sounds like trigeminal neuralgia. You need a good anti inflammatory drug like CARBAMAZEPINE which is also used as an anticonvulsant in other cases.

After having seriously invasive procedures like root canals done, it can tale several months for possiblly damaged or inflamed facial nerve endings to heal.

During that time, take the above mentioned drug - It should start helping possibly even after the first dose!

AND - if it turns out to not be damaged nerve/tissue - taking the above mentioned medication won't kill you and can deliver much needed, non-narcotic analgesia.

Also alternating hot and cold compresses can be of some help.