DOCTOR EDUCATION · OCCLUSION CONNECTIONS
The promise behind a generation of airway courses — weighed against what the airway actually responds to.
A colleague told me recently that he had noticed something about my practice: I advocate much less for airway sleep appliances than most dentists he knows. He wanted to know why.
I told him it was true — not because I don’t believe in sleep appliances and airway issues. It is because of what I found when treating these patients with an optimized orthotic, with the disc reduced and recaptured: the comfort of the patient improves, they don’t grind and clench as much, their tongue is functioning better — not entrapped as before — and their central nervous system is calmer.
By the end of the call he had arrived somewhere on his own: before any appliance is delivered — including a sleep appliance — the joints and the position deserve attention first.
So when a dentist asks me whether opening the vertical will open the airway, the honest answer is: that is the wrong dimension to ask about. This article is about why.
THE PROMISE
The pitch is everywhere in dental continuing education right now: the airway is the missing diagnosis, the bite is collapsed, and opening the vertical dimension will give the tongue room and the pharynx relief. Raise the bite, open the airway, change the patient’s life.
Be fair to the idea: it is not nonsense — which is exactly why it sells. The tongue is suspended from the mandible. The pharynx sits directly behind it. Mandibular position genuinely does change airway dimensions — that much is measured, replicated, and not in dispute. The airway is real, and this series takes it seriously.
What the pitch skips is one word: direction. “Opening” is not a destination. When the bite is opened, the mandible swings somewhere — and where it swings decides whether you open the airway or close it, whether the tongue moves away from the pharynx or into it. The literature on that point is unusually consistent, and it was not written by occlusion advocates. It was written by the sleep and imaging communities. How amazing the profession is waking up to the fact that mandibles function better in general down and forward than up and back.
THE DIRECTION PROBLEM
Start with the cleanest experiment: image the same airway with the jaw closed and the jaw open, and simply subtract. When that was done with three-dimensional CT, opening the jaw did not add airway — it redistributed it. The nasopharynx gained volume while the oropharynx lost it, and the most constricted region — the choke point that matters in sleep — got smaller1. CT in patients with obstructive sleep apnea agrees: wider mouth opening narrows the minimum oropharyngeal cross-section2.
The mechanism is rotational. A bite opened without regard to trajectory rotates the mandible clockwise — down and back — carrying the tongue base toward the pharyngeal wall. When investigators closed anterior open bites by intruding posterior teeth — rotating the mandible counterclockwise, up and forward — the retroglossal airway gained dimension on both cephalometry and MRI3. Same vertical question, opposite rotations, opposite airways. The 2025 scoping review on vertical-dimension myths — whose senior author is dentistry’s most-cited occlusion skeptic — draws the same line: a vertical increase that drives posterior rotation and distalization can worsen airway patency, most readily in high-angle patients4.
If the bite is vertically opened but the patient is opening on the wrong trajectory path, the tongue can still be entrapping the airway in the oropharynx. The airway does not respond to “open.” It responds to “where.”
Same opening, different trajectory. Down-and-back carries the tongue base toward the pharynx; the measured down-and-forward path — condyle translating with it — leaves the tongue functioning in front of an open airway.
And the patients with the least room for error are the ones the airway movement most wants to treat: across 368 CBCT volumes, hyperdivergent, high-angle growth patterns showed the smallest pharyngeal volumes and the tightest minimum constrictions of any facial type5. The patient most likely to be offered a vertical-opening solution is the one most vulnerable to its wrong direction.
THE MECHANISM
Strip the debate to its anatomy and it becomes almost simple. The genioglossus — the bulk of the tongue — anchors to the mandible. The hyoid hangs in the same sling. The pharynx is the space left behind them. Move the mandible, and the tongue base and hyoid move with it. Three directions, three different airways:
One more finding deserves a highlight, because it quietly ends every one-size-fits-all protocol: in the mouth-opening CT study, the velopharyngeal response reversed depending on the patient’s resting tongue position — opening helped patients with a low, forward tongue and hurt those with a high, posterior one2. The same maneuver. Opposite outcomes. Decided by anatomy nobody can see from a smile photograph — which is another way of saying the answer is unique to each patient, and has to be found, not assumed.
