Condensed sodium vs. coffee
Makino et al. studied this hypothesis in a double-blind randomized clinical trial, with 30 participants. Each subject held (with an appliance) a hydroxyapatite pellet on the lingual side of the mandible for two hours, allowing for pellicle formation. The appliance was later submerged for 48 hours in a coffee solution.
Following coffee exposure, the subjects wore the appliance again, this time chewing two pieces of gum containing 7.5mg of sodium metaphosphate or a control gum. The hydroxyapatite pellet’s change of color was measured used a spectrophotometer.
Following cycles of chewing gum with sodium metaphosphate, the stained pellicle showed significant (p<0.05) color change, demonstrating the chemical “de-staining” effect of sodium metaphosphate. This was compared to a control gum.
Other studies (Baig et al.) have also examined other forms of condensed phosphate, such as sodium hexaphosphate. In these studies, it was further shown that sodium hexaphosphate produced reduction of tooth staining, likely due to its affinity for tooth calcium ions.
Although further studies need to be done in order to test this hypothesis in a variety of settings, condensed phosphates could soon be a critical component of chewing gum.