Local anesthesia generally works fast and the effects don’t last long. For instance, the numbing effects of lidocaine usually kick in within five minutes or less of the injection and last about one to two hours. Local anesthesia frequently contains epinephrine (also known as adrenaline), which can help its effects last up to an hour longer.
How long the anesthetic lasts depends on the:
- Dosage given: Higher doses last longer and are needed for more complicated procedures. For example, a root canal may require a higher dose than a filling.
- Person receiving the dose: Some medical conditions can influence how long the anesthetic lasts.
- Condition of the tooth: Infection can cause the anesthetic to be less effective, so the dentist may use a higher dose.
The anesthetic can wear off sooner if you increase blood flow in the area with a warm compress or gentle massage. Be careful not to bite down on the numbed area, as you could cause damage. You may find it difficult to eat, drink or speak clearly before the numbness wears off. As the effects of local anesthesia diminish, you’ll usually have feeling in the tooth before you do in your lips, cheeks or tongue.