Your tooth usually gets its feeling back before your lip and tongue do. For most people, the soft tissue numbness from a dental injection fades within about two to three hours, although it can be shorter after an upper tooth and longer after a lower one. A lip that still feels thick after the dentist has finished is normal, not a sign that something went wrong.
What a large trial measured
The clearest figures come from two clinical trials of more than 480 adults and adolescents, published by Hersh and colleagues in the Journal of the American Dental Association in 2008. The trials were testing an injection designed to reverse numbness, and for comparison the researchers timed how long normal feeling took to return without it. People had received one of four common dental anaesthetics for fillings or cleaning.
In that comparison group, the median time to normal feeling was about 155 minutes for the lower lip, 125 minutes for the tongue and 133 minutes for the upper lip. In other words, around two to two and a half hours for a typical person, with some recovering faster and some taking longer.
Why lower teeth tend to stay numb longer
Upper teeth can usually be numbed with an injection close to the tooth, because the bone around them is thin enough for the anaesthetic to soak through. Lower back teeth sit in thicker bone, so dentists often numb the main nerve that supplies that side of the lower jaw instead. This is called a nerve block. It numbs several teeth, half of the lower lip and often half of the tongue, which is why a lower filling can leave you with a lopsided feeling for a few hours.
What else changes the timing
- The anaesthetic and the dose. Different anaesthetics last for different lengths of time, and more anaesthetic usually means longer numbness. Your dentist chooses based on how long the treatment will take.
- A vasoconstrictor in the solution. Most dental anaesthetics contain a small amount of a vasoconstrictor, which narrows the local blood vessels and keeps the anaesthetic in place longer.
- Where it was given. A nerve block lasts longer than an injection near a single tooth.
- Inflammation. A tooth that is badly inflamed or infected can be harder to numb in the first place.
Looking after yourself until feeling returns
The main risks while you are numb are injuries you do not feel at the time:
- Avoid chewing, especially on the numb side, so you do not bite your lip, cheek or tongue.
- Hold off on hot drinks and hot food, which can burn numb tissue.
- Watch children closely. Many will chew or suck on a numb lip out of curiosity, which can leave a painful sore once the numbness goes.
- Do not test the numbness by pinching or biting.
There is no reliable trick for making numbness disappear faster at home. Time is what works. Once you can feel your lip and tongue normally, you can eat as usual, and our guide to eating after a filling covers the first day.
Numbness that lasts much longer
Very rarely, an injection is followed by numbness, tingling or altered feeling that lasts for days or longer. This is called paraesthesia. In a 21-year review of reports in Ontario, Canada, published by Haas and Lennon in 1995, every case involved the lower jaw, usually the tongue or lip, and the reported rate in one year was estimated at about 1 in 785,000 injections. Reported rates like this may underestimate the true figure, but the condition remains uncommon.
If your lip, chin or tongue is still numb the day after treatment, or you notice tingling, burning or altered taste that is not improving, contact your dentist so it can be checked and monitored.
A little tenderness where the needle went in is common for a day or two. Increasing pain, swelling or difficulty opening your mouth should be checked. Ongoing sensitivity in the treated tooth is a separate issue, which our article on sensitive teeth explains.
What patients ask about numbness
Why can I feel the tooth but not my lip?
The anaesthetic usually wears off from the tooth sooner than from the soft tissue around it. It is common to finish treatment with a comfortable tooth and a lip that stays numb for a couple more hours.
Can I go back to work after an injection?
Most people can. Speaking and drinking may feel a little clumsy for a few hours, especially after a lower nerve block, so it helps to plan meetings or meals with that in mind.
How long is too long?
If feeling has not returned by the next day, or you have tingling or burning that is not settling, let your dentist know.
If you have treatment coming up and want to know what to expect, our team is happy to talk it through. See current new patient offers on our offers page or read about general dental care at Melrose Park. If a temporary filling is part of your plan, that guide covers the aftercare.
