Bending properties and ash content of fetal cranial bone.

Abstract Forty-five specimens of fetal cranial bone ranging in estimated gestational age from 25–40 weeks were tested in three-point bending. Five specimens of a six-year-old calvarium were tested for comparative purposes. The elastic modulus of each specimen was derived from the bending stiffness and geometrical property data. Following mechanical testing, each specimen was oven-dried and ashed to a constant weight. Ash content was determined as the ratio of ash weight to dry specimen weight. The results indicate that the ash content of fetal cranial bone increases significantly (from 50% to 68%) with increasing gestational age. (The elastic modulus of fetal cranial bone significantly increases with increasing ash content.) However, the ash content of the term fetal cranial bone or the six-year-old cranial bone is not significantly different from that found in the adult. These results are discussed in relation to a structural hypothesis for increasing cranial bone stiffness with increasing maturity.