You’re terrified because cancer is terrifying. There’s nothing inappropriate or abnormal about your fear. Sadly, you’ve also lived in fear of death for a long, long time. That’s probably embedded in some experience that you never found a way to make sense of or put aside. I’m very sorry you’ve lived with that shadow. Now the shadow becomes more real.
The worst thing you can do is to put off getting whatever testing your dental specialists think necessary. Hopefully, there is another explanation for the bone loss. If you had braces on your teeth when you were young, for example, it’s possible the teeth were moved too far or too fast. Orthodontia has changed markedly since the 60s and 70s, resulting in less trauma to the mouth and better outcomes. But if your fear is confirmed and you do have a cancer, early detection is key to recovery. Don’t let your fear get in the way of getting a good assessment. Only then will you know what you’re dealing with and, if necessary, what treatment options are available to you.
Once you’ve coped with the dental issues, please consider talking to a counselor about your anxiety around death. We all die. As I’m close to you in age, I fully understand the sense that time is getting shorter. Death isn’t such an abstraction when friends start to sicken and pass on. On the other hand, you could live another 30 years or so. Coming to terms with the inevitable will let you live the time you have, whether a week or decades, with more joy and less anxiety.
I wish you well.