I wasn't given as much info on the pathology as what you were. But my intial biopsy showed moderate cell dysplasia which was treated in day surgery by surgical excision (bascailly they just scraped the surface) and I recovered and was eating normally within 2 days. The pathology results from the the scraping they took however showed 3 SCC "foci" - which from what they told me are tiny, tiny cells. From then on in I was refered to ENT specialists as previously I was being treated by dental specialists. THe intial dental surgeon I was dealing with felt we could just leave it be and monitor it, but the MRI and cat scans showed enlarged lymph nodes so it was all a downward spiral from there. I've had fleeting thoughts that the neck dissection and further partial glossectomy were unnecessary but I've found that dwelling on those thoughts is just too negative- I'm comfortable with the treatments that I've had as precautionary and hopefully preventative. The way one ENT surgeon put it was that they have cut out all the pathways therefore elminating its possible spread.
THe chronic irritation hypothesis is interesting, will be curious to see what others say.