A critical assessment of a new approach to identify pregnancy signals based on irregular incremental lines in the tooth cementum of recent and archaeological teeth

There is evidence from previous research that pregnancies and diseases are recorded in the human tooth cementum. This study aims to assess the degree of concordance between signals based on irregular incremental lines (ILs) in the tooth cementum and reported pregnancies in recent and archaeological human teeth. This research assessed a novel methodology to identify pregnancy signals based on irregular IL width and irregular appearance in terms of brightness and contrast. 156 histological sections of 24 recent teeth and 32 archaeological teeth from the skeleton series Basel-Spitalfriedhof (timeframe: 1845-1868) with known birth history were assessed microscopically blinded for any pregnancy history. As part of a pilot study non-invasive conventional micro computed tomography (µCT) and synchrotron radiation-based micro computed tomography (SRµCT) techniques have been explored in seven archaeological teeth from the Basel-Spitalfriedhof collection to display the tooth cementum. This work showed that pregnancies leave signals in the tooth cementum identifiable by the applied methodology in recent and also archaeological human teeth. More irregular ILs were observed in the archaeological sample, a group predominantly including women from the lower class in particular exposed to demanding life conditions. Not all pregnancies were identifiable and there are some hints that more demanding ones lead to identifiable signals. The SRµCT imaging technique allowed to display the ILs in a 3D view and to identify irregular ILs showing the potential of this technique to identify signals in the tooth cementum in a non-invasive manner. The results added to the evidence that the tooth cementum is a rich source of information able to support the reconstruction of life history events