Inlay or onlay possible, or is crown the only option?

[abi1335]

I took a full mouth xray for the first time in years and it discovered a large cavity on the side of #29, between that tooth and the one in front of it, that looks like it has gone down to the dentin layer of the tooth. The dentist, whom I was seeing for the first time, said it might even need a root canal, but in any case she recommended drilling, cleaning out the cavity, and then adding a crown.

I would like to know if this is the best/only option possible, or if something more conservative, like an inlay/onlay is possible. I asked my dentist and she said she "didn't think it (an inlay/onlay) would help", but she didn't elaborate, and as I have only seen her once I would really like a second opinion. Help please?

[Jerome Tsang, DDS]

Assuming your profile pic is the x-ray and tooth in question, I would say that a crown with a possibility of a root canal is the more reasonable treatment at this stage.  An inlay or onlay could be possible but if the tooth needed a root canal down the road, the inlay/onlay would need to be replaced and a crown placed on the tooth.

[Jerome Tsang, DDS]

I don't think anyone can really calculate a chance on that.  Based upon the radiograph, it looks pretty deep and close to the nerve.  Probably 3 things will happen.

1) Its deeper than it looks and you'll need a root canal right away.
2) Its not deep enough to expose the pulp chamber and after treatment, there's no pain so they'll just keep an eye on it until it becomes a problem or shows some signs of problems.  If so, you'll need a root canal and it could be in a week, it could be in 10 years.  No one really knows.
3) Its not deep enough again but after the numbness wears off there's pain and you need the root canal.

[abi1335]

Thanks so much for your reply, Dr Tsang! What are the chances that a root canal would be needed even after I got a crown or inlay/onlay, and what would cause that to happen?