Why is a topical anesthetic used before a dental injection?

That dab of gel on your gum right before the shot has a job. It’s a topical anesthetic, and it numbs the surface of the tissue so the needle’s entry may feel more comfortable.¹ It doesn’t replace the injection, but it can make that first step a little easier on you. 

What you'll learn in this article: 

• How numbing gel helps with the surface pinch of an injection 

• Why your tooth may still need deeper numbing 

• What happens between applying the gel and starting treatment 

• What to share with your dentist about past reactions and injection anxiety 

Have questions about getting numb? Schedule an appointment with an Aspen Dental provider to discuss your comfort options before treatment begins. 

What does topical anesthetic do before a dental injection? 

Topical anesthetic acts on the outer layers of tissue inside your mouth. Ingredients such as benzocaine or lidocaine temporarily reduce sensation there. Applied before an injection, it may lessen the discomfort of the needle entering the tissue.¹

Think of it as preparation for the injection. The gel doesn’t reach far enough into the tooth to numb the tissue inside it.¹ That means a numb patch of gum isn’t a sign that your tooth is ready for a filling. 

It also doesn't promise a completely painless shot. You may still notice a pinch or pressure. If something hurts, let your dentist know rather than trying to sit through it quietly. 

Why do you still need a numbing injection? 

Injected local anesthetic numbs a specific area by stopping the nerves there from sending pain signals. Dentists use injections for procedures such as fillings and crown work, where surface numbing alone isn’t enough.² 

The medication is placed near the nerves serving the area being treated, and knowing the anatomy helps the dentist place it properly. Depending on the injection, it may affect one small area or a wider part of your mouth.¹ 

The gel and the injection do different jobs: The injection is what provides the anesthesia for the planned work. Afterward, your dentist allows time for it to take effect and checks your comfort before proceeding. 

What can you expect when numbing gel is applied? 

Your dental team places a small amount of gel on the gum where the injection will go.¹ Using only the amount needed helps keep the dose low.¹^,³ 

You'll wait briefly before the injection. The timing depends on the product and where it's applied, so there isn't one waiting period that fits every visit.  

You may notice the product's taste or a change in how that patch of gum feels. Let the team know if the sensation bothers you. They can explain what's happening and check the area. 

When it's time for the injection, keep using the communication plan you've agreed on. A raised hand can let your dentist know you need a pause. Having gel applied doesn't mean you have to ignore discomfort afterward. 

Is topical anesthetic used before every dental injection? 

Not always. Your dentist builds an anesthesia plan around you, looking at the treatment you need, your health and allergy history and how anxious you feel.² The product and injection site also matter. 

If gel helped at a previous visit, say so. If you'd prefer to avoid it because of an unpleasant experience, explain what happened. Your dentist can talk through the options and whether topical anesthesia makes sense for the planned injection. 

Not using gel by itself doesn't tell you how carefully your care is being managed. It's reasonable to ask, “What will you do to help keep this comfortable?” 

What should you tell your dentist before getting numbed? 

A quick conversation before treatment gives your team useful information. Mention: 

• Previous reactions: Describe what happened, how soon it started and whether you needed medical care. Include reactions to gels, sprays or injections. 

• Health conditions and medicines: Share your medical history, known allergies and current medications, including any numbing products you've used yourself. 

• Injection anxiety: Explain what worries you most and whether you want each step described before it happens. 

If fear has made it hard to book, there are ways to plan dental care when you're afraid of needles. You can bring this up when scheduling rather than waiting until you're in the chair. 

Topical products still need precautions. Benzocaine can rarely cause methemoglobinemia, a serious condition that reduces oxygen delivery in the blood.¹ The label on one dental benzocaine gel says to stop using it and get immediate medical attention if you or a child in your care develops pale, gray or blue skin, shortness of breath, a rapid heart rate, headache, dizziness or fatigue. It also notes this can happen even if you’ve used the product before.³ 

To talk through a numbing plan for your next visit, schedule an examination with your local dental provider. 

Why is a topical anesthetic used before a dental injection? FAQs 

Does topical anesthetic only come in gel form? 

No. Dental topical anesthetics also come as liquids, ointments, sprays and patches.¹ A different form doesn't automatically mean stronger numbing. Ask which product your dentist plans to use if you've had a preference or concern in the past. 

Can children receive topical anesthetic before a dental injection? 

Yes, when appropriate. The dentist considers the child's age, weight and medical history when selecting anesthesia and the amount to use. Benzocaine should not be used in children younger than 2.¹ Ask your child's dentist which product is planned rather than applying a numbing gel yourself beforehand. 

Can you still receive anesthesia after a previous reaction? 

Possibly, but the reaction needs to be reviewed first. Your dentist may need records or allergy testing to identify an appropriate option. A past reaction doesn’t establish that every anesthetic is unsafe, and your dentist needs to review the details before choosing a different product.¹ 

Should you use a toothache gel before your appointment? 

Ask your dental team first. Some store-bought gels contain ingredients, such as benzocaine, that are also used in dental settings.¹ Applying extra medication isn’t a substitute for the office’s numbing plan. If you’ve already used a product, bring its name and tell the team when and how much you applied. 

Sources 

¹ American Academy of Pediatric Dentistry, The Reference Manual of Pediatric Dentistry: “Use of Local Anesthesia for Pediatric Dental Patients.” https://www.aapd.org/globalassets/media/policies_guidelines/bp_localanesthesia.pdf 

² American Dental Association, MouthHealthy: “Anesthesia and Sedation.” https://www.mouthhealthy.org/all-topics-a-z/anesthesia-and-sedation/ 

³ National Library of Medicine, DailyMed: “Bencocaine Topical Anesthetic- benzocaine gel.” https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=89b7e919-2656-4b1b-ab5c-5b11d42b52f3