Q. About 2 years ago my dentist made me a set of trays to use for teeth whitening. I used the whitening gel he provided and was very pleased with the result. I would like to treat my teeth again but my dentist will charge me £25 for a 1.3mg syringe of Polanight 13% peroxide gel. I can buy four syringes of the same product on the internet for about £34. Would it be safe/sensible for me to buy it in this way? Is this a good product or could you recommend a better one?