Confused about options to whiten a grey tooth

Hi,

I have one tooth (top, front) that has turned a shade of grey over the last 10 years. I knocked both my front teeth to the point where they were wobbling. Both recovered, but one turned a little off colour.

I have considered internal bleaching, but I'm not sure that the tooth ever had a root canal (which I understand is essential for internal bleaching to be applied). 

I have been told by one dentist to 'try external bleaching first' at a cost of £200 to see if it helps. I've read that if the tooth is dead this will not be successful. 

So a couple of questions:

1. Is the tooth definitely dead if it has turned a little grey over 10 years?

2. What are the chances external bleaching will work on that tooth?

3. What are the risks of having root canal treatment on that tooth in order to have internal bleaching?

4. How successful is internal bleaching?

5. Do I have any other (non destructive) means of whitening the tooth?

Thanks

[Jerome Tsang, DDS]

If the tooth is dead, it may need a root canal to do an internal bleaching.  External bleaching probably would not work.  Have you considered doing a veneer?