Drs. Cox or Rees makes every effort to administer local anesthetics (novocaine) in a slow, gentle, and comfortable manner, thus eliminating any pain that may accompany dental treatment. The duration of numbness after treatment varies from patient to patient and depends on what drug was used. Generally the numbness wears off after two to three hours. Parents must be careful to watch their child for chewing or biting of inner cheeks or tongue that can cause them to be injured.