Effect of two organic phosphonates on protein adsorption in vitro and on pellicle formation in vivo

Organic phosphonates have been introduced in dentifrices to reduce the formation of dental calculus. They may conceivably act as calcium sequestrants or crystal growth inhibitors, interfering directly with the calcium ions on the hydroxyapatite (HA) and enamel surfaces. The aim of the present study was to examine the effect of two organic phosphonates on protein adsorption to hydroxyapatite in vitro and on pellicle formation in vivo. The effect on protein adsorption in vitro was studied by adsorption of albumin to either untreated or phosphonate treated HA powder. Ion exchange chromatography was also performed with columns with untreated and phosphonate treated HA as bed materials and with linear gradients of either phosphate or phosphonates. The effect on pellicle formation in vivo was studied by scanning electron microscopy on untreated and phosphonate treated enamel fragments which had been carried in the mouth to acquire pellicle materials. The present study showed that phosphonate-treated HA took up less protein. The adsorbed protein was, furthermore, less firmly bound to phosphonate treated hydroxyapatite. Phosphonate-treated enamel fragments carried in the mouth also exhibited a slower rate of pellicle formation as compared to the untreated enamel fragments.