My front incisor tooth has been a bit sensitive lately. It doesn't hurt and hot/cold food causes no problems, neither does eating, but I am aware of it. It feels a bit different. I went to the dentist today and she took an X-ray which didn't show up anything. She placed some very cold stuff on the tooth and it felt awful but just for a second, then it was fine. Then she says I need a root canal and wanted to get started right away. I said no as I'm not happy with root canals after what I've learnt on this site and others (Thanks Bryanna!). I'm just confused about this. The tooth has never had the slightest problem before, has no decay or cavity and I don't have gum disease. In fact, the dentist commented that my gums were very healthy. So I'm wondering how on earth bacteria has got in the tooth?