You leave the clinic with one side of your mouth numb, and the first question is always the same — how long until this wears off, and what should I not do until it does?
How long does the numbness last?
It depends on which anaesthetic was used, how much of it, and where it was placed. Your dentist can tell you the expected range for the injection you were given, and it is worth asking before you leave.
Two general patterns hold. Numbness in the upper jaw tends to fade sooner than numbness in the lower jaw, because the upper teeth are usually anaesthetised by depositing the solution near the tooth itself, while the lower back teeth are usually anaesthetised by blocking a nerve further back. A nerve block covers more territory and takes longer to wear off.
The other pattern is that soft tissue stays numb longer than the tooth does. The treatment can be entirely comfortable while your lip and tongue are still asleep for some time afterwards. That gap is normal, and it is exactly the period the rest of this page is about.
Why you should not eat until sensation returns
The risk is not the food. The risk is that you cannot feel the parts of your mouth that get in the way of it.
People bite the inside of the cheek, the lip or the side of the tongue without noticing, and the injury only becomes obvious hours later when the anaesthetic wears off and the area is already sore and swollen. Hot drinks carry the same problem in a different form: the usual signal that tells you a cup is too hot is not working.
The NHS gives the same advice for local anaesthetic generally — move carefully until the anaesthetic has fully worn off, as you may not notice if you injure yourself.
This matters most with children, who will explore a numb lip because it feels strange, and can chew it badly before anyone notices. If a child has been treated, it is worth watching them until the feeling comes back.
What is normal in the first day
Expect numbness that fades gradually rather than switching off, often with tingling or a mild burning feeling as sensation returns. The injection site may be tender to touch for a day or two, and a small bruise there is not unusual. Some soreness around the tooth that was treated is expected, particularly once the anaesthetic has gone.
When to contact the clinic
Three things are worth a call rather than a wait.
If an area is still completely numb the following day, tell us. Persistent numbness after dental treatment is uncommon and usually resolves, but it should be recorded and followed rather than watched at home.
If swelling is increasing rather than settling, or you develop a fever, that is a different problem from the anaesthetic and should be seen.
If you develop a rash, or any difficulty breathing or swallowing, treat it as an emergency and seek immediate care rather than waiting to reach us. For anything urgent outside our hours, see emergency dental care in Seongnam.
If you are visiting Korea
Two practical points come up often with patients who are here for a short stay.
Pharmacies in Korea are separate from clinics, and are usually within a short walk. If you are given a prescription, take it to a pharmacy rather than expecting to receive medication at the clinic itself.
And if something does not feel right after you have left, write to us rather than waiting for your next appointment. Our contact details are on the clinic location page, and we answer in English.
Frequently asked questions
Can I drive after a dental anaesthetic?
A local anaesthetic numbs the area it was injected into and does not affect alertness, so driving is generally not a problem. Sedation is a different matter entirely — if you were sedated, you will have been told not to drive, and you should arrange for someone to take you home.
Can I drink coffee while my mouth is still numb?
Wait until the feeling has returned. The reason is temperature rather than the coffee itself: while the area is numb you cannot judge how hot a drink is against your lip and palate, and scalds happen. Cool water is fine.
Why is my lower lip still numb hours later?
Lower back teeth are usually treated by anaesthetising a nerve some distance from the tooth, and that nerve also supplies the lip and part of the tongue. Numbness in those areas therefore lasts longer than in the tooth being treated. It fades on its own.
Is it normal for the injection site to hurt afterwards?
Mild tenderness at the injection point for a day or two is common, and a small bruise can appear there. Pain that worsens over several days, rather than settling, is worth telling us about.
None of this replaces what you were told at your appointment. If the instructions you were given at the clinic differ from anything here — because of the treatment you had, or your medical history — follow the instructions you were given.