Masterclass

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Complete Reflection

Tapan Patel (TP):

John, I want to focus now on surgical options for the chin. If I speak for myself, I can tell you I could write everything I know about chin surgery on the back of a very small postage stamp. It’s not something I’ve really ever had any training on, but I think now we’re getting into that era where many of our patients have either had surgery or might be contemplating it, and I think what would be really useful is to just give us an overview of some of these techniques and what’s involved. I think it might help us with referrals and it will help us understand what some of our patients have already had. If you could just kindly give us an overview.

John Blythe (JB):

Certainly. So there are three approaches that I will touch upon. One is the mandibular osteotomy, one is the genioplasty, and then the final one is chin implants, which may be customised or off the shelf.

TP:

Sure.

JB:

So let’s go back to the beginning and the mandibular osteotomy. In a number of patients that will be turning up to the clinic requesting chin or jawline augmentation, they may have an abnormality with the position of their jaws, whether it is the upper jaw and the lower jaw or just the lower jaw in combination, and running alongside that they may have a dental malocclusion, so an abnormal bite. If, for example, the lower jaw is several millimetres, let’s say 5-7mm, behind what is normal – and I’ll discuss the classifications a little bit later – then surgery can address and improve the bite, so improve the function, and if you get the teeth and the jaw into the right position then the chin should follow, providing that the chin is in normal proportion.

TP:

So this is the mandibular osteotomy? And you’ve got a little mandible there resting on your knee; in layman’s terms, tell me exactly what you would do during this procedure.

JB:

The patient is under general anaesthesia –

TP:

I should hope so!

JB:

– and the patient will have had some presurgical orthodontics beforehand because the soft tissues around the teeth; the cheeks, the lip, the tongue, etc., will have moulded the teeth from an abnormal position into as best a bite as possible to compensate for the abnormal disparity between the jaw. The orthodontist may spend 12 to 18 months realigning the teeth, rounding out the arch, and getting the jaw ready so when you move the lower jaw to meet the upper jaw, everything fits snugly.

TP:

Understood.

JB:

When the patient is asleep, local anaesthetic is infiltrated around the posterior part of the jaw and ramus and a very fine incision is made on the outer part of the mandible near to where the wisdom tooth would be lying. The ramus, which is the vertical part of the jaw, is exposed, and the medial aspect is dissected, so you’re dissecting underneath the periosteum. With this view here, you will see the lingula and the foramen here for the inferior alveolar nerve and the artery and adjoining vein, a structure here which is an aperture. This is where the inferior alveolar nerve and the vasculature running in to supply the teeth is entering the jaw. This is the structure that we must protect at all times.
With a long bur or a piezoelectric saw, you’re just gently making a cut just above that area, either all the way back to the border or just in front. If you think about it as a little bit like a Crunchie bar, where you have an outer layer of chocolate and honeycomb in the middle, we are only wanting to go through one layer of the cortex. That cut is then brought forward, and then you continue the cut on the external oblique ridge to the second molar, where a vertical osteotomy is made to the lower border. It’s important that you go through the dense bone of the lower border. Once you have created your osteotomy through the cortex of the bone, you’re working away from the roots of the teeth and you’re working within very, very tight dimensions so that you’re not damaging the nerve which supplies sensation to the gums, the lips, and the chin area, and then once you’ve made the initial osteotomy, you use osteotomes to propagate the fracture –

TP:

What are osteotomes?

JB:

They’re like very fine chisels, surgical chisels.

TP:

Okay.

JB:

So you’re initiating – by just going through the cortex with the burs and then using the osteotomes – so it’s like slicing a piece of wood down the grain; you’re using the chisels to just very carefully fracture, and what you will then get is a proximal fragment which is the ramus and the condyle, which is the jaw joint. You’ll then get the distal fragment, which is the tooth-bearing section. For patients who have a short or deficient lower jaw and chin, the tooth-bearing segment is then advanced.

TP:

What sort of distance can it be advanced?

JB:

Treatments of up to 8 to 10 mm are possible.

TP:

So quite substantial?

JB:

Yes, the average movements are probably between 4 to 7 mm. If the patient has an over-pronounced chin and jaw then you can slide it back. Once you have got the jaw and the tooth-bearing areas into the right position, you then attach it to the upper jaw by temporary elastics or some wiring and that will give you a stable structure to then place mini plates and screws to hold the new position together.

TP:

Okay, so the patient’s had the procedure, what’s their recovery – what are the main factors? How long before they can resume normal activities, like eating, etc.?

JB:

A lot of people in the country will have had their wisdom teeth out and know that they probably will have had 3 to 5 days of downtime and relaxing at home. It’s similar, it’s going to be 3 to 5 days of quiet time at home with regular pain relief and maybe some antibiotics and an antiseptic mouthwash. They need to be on a soft diet for 4 to 6 weeks during that period. 80% of the swelling, which would be similar to having wisdom teeth out, will go within about 2 weeks, and then the residual 20% may take 6 to 8 weeks to fully go. However, all patients are a little bit different but provided that they carry out meticulous post-operative instructions, then they should do very, very well.

TP:

I’m surprised! I would have thought, just from the description of the surgery, that the downtime and recovery would be much longer, so that’s quite encouraging that you’re talking about a resumption of normal activity so soon, which is great for the patients. Is there anything relevant to that that you would want to share with us?

JB:

I think the timescale, you have to be aware that you have to invest a lot of time with this, so the orthodontics may require 12 to 18 months of decompensation and starter treatment, then you have surgery, and then you might require a further 6 months of fine-tuning of your bite with the orthodontics before your braces are removed. Certainly, with any surgery, there are side effects and complications, and as I talked about earlier, the inferior alveolar nerve is something that we pay a lot of respect towards, but there is a percentage after surgery that may notice temporary pins and needles or numbness to the lower lip and chin area. This can have a knock-on effect socially, but should in the majority of cases recover fully.

TP:

Is there any risk of damage to the marginal mandibular nerve?

JB:

There are probably 1 or 2 cases worldwide but if you’re working within the envelope that I’ve discussed there you are a long way away from the facial nerve.

TP:

Fabulous, okay. So just to summarise, and do correct me if I’ve got this wrong, this is going to be your gold standard approach for somebody who’s presenting with chin and/or jaw issues but has an impairment to their bite?

JB:

Yes, so this is really set aside for patients who have what’s known as a Class II malocclusion or a Class II skeletal pattern when the lower jaw is smaller or in a more retrograde, retruded position compared to the upper jaw.