The effect of prenatally increased oxygen tension on the development of the mandibular condyle

Twenty-four Long Evans/Turku rats were used to study the effect of prenatally increased oxygen tension on the mandibular condylar cartilage. Pregnant rats were exposed to increased oxygen tension in an air chamber for 14 days. The animals were returned to normal laboratory conditions after parturition. Three control and three experimental young rats were killed at the ages of 1, 5, 10, and 20 days for microscopic studies. Sagittal sections of the temporomandibular joint showed the cartilagenous condylar process to be narrower anteroposteriorly at 1, 5, 10, and 20 days postnatally, and it seemed to be bent backwards in experimental animals at the age of 1 day, in comparison with controls. The mesenchymal and chondroblast cell layers were thickened at the ages of 1, 5, 10, and 20 days. The findings indicate that prenatally increased oxygen tension increases the postnatal mesenchymal cell population and support the hypothesis that the size of the mandible is partly determined by the number of mesenchymal cells present during the prenatal phase.