I used Pearl Drops Instant Natural White Toothpaste in January 2017 and it instantly turned some of my teeth (the ones with some amalgam fillling in them) to dark grey/black and it is still the same as I write - 12th March 2018. I have been in correspondence with the makers but to no avail as they insist the trials reported no permanent discolouration of teeth, even on volunteers with fillings. They wish to have a report from my dentist and my dentist is unwilling to give one. I know my own teeth and they weren't like it before I used the toothpaste. The discolouration is only where I have amalgam fillings. One is particularly bad (a pre-molar) and now the whole tooth looks blackish whereas before it only showed a bit of filling on the top of the tooth and the rest of the tooth looked tooth colour, so I am conscious this shows when I open my mouth to talk or laugh. I did use Colgate Max White first on a manual toothbrush and then the Pearl Drops on an electric toothbrush, so I am wondering if the reaction was something to do with the Colgate Max White.