Could you tell me when would a dentist recommend an onlay and when would a dentist recommend a root canal?

The answers are:: The indication for an onlay would be when there is too much tooth that needs to be replaced with merely a filling, but not enough to warrant a crown. Rct is mainly indicated when the nerve of the tooth is irreversibly damaged.

Two different items: Onlays restore structural issues with a tooth, usually suggested for decay issues, fractures, etc. That do not involve the pulp of the tooth. If decay/fracture/bacteria from the mouth find their way into the pulp of the tooth, then a root canal may be suggested and an onlay or crown would also be likely in addition to the root canal.

Cavity vs. Infection: An onlay would be recommended when you have a cavity in a back tooth which is too large to fill predictably with a composite (plastic) material. An onlay is a stronger material and it protects the tooth more than a filling. Root canal treatment would be recommended if you have an infection within a tooth. This would remove the infection and seal the root to prevent future problems and pain.