Expert article: jaw
Jaw surgery (BiMax)The shape is repositioned, function has to follow
Have you been recommended a BiMax operation or a corrective osteotomy, or have you already had one? Here you can find out what happens during jaw surgery, what it can achieve, which risks are documented, why a jaw can shift again after the operation and what role breathing, swallowing and head balance play in this.
Does this sound familiar?
Jaw surgery is on the table, and you want to understand it?
What applies to you?
Tap whatever applies to you.
If several of these apply, it is worth looking at both sides. The operation changes the shape of the jaws. How the lips, tongue and head work afterwards is determined by a stored pattern of breathing, swallowing and head balance, and this can be trained.
What is documented: risksWhy relapses occurThe key points at a glance
- BiMax surgery surgically repositions the upper and lower jaws. For pronounced jaw malposition it is a recognised treatment, and studies show gains in quality of life and, as an advancement procedure, in severe sleep apnoea.
- It has risks, such as an altered sensation in the lower lip and chin, and some of those who have had surgery show shifts again years later.
- The operation changes the shape, but it does not automatically reset the pattern of breathing, swallowing and head balance. If this pattern continues to act, the bone continues to receive the same stimuli, and relapses and tension can follow. In our view, training the function therefore belongs before and after the operation. Whether surgery is performed is decided by your medical treatment.
Video
Jaw surgery and BiMax: why function is part of it
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Fundamentals
What is BiMax surgery? Corrective osteotomy explained briefly
When the upper and lower jaws are positioned so unfavourably in relation to each other that moving the teeth alone is not enough, orthognathic surgery comes into play.
In a BiMax operation, both jaws are operated on. The upper jaw is released horizontally above the tooth roots, and the lower jaw is cut lengthwise on both sides behind the molars. The parts are then moved into the planned position and fixed with small plates and screws. Specialists speak of a corrective osteotomy or orthognathic surgery. If only one jaw is moved, for example to advance the lower jaw, the procedure is called monomaxillary.
of the population deviated from the ideal bite position in a large US survey1
had a deviation so pronounced that it lay at the limit of what can be corrected by orthodontics alone1
Jaw misalignments are therefore common, but those requiring surgery are rare. Jaw surgery may be considered in cases of a marked retrusion or protrusion of the lower jaw, a skeletal open bite, asymmetries and some forms of sleep apnoea. Whether it is indicated is decided jointly by orthodontics and maxillofacial surgery. The decision is a medical one and depends on the clinical findings.
Course
Jaw surgery procedure: braces, surgery, braces
The operation itself takes a few hours. The treatment around it usually extends over many months.
A repositioning osteotomy is usually part of a combined treatment. Before the procedure, the teeth are aligned with fixed braces so that they fit together after the repositioning. Often the bite even becomes temporarily less favourable as a result.
The procedure is performed under general anaesthesia, followed by a few days in hospital, swelling and a soft diet. The fine adjustment of the teeth is then taken over again by orthodontics.
- Before
Diagnostics and planning
X-rays, models, often digital planning. This is where the decision is made whether one or both jaws will be operated on.
- Preparation
Orthodontics
Fixed braces are used to align the teeth to the future jaw position.
- Procedure
Repositioning
The jaws are cut, repositioned and fixed with plates and screws.
- The first weeks
Healing
Swelling, soft diet, limited mouth opening. Sensation in the lip and chin may be altered.
- After
Follow-up treatment
Orthodontics fine-tunes the bite, often followed by a retainer. Now function also has to adapt to the new shape.
Benefits
What jaw surgery can achieve
A fair assessment begins with what is supported by evidence, and in pronounced cases that is quite a lot.
A review from Brazil evaluated twelve studies on the quality of life of people with pronounced jaw misalignment. After surgery, it scored better in the questionnaires than before2. Anyone who cannot bite off food with their front teeth or suffers because of their profile often experiences a successful operation as a relief.
was the mean fall in the apnoea-hypopnoea index in 627 adults with sleep apnoea after advancement of both jaws3
of those operated on met the success criteria in this analysis; serious complications occurred in 1 %3
In severe obstructive sleep apnoea, advancement of the upper and lower jaw is therefore an effective option, especially when other treatments are not tolerated or are not sufficient. It enlarges the space behind the tongue and soft palate by bringing the facial skeleton forward.
