Early-life stress signatures in deciduous incisor microstructure: An odontochronological case study of monozygotic twins discordant for cleft lip and palate

This study examined whether early-life stress events can be detected and chronologically dated through microscopic analysis of deciduous teeth. A unique case of monozygotic twins was used—one born with cleft lip and palate (CLP) who underwent early surgical interventions, and the other born without major health conditions. Histological thin sections of four naturally shed deciduous incisors were analyzed using polarized light microscopy. Accentuated growth lines—microscopic features that form in response to systemic stress during tooth development—were compared with medical records and parental reports to assess correspondence with known stressful episodes. Both twins exhibited similar accentuated line formations for shared events (prenatal maternal stress, birth, routine vaccinations), and unique responses to individual issues. The CLP twin showed additional lines related to surgical interventions and associated care, while the non-CLP twin had markers corresponding to aspiration episodes and weaning. Mild lines were also observed in periods without recorded events, suggesting high sensitivity of dental tissues to physiological perturbations. Deciduous teeth preserve a high-resolution chronological record of stress and may serve as a biomarker and tool for early life history and adversity revelation. Our findings highlight the value of analyzing dentin and mildly accentuated lines across multiple time-overlapping teeth per individual in polarized light. By utilizing odontochronology, researchers and clinicians can retrospectively assess the timing and impact of developmental disruptions. In children with conditions such as cleft lip and palate, this non-invasive approach could support targeted early interventions and improve understanding of stress-related outcomes. • Deciduous teeth record early-life stress as accentuated growth lines. • Monozygotic twins were used to compare shared and individual stress events. • Surgical and medical stress in CLP child correlated with dental stress markers. • Polarized light microscopy revealed precise timing of developmental disruptions. • Dental histology offers a non-invasive tool for assessing infant stress exposure.