Vital Structures around Mandibular Third molar

Updated: Mar 15, 2020

There is a well-known saying among surgeons.

"A surgeon is as good as his anatomy"

I can’t agree more with these words.

I always say that performing a surgery is like driving and knowledge of human anatomy is like looking ahead while driving.

While driving, Your eyes are always on the lookout for thing to avoid crashing into.

If you drive blindly, you will surely crash your car into something or someone.

Not having knowledge of anatomy is like driving blindly.

If you do not possess the good knowledge of anatomy while performing a surgery, sooner or later you will end up with a surgical complication.

Surgical removal of Mandibular third molar is one of the most common surgical procedure performed by a dentist.

So, it is important to have good knowledge of the surgical anatomy the region.

Today I will be talking about the important vital structure that we may encounter while performing the surgical removal of the mandibular third molar.

The structures that I will be focusing on in this article are –

  • Mandibular Canal (Inferior Alveolar Neurovascular Bundle)

  • Lingual Nerve

  • Facial Artery

These 3 structures, if damaged, will lead to some serious complications.

So, without wasting much time. Let’s get started.

Mandibular Canal

Mandibular canal houses the Inferior Alveolar Neurovascular bundle which includes Inferior Alveolar nerve, artery and vein.

During surgical removal of Mandibular third molar, injury to the inferior alveolar nerve is one of the most common intraoperative complications.

We all know that injury to Inferior Alveolar Nerve will lead to lower lip paraesthesia.

Injury to Inferior Alveolar Nerve causes paraesthesia of the ipsilateral lower lip

This complication occurs intraoperatively, but its consequences are felt when the effect of Inferior Alveolar Nerve Block fades away (which is postoperative).

But, as I mentioned earlier, Inferior Alveolar Nerve is accompanied by Inferior Alveolar artery and vein.

So, injury to Inferior Alveolar Nerve mean that there is injury to these blood vessels.

The injury to these blood vessels will lead to excessive intraoperative bleeding from the socket.

This will lead to less visibility due to the blood in the surgical field. Also, if the bleeding is not controlled on time then it may lead to syncope.

Having said that, I would say that bleeding in this case is a good thing.

Two separate studies published by Dr. M. Anthony Pogrel in 2009 and by Dr. Jay D. Matani in 2013 shows that in majority of the cases the veins are placed superior to the nerve inside the mandibular canal. While artery is placed superior or at the same level to that of the nerve.

Inferior Alveolar Vein & Artery are usually placed superiorly to the Inferior Alveolar Nerve

If you accidentally open up the mandibular canal while bone cutting, you will first encounter the blood vessels and then the nerve

So, when you encounter sudden excessive bleeding (while bone cutting), if you stop at that point the chances are that you may prevent injury to the nerve.

So how do we prevent injury to the Inferior Alveolar Nerve?

Always have a radiograph of the mandibular third molar you are removing. From the radiograph, you will have an idea of the position of the Inferior Alveolar Nerve.

If you want to know if the nerve is buccal or lingula to the roots, you can go for the Frank’s Tube Shift Technique. I have posted a video on Frank’s Tube Shift Technique on our YouTube channel and the blog page.

If you want to know the exact location of the nerve, then a CT scan or a CBCT would be the best option.

Once you know the position of the nerve from the alveolar crest, you should try to avoid it while bone guttering.

While tooth sectioning, you should not cut the tooth through and through

Always leave 1-2 mm tooth structure and then fracture it using the Coupland elevator or a straight elevator.

Then take out the fractured crown followed by the root.

Tooth is sectioned and fractured without damaging the Inferior Alveolar Nerve

Leaving 1-2 mm tooth structure ensures that you are not pushing the surgical bur into the bone which increases the chances of Inferior Alveolar Nerve injury.

By avoiding entry into the bone you ensure that you do not damage the nerve while tooth sectioning.

Lingual Nerve

Lingual nerve supplies the general sensory innervation and special taste sensation to the anterior 2/3rd of the tongue. It also supplies the lingual mucoperiosteum and floor of the mouth with the general sensory innervation.

A study by Dr. Kiesselbach JE in 1984 shows that the mean distance of the lingual nerve from the alveolar crest inferiorly is 2.28 mm while the mean distance medially 0.58 mm from the lingual plate.

Lingual nerve is in close contact with the lingual plate of the mandibular third molar socket. Only a thin periosteum is present between them.

The thin Lingual periosteum is the only thing that separates the Lingual nerve and the lingual plate to be in direct contact.

So how do we prevent lingula nerve injury?

It is actually very simple. Just don’t do any lingual instrumentation.

In my experience, there is no need of reflection of lingual mucoperiosteum for surgical removal of mandibular third molar. So, no instrumentation is required on the lingual soft tissue.

Also, while placing the incision make sure that your distal releasing incision should be directed buccally towards External Oblique Ridge.

The reason for this is that the ramus is at an angle to the body region of the mandible. So, if your distal releasing incision is directed straight posteriorly then your blade may slip and damage the lingual nerve.

Distal releasing incision should be directed buccally towards External Oblique Ridge

Another reason for injury to the lingual nerve is the damage from the surgical bur while tooth sectioning.

As mentioned earlier, while tooth sectioning, leave 1-2 mm tooth structure lingually and then fracture it using the Coupland elevator or a straight elevator.

Tooth is sectioned and fractured without damaging the Lingual Nerve

This would prevent the slippage of the surgical bur lingually and in turn prevent lingual nerve injury.

Facial Artery

It is a branch of external carotid artery.

In the first and second molar region just anterior to the anterior border of Masseter muscle, it curves upwards over the body of the mandible.

Facial Artery curves upwards over the body of the mandible in the first & second molar region

Buccinator muscle and buccal mucosa separates the facial artery from the oral cavity.

While placing the anterior releasing incision, your blade may slip and pass through the buccal mucosa and damage the facial artery and that is something no dentist would want to happen in his clinic.

Facial artery haemorrhage can be controlled only by ligating the facial artery and this requires the proper operation theater.

So how do we prevent an injury to the facial artery?

While placing the anterior releasing incision, your hand should be steady and you should always take support from the adjacent structures using your little finger.

If you do not have adequate experience then I would suggest you start your anterior releasing incision inferiorly and move superiorly away from the buccal sulcus.

Anterior releasing incision should be started inferiorly and extend superiorly away from the buccal sulcus to prevent injury to Facial Artery

This way you avoid the chances of slippage of blade into the buccal sulcus and thus preventing injury to Facial Artery.

There are other less important vital structures that are present around the third molar.

They are Temporalis Muscle, Buccinator Muscle, Superior Pharyngeal Constrictor Muscle, Mylohyoid Muscle, Buccal Nerve and Mylohyoid Nerve.

Injury to these structures does not lead into any major intraoperative or postoperative complications hence I did not go into details of these.

So now you know what you should keep in mind regarding the vital structures while performing surgical removal of the mandibular third molar.

Let me know in the comment section if you had any such complication at your clinic and how you managed it.

Also, do let me know what topics would you want me to write about in future.

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