November 4, 2026 · Treatments, Explained

Getting Numb at the Dentist: What to Expect

By Dr. Jill Kollar, Precision Dental of Windsor

Tooth model, anesthetic cartridge, and dental mirror in a dental office.

Most fillings, crowns, and deep cleanings start with getting the area numb. Patients ask what we use, whether the injection hurts, and how long the numb feeling lasts. This is what happens at our office.

First, the topical: benzocaine

Before the injection, we place a numbing gel on the gum where the needle will go and give it a minute or two to work. The gel is benzocaine (brand name Candi-Caine), the same ingredient in over-the-counter toothache gels. It numbs only the surface. It cannot numb a tooth, but it takes the edge off the first pinch.

We dry the spot first, because the gel works better on dry tissue. It tastes medicinal and leaves the area feeling tingly and thick. Because it works only on the surface, you may still feel some of the injection, and how much it helps depends on where it is placed.

Tell us if you have had a reaction to a numbing medicine, or if you have a history of methemoglobinemia, a rare condition in which the blood carries less oxygen. We do not use benzocaine for children under two, or for anyone with that history. Blue or gray lips or skin, or trouble breathing after a numbing medicine, need immediate medical attention. [1]

Where the jelly helps, and where it helps less

How much the gel helps depends on where it is placed. It soaks in well where the tissue is thin, such as inside the cheek and lip and the gum fold above the upper front teeth. It helps least on the palate, where the tissue is thick and tightly bound down. In one study of topical anesthetic on the palate, the topical reduced the pain of the needle going in, but not the discomfort of the anesthetic being delivered. [9] Either way, the gel can reduce the initial pinch; it does not remove the sensations of the injection itself, and palate injections tend to be the ones patients notice most. We use pressure and slow delivery there, and the area goes numb quickly once the anesthetic is in.

The injectable anesthetics we use

We choose the anesthetic based on the procedure, how long it will take, your health history, and how you have responded before.

Lidocaine (Xylocaine) is the standard dental anesthetic and the one we reach for most. It starts working within a few minutes. The tooth is ready for treatment well before the numb feeling in your lip and cheek wears off. [2]

Articaine (Septocaine) also contains a small amount of epinephrine. We choose it for certain teeth and when a tooth needs more anesthetic than usual. [3]

Mepivacaine (Carbocaine) is the one we use without epinephrine, when a shorter period of numbness is better or when your medical history points that way. How long it lasts depends on the procedure and the injection site. [4]

If you have had trouble getting numb in the past, tell us. It changes how we plan your visit.

Which teeth and areas will feel numb?

Where we place the anesthetic depends on which tooth we are treating. The areas below are on the treated side. Nerve patterns vary from person to person, so we always check that you are numb before we start. [5, 6]

Patients sometimes ask why their lip or tongue feels numb when the treatment is on a tooth. The reason is how the nerves are laid out. An injection can affect a tooth’s nerve and nearby nerves that supply the lip, chin, cheek, or tongue. When we numb those nerves, especially with a block, everything they supply goes numb along with the tooth. That extra numbness is expected, and it wears off as the anesthetic does.

Local infiltration: numbs one tooth or a small group of neighboring teeth and the gum next to them. We use it most around upper teeth, and around some lower teeth as well.

Upper jaw

ASA (anterior superior alveolar): the upper central incisor, lateral incisor, and canine, and the tissue that supports them. Your upper lip may feel numb too.
MSA (middle superior alveolar): the first and second upper premolars, and sometimes part of the first molar. Some people do not have a separate MSA nerve; neighboring branches supply that area instead.
PSA (posterior superior alveolar): the upper molars. One root of the first molar sometimes gets its nerve supply from another branch and needs additional anesthetic.
Greater palatine: the palate and the palate-side gums near the upper premolars and molars. This numbs the tissue, not the teeth.
Nasopalatine: the front of the palate and the palate-side gums behind the upper front teeth, roughly canine to canine. This also numbs the tissue, not the teeth.