The operation is sometimes also presented as a solution for mouth breathing and snoring. In our view, it does not address the cause. It creates space in the throat, but does not change how the tongue, throat muscles and lip closure use it during sleep. In the meta-analysis, this was not enough to meet the success criteria in 14 % of those operated on3. Before such a major procedure, it is therefore worth looking at breathing, swallowing and head balance, and afterwards the training belongs alongside it. More under Snoring and sleep apnoea.
Surgery can improve the preconditions.It creates space and a suitable shape. How the lips, tongue and head use this space afterwards is decided in everyday life.
Risks
Jaw surgery risks: what the evidence shows
No operation is free of risks. What matters is knowing them as studies describe them, neither larger nor smaller.
The best-known risk concerns the mandibular nerve. It runs through the bone and supplies sensation to the lower lip and chin. When the lower jaw is cut, it lies close to the surgical site. In the first weeks, numbness or tingling is common; in many people it subsides within months4. How often it persists depends heavily on how it is measured. A Belgian review found widely varying figures across 61 reports because standardised measurement methods are lacking5.
of 376 patients reported altered sensation in the lower lip or chin three years after lower jaw osteotomy in a follow-up study. Older age was a risk factor6
In addition, there are the risks of any major procedure, such as bleeding, infection and wound healing problems. And the airways are also a concern. If the lower jaw alone is moved backwards, the throat behind it becomes narrower. An overview of six systematic reviews confirmed this; when the upper jaw was moved at the same time, the narrowing was smaller. Sleep apnoea newly developing after surgery was not demonstrated, but the authors advise taking this seriously during planning7.
Individual information about risks belongs in the consultation with your maxillofacial surgeon. Ask about breathing there, too. Where will the lower jaw be moved, and what does that mean for the space behind the tongue? If you already breathe through your mouth at night or snore, this should be part of the planning.
Stability
Relapse: when the jaw moves back
After healing, the result is not final in every case. Some of those operated on show changes again over the years.
William Proffit and colleagues at the University of North Carolina followed the stability of various jaw movements over many years. Their finding: clinically significant changes of more than two millimetres occurred between the first and fifth year after surgery in a surprisingly large proportion of patients, long after the bone had healed. The teeth often compensated for the shift, so that the bite appeared more stable than the skeleton8.
of surgically treated open bites were still closed after at least one year in a meta-analysis of case series9
A study from 2025 is revealing. Of 50 patients operated on for open bite, 16 already showed a relapse after six months. This group was older and had received accompanying rehabilitation less often and for shorter periods. 19 % of them had received speech therapy, compared with 62 % in the stable group. The authors name a persisting infantile swallowing pattern as one of the main causes of relapse in open bite10. The study is retrospective and small, and it does not provide proof. But it shows where the question lies.
A jaw has a history of form.It arises from early developmental conditions and from functions that continue in everyday life. Surgery changes its outcome. It does not by itself change the forces that continue to act.
Causes
How a jaw misalignment develops
Not every misalignment is acquired. Genes, growth and illnesses play a part. Functions, however, act every day, over years.
Experiments on young rhesus monkeys in San Francisco showed how important breathing is for jaw growth. When their noses were blocked, they kept their mouths open, lowered the lower jaw or pushed the tongue forward. Over time, the face and bite changed in all the animals11. In humans, a Swedish longitudinal study found that after removal of enlarged adenoids, the lower jaw grew markedly more horizontally in girls, while in boys the trend remained uncertain12.
The control pattern deviates
Mouth breathing, a low-lying tongue or a head that moves forward, often already in early childhood.
The body compensates
The lips, tongue and lower jaw compensate so that breathing and swallowing still work. The nervous system stores this compensation as a preferred pattern.
