What is dental caries?
Dental caries is a destruction of enamel, dentine and cement, ultimately leading to the formation of a cavity in the crown or root surface (Hillson, 1996: 269). It is caused by the fermentation of food sugars, especially sucrose in the diet, by bacteria that occur on the teeth in plaque, such as Lactobacillus acidophilus and Streptococcus mutans (Roberts and Manchester, 2005: 65). Carious cavities usually develop in three regions of the tooth (Brothwell, 1981: 153):
- on the occlusal (biting) surface, generally in the region of natural fissures;
- in the region of the neck (cervical area) of the tooth, either on the lingual (tongue) or labial (lip) side;
- in the region of the neck of the tooth, but between the teeth (mesial and distal).
Caries in modern human populations
In living human populations, caries has a characteristic pattern. For all types of carious lesions, molars are most commonly affected, followed by premolars and then anterior teeth. Coronal caries is a disease of children, rising steadily to fifteen years or so of age, and then falling away in early adulthood. It is more common in girls than boys, but earlier dental eruption in girls exposes their teeth to risk for longer (Hillson, 1996: 281-282). Root surface caries also particularly affects the approximal surfaces of cheek teeth, but is a disease of adults (Hillson, 1996: 282). The pattern of caries is similar in members of the same family over several generations, perhaps due to inherited factors, but environmental factors such as dental treatment and diet also have a large role (Hillson, 1996: 282). The clearest single factor in caries is sugar, as shown by the decrease in caries rates during sugar rationing in Japan, Norway and Jersey during the 1939-45 war, which was followed by a rise when normal supplies resumed (Hillson, 1996: 282).
Caries in archaeological populations
Caries was very uncommon amongst fossil hominids, into Palaeolithic and Mesolithic contexts. Nevertheless, there are celebrated examples such as the rampant caries in the Middle Pleistocene skull from Broken Hill, Zambia, and coronal caries has also been noted in Australopithecus and Paranthropus (Hillson, 1996: 282). In European material, there is a an apparent gradual rise from very low caries rates in Palaeolithic to Iron Age contexts, to a rapid rise through medieval and post-medieval times (Hillson, 1996: 282). In parallel, the number of carious teeth per mouth increased, with more pit and fissure caries, less cervical caries, and more children affected. Similar trends have been demonstrated for Egypt and Nubia (Hillson, 1996: 282).
In North America, increased reliance upon maize agriculture is a clear cultural horizon (Hillson, 1996: 283). Several studies have show an increase in caries rate associated with the change from a hunter-gatherer diet to a diet heavy with starch-rich cereal (Hillson, 1996: 283). Similar rises in caries rate have been associated with increased reliance on arable agriculture in South America, South Asia, Egypt and Nubia (Hillson, 1996: 283). Meanwhile, a recent innovative survey of a Mayan population dated to the Classic period in Mexico (AD 250-900) demonstrated that the lowest rate of caries, and the highest rate of ante-mortem tooth loss, occurred in elite males; this correlated with poor oral hygiene and a softer and more refined diet (Roberts and Manchester, 2005: 67).
Caries in animal populations
Caries is an ancient phenomenon in non-human populations. Carious lesions have been reported in Permian fish, as well as mastodon and cave bear teeth. Caries with possible actinomycosis infection has also been noted in the three-toed horse, Merychippus campestris (Rothschild and Martin, 1993: 211-212). They are moderately common amongst wild great apes, particularly chimpanzees, whose diet includes a lot of fruit and, therefore, sugar. Gorillas, which eat considerably less fruit, have much lower caries rates, whereas orangutans seem to occupy an intermediate position (Hillson, 1996: 282).
Brothwell, D. 1981. Digging up Bones. Third Edition. New York: Cornell University Press.
Hillson, S. 1996. Dental Anthropology. Cambridge University Press: Cambridge.
Roberts, C. and Manchester, K. 2005. The Archaeology of Disease. 3rd Edition. Stroud: Alan Sutton Publishing Ltd.
Rothschild, B.M. and Martin, L.D. 1993. Paleopathology: Disease in the Fossil Record. CRC Press: London.