Dental histology: study of aging processes in root dentine

The amount of sclerotic root dentine increases with age, proceeding from the apex towards the crown. There are obvious optical changes in the tissue, which becomes translucent (dentine is normally opaque). Therefore, the sclerosis of root dentine could be a reliable indicator of age in anthropological studies of human remains. We studied the histological aspects of sclerotic dentine in longitudinal thin sections (70-140 microns) of undecalcified premolars, cut in the bucco-lingual plane. To quantify the sclerosis and to construct a reference standard, we sectioned 85 premolars from subjects of known age (70 from odontological extractions and 15 from a university collection). Another 10 teeth from medieval subjects were studied to assess the applicability of the method to ancient skeletal collections. The technique consists of embedding the tooth in a polyester resin (cold method), sectioning it with a diamond blade microtome. Qualitative analysis was performed with polarized light microscopy and measurements were made with a quote 2D x,y viewer and on digital images. The sclerotic root dentine was quantified with both linear and surface area parameters in order to assess the correlation with age. The quality of the sections was sufficient for the clear discernment and quantification of the sclerotic dentine. Indeed, the technique allowed us to obtain good results with a considerable saving of time and money compared with other dental histological techniques. The best correlation with age was obtained from the surface area parameter, particularly after exclusion of the cementum and pulp chamber. To produce comparable data from similar studies, we advise the use of cold resins, as used here, and digital computerized analyzers because of their accuracy, precision and quickness. The qualitative analysis of the ancient teeth indications that this dental aging techniques can be applied to both recent and ancient dental tissues.