Form follows
Over the years, the missing or incorrect forces change the shape of the palate, the position of the teeth and the relationship of the jaws to each other.
The findings become visible
Open bite, a retruded or protruded lower jaw. In the end, many people face the question of surgery.
The chain often begins in infancy. During breastfeeding, the tip of the tongue seeks a palpable point on the front of the palate, and sucking, swallowing and nasal breathing run in rhythm. This is an early training of the pattern. If breastfeeding does not take place or is short, which can have many reasons, part of this training is missing. If disruptive factors such as constant dummy use, thumb sucking or a blocked nose are added, a deviating pattern can become established.
A Brazilian birth cohort fits with this. Adolescents who had been breastfed for longer less often had an increased overjet, and this association ran to a substantial extent via lower dummy use13. In our view, the starting point of many causal chains usually lies in the basic functions of breathing, swallowing and head balance. You can also find the basic idea in the article on TMD, where the same patterns act on the jaw joint.
Context
New form, old pattern?
Surgery repositions the bones. The muscles that pull on them, and the control behind them, do not automatically reposition themselves as well.
Teeth and jaws are held in a balance of forces. In 1978, Proffit described the resting pressure of the tongue and lips as the most important factors. Breathing influences the posture of the head, jaw and tongue14.
What matters, then, is what is present for hours at a time. If the tongue lies low and the lips are open, even a freshly repositioned jaw continues to receive the same stimuli. In our view, the cause of a jaw misalignment usually lies in this pattern of breathing, swallowing and head balance, and the operation does not automatically reset it. If it continues to act, relapses can follow, or tension in the masticatory muscles and jaw joint, because the muscles and the new shape do not fit together.
Whether function adjusts by itself after surgery has not been consistently demonstrated. In ten operated patients, tongue pressure against the upper teeth, which had been too low, rose to normal values after the repositioning. Proffit interpreted this as function following form15. Other studies show that function does not adjust by itself in all operated patients, and that the position of the tongue and head changes as well.
still needed therapy after completion of combined orthodontic and surgical treatment to relearn swallowing and tongue posture16
with setback of the lower jaw: afterwards, the tongue and hyoid bone were positioned further back, the pharynx remained narrower, and head and neck posture changed17
Like a newly furnished room
If you rearrange the furniture, you still walk the old routes for weeks. The room is new, the habit is not. This is roughly how we see the jaw after surgery. The stored movements first have to adapt to the new form, and that takes repetition.
There is initial evidence for training after surgery. A 2025 review found indications that myofunctional therapy can improve functional disorders after jaw surgery. Overall, high-quality studies are lacking18. In a randomised study, chewing improved in operated patients receiving therapy up to six months after the procedure, and the measured values approached those of people with a normal bite19. There is no dedicated study on the FaceFormer in connection with jaw surgery; our body of research is listed under Studies and science.
The triad
Breathing, swallowing and head balance around surgery
Three basic functions determine which forces act on the new form after surgery.
Breathing
Through the nose with lips gently closed. With mouth breathing, the lower jaw drops and the tongue follows it downwards. Why free nasal breathing is a skill is explained in the article on the nasal septum.
Swallowing
Many hundreds to a thousand times a day. In a physiological swallow, the tongue rests against the palate, the teeth touch briefly and the lips stay relaxed. If the tongue pushes forward, this affects the bite. More in the article Swallowing and swallowing disorders.
Head balance
When the head is balanced over the body, the lower jaw, hyoid bone and tongue find their place. If it drifts forward, in our view the pull and tension on the lower jaw and the width of the pharynx change.
The starting point is the tongue reference position. The tip of the tongue rests on the small ridge behind the upper front teeth, and the back of the tongue nestles against the palate. A fixed “tongue resting posture” does not really exist as such, because the tongue is constantly moving and returns to this shape.
Why this is so and how you can find it is explained in the article on tongue resting posture.
Where is the tip of your tongue right now, as you read this?
3D film
The pull exercise in three directions
In 45 seconds, the animation shows how the lips, tongue and swallowing work together against a gentle pull, with the head balanced upright. Pulling upwards and downwards are part of the advanced modules 4 and 5.
