Extended-field synchrotron microtomography for non-destructive analysis of incremental lines in archeological human teeth cementum

Tooth cementum annulation (TCA) is used for determining age-at-death and stress periods based on yearly deposited lines in the root cementum of human teeth. Traditionally, TCA analysis employs optical microscopy, which requires cutting sections of the root and provides only sparse sampling in the third dimension. Ancient teeth are unique specimens that should not be sliced. In this imaging study, we show that extended field of view synchrotron radiation-based tomography provides true micrometer resolution and coverage for non-destructively surveying for incremental lines. To rapidly review the root cementum layer of four teeth from early 19th century cemetery with historical records of life events, we employed machine learning for semi-automatic detection and analysis of incremental lines. Surveying large regions of the root cementum enables detection of incremental lines and hence improves TCA analysis as an alternative to slicing of the unique teeth.