Why does the tooth need a crown if it feels fine?
A root-treated back tooth is more likely to split, and a split tooth usually cannot be saved. A crown holds it together and takes the chewing load off the weakened walls.
Feeling fine is not the point. The nerve has been removed, so the tooth cannot warn you. It is structurally weaker than it feels.
What actually makes it weaker?
Two things. The decay or fracture that made the root canal necessary had already removed tooth structure, and the treatment itself requires an opening through the top.
What is left behaves more like a shell than a solid tooth. Under chewing forces a shell flexes, and eventually it cracks.
Do front teeth need one too?
Not always. Front teeth take far less chewing load, so a well-sealed filling is sometimes enough.
Back teeth are the ones that carry the load, and they are where the recommendation is strongest.
What happens if I wait?
Some teeth last a long time without a crown. Others split, and a vertical crack through the root usually means the tooth has to come out.
That is the real risk of waiting. You do not lose a filling, you lose the tooth you just paid to save, and then the conversation becomes an implant or a bridge instead.
Common questions
Do I really need a crown after a root canal?
For back teeth, usually yes. A root-treated back tooth is more likely to split under chewing load, and a split tooth generally cannot be saved. A crown holds it together.
Does a root-treated front tooth need a crown?
Not always. Front teeth take much less chewing force, so a well-sealed filling is sometimes sufficient.
What happens if I do not get a crown?
Some teeth last a long time. Others split, and a vertical crack through the root usually means the tooth must be removed, which turns a saved tooth into a lost one.
How soon after a root canal should the crown be done?
It is not something to leave indefinitely, because the tooth is at its most vulnerable while unprotected. Your dentist will advise the timing for your case.