Lower jaw

Inferior alveolar block: the lower molars, premolars, canine, and incisors on that side. The lower lip and chin go numb too. The tongue and the tongue-side gum often feel numb as well, because the lingual nerve runs nearby. Front teeth can vary, because nerve supplies overlap there.
Incisive block: the lower premolars, canine, and incisors on that side, plus the lower lip, chin, and nearby gum.
Mental block: the lower lip, chin, and nearby lip-side gum. On its own, it does not numb the teeth. [7]
Long buccal block: the cheek-side gum and soft tissue around the lower molars. It does not numb the molar teeth themselves.

A numb lip or cheek does not always mean the tooth is fully numb. Pressure and movement are normal feelings even when a tooth is numb. Sharp pain is not. If something hurts, tell us and we will stop.

Why can a tooth be hard to numb?

Nerve pathways vary, and neighboring branches overlap. Inflammation works against anesthetic too: an infected or badly inflamed tooth is harder to numb than a quiet one. If a tooth is still sensitive, we give the medicine more time or add an injection in a different spot. You do not need to sit through pain while we work.

About epinephrine

Some cartridges contain a small amount of epinephrine. It narrows the blood vessels near the injection site, which keeps the anesthetic in place longer and reduces bleeding. [2, 3]

Some people briefly feel their heart pound or feel shaky afterward. Epinephrine can do that, and so can anxiety. Either way, tell us right away if you feel unwell, and always tell us if you have chest pain, trouble breathing, or dizziness that does not settle. [8]

Tell us about your health conditions, your medications, and any reaction you have had to an anesthetic or to epinephrine. That is how we choose the right medicine for you.

What the injection feels like

Most patients feel a pinch at the start, then pressure. We give the anesthetic slowly and give it time to take effect before we begin.

If you feel a sharp, electric sensation in your tongue or lip during an injection, tell us right away so we can pause and adjust. [1]

If anything hurts during treatment, raise your hand or speak up. We will stop and reassess.

Why we pull back first: aspiration

Before we inject, we briefly pull back on the plunger. This is called aspiration. If blood shows in the cartridge, the needle tip is in a blood vessel, so we reposition and check again.

Aspiration lowers the chance of injecting into a blood vessel. It does not reduce it to zero, which is why we also inject slowly and watch how you are doing, even when no blood appears. [2, 3]

While you are numb

Your lip, cheek, or tongue may feel large and heavy without actually being swollen. If you see real swelling, tell us.
Do not chew until the numbness is gone. It is easy to bite your cheek, lip, or tongue and not feel it happen.
Be careful with hot food and drinks. A numb area does not sense heat normally.
Watch children closely until the numbness wears off. Kids chew on and play with a numb lip or cheek.
Some drooling and slightly different speech are normal while you are numb. Both resolve as sensation returns.

How long does it last?

The tooth and the surrounding lip, cheek, or tongue do not always regain sensation at the same time. How long you stay numb depends on the medicine, the amount, and where we place it. With lidocaine (Xylocaine) and epinephrine, for example, the manufacturer describes tooth anesthesia lasting at least about an hour after an infiltration and at least about an hour and a half after a nerve block. Soft-tissue numbness lasts longer on average. Your experience can differ. [2]

Some people notice that numbness wears off sooner than expected; for others, it lasts several hours. Tell us if it has been difficult to stay numb during treatment, or if the numb feeling is lasting longer than you expected. If your lip or tongue is still numb the next morning, call us so we can assess it and follow up. You do not need to wait until morning to call about something that worries you.

The injection site may be sore afterward, and your jaw may ache from being open during treatment. Both usually improve on their own. Call us if soreness gets worse instead of better.

When to get emergency help

Call 911 for trouble breathing or swallowing, swelling of the tongue or throat that is increasing quickly, or collapse. Do not wait for a call back from our office. For a new rash or swelling after treatment, seek medical advice promptly and let us know what happened. [8]

Once your treatment is finished, our after-visit instructions cover what to expect after a filling, a crown, or a deep cleaning, including eating and drinking while the area is still numb.

My takeaway as a dentist

Getting numb is what makes the rest of the appointment comfortable. If you have had trouble getting numb, have reacted to an anesthetic before, or are anxious about the injection, tell us at the start of your visit. We will plan around it.

Questions about your appointment? Call us at 970-237-4313, and let’s talk.

References

Safety data sheets for the products we use are kept at our office and are available on request.