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IMDO™ | Your questions answered

IMDO is a unique surgical process designed specifically to treat adolescents with a small lower jaw. IMDO describes not just the surgical process, but also the wider philosophies for ideal treatment of the small lower jaw.

A small lower jaw is typically described by dentists and orthodontists as a class II malocclusion, which is essentially an observation that the bottom teeth are further back in the mouth than they should be.

A class II malocclusion looks like the upper arch of teeth is too big for the lower arch. It can appear that your child has too many teeth for their mouth, they have obvious dental crowding, and their upper front teeth are too big.IMDO-Short-Lower-Jaw-Surgery-Overbite-Orthodontic-BuckyTeeth-WeakChin-Sydney-Newcastle-1.jpg

IMDO identifies and treats the underlying cause of the condition, which is purely a lack of jaw growth. The simple and logical reason that all the lower teeth sit further back in the mouth, is because the lower jaw has failed to grow.

What does having a small lower jaw really mean?


The causes of a small lower jaw are complex and many, but the most common one we see is AMHypo. AMHypo is a medical diagnosis, and simply means the front part of your child's jaw is too small, and has not grown enough.

Having a small lower jaw leads to significant teeth crowding, and the impaction of teeth, most notably the wisdom teeth. Teeth that are impacted are unable to erupt in the mouth, and cause damage to the other teeth as well as infection.

The upper jaw and the nasal airway are often narrow, and there is usually obstruction of the major airway behind the tongue. This causes problems with breathing, sleeping, and snoring, and increase the risk of future sleep apnoea.

A small lower jaw has other primary effects, such as speech difficulties, inability to chew normally, and poor jaw or neck posture. Secondary issues may include behavioural changes, poor concentration, and daytime sleepiness.

It is important to remember that a small lower jaw is a medical diagnosis, and not just a dental one. Looking at your child's teeth is but one of many important factors to consider when evaluating how best to treat them.

How does IMDO surgery work?


IMDO™ is a means of growing and lengthening your child’s lower jaw. By growing the lower jaw to a correct size and proportion, and at the right age, it is possible to almost completely eliminate the many effects of AMHypo.

IMDO™ works by growing the lower jaw between the 1st and 2nd molars. There is an increase in not only the length, but in the width and depth as well. There is an 3 dimensional increase in the size of the lower jaw.

As new bone is growing between the molars, room is created to help decrowd the lower teeth. There is a good possibility that wisdom teeth may grow and erupt normally, allowing your child to keep all of their teeth.

There are other health reasons to correcting a small lower jaw. The most medically oriented is that it brings the main muscles of the tongue forward. This opens, or rather “tents” the major airway behind the tongue.

Improved airway tenting prevents collapse of the airway while sleeping. Improving sleep, and particularly REM sleep, improves daytime alertness. Upper airway tenting should have an effect on breathing while exercising.

There is evidence that snoring in adults is strongly associated with having AMHypo. Correcting the condition at an early age eliminates adolescent snoring, which minimises the risk for future sleep apnoea development.

What changes can I expect with IMDO surgery?


Changing Facial Appearance The facial profile will have noticeably changed by the end of the first week. As the chin point advances, the jaw line becomes more defined, and the skin under the chin becomes more taut. 

There is an increase in lower lip prominence, and the appearance of the nose, lips and chin should becomes more balanced. The sense of prominent upper front teeth will disappear, as the relationship between the teeth normalises.

Changing Airway Volume Your child should almost immediately stop snoring, and breathing during sleep will become naturally easier. With exercise, your child should expect immediate improvements to their breathing.

Maximising the IMDO™ distance, maximizes the amount of upper airway tenting that can be achieved. It is airway tenting that prevents snoring, and enables increased airflow and breathing rate during exercise.

Changing Bite Relationship The change in your child's bite will be the first thing they notice. The lower front teeth move gradually further forward, and a gap appears between the lower molars. 

Gum and bone will be filling the space between these teeth, and surrounding skin, muscle and nerves will be stretching and growing. Though the changes are subtle, crowded teeth are already starting to shuffle, erupt and unwind. 

For some, lower teeth will land normally behind the upper front teeth, some will be edge-­to-­edge, and others will have a subtle “under­bite”. The final position is determined by assessing the facial profile and airway changes. 

Changing Tongue Position The tongue and upper airway are pulled forward and upward with the advancing lower jaw. As the lower jaw becomes longer and wider, the tongue lifts up and stretches forward.

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This gives a feeling of the tongue becoming smaller or having more room, as the inside of the mouth becomes larger. There should be no change to speech, however pre-existing difficulties with lisping may improve.

Changing Jaw Posture People with large overbites tend to push their lower jaw forward. Forward jaw posturing helps relieve airway obstruction and breathing issues, improve facial appearance, and normalises the bite. 

