Can Bacteria caused by dental 'caps' be reversed?

Been to Dental Hosp and x ray showed that where my two caps were there was a shadow of bacteria going upwards and that it had caused bone loss. It also showed that there is a 'leakage' (which i can feel). They could only offer extraction and said that because the caps were 20 years old they could not be replaced. It is in a visible part of my mouth and i am petrified of looking awful. I am on disability benefit and when i last had a tooth extracted i was not even given the option of another tooth. Is this normal in the NHS or should i go private to get a second opinon?