers other forms of physiological stress (i.e. disease, metabolic disorders), this can lead to a cessation of enamel formation by ameloblasts so that the limited mineral intake can be redirected towards other processes (i.e. bone growth) (King et al. 2005). Therefore, when the permanent adult dentition erupts (assuming the child survives the period of stress), their teeth will have areas of missing enamel, which are permanent.
LEHs can help bioarchaeologists and forensic anthropologists understand if there was a period of physiological stress in an individual’s life if they are present, although the exact cause or deficiency cannot always be pinpointed. They are rarely helpful in making an identification for forensic cases, but are usually noted in reports, regardless!
Goodman AH, Rose JC. 1990. Assessment of systemic physiological perturbations from dental enamel hypoplasias and associated histological structures. Yrbk Phys Anthropol 33:59–110.
Hillson S, Bond S. 1997. Relationship of enamel hypoplasia to the pattern of tooth crown growth: a discussion. Am J Phys Anthropol 104:89–103.
King T, Humphrey LT, Hillson S. 2005. Linear enamel hypoplasias as indicators of systemic physiological stress: Evidence from two known age-at-death and sex populations from postmedieval London. Am J Phys Anthropol 128:547–559.
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