Microvascular architecture and exchange in teeth.

Dental pulp is a low-compliance tissue surrounded by an avascular hard tissue case. Resin casts of the microvasculature in teeth of limited growth show arterioles and venules arranged axially in the pulp with capillary loops extending out toward the dentine. The capillary density is high. There is ultrastructural evidence for lymphatics in pulp. Pulpal blood flow has been estimated in intact teeth using radiolabeled microspheres and found to be in the range 20-60 ml/min per 100 g tissue. One of the difficulties of studying this tissue is that a cavity has to be cut into the tooth with the inherent risks that this may affect the parameters under study. Measurements from exposed pulp indicate that the tissue fluid pressure is high and pulsatile. Furthermore, micropuncture studies have shown that the arteriolar pressure is lower and the venular pressure higher than in other tissues. When dentine is exposed in vivo, fluid moves out through the dentinal tubules and this appears to be formed by a process of ultrafiltration from the pulpal interstitial fluid. The flow is sufficient to retard significantly the diffusion of chemicals into dentine from the oral cavity.