Why is there discoloration under temporary crowns? (photo)

This is an easy one.  The odds are that you have a small crack somewhere around the roots of the tooth.  In my opinion, a retreat would likely not be successful.  I would recommend to have an extraction, bone grafting, and an implant placed.  This will cost more, but you will not have to wor...

No easy solution.  At least one new crown but without a photo I can't suggest further than that.  There are so many considerations in matching teeth.  

Sensitivity might have more than the crowns involved here so their replacement may not be total solution.  You should contact the local dental society and ask about what is called "peer review".  You should be able to get them to have an impartial third dentist take a look at things and make a r...

It looks as though a crown would be he best restoration for this tooth.  In addition,  her gums look red and inflamed.  Schedule her an appointment with a dentist for a cleaning and exam to help reduce any gingival irratation.  They should go over brushing and flossing with her as well.  Good luck. 

You are correct that peroxide should be used to clean this.  Do not do this on your own.  Have your dentist clean this properly for you when bonding on your permanent crown.  Good luck.  

If money is not an issue, replacing the gold crown would be the best idea. A bonded restorative material would be the best way to fill the root canal access opening, not mechanically retained amalgam. I wouldn’t worry about having the old crown removed.