Training
Training before and after jaw surgery: setting the pattern
Deciding to breathe through your nose with your lips closed works for a while. In conversation and during sleep, the old pattern takes over again. A compensation pattern is not given up through insight; it is displaced by precise, frequent repetition. FaceFormer training practises lip closure, nasal breathing, tongue alignment, the swallowing act and head balance in the same sequence. It is used before and after surgery on the face, jaw or tongue.
In the basic exercise, the FaceFormer sits in the oral vestibule, behind the lips and in front of the teeth. You press the lip wedge together with your lips, bite down briefly with your back teeth and swallow once.
Your lower jaw stays in its usual position and is not pushed forward. This is especially important after jaw repositioning, because what is trained is the interplay, not a new jaw position.
From week 3, the pull exercise is added. You gently pull the lip wedge forward while your lips keep the mouth closed.
Negative pressure builds up in the mouth, the membrane draws itself against the rows of teeth, and the tongue is pulled up to the palate. In this way, lips, tongue and swallowing also work together under load.
- Before surgery
Get to know the pattern
Basic exercise three times a day with the FaceFormer ZERO. You learn lip closure, the tongue reference position and nasal breathing even before the procedure.
- After the procedure
Wait for healing
You take a break until the wounds have healed and the operating practice gives its approval.
- Getting started again
Start gently
A few repetitions of the basic exercise with the softer ZERO. Mouth opening and sensation in the mouth set the pace.
- From around week 3
Pull exercise
The pull exercise is added. After a few weeks, you train during the day with the FaceFormer ONE, the same size, just made of firmer material.
- Over months
The pattern runs by itself
The exercise manual allows six to twelve months until the new sequences run without thinking, followed by maintenance training.
After jaw surgery, it is best to clarify when to start beforehand with your practice or with us on 02303 89991. Do not stop using retainers, splints or other prescribed aids on your own; the training can be combined with them. You can find more articles under Before and after surgery on the face, jaw or tongue.
Decision
Before you decide: questions for your consultation
In our view, jaw surgery is experiencing a hype on social networks, where it is sometimes presented as a shortcut to a different face. It is a major procedure under general anaesthesia, with months of pre- and post-treatment, a documented risk of altered sensation in the lip and chin, and the possibility that the jaw shifts again years later. Anyone who wants surgery for aesthetic reasons should weigh all of this calmly beforehand.
Whether jaw surgery makes sense for you is something you decide together with your orthodontist and oral and maxillofacial surgeon. These questions help you prepare for the consultation. How surgery, braces, splints and training fit together is described on the page FaceFormer and other treatments.
Why have surgery?
Is it about chewing and bite, breathing during sleep or your profile? This determines what you can expect.
Which movement is planned?
Will the lower jaw be moved forward or backward, one jaw or both? Ask about the effect on the throat space.
How stable is the result?
Ask how often, with your type of malposition, the jaw later shifts again and what the practice does to counter this.
Who takes care of function?
In our view, every jaw operation should be preceded by the question of why the jaws are positioned this way. Ask whether breathing, swallowing, tongue reference position and head balance are examined and trained before and after the operation.
What about sensation in the face?
How high is your risk of altered sensation in the lip and chin, also in view of your age?
Questions
Frequently asked
What is BiMax surgery?
A BiMax operation is a corrective osteotomy of both jaws. The upper and lower jaws are cut, moved into a new position and fixed with plates and screws. It is used for pronounced jaw malpositions, usually in combination with orthodontic treatment before and after.
When does jaw surgery make sense?
When the jaws are positioned so unfavourably in relation to each other that tooth movement alone is not enough, for example with a marked retrusion or protrusion of the lower jaw, a skeletal open bite, asymmetries or some forms of severe sleep apnoea. In our view, every jaw operation should be preceded by the question of why the jaws are positioned this way, that is, an examination of breathing, swallowing, tongue reference position and head balance. This is particularly important in growing children and adolescents, because the shape of the jaw develops under daily function. Whether surgery is performed is decided by orthodontics and maxillofacial surgery on the basis of the findings.
