Dispersion and polar surface free energies of human enamel.

In this study, the dispersion (gamma ds) and polar (gamma ps) surface free energies of human enamel with and without an acquired enamel pellicle and of crystalline hydroxyapatite were determined from contact angle measurements. The results show that gamma ps is strongly influenced by the presence of a pellicle; the total surface free energy (gamma s) is considerably smaller for enamel with an acquired pellicle than for enamel without an acquired pellicle. Enamel without an acquired enamel pellicle shows surface free energies comparable with those of crystalline hydroxyapatite.