1. Complete the RCT, restore, and recall. I explain the decreased prognosis. There is really no evidence/research (I am aware of) that would tell them how much a crack in the tooth will change the long term prognosis.
2. Extract the tooth. Replacement options are discussed. In this case, with a full complement of teeth, an implant would be the only practical replacement option.
In this particular case, the patient decided that she did not want to extract the tooth. With good informed consent we completed the case, reduced the occlusion & temporized the tooth. She will return to her G.P. for build-up & crown. You may see that I removed a little extra gutta percha from the distal canal, to allow the bonded restoration to seal off the distal a little better.
We will recall her in 6 months to re-evaluate the distal lesion. I really feel that the key to this type of treatment is informed consent. When presented the options & prognosis, some patients will elect to extract and move on. However, most patients want to try and save their natural tooth. Endodontics can help them retain their natural teeth for many years.
Here is another case where a cracked tooth was found and it was recommended that she extract the tooth and have an implant placed. The patient followed the recommendation and had tooth extracted, bone grafting, and an implant placed by a specialist.
4 years later, she returned for re-eavluation. The implant was loose, probed to the apex, and there was purulence. You have to wonder if it wouldn't have been better to have tried to save the tooth originally. I can't guarantee that the tooth would have lasted with endodontic treatment, but it is an option that shouldn't be left out of the treatment planning process.