Root canals work 90% of the time, and root canals done today with better techniques even exceed that success rate! It is possible that all the bacteria weren't removed before the root canal filling done. Also possible is that the root canal filling, although removing the entire nerve, did not...
If the pain from cold lasts longer than 60 seconds after the cold is taken away you may have a nerve issue requiring a root canal. I would have the dentist take a CBCT (a 3D type of xray) of the area if he has the machine to do it. Or just a standard xray and check the ends of the...
This is very common. And the cause is because the bone where you have both implants is flat. Therefore the gums are also flat in between. Reshaping of the gums before making the crowns and/or bulkier crowns around the gumline may help. Even then, it will be difficult to duplicate bone and gum...