How to decide betweeb composite filling instead of root canal?

Discuss with dentist: If a cavity is deep, these's a strong possibility the tooth needs root canal therapy. Even if you place a large restoration, no guarantee the nerve will not be affected.

What's to decide: There is no comparison between the two. The composite filling is used to fill the tooth after decay has been removed and a root canal is done when the nerve of the tooth has died and is causing pain and swelling. Maybe you are asking about after the root canal is done, should you have an amalgam or a composite filling. I prefer composites because they bond to the tooth and strengthen it.

Treatment decisions: The answer to your question is best addressed by your dentist. It's a case by case situation. Root canal therapy is performed only when needed.