Abnormal jaw posturing may lead to tension headaches, and jaw joint symptoms. Jaw posturing is a hard habit to break, and unless you are aware of its presence, the distance achieved with IMDO™ might be underestimated.

Changing Neck Posture Bad neck posture is common in people of all ages with short lower jaws. Forward head posturing is needed to open the major airway behind the tongue, to relieve airway obstruction and enable breathing.

There is a rounding of the shoulders that can lead to abnormal growth of the spinal column in the neck. As the lower jaw advances with IMDO™, forward head posturing to overcome airway obstruction is no longer required. 

How does IMDO compare to conventional orthodontics?


A small lower jaw is typically described by dentists and orthodontists as a class II malocclusion. This is simply an observation that the bottom teeth are positioned further back in the mouth compared to the top teeth.

A class II malocclusion looks like the upper jaw of teeth is too big for the lower. It may like your child has too many teeth for their mouth, that they have obvious dental crowding, and that their upper front teeth are too big.

The common orthodontic treatment of a class II malocclusion, is to convert it to an ideal class I occlusion. The aim is to position the upper incisors just in front of the lower incisors, so as to eliminate the large overbite.

Their are two ways of achieving this, and this depends on how the condition has been orthodontically diagnosed. The classifications are somewhat arbitrary, and skew treatment towards two primary forms.

The cause of the class II malocclusion may be determined as "maxillary protrusion", where the upper jaw has grown too far foward, or "mandibular retrusion", where the lower jaw hasn't grown forward enough.

Jaw Surgery is used to treat "mandibular retrusion" by advancing the lower jaw and aligning it with the upper jaw. The Bilateral Sagittal Split Osteomy (BSSO), is a cut at the angle of the jaw, that allows the front of the jaw to slide forward.

This is carried out once jaw growth has finished, typically around the age of 18. Around one year of orthodontic treatment is required beforehand, to move the teeth into a position where the jaws can then be surgically aligned.

Elastic bands are worn for a number of weeks after surgery, to fix the upper and lower jaws together, keeping them in a stable position. It can take up to 3 months or more for numbness to disappear, and normal jaw function to return.

With "maxillary protrusion", orthodontic treatment is used in isolation to pull the upper front teeth backwards. Teeth are taken out to create the space to pull the upper teeth back, and to a small extent move the lower teeth forward.

In addition to the removal of teeth, devices are often used to push the lower jaw forward. The theory is that dislocating the developing jaw joints will stimulate growth of the lower jaw, by increasing the length of the jaw joint.

An alternative view is that the jaw joint finds a new physiological position that is in a more forward location. Despite numerous studies to prove the success of such treatment, there is nothing to date that supports it.

Can IMDO be performed in adults?


Whilst IMDO was initially designed to treat adolescents in the early to middle teenage years, the procedure has proven to be successful in adult patients of an increasingly broad age range, and for more diverse medical conditions.

The options for surgically advancing the lower jaw are currently limited to the BSSO, which provides some benefit to increased airway volume and alignment with the upper jaw, but is limited by the amount of forward jaw advancement.

IMDO allows for a significantly greater degree of jaw advancement, and unlike the BSSO which increases only the length of the lower jaw, IMDO provides a 3-dimensional increase to the width, length and depth of the lower jaw.

This is significant because it means a more substantial increase to the volume of the primary airway behind the tongue, with greater improvements to breathing and the potential elimination of sleep-disordered breathing.

IMDO advances the jaw gradually over a number of days, and the effects of an enlarging airway on breathing can be measured. The point at which airway obstruction is eliminated can be determined precisely.

What is the IMDO process?


IMDO™ is a combined process that is managed by both your surgical specialist and orthodontic practitioner. The first aspect is a detailed consultation with your IMDO™ surgeon, which involves an extensive examination and history.

Clinical photography and digital models of the teeth are taken to assess your child's bite and jaw relationship. 3D Facial Imaging is used to analyse in detail the effects their jaw growth has on the airway, teeth, and facial structures.

The pre-IMDO™ phase is coordinated by your orthodontic practitioner. This involves two key aspects, the widening of the upper jaw (palatal expansion), and the forward positioning of the upper front teeth

This produces an upper jaw that is big enough to allow for the healthy eruption and retention of the biggest number of teeth. It also maximises the amount of jaw distraction that can be achieved with active-IMDO™.

The active-IMDO™ phase involves a conservative surgical procedure where a small separation is made between the 1st and 2nd molars, and growth stimulating devices called Coceancig distractors are placed.

Your child will have a 1-2 night stay in hospital, after which they will see us to begin distraction. We will show you the parents how to turn the distractors, and you will be able to continue and finish the process at home.

Two turns a day per side grows the lower jaw by 1mm, so a distance of 12mm will take exactly 12 days. The distractors are in place for around 40 days to let the new bone solidify, after which they are removed in a minor procedure.

