Can unsuccessful root canal of the upper right pre-molar tooth cause trigeminal neuralgia?

Possible but Rare: Root canals are severing of neural tissue. Trigeminal neuralgia involves neural tissues of the fifth nerve gone bad, sending unwanted feedback of pain when stimulated. Most teeth with root canals don't cause this and there is never a direct cause and effect that ties trigeminal neuralgia to the root canal procedure. Some root canals do fail and cause bone cavitations and residual pain.

No: Trigeminal Neuralgia or paroxysmal episodic face and jaw pain is thought to be caused by changes in the insulating layer around the Trigeminal nerve . It has nothing to do with root infection or root canal therapy.