It is difficult to comment anything without seeing the tooth. If a picture was provided I could better guide you. We can tell only after seeing weather one tooth support was needed or two teeths. You don't have to regret RCT dint kill your teeths it in fact saved your teeths. Trust your doctor. Don't be confused.

Hello sir, Implants are always the best option for replacement of your missing teeth without involving the adjacent teeth.... But for ceramic bridge, it always required to take support from adjacent two teeth for a strong bridge and for its longevity... When we take adjacent teeth support it's better to do Root Canal for both the teeth, so that there won't be any pain or sensitivity in future...

Good morning Without seeing case cannot give what was and what must have been done Only on seeing clinically  treatent plan can be given You can also practo consult us Regards

Support of other teeth is required only when there is a missing tooth. An RCT is done on a tooth with infected pulp and layer capping is done to restore the tooth