ASK THE FIELD
Here is the argument-ender most airway courses never mention. There is an entire discipline that treats the airway with the mandible every night: oral appliance therapy for sleep apnea. Ask what that field does with vertical opening, and the answer is: as little as possible.
In the randomized trial that isolated the question — four millimeters of interincisal opening versus fourteen, protrusion held constant — the extra vertical added nothing: both settings reduced the apnea-hypopnea index about equally, and patients overwhelmingly preferred the thinner appliance11. Honest note: that trial means added vertical did not destroy efficacy either. But the field’s own meta-analysis found the lower-vertical one-piece designs succeeded in 82 percent of cases against 55 for bulkier designs, in part because added thickness rotates the mandible back and spends the protrusive range that actually drives the therapy12. A four-arm trial landed in the same place: best sleep parameters at the smaller vertical13.
Because the therapeutic lever is not vertical at all. Efficacy tracks protrusion — dose-dependently, measurably, in pharyngeal collapsibility itself14,15. The prescription in every titration protocol is forward, never open. The medicine is position. The opening is packaging — and the packaging is minimized like a side effect, because that is what it is.
And here is the irony worth sitting with. Sleep-focused dentists have learned to measure and quantify nearly everything — the quality of the airway, the AHI, the oxygen, the hours of wear. Everything except the position they prescribe. The standard teaching is to advance the mandible to 60–70 percent of maximum protrusion with a George gauge or a similar guessing device — a percentage of a strained border movement — and titrate from there. Not once in that protocol is the musculature relaxed to find the optimized myo-trajectory: the unstrained physiologic opening-and-closing path of the mandible — measurable, quantifiable — where the tongue functions best. The field measures the physiologic airway with diagnostic precision and chooses the input by subjective percentages. The one number nobody records is the physiologic mandibular position (measured in tenths of millimeters) the whole therapy stands on.
To be fair, some go further and measure the airway itself with a pharyngometer. But notice what is being measured even then: the tube, not the jaw. The most instrumented sleep practice still stops one measurement short of the one the therapy stands on. Relax the musculature and record the optimized trajectory, and the mandibular position stops being an estimate — it becomes a confirmed position. And not merely for the mandible: positioned physiologically, it becomes the key that settles the complete postural system, head to toe — the descending chain examined in Postural Alignment: Chan’s Dental Model.
And the facial-pattern data closes the loop from the imaging studies: high-angle, hyperdivergent patients — the ones with the least airway reserve5 — respond worst to mandibular advancement therapy16, need more protrusion to reach the same result, and hit a ceiling precisely because pushing further forward drags more vertical opening with it17.
THE VERDICT
So put the title question to the literature straight: what is the evidence that raising the vertical dimension of occlusion, by itself, will open the airway, treat obstructive sleep apnea, or improve breathing? There is none. Not weak evidence — no evidence base at all. No trial, no cohort, no imaging series showing that vertical opening alone will open the airway or lower an apnea-hypopnea index. Where isolation was attempted, added vertical was neutral at best11 and mechanically unfavorable at the oropharynx1,2.
The 2025 meta-analysis of dentofacial morphology found that adults with sleep apnea characteristically present with a clockwise-rotated mandible, increased vertical facial height, and a low-hanging hyoid18. The OSA face is the clockwise face — and a blind vertical increase rotates a patient toward it, not away from it.
Even the airflow physics has been modeled: computational fluid dynamics shows mouth opening promotes jet formation and greater pharyngeal pressure loss — more suction on a collapsible tube, the exact force obstructive apnea is made of19. Meanwhile the interventions with genuine airway efficacy — appliance protrusion14 and maxillomandibular advancement surgery, with apnea-index reductions of 61 to 92 percent20,21 — are, without exception, position treatments. The profession already believes mandibular position treats the airway. It prescribes it every night. The only question left is whether the position is guessed — or measured.
ONE SYSTEM
There is one more place the airway shows itself in your operatory, and most exams walk right past it. Pharyngeal caliber is coupled to the cranio-cervical angle almost linearly: extend the head and the airway widens; flex it and the airway narrows22. On CBCT the relationship is strong enough that a ten-degree change in head position can swing the minimum airway cross-section by tens of percent23.
