Sensitivity and Pain After Veneer Preparation

You mentioned that  the gap was closed by bonding from the first dentist you saw and it lasted eight years.  You now go to a second dentist and do a veneer prep with him and you are now in pain!  I would look to the second dentist who did the veneer prep and make sure he finds the source of it!  You had no pain with the amount of tooth taken down for the bonding for  8 years.....seems to me, i would question the cosmetic ability of the second dentist and his prep of the veneer....The pain you are having is abnormal....sensitivity is one thing and this type of pain is something else!  Get to the bottom of this...i am sorry you are suffering so!

Many dentists don't know how to do cosmetic dentistry, so when a fantastic case stares them in the face they don't know how to react. Just because the dentist expressed shock does not mean the original dentist was wrong. It is VERY possible that the new dentist simply doesn't know up from down.
Most dentists have no clue about cosmetics.
Pain TODAY means nothing more than pain TODAY. Find out the source and get it treated.

Anytime a tooth is prepared for a new restoration, whether it is a tiny filling or a full crown some post op sensitvity may occur. This could be due to several reasons.
1. The tooth has a pulpitis which is normal and should improve with time. If it gets worse, lingers or becomes spontaneous then it is possible a root canal could be indicated.
2. Because temporaries are meant to be removed, they often leak or experience "micro movement." The bacteria that gets under the temp will create short term sensitivity.
3. If the bite is off then this could also cause some sensitivity.
I would mention this to your dentist and if the sensitivity becomes a toothache or a swelling develops you need to be seen immediately.