I've been having dental treatment for about a month for one tooth. Failed root canal, failed extraction, so waiting for a surgical removal of the roots. I'm in a lot of pain which has peaked twice in the past week meaning I need to go in for the dentist to clean it out. I went this morning and after I had the numbing injection the dentist asked me to rinse my mouth. As I brought the plastic cup away from my mouth I noticed something on the side of it(not the side that I drank from). It was brownish red, in the semi circle shape of a mouth with dribble coming down. i.e. Blood. Straight away I said to the nurse 'er is that cup clean there's something all over the side of it?'. She immediately took the cup away and replaced it. I feel quite sick. Not sure I can complain because I have absolutely no proof that it happened. No one acknowledged it apart from to replace the cup. The treatment I've had so far has been pretty awful but this just takes the piss surely? What do I do?