It takes three to five hours for the effects of novocaine and other local dental anesthetics to wear off completely, according to Jonathan G. Campbell, D.D.S. The tooth remains numb for one to two hours, while the tongue and lips remain numb for up to five hours.
Dentists use a variety of anesthetics, states Dr. Jay Kansal, and each remains effective for a different length of time. When choosing the type and amount of anesthetic, the dentist considers the type of procedure, whether or not infection is present and the patient's sensitivity to anesthetics, notes Dr. Campbell. Most dentists use lidocaine or articaine, as of 2014. The addition of adrenaline or epinephrine increases the amount of time that the anesthetic is effective.