A scanning electron microscope study of vascular development in the dental papilla of prenatal rat molars.

Prenatal development of the vascular supply to the dental papilla was studied in the maxillary first molar teeth of rats from 18.5 to 22.0 days gestation, using the vascular casting/scanning electron microscope method. Five pulp horns developed in order, central, distal, mesial, disto-lingual and mesio-lingual with the development of the dental papilla. The first vessels that invaded each pulp horn were slightly depressed and formed an irregular network. The newly developed blood vessels were found to grow by sprouting and loop formation. After the invasion, blood vessels at the top of the horn became wider and then diminished in size to form a dense vascular network. The growth of the blood vessels in the latter stages is thought to take place mainly at the tops of the horns, and it is suggested that narrower capillaries arise from wide vessels. A dense and flattened vascular network consisting of thin blood vessels was formed when mesenchymal cells were beginning to differentiate into odontoblasts. The increase in density is thought to correlate with the differentiation of odontoblasts.