Dentine
Description
Dentine is the predominant hard tissue of teeth and forms both the inside of the crown and the root. It consists of approx. 70% of inorganic material (bioapatite) and approx. 20% of organic material (collagen). Dentin is softer than enamel and harder than bone.
Dentine is radially penetrated by dentine canals, that contain extensions of the odontoblasts, which supply the tissue during life time. Most of the dentine is primary dentine, which, depending on the type of tooth, forms during different phases of childhood and adolescence. Secondary dentine forms throughout life and increasingly fills the pulp cavity, whereas tertiary dentine (also reparative or irritant dentine) forms in areas affected by abrasion, caries or chemical or thermal stress.
Primary dentine does not remodel continuously throughout life and therefore records information on diet and mobility during childhood. Differences of carbon and nitrogen isotope ratios among a series of micro-samples of collagen of a tooth can reveal diet changes during the time of dentin formation. Such changes may provide detailed information, for example, on the duration of breastfeeding, on metabolic stress or on fundamental changes in the average dietary composition.
Dentine may also be used for 14C dating, although bone samples are preferred for human individuals.
The bioapatite of dentine is principally suitable for strontium and oxygen isotope analyses. However, with regard to the structural carbonate in particular, a certain susceptibility to diagenetic changes during burial must be taken into account, due to which the elements investigated are not always of exclusively biogenic origin.
Sample properties
Element and isotope analyses
Unlike enamel or bone, dentine is not a standard sample material for element and isotope analyses in bioarchaeometry. Its examination and the sampling strategy to be applied therefore depend on the research question posed to the analyses.
As a rule, complete teeth with corresponding documentation of the anatomical position of the tooth should be submitted, and the sampling strategy should be agreed upon.
14C dating
14C dating of collagen from teeth can only be performed on dentine, which is usually taken from a root. Samples should comprise 0.5 – 1g of dentine. If necessary, samples may be composed from several roots of the same tooth.