What are the risks of jaw surgery?
Besides the general risks of any operation, above all an altered sensation in the lower lip and chin. In a study of 376 patients who had surgery, 15% reported this three years after the procedure. If the lower jaw alone is moved backwards, the airway space in the throat can become narrower. The maxillofacial surgery team will inform you about your personal risk.
Can the jaw shift again after the operation?
Yes, in some of those who have had surgery. Long-term data show clinically significant changes even years after healing. In the case of open bite, the authors of a recent study name the persisting infantile swallowing pattern as one of the main causes of relapse. The operation repositions the bones, but it does not automatically reset the pattern of breathing, swallowing and head balance along with them. If this pattern continues to act, the bone continues to receive the same stimuli. In our view, training the function therefore belongs before and after the operation.
Does jaw surgery help with sleep apnoea?
Advancement of the upper and lower jaw is an effective option in severe obstructive sleep apnoea. In one meta-analysis, the apnoea-hypopnoea index fell on average from 63.9 to 9.5 per hour. However, the tongue and throat muscles continue to use the space gained during sleep according to their habitual pattern, which is why, in our view, training the function belongs alongside it. Whether the operation is an option for you is decided by sleep medicine together with maxillofacial surgery.
Can I train with the FaceFormer after jaw surgery?
The training is used before and after operations on the face, jaw or tongue. After the procedure, you only start once the wounds have healed and the operating practice agrees. It is best to clarify how to start beforehand with your practice or with us on 02303 89991.
I wear a retainer after the surgery. Do I still need to train?
In our view, yes. A retainer holds the teeth in the position achieved, but it does not change the forces of the lips and tongue. They continue to act on the teeth and jaws at rest and with every swallow. Retainer and training therefore complement each other: the retainer secures the shape, the training addresses function. You train during the day. Whether you take out a removable retainer for this, you should clarify with your practice. You should not stop wearing it on your own initiative.
What does mouth breathing have to do with jaw malposition?
With mouth breathing, the lower jaw drops, the tongue lies lower, and the forces on the palate and teeth change. Animal experiments and studies in children show that jaw growth responds to this. In our view, this is as a rule where many causal chains begin.
More articles from the knowledge section
Where to go next
Sources
- Proffit WR, Fields HW, Moray LJ (1998). Prevalence of malocclusion and orthodontic treatment need in the United States: estimates from the NHANES III survey. International Journal of Adult Orthodontics and Orthognathic Surgery 13(2):97-106. PMID 9743642. Source
- Meger MN, Fatturi AL, Gerber JT, Weiss SG, Rocha JS, Scariot R et al. (2021). Impact of orthognathic surgery on quality of life of patients with dentofacial deformity: a systematic review and meta-analysis. British Journal of Oral and Maxillofacial Surgery 59(3):265-271. PMID 33546846. Source
- Holty JE, Guilleminault C (2010). Maxillomandibular advancement for the treatment of obstructive sleep apnea: a systematic review and meta-analysis. Sleep Medicine Reviews 14(5):287-297. PMID 20189852. Source
- Colella G, Cannavale R, Vicidomini A, Lanza A (2007). Neurosensory disturbance of the inferior alveolar nerve after bilateral sagittal split osteotomy: a systematic review. Journal of Oral and Maxillofacial Surgery 65(9):1707-1715. PMID 17719387. Source
- Agbaje JO, Salem AS, Lambrichts I, Jacobs R, Politis C (2015). Systematic review of the incidence of inferior alveolar nerve injury in bilateral sagittal split osteotomy and the assessment of neurosensory disturbances. International Journal of Oral and Maxillofacial Surgery 44(4):447-451. PMID 25496848. Source
