Pathogenesis and Lines of Salter: insights into the biology of dental cementum for forensic applications

Abstract

Cementochronology (also known as Tooth Cementum Annulation or TCA) is a technique that relies on the incremental growth of the dental cementum (i.e. lines of Salter) to estimate age and season at death. It has been widely applied as a black box technique for wildlife management, archaeology, and only occasionally forensic cases. Limitations include lack of clinical knowledge and of standardized protocols, limited samples availability and time-consuming procedures. As in the majority of cases the only samples
available for research are pathological, this study investigates the effects of dental diseases, lifestyle and conditions more specifically related to the metabolism of calcium, on the microstructure, growth and reliability of the estimates from the cementum. The main purpose of this research was that of gaining some more insights on the inner mechanism of this tissue by analysing what it is affected by and how. Preliminary results show that, on pathological teeth, age at death can still be estimated within a margin error of ca. 10 years (which is still to be considered a remarkable achievement in age estimation of adult, individuals). Recurring trends also show that the cementum thickness is significantly thinner in people affected by kidney stones, chronic kidney disease, osteoporosis, hypothyroidism and arthrosis; whereas its microstructure (i.e. the lines of Salter) appears altered or not visible in individuals that smoke regularly. Future studies will not only investigate whether these findings might give a hint on the biological causes and rhythms of the lines of Salter, but also address their seasonal aspect by comparing samples collected from the Southern Hemisphere and rely on measurements rather than manual counting for the estimates. Finally, all these efforts aim to maximize the potential of the cementochronology technique and to justify its use in the forensic arena.