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Updated: Dec 7, 2020

Are you Mental or just Incisive?

Okay, I couldn’t resist the play on words with these injections. I know it’s a bad joke, but we need to find the fun when we can.

After listening to several of you it sounds like administering anesthetic over the mental foramen is the go-to mandibular injection for most hygienists. This makes sense since most patients have a good amount of deposit on the lower anterior teeth and this region is sensitive.

So, are you doing this injection correctly?

Actually, there are two different injections you can do over the mental foramen. Well kind of two. The Mental and Incisive injections are technically the exact same process except for ONE major step…PRESSURE.

When depositing anesthetic over the mental foramen the nerves which supply sensation to the lower lip and the mucosa of the anterior region are impacted. Generally, any soft tissue anterior to the mental foramen of the side injected will be numb. However, the pulp of these teeth is not impacted unless you apply pressure to the region after anesthetic is deposited. This pressure causes the anesthetic to flow into the mental foramen where it will bathe the incisive nerve. This nerve is what provides sensation to the premolars and anterior teeth.

So, how are these injections done?

Mental Foramen on Mandibular Model

First, identify the mental foramen. This can be done by evaluating radiographic images and palpation. In general, the foramen is between the 1st and 2nd premolars a few millimeters away from the base of the mandible. O.K. pause what you are doing right now and feel this region on yourself. I'm serious give it a try. When you do, you may feel a little twinge into your lip and maybe even your teeth. You might even notice a small knotty cluster of nerves and vessels in that area. This is a good sign that you are in the correct spot.

I prefer to use a short needle for this injection, but you can use a long one if you already have it out and available (just make sure you remember you are using a long). The goal is to deposit the anesthetic above the mental foramen. I prefer giving this injection from the 12 o’clock position so the barrel is almost parallel with the midline. I know there are those who prefer to sit in the front of the patient and inject with the barrel more inline with the occlusal plane. Either way is fine. I just like the first method because I can really create an open space by pulling the lip out away from the teeth and gain extra stabilization with my retraction hand.

Insert about 4-6 mm
Incisive Depth of Insertion

After inserting the needle about 4-6 mm (depending on the patient’s anatomy) deposit your solution. Generally, about one-half cartridge will work. Articaine is a great option for this injection. Immediately after depositing the solution you'll notice a bolus of anesthetic in the area you injected. Once you've capped your needle, quickly apply pressure to the injected area and massage the solution into the mandibular canal. This step pushes the anesthetic into the foramen where it can bathe the incisive nerve, allowing for greater pulpal anesthesia. If you don’t apply pressure you have given a mental injection, which will not provide profound anesthesia to the pulps of the teeth.

Here is another kicker we must remember, neither the mental nor incisive injection will anesthetize the sensitive lingual tissue. While using an anesthetic like Articaine could aid in profound anesthesia it might not impact the lingual tissue. To ensure lingual tissue anesthesia you have a couple of options.

Applying topical versions of anesthetic could work, but it may not be profound. You could do an infiltration of the lingual tissue in the zone you are working (most people don’t like that) or go ahead and do an IA injection. Please note that there have been cases when using articaine (Septocaine) patients have noted lingual anesthesia.

Some items to remember when doing the mental/incisive injection…

There is a high rate of positive aspiration in this area. I encourage you to aspirate a couple of times before depositing. Due to the high vascularity, it is likely for the patient to develop a hematoma as well. In my opinion stabilization is crucial to your success. It is easy for the needle to slide a little further while you are depositing. This could impact the effectiveness of the injection. Also, I have yet to see it personally, but I have heard enough stories about someone penetrating right out of the cheek. While this isn’t a major complication, it does make for an uncomfortable situation. Creating an open space with the vestibule, having strong stabilization and aspirating will help avoid all these complications.

Stabilizing the barrel will keep you in the correct location.
Barrel Stabilization

I can’t wait to hear if you are mental or incisive (hahaha)

Go out there and give your best shot!



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