- da Costa Senior O, Gemels B, Van der Cruyssen F, Agbaje JO, De Temmerman G, Shaheen E et al. (2020). Long-term neurosensory disturbances after modified sagittal split osteotomy. British Journal of Oral and Maxillofacial Surgery 58(8):986-991. PMID 32631751. Source
- Tan SK, Leung WK, Tang ATH, Zwahlen RA (2017). Effects of mandibular setback with or without maxillary advancement osteotomies on pharyngeal airways: An overview of systematic reviews. PLoS One 12(10):e0185951. PMID 29016682. Source
- Proffit WR, Turvey TA, Phillips C (2007). The hierarchy of stability and predictability in orthognathic surgery with rigid fixation: an update and extension. Head & Face Medicine 3:21. PMID 17470277. Source
- Greenlee GM, Huang GJ, Chen SS, Chen J, Koepsell T, Hujoel P (2011). Stability of treatment for anterior open-bite malocclusion: a meta-analysis. American Journal of Orthodontics and Dentofacial Orthopedics 139(2):154-169. PMID 21300243. Source
- Morand S, Lange E, Brochet L, Chauvel Picard J, Gleizal A (2025). Orthognathic Surgery in Anterior Open Bite: A Retrospective Study of 50 Patients With Initial Tongue Malposition. Journal of Craniofacial Surgery (online ahead of print). PMID 40845374. Source
- Harvold EP, Tomer BS, Vargervik K, Chierici G (1981). Primate experiments on oral respiration. American Journal of Orthodontics 79(4):359-372. PMID 6939331. Source
- Linder-Aronson S, Woodside DG, Lundström A (1986). Mandibular growth direction following adenoidectomy. American Journal of Orthodontics 89(4):273-284. PMID 3515955. Source
- Feldens CA, Petracco LB, Nascimento GG, Li H, Vítolo MR, Peres KG (2023). Breastfeeding Protects from Overjet in Adolescence by Reducing Pacifier Use: A Birth Cohort Study. Nutrients 15(15):3403. PMID 37571340. Source
- Proffit WR (1978). Equilibrium theory revisited: factors influencing position of the teeth. The Angle Orthodontist 48(3):175-186. PMID 280125. Proffit WR, Knight JM (1977). Tongue pressures and tooth stability after anterior maxillary osteotomy. Journal of Oral Surgery 35(10):798-801. PMID 269230. Source
- Gallerano G, Ruoppolo G, Silvestri A (2012). Myofunctional and speech rehabilitation after orthodontic-surgical treatment of dento-maxillofacial dysgnathia. Progress in Orthodontics 13(1):57-68. PMID 22583588. Source
- Hwang S, Chung CJ, Choi YJ, Huh JK, Kim KH (2010). Changes of hyoid, tongue and pharyngeal airway after mandibular setback surgery by intraoral vertical ramus osteotomy. The Angle Orthodontist 80(2):302-308. PMID 19905855. Source
- Stefani CM, de Lima AA, Stefani FM, Kung JY, Compton S, Flores-Mir C (2025). Impact of myofunctional therapy on orthodontic management and orthognathic surgery outcomes: a scoping review. European Journal of Orthodontics 47(3). PMID 40237387. Source
- Prado DGA, Berretin-Felix G, Migliorucci RR, Bueno MDRS, Rosa RR, Polizel M et al. (2018). Effects of orofacial myofunctional therapy on masticatory function in individuals submitted to orthognathic surgery: a randomized trial. Journal of Applied Oral Science 26:e20170164. PMID 29412368. Source
Get started
Ready for the training?
The free FaceFormer app guides you through the basic exercises, counts along and reminds you of your sessions. If you wish, a practice from the practitioner directory can support you.
FaceFormer ZERO + ONE
Both material hardnesses for getting started, day and night. The set for adults.
FaceFormer ZERO
The softer FaceFormer for getting started, for children and for the night.
FaceFormer ZERO Children’s Set
ZERO with hygiene box, plush bag and success book with stamp.
FaceFormer training aims to restore the physiological setting of the basic functions of breathing, swallowing and head balance, with lip closure and the tongue reference position, thereby creating the conditions under which symptoms can improve. It does not replace a medical assessment. You can find practitioners near you in the practitioner directory.
