In vitro evaluation of editempa on hydroxyapatite formation and its effects on dental enamel

N,N,N',N' ethylene diamine tetra (methylene phosphonic acid)-Editempa inhibited the formation of hydroxyapatite (HA) in vitro at 4 ppm. In the seeded crystal growth of HA at 37 degrees C, it completely inhibited the crystal growth at 0.5 ppm. C14-Editempa adsorbed to HA crystal at 37 degrees C. The maximum adsorption was 1.29 mumol/m2 of HA and the adsorption was monolayer. Compared to the natural inhibitors of HA in saliva (Statherin and Proline-rich proteins), Editempa was more effective in vitro on weight basis. At 0.3 ppm, it inhibited growth rate of the crystals by 80% while 4 to 5 ppm of the natural inhibitors were needed to get the same effect. The inhibition of rates with Editempa was not directly proportional to the area covered by it on the HA seeds (occupied less than 10% of the surface). The natural inhibitors, on the other hand, seemed to cover all the available surface. These data indicate that the inhibition with Editempa was due to binding to specific sites on the surface of the seeds. The solutions up to 5% of Editempa did not damage or etch the surface of human dental enamel in vitro at pHs 5.0 and 7.5, as evaluated by scanning electron microscopy and calcium released in the exposed solutions.