I wanted to share a few pieces of advice. I also have unhealthy teeth and I hope these ideas help you out.

1. Get an annual cleaning even if your teeth feel fine. The dentist does x-ray and other preventive tasks to prevent major problems from forming. Many people get their car's oil changed, but only visit their dentist if they have a major problem.

2. You mentioned being on a fixed income and I assume that you don't have any dental insurance. A good option for people who don't have dental insurance is something called a "dental discount plan". With a dental discount plan, you pay a monthly premium, there is a network of dentists, and you pay a set amount for each procedure done by the dentist. With a dental discount plan, you get no benefit if you do not go to a network dentist, so be sure to check the network before joining one. There are generally no age restrictions and in my region plans cost about $100/year.