Teeth that need onlays or dental crowns are usually already compromised, and therefore may require root canal treatment sometime after the tooth has been prepared; this can be weeks, months or even years after the dental crown or onlay has been fitted. If the tooth is very compromised, then we may advise you to have root canal treatment before the tooth is prepared for a crown, or before the crown is finally cemented into place with a permanent adhesive cement. Infrequently, the tooth or teeth may develop an abscess and if root canal treatment alone is unsuccessful, the tooth may require root surgery or possibly an extraction.