Mapping the Prenatal Growth of the Mandible

To establish normative data for key morphometric measurements in prenatal mandibular development.

Forty-two human embryonic and fetal specimens, ranging from 8 to 37 weeks of gestational age (GA), without known abnormalities, were selected. Mandibles were segmented on histologic, micro-CT, or MDCT images. Fourteen anatomic landmarks were annotated, and key morphometric measurements were extracted, including bigonial width, bicondylar width, body length, ramus height, and gonial angle. Quadratic regression models were fitted to the measurements as a function of gestational age to assess developmental trends.

Mandibular ossification was first observed at Carnegie stage 19 (8+4 wk GA), adjacent to Meckel cartilage. Strong, statistically significant correlations with GA were found for all linear measurements ( R2 >0.95, P <0.0001). The gonial angle showed a moderate but significant inverse correlation with age ( R2 =0.65, P <0.0001).

This study provides comprehensive normative reference data for prenatal mandibular development, spanning early embryonic to late fetal stages. The established growth curves can serve as valuable tools in prenatal diagnostics, enabling earlier and more accurate detection of craniofacial anomalies associated with syndromic and nonsyndromic mandibular malformations. The presented normative data may also aid age estimation in forensic and archeological investigations.