Yes, it's unlikely that root canals would cause nosebleeds
by rupturing the sinus
cavity as the needles are pretty small in caliber and the length of the root is measured beforehand. However, a previous infection of the canine tooth
root (which has in fact the longest root) can progress to the sinus and can cause nosebleeds but again this is pretty rare. Your husband should have his blood pressure checked and a nasal examination done to identify the cause of nosebleeds.