Kindly suggest me a way to restore my tooth.

Hi doctor,

I have neglected my dental health for a long time. I am a 62 year old married male. I have had several teeth extracted. I lived with a couple teeth whose caps have broken off on my left side and a few molars on the right for chewing. I am suffering from hypertension and is controlled with medicines over 10 years. I am also a known diabetic and it has been controlled with drugs and diet for the last few years. My main problem is moderate neuropathy in hands and feet for more than 12 years. I am on Neurontin and Fentanyl patch. Six months ago, I went to my dentist with the right top rear molar sharp pain. She filled it, but was not sure whether it would need a root canal. About two months later, the pain started and this time as a more typical, throbbing toothache and she decided a root canal was appropriate. I was surprised with the amount of pain in the recovery. The pain was more diffuse than the original, sort of like the pain from a loosened tooth. I complained and re-visited the dentist. She did an x-ray and said that she did not miss any roots or went too deep. But, she saw something and she described it as an injury in the spot next to it and that is where a tooth had been extracted years before. She gave me a course of antibiotics, just in case and recommended to consult an oral surgeon. But, I decided to wait and see if it resolved. It slowly got a bit better, but in a month or so started to get worse. So, I went to the oral surgeon and he said that he saw nothing wrong and suggested I could be feeling pain from a tooth on the bottom. For a number of reasons, I do not believe this. I am now at a point where the pain is endurable, but annoying. The pain changes over time. Sometimes, it abates almost completely and there is no pain at all. While the tooth is still slightly cold sensitive, there are no other symptoms. This lasts for about a few days to over a week at a time. Most of the time there is an annoying sensitivity, high sensitivity to cold, pushing the tooth to the side with my tongue is mildly painful, sort of like a loosened tooth but chewing down on it does not give me any pain. There is a full time ache and that is most pronounced at night. The symptoms are basically the same as the moderate pain, just more intense with the addition of it feels deeper and more diffuse. It sometimes feels like it goes up into the jaw or sinus. But, I really need to keep this tooth in order to have a half-functional mouth. Please help.