When I was a kid, my dentist used to do fillings (cavities) all the time without injections. It is only where the root is involved that the drill hurts - if your dentist is saying it is only a small one then maybe it wouldn't hurt without an injection. However saying that when my dentist gives me an injection I don't ever see the needle, just feel the stinging for a few seconds when the anaesthetic first goes in. For me the worst bit is the noise of the drill so close to my brain - hate dentists with a vengence BTW. Good luck.