As with any medical condition, treatment starts with identifying the root tooth pain causes. The main cause for this dental problem is inflammation of the pulp that is present inside the pulp chamber, a condition called pulpitis. Other reasons for severe toothache are tooth decay, tooth fracture, abscessed tooth, and gum infection. Apart from these, faulty tooth filling is another cause for pain in tooth. Thus, toothache after filling is also reported by many who have undergone the procedure.