ZETA-POTENTIALS OF ENAMEL AND APATITES

In this paper the results of Zeta-potential (ζ-potential) experiments on enamel and hydroxyapatites are presented. Human enamel and 3 apatites with various purities were investigated. With a low solid: liquid (S: L) ratio the potentials were negative. The values depended strongly on pH, pretreatment and material purity. The enamel values were always less negative than the hydroxyapatite values. With a high S : L ratio and at pH 7·0 the ζ-potentials were all positive. Pretreatments with submandibular saliva at a high S : L ratio change the ζ-potentials to negative values. The consequences for pellicle formation and bacterial attachment are discussed. Furthermore, the effects of 0·5 × 10-4 M pretreatments with EHDP, mellitic acid or pyrophosphate solutions on the ζ-potentials have been measured, both with and without a submandibular saliva treatment. © 1979.