Backstory:

My Dentist reviewed some x rays from a previous visit and suggested I return for a followup. He said that he noticed some spots under very old fillings and suspected there might be decay under them. These old fillings on my top molars on the left side are probably 15+ years old or more. 

I went to the followup and he started drilling away in late June. He ended up spending 90 minutes drilling away at the back two molars on the upper left side, then filling them and shaping. 

He mentioned there was a lot of deep decay underneath and that's why it took so long. 

2 months + later and I was still experiencing high sensitivity to cold on that top molar second from the back. He had me return to the office in September and he did an adjustment after testing the bite saying it might be high. Again 2 months go by and I'm still experiencing high sentivity to cold (cold air even, even an apple fro sitting on the counter provokes a response from the nerve - its only on the second last molar on the left side and only on the outside of the molae). I can also stimulate it by pressing with my fingernail. 

He had me come back I again and he did a big bite adjustment after  I describe my symptoms (I can press in that tooth on the outside of it with my nail and provoke a response, it's only on the outside of that molar that's sensitive - the inside and middle shows no response). He says the bite was really high and it was likely infalming the pulp (which wouldn't he have adjusted it and noticed thst in the first visit?). 

Its now been another two months and still extreme sensitivity on that side to cold. I took a picture of this weird opaque white spot on that tooth, if I cover that with my finger and breathe in there's no cold response. 

My questions are - what is that spot? What is the likely diagnosis and what is the possible treatment plan going forward. 

Attached are the original X Ray's. 

Extreme Sensitivity Post Filling Replacement 6+ Months Later