Now read the posture of the struggling patient correctly: adults with sleep apnea carry the head forward and extended — measurably more than controls — and the worse the apnea, the worse the forward head posture24,25. The spine is not misbehaving. It is compensating — holding a compromised airway open all day, and billing the neck, the shoulders, and even inspiratory muscle strength for the service27. Let the head fall into flexion during supine sleep and the apnea index climbs by thirteen events an hour26. The patient with the forward head, the tight neck, and the morning headache is often showing you an airway problem and an occlusion problem braided together — the same braid this practice untangles in the cervical-posture work.
After the teaching slides of Dr. James F. Garry: the standing posture of the airway-obstructed child — head forward, mouth open, the whole frame organized around getting air. The profession has known this longer than the airway movement has existed.
It also means something practical for measurement itself: airway and bite records taken with the head unnaturally postured are records of a different patient. The imaging literature now requires posture standardization for exactly this reason23 — and it is why a physiologic workup records the patient upright, in natural head posture, the way they actually function.
THE GNM ANSWER
Everything above collapses into one working principle, and it is the same principle this series has built four times now: the airway is not waiting for more room. It is waiting for a physiologic unstrained position — one the tongue can function in front of, on a trajectory the musculature can live with.
The trajectory from the diagram above, measured with computerized mandibular scanning (the K7 kinesiograph, with J5 dental TENS): the habitual closing path found posterior of the physiologic trajectory — and the corrected bite verified coincident with it. (Click to enlarge.)
And the discipline cuts both ways — this is not open-every-bite dressed up in instrumentation. A patient with healthy joints, a normal swallow with the teeth bracing properly, no airway or sleep complaint, and no symptoms has no vertical problem to fix — the vertical dimension article made that case in detail. Measurement is how you know when to act. It is also how you know when to leave things alone.
ABERRANT SWALLOW — TONGUE BRACING BETWEEN TEETH
NORMAL SWALLOW — TEETH BRACING AGAINST TEETH
The swallow on the same instrument (Scan 6). With the tongue bracing between the teeth — the aberrant pattern, driven by a vertically and AP-deficient intraoral tongue space — every swallow throws the mandible through wide excursions. With teeth bracing against teeth (sufficient intraoral tongue space) during swallow, the tracing barely moves.
THE HONEST LEDGER
Because this series does not caricature the other side: mandibular advancement devices work for many patients, and their joint safety record is better than dentists often assume. On eighteen-month MRI, disc position did not pathologically change28; joint and muscle symptoms cluster early and usually fade29; pre-existing TMD is not, by itself, a contraindication30. If you were waiting for this article to claim sleep appliances wreck joints — it won’t, because the evidence says otherwise.
What the evidence does say is quieter and, for a dentist, more uncomfortable. First: the appliance’s best-documented long-term effect is on the bite itself — progressive, dose-dependent, largely permanent reduction of overjet and overbite, significant enough that the clinical guideline requires counseling patients about it in advance31,32. Sit with what that means: nightly mandibular repositioning changes occlusions permanently, as an accepted side effect, in whatever direction the appliance happens to push. If long-term repositioning is going to reshape the bite anyway, it deserves to be a position somebody measured and chose.
Second: the patients who hurt during appliance therapy are not random. The identified risk profile — pre-existing pain, joint noises, limited opening, clenching and grinding, muscle tenderness, headache, mandibular retrusion33 — is, line for line, the untreated TMD patient. The sleep field’s own data points to the conclusion my colleague reached on the phone: evaluate and stabilize the masticatory system before the appliance is delivered — not after it starts hurting.
And the lane markings, stated plainly: obstructive sleep apnea is a medical diagnosis, made by sleep physicians with sleep studies. Nothing in dentistry — no orthotic, no vertical, no appliance — replaces that. The argument of this article is narrower and firmer: whatever role the mandible plays in a given patient’s airway, it plays through position — and position is measurable. The broader philosophy — why airway became dentistry’s comfortable answer to everything — is taken up in Airway Is Not the Answer to Everything.
GO DEEPER
Where the diagnostic discipline is taught: Level 2 — Advanced GNM Diagnostic Principles · and the question most dentists ask next: Do you need a K7 to practice GNM?
SOURCES
Updated: August 14, 2026
Written by Clayton A. Chan, D.D.S. — Founder and Director, Occlusion Connections | Las Vegas, Nevada
Where to Begin
This article examines what opening the vertical dimension does, and does not, do for the airway. Level 1 is where dentists learn to measure the jaw position