Everything will then be removed from your child's mouth, allowing their jaws and face to continue to grow normally. The aim is not to have appliances in the mouth for extended periods of time, as they may restrict normal facial growth.

Your child's teeth should begin to naturally decrowd and align, and gradually settle into a normal bite. Most children will still need a short period of orthodontics after IMDO™, to obtain the perfect alignment of their teeth.

What is the recovery from IMDO surgery like?


IMDO™ is more conservative than other forms of surgical jaw advancement. The healing process is quicker and the recovery times shorter. Elastics are not required to hold the jaws together, allowing you to still eat and speak.

A number of medications are prescribed to aid in the recovery process. Antibiotics will minimise the chance of infection, anti-inflammatories will reduce any swelling, and painkillers will minimise possible discomfort.

Dietary supplements are recommended to maintain energy levels and digestive function. Sustagen, Ensure and Up&Go are available for use as meal replacements, and multi-vitamins such as Berocca can be of benefit.

Immediately following the IMDO™ operation you should experience… 

  1. Mild­ to moderate lower facial & lip swelling  
  2. Mild­ to moderate lower jaw discomfort & general chin & lower lip numbness  
  3. Sutures (stitches) along the inside of the lower back of your mouth & inside your lower lip  
  4. In some cases, you may have a single suture on the outside of each lower cheek. 

These immediate effects of surgery are normal, temporary, and last only a few weeks. As active IMDO™ proceeds there should be gradual changes, as discomfort eases, swelling settles, and the bite and profile noticeably improve.

Are there any risks with IMDO surgery?

While IMDO™ is by design a highly conservative surgical process, it is still important to remember that any surgical procedure carries an element of risk, despite all the measures taken to minimise possible complications.

The general risks associated with IMDO™ surgery are:

Numbness | Generally, the most feared complication is damage to the main sensory nerve within the jaw bone. Whilst this has never been known to occur, it does remain a possibility. It is important to stress that the operation is specifically designed to avoid this from occurring. 

It is possible to bruise or stretch that nerve, like the funny arm you get after hitting your funny bone nerve in your elbow. Bruising of the lower jaw nerve will produce a temporary numbness in your child’s lower lip and chin, which can take from days or weeks to resolve.  

Loss of teeth | Rarely, the “separation” passing through bone can involve adjacent molar teeth. Without IMDO, severely crowded teeth are usually doomed to later surgical removal. 

The small risk that the "separation" may lead to molar loss, is matched against the much higher risk that molar teeth are removed anyway due to the complications caused by dental crowding. 

IMDO™ is designed to increase the length of the lower jaw, and create the space for already crowded teeth to erupt. IMDO™ does not guarantee that all teeth will be kept, but the chance of keeping all your teeth with IMDO™ then without is much higher. 

Infection | Titanium is an inert bio-material, and is usually well tolerated by the body. The titanium distractors contain nooks and crannies where bacteria and food can hide, and which can produce local swelling & infection. 

The possibility for this occurring is reduced by use of chlorhexidine and hot saline mouth soaks, and by the judicious cleaning of your teeth using tooth paste.

Anterior Open Bite | In technical terms, IMDO™ works best where there is a deep overbite, a long overjet , and a near-scissor molar bite . IMDO™ corrects overjet very well, but it also acts to reduce overbite. 

Open bite occurs where the front teeth do not touch in a natural “closed” jaw position. If your child has a shallow overbite, and because of how their back teeth touch, IMDO™ can turn a small open bite into an obvious one, even with the overjet being corrected. 

Most cases of open bite resolve spontaneously with a short period teeth settling, and sometimes with mild orthodontic intervention.

The bite is changing and adding new forces on the distractors. Whilst the distractors are designed to resist these stretching forces, excessive chewing and biting pressure can cause them to pull away from bone. 

It is important that your child not eat solid food, attempt biting, or engage in contact sports while the distractors are in place. 

After IMDO finishes | Like keeping the same sized shoes on growing feet, keeping orthodontic appliances in a young growing mouth for long periods can lead to abnormal face and dental growth restriction. Growth restriction is the opposite of what IMDO™ wishes to achieve. 

Crowded teeth should naturally de-crowd and align, and normal chewing forces will settle your child’s teeth into a natural bite and close any gaps. Normal orthodontic braces are usually required in the future to produce the perfect alignment of teeth. 

Wisdom teeth | Eventually, wisdom teeth will develop and attempt to erupt. IMDO™ aims for the natural eruption and function of these teeth. Rarely, wisdom teeth may need to be removed, but such advice should be carefully considered with your treating IMDO™ specialist.

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‘Any surgical or invasive procedure carries risks. Before proceeding, you should seek a second opinion from an appropriately qualified health practitioner.’ 

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