Interproximal tooth grooves in Pacific Basin, East Asian, and New World populations

Abstract

Cylindrically-shaped grooves that occur on the interproximal surface at or near the crown root (dentine-enamel) junction in human teeth are characterized by their shape, sharp margins, horizontal parallel striations, and shiny polishing. Ancient examples reported in the literature provide the oldest direct evidence of hominid tool use. Like other workers, we found these grooves in many populations of the Pacific Basin and adjoining continents. Of the various explanations for interproximal grooves, the most reasonable one is they represent the habitual use of toothpicks. In our pooled sample the frequency per tooth for interproximal grooves is 0.78% (1,199/154,167 teeth). The frequency of individuals with one or more interproximal grooves is 3.5%. Oceania has the greatest number of individuals with interproximal grooves (8.9%). Most of these crania originated in Australia. The American Arctic sample has no individuals with interproximal grooves, and prehistoric Arctic teeth lack crown caries. Elsewhere, frequencies of interproximal grooving vary markedly within and between regions suggesting multiple causes. Interproximal grooves are the result of habitual back-and-forth rubbing with a toothpick or some other artifact. In some cases rubbing may have started in an effort to deaden or desensitize a carious or inflammed site. Whatever the original stimulus, groove depth varies with individual age, indicating many years of habitual rubbing.