Measuring incremental line width and appearance in the tooth cementum of recent and archaeological human teeth to identify irregularities: First insights using a standardized protocol.

Objective: Irregular incremental lines (ILs) in the tooth cementum were previously associated with pregnancy and certain diseases. This study aims to identify irregular ILs and assess their patterns and reproducibility.

Materials: 24 recent and 32 archaeological teeth from the nineteenth century with known birth history.

Methods: Histological sections of tooth roots were microscopically assessed. The width and appearance of 16,605 ILs were measured according to a standardized protocol.

Results: Irregular appearing ILs were present in earlier deposited ILs, which correspond to younger years in life. Irregular appearances decreased as the IL number increased, whereas irregular width was spread evenly across all ILs. Within-section reproducibility was relatively high for irregular appearance (intra class correlation close to 0.70 in recent and archaeological teeth) and irregular width (intra class correlation: recent: 0.49; archaeological: 0.58), whereas the across-section reproducibility was moderate.

Conclusions: Irregular width and appearance in ILs were identified successfully with within-section reproducibility. The moderate reproducibility across sections needs to be addressed in further studies by more systematic sampling of sections.

Significance: The proposed protocol identifies irregularities in a reproducible manner and may suggest that irregular ILs could be used in paleopathology to identify pregnancies and diseases.

Limitations: The correlation between the identified irregular ILs and known pregnancies has not been assessed as part of this study.

Suggestions For Further Research: The identified irregular ILs need to be validated by correlating them with known life history data.