The lipid metabolism of dental pulp will be investigated by analytical and isotope tracer methods. Dental pulp phospholipids contain at least 30 percent polyunsaturated fatty acids, including docosapolyenoic acids, and dentine phospholipids contain less than 10 percent polyunsaturated fatty acids, none of which are docosapolyenoic acids. The dental pulp synthesizes the dentine lipids. Phospholipid species in dental pulp will be analyzed to determine whether any particular phospholipid contains a high concentration of saturated species. The incorporation of radioactive isotopes into dental pulp lipids will be measured by using C14-glycerol, C14-choline, C14-ethanolamine, C14-serine, and C14-fatty acids. These studies will be done in different sections of rat incisor dental pulp, because the root section is forming dentine whereas the apical section is not. This will allow a comparison of lipid metabolism in calcifying and non-calcifying dental pulp. Studies on bovine pulp at different stages of tooth formation will demonstrate whether lipid metabolism in dental pulp changes with age as dentine formation decreases.