The Discolouration of Human Teeth from Archaeological Contexts: Elemental Analysis of a Black Tooth from a Roman Cranium Recovered from the River Witham, Lincoln, UK

A human cranium was recovered from the River Witham, Lincoln, UK, at Stamp End Lock during a police operation in 2002. Although extensive trauma was noted, the skull was not of forensic interest since radiocarbon dating revealed that the individual had lived during the Roman occupation of Lincoln, almost 2,000 years ago. The skull had unusual black “metallic” staining on the occlusal surfaces of the teeth. As this kind of staining is relatively uncommon, it was investigated to determine the possible cause. An individual tooth was subjected to two elemental analyses: inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX). A small sample of modern teeth was also analysed for comparison to determine “normal” ranges of certain elements. Analysis of the ancient tooth shows very high levels of manganese (275？μg/g) and iron (1540？μg/g) compared to modern teeth values (1.90？μg/g？Mn and 40.81？μg/g？Fe). These results were consistent with the black staining arising from iron and manganese infiltrating bone and dental tissue from the depositional environment, and not a consequence of diet, pathological process or cultural practices. 1. Introduction There are many reported cases of discoloured teeth from both living and deceased individuals in the scientific literature. In living individuals, tooth discolouration is a well characterised feature of some diseases, medical treatments, cultural practices, and occupations, whilst discoloured teeth in deceased individuals may be due to the action of fungi, interaction with the burial environment, or a visual marker of a habit during life. A number of metabolic and congenital conditions cause human teeth to become discoloured; for instance, fluorosis causes brown staining of the teeth and purple staining of the gums, whilst congenital erythropoietic porphyria can produce red-purple dentition [1, 2]. Discoloured dentition is also associated with some occupations—most notably workers in the metal industry, where a variety of staining has been reported [3, 4]. Certain habits, such as smoking and chewing tobacco and drinking coffee, are known to cause yellow-brown discolouration of dentition [5, 6], whilst chewing betel nut produces a deep red staining of the dentition and oral mucosa [7]. Some drug treatments are also known to cause dental discolouration; for example, the antibiotic tetracycline is well documented as causing black discolouration of dentition [8, 9]. Deliberate staining of teeth as a form of body modification has a long