There was a time that almost all orthodontic patients had healthy teeth extracted.
There was a time that no one cared, or really knew about how faces grew. And there was a time that no one recognised the importance of the airway and how breathing is affected by how faces grow.
The new view is that the airway is ALL important, more important than a healthy bite. New developments have come into how orthodontics is practised. Slowly but surely, these ideas are entering into the public consciousness as well.
These exciting developments are less about teeth, and more towards an understanding and manipulation of the facial skeleton. When thinking about a bad bite or smile, people usually vocalise the problem in terms of their teeth.
But there is an increasing community expectation that treatment involves much more than just how to straighten front teeth, and more about how to straighten and correct the proportion of the face.
Preserving teeth. Understanding snoring. Looking at facial symmetry or proportionality. Assessing jaw joint health. Understanding facial appearance.
Having a small lower jaw seems to be at the heart of many dental problems we see today, and IMDO™ addresses the fundamental cause that intimately connects all of these considerable issues.
What is IMDO™?
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™ 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.
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.
Further information on IMDO™
There are many known, though rare causes of a small lower jaw. You may have heard of Hemifacial microsomia, Treacher Collins, or Sticklers Syndrome.
Fortunately these are very rare "genetically determined", or "embryological causes" of small lower jaws.
More common, are some still-rare medical conditions that can adversely affect how the child's lower jaw would have normally grown.
Juvenile Rheumatoid Arthritis (JRA) can cause disruptive or even frankly destructive effects to growing jaw joints.
Vitamin D deficiency (Rickets) or frank malnutrition can also affect how the lower jaw & teeth can normally, or abnormally grow.
Occasionally a fall on the chin, often as a child, can bruise the jaw joint too. This can lead to asymmetrical & abnormal growth of the child's lower jaw.
But these rare causes do not explain the very high frequency of small jaws that we see in most modern societies.
If you look around you, you will see that almost all people can be facially characterised by the size & shape of their jaw line.
Broadly speaking they can be...
1. Very large.... which happens to be relatively rare. About 1-3% of people have a proportionally larger lower jaw compared to their upper jaw
2. Normally shaped & proportional... which we think would be the most common
3. A diminutive or relatively smaller lower jaw... & finally
4. The very small lower jaw
There really are no scientific statistics that count the number of small lower jaws in our communities, or in which age or ethnic groups they may more commonly fall. But you only need your own eyes to figure it out.
To do this, you need to count the numbers alone, to yourself. Sit quietly at any shopping centre in the world... And just watch the people walk by, with a discreet click counter in your hand.
To help you understand what we are looking for... Or what it is that you are counting... we have included a photo that was first published in 1923 by a famous Parisian doctor, called Pierre Robin.
Pierre Robin was a French dentist, or "Stomatologie".
He is also widely regarded as the first person in the world to draw attention to the effects of the small lower jaw. He eventually became famous for helping dentists, nurses, doctors & young mothers to learn to identify the "very small" lower jaw from when it first starts to have noticeable effects... in newborn babies.
Of course, all babies have small lower jaws. They don't have teeth or bad bites to help you identify a severely small lower jaw from a "normally" small lower jaw, or even from a "normal" jaw. There is literally no measurement, or clinical definition that defines normal from abnormal.
But correctly identifying the severely small lower jaw in newborn babies is very important. Early identification of the suffocating baby today helps prevent cot death, as it did way back in the Paris of 1923.
What Robin said was that “very small lower jaws leads to suffocation, especially when you lie the baby on their back.”
He even gave the phenomenon a new word... "glossoptosis". Or in lay speak, "tongue suffocation".
In Pierre Robin's time, all he could do was invent new feeding bottles, & draw medical attention to the dangers of neonatal suffocation & feeding difficulties.
Today, most modern major children's hospitals have neonatal surgical specialists who use distraction osteogenesis to help grow very small jaws (where it is noticed the baby is obviously suffocating), & thus help the newborn baby with breathing & suckling.
These surgeons & paediatricians & neonatologists are literally lifesavers. Every year about 15 children in Australia will have neonatal jaw distraction to help grow their severely small lower jaws so that they can breath & suckle normally.
This means that for an Australian population of 22 million people, with an annual birth rate of 12.4 per 1,000 (or 275,000 babies a year)... that 1:20, 000 babies will have been the life threatening form of Pierre Robin Syndrome.
But in Australian neonatal wards, doctors are only identifying & growing the very small jaws that are obviously leading to suffocation.
No one really knows the true numbers of how many babies are born with abnormally small jaws. We do know that the overwhelming majority of small jaws are just not picked up by nurses or doctors at the time of birth.
After all, a baby with a very small jaw looks just like any other baby. The only thing we know is that about 15 babies a year would otherwise suffocate because their small jaws are just so very very small.
After they leave the hospital, babies will grow. Teeth will develop. And eventually the manifestations of the hidden small jaw will become obvious.
From about the 1940's, Pierre Robin's name became increasingly synonymous with the association of a very small jaw, & life threatening airway obstruction... in newborn babies.
Why he became synonymous with the small jaw condition only in neonates is somewhat hard to understand.
Today, if you ask most paediatricians & neonatal-paediatric facial surgeons “what is Pierre Robin Syndrome?” they will say that "it is the small lower jaw found in neonates that leads to severe respiratory difficulty."
What neonatal paediatricians & neonatal-paediatric facial surgeons will not say is that "Pierre Robin Syndrome is a disease found at all ages & is a major cause of small lower jaws in adolescents & adults."
So is it possible that the very small lower jaw exist in other age groups apart from newborns? Is it as rare as 1:20,000 live births? And if Pierre Robin Syndrome does exist in adolescents or adults, what would it look like?
Fortunately we have an answer to this. More fortunately it was all written down by a very famous man.
This scientist wrote books & articles & gave many lectures about the adolescent & adult manifestations of Pierre Robin Syndrome. More importantly he actually also figured out that it occurred in around about 40% of all Europeans.
Who was he? It was none other than Pierre Robin himself.
Monsignor Robin was around 43 years old when he wrote his first landmark paper in 1923. When he did write, it was to the Parisian Academy of Medicine, & what he wanted to draw attention to was his insights into a new cause of breathing difficulties... in adults.
Today, we are very aware of obstructive sleep apnoea, or OSA. But in 1923 there were no CT scans, MRI machines or even sophisticated x-ray equipment. There was no such thing as oximetry or sleep study EEG devices.
In 1923 there was literally no way to help explain how adults snored or breathed or how they might even "obstruct" their airways. Less known was how small-jaw-size, a dental overbite, neck posture, a backward tongue position or a compressed airway volume could be inter-related.
It was an enormously huge leap of medical imagination that lead Pierre Robin to figure it all out. He drew examples. Gave pictures. He even invented a jaw splint that helped hold the adult jaw forward, which in turn opened the airway behind the "fallen" tongue.
Today the "monobloc" Robin invented & named, has been reinvented by sleep-specialist dentists, & is the basis for a world-wide anti-snoring dental-device industry.
But what did Pierre Robin fundamentally discover? It was these facts.
Small lower jaws were very common. Small jaws were so common that no one saw them as abnormal.
The small jaw lead to a bad bite, crowded & impacted teeth, & the aesthetic sense of a lack of chin projection. Robin felt that the lack of forward-projection of the lower jaw lead to the back of the tongue to fall backwards & down.
The combination of a poor airway volume & bad bite lead eventually to a distortion in facial proportion & cervical posture. It gave the sense that the nose & ears & upper face was too big. It lead to poor food intake & a lack of general physical health & a general susceptibility to illness.
In combination, he brought together all the effects that he saw & he gave it a name... “Grande Syndrome du Glossoptosisme”... which he said started from birth.
If it was severe enough, it lead to neonatal death from airway obstruction & malnutrition. If it was milder it had other effects that persisted & became obvious with growth & eventual adulthood.
Seen as a condition, the small lower jaw lay on a spectrum from severe to mild, but overall it could be seen in all age groups, & to him was as common as 40% of the adult population.
The most obvious manifestations of a small lower jaw are related to teeth, facial aesthetics & to the effect on airway patency.
Medicine & dentistry has evolved greatly since Pierre Robin's day. Dental appliances, CPAP machines & jaw osteodistraction surgery have evolved, as well as enormous advances in imaging technology.
And we are coming closer to realising just how inter-related & aligning the various disciplines of radiology, respiratory medicine, maxillofacial surgery & orthodontics are becoming.
As treatments evolve, & new ways of seeing the effects of treatment become more commonplace, our insights of disease become more intuitive.
And when we look back & analyse the work of Pierre Robin, it is amazing that this man & his insights existed in an age where today's technologies were just so completely unimaginable.
What we know today is that the small jaw is indeed very common. Class II malocclusion, a major sign of the small lower jaw, is roughly seen in 25% of children. Dental crowding is seen in around 75% of all children.
Almost 40% of all adults over 40 snore. Almost everyone has impacted wisdom teeth. And if you ever have the time to sit with a click counter in a shopping centre, approximately 40% of people who walk by have will have a short lower jaw.
All will fall on a range from very severe to very mild. But if you add them all together, the tally is very close to what Pierre Robin said almost a century ago in Paris.
Why is a small lower jaw so common? Why does it lead to a bad bite or crowded teeth, or impacted wisdom teeth? Why does it have such a severe effect on the airway?
Pierre Robin was right when he said that a small lower jaw was the cause of everything he saw. But what he never could explain, was how the small lower jaw occurred.
But we probably now know the answer.
What we know, is that having a small jaw is remarkably common. All races of humans have people with small jaws, but the incidence is highest in those descended from white Europeans.
At least 25% of Caucasians have an obviously smaller lower jaw. We know this because, scientifically, around the world, orthodontists have counted the incidence of Class II malocclusion in Western (that is, Caucasian) communities. And from these studies we also know that the figure of ~25% occurs equally among males & females.
A small lower jaw is three dimensionally small. It isn't just short, but it is also narrow, & relatively squat. Because of it's smaller volume, it can contain fewer teeth.
This means that many people with a small lower jaw have crowded teeth, impacted teeth (especially wisdom teeth)... & worse, also have a bad bite, which dentists universally call "Class II malocclusion".
Unlike the old days, where medical schools could only dissect cadavers (usually in geriatrics with no teeth), modern three dimensional radiology has revolutionised modern anatomical study...
...so now a dissection can be performed in real time, individualised & "alive"... & thus without the inconvenience (for the patient) to become a formaldecised cadaver.
What we know is that the lower jaw doesn't have some intrinsic ability to grow big or grow small. It only has the capacity to be able to grow... or not.
Or rather, it has the collective cellular capacity to react, through growth, to eventually become an adult mandible. The lower jaw doesn't have a brain to know that it must be a certain size or shape or symmetry. How could it?
The jaw bone grows or does not grow... as a reaction. But a reaction to what? Just like having two legs, growth in bones is defined by the stimulating effects of attached growing muscles & tendons as much as by the epiphyseal cartilages.
One leg does not know to grow longer, shorter, or to the same size as the other leg. In order for any one leg bone to grow at all, means it has a certain enormous complement of incredibly complex bone cells, the collective of which is reactive to a combination of stimuli that includes hormones, nutrients, oxygen & functional use.
That your leg bone grows at all is a miracle of nature. That it grows exactly as a mirror of the other, in exact duplication of length & volume & architecture is equally a miracle.
Unlike leg bones, the mandible does not have an epiphyseal cartilage. There is no innate growth centre at all to be found in any part of the lower jaw.
Collectively, it is a reactive tissue. The mandible starts out as a template, made of cartilage.... And it is given the wonderful sounding name of Meckel's cartilage.
If you look at modern fish, & compare how a fish develops & how a human develops, you'll see that Meckel's cartilage comes from the same origin as that which develops the 1st gill of a fish.
Way back about 1 billion years ago, two brothers (or sisters) went separate ways. One line of descendants became fish with a gill to help it breath under water.
The other line of descendants used that 1st gill to develop a cartilage that became a lower jaw, & eventually to help it eat.
How we know this is rather ingenious. But whoever discovered it also discovered that the first gill arch also lead to the development of the front of the tongue.
Two little buds. Each becoming one half of a collection of muscles that would attach to the inside of the front of the primitive mandible. As the tongue buds grew, their muscle attachments became larger.
The tongue itself grew ever bigger. It in turn became served by no less than four major pairs of nerves & a significant portion of the evolving brain.
The tongue was as important to evolutionary progress in mammals & reptiles as the hand or the foot would later become to primates.
And just like that... the lower jaw grew. Not because it had some innate way to grow, but because it was stimulated to grow… By the tongue.
A big tongue, a big jaw. A small tongue a small jaw.
It was like the carapace to the tortoise. The shell to it's snail. And if it grew small, the normal complement of normally sized teeth became crowded or impacted. If it grew to a normal volume, the teeth grew & erupted normally.
And about 100 million years ago, mammals developed. 3 million years ago Australopithecus emerged. Homo emerged about 1 million years ago. Homo sapiens 200,000 years ago.
This process that lead to man is called human evolution. The last ice age ended 20,000 years ago. Civilisation began 6,000 years ago.
Since man first settled & developed agriculture, it also developed the science & practical art of breeding. Grass became wheat. Wolves became dogs.
And with our new found knowledge, culture developed a sense of human beauty that was specific to regions & people & races.
It is no coincidence that the HERC2-OCA2 genes that coded for light eyes & fair skin were found at around the same time as we discovered the domestication of animals & the settlement of Europe.
We still celebrate the Grecian, then Roman, & later renaissance idealisation of male & female facial beauty. Diminutive jaw. Beautiful female. Square, defined jaw. Male beauty.
As Western Society culturally evolved, Western Medicine also formed. And about 110 years ago orthodontics emerged to deal with the effects that breeding introduced into how Caucasian faces & dentitions & occlusions would form.
The concept of Class II malocclusion crystallised. It’s status as a dental disease became unquestioned. It was known that boys & girls were equally affected.
But what was the relationship of Class II malocclusion to the small jaw?
IMDO treatment requires the close interaction & coordination of an orthodontic practitioner & an oral and maxillofacial surgeon. Both need to be accredited in the IMDO process.
To start, the orthodontic-surgical team has to recognise that the small lower jaw causes dental crowding, & Class II malocclusion.
The whole philosophy of treatment is to correct the bite, allow teeth to un-crowd & be retained, & to manage the tongue position in order to open up the airway behind it.
The pre-IMDO system typically begins with expansion of the upper jaw. Upper jaw expansion opens the nasal airway, & expands the dental arch length.
Expansion is done with a simple dental device, a hirax, placed by the orthodontic practitioner.
Braces are placed on the upper front teeth to develop the front of the upper jaw, creating the optimal amount of space to grow the lower jaw forwards.
Active-IMDO then lengthens, widens, & advances the lower jaw over a period of 12-14 days. This is done at home by a child's parents, with review by an IMDO-accredited specialist surgeon.
With this part of treatment complete, full upper & lower braces are usually placed to optimise smile aesthetics, & to bring the back teeth into an intimate bite relation. This is called the post-IMDO phase.
Comprehensive orthodontics is usually left until facial growth is nearly complete, to avoid the potential for orthodontic appliances to hinder normal facial development.
‘Any surgical or invasive procedure carries risks. Before proceeding, you should seek a second opinion from an appropriately qualified health practitioner.’