Root exposed after grinding from filling -- will gum grow back over?

[frankjohnson]

I went in for a regular cleaning recently and was told I had a cavity near the gum line on my lower back molar. The dentist ground the tooth down to do the filling and it was slightly painful as she did that. I didn't have any sensitivity/pain there before the filling. However, after the filling it became very sensitive along the gum line to hot or cold. I went back in a week later and they confirmed that the gum had been ground away slightly and the root was exposed. They put some 'desensitizing solution' on it, which seemed to cause more pain than reduce any. They said it would just take time for the gum to grow back over the root (maybe 30 days or so, they estimated). It's been about 30 days now and it's still very sensitive. I have had some gum recession too so I'm worried that the gum will not grow back over the root. The whole thing seemed a bit hastily done to me and I'm a bit frustrated that I went into the dentist without pain and now I have a recurring sensitivity.

Is this a normal thing to happen when doing a filling?

Could it be that it will just take longer for the gum to grow back over or should something else be done?