Is there any form of thermal ablation that is a permanent pain stop for chronic back pain or will the nerves still grow back?

Not exactly: If you are referring to ablation of the peripheral nerve that supplies sensation to the facet joints-- the medial branch of the dorsal primary ramus? The nerve can regenerate over time, but the ablative procedure can be repeated. The procedure is only effective in a patient with pain coming from the facet joints. Doesn't work for any other cause of chronic back. Proper diagnosis is the key!

Nothing Permanent: Usually RFA lasts at least 12-18 months on average. Some people can get less relief if nerves re-grow sooner. In my patient base most people will come back for repeat treatments at around 12-15 months. Some of my patients have had multiple years of relief. Sometimes after the 2nd or 3rd treatment the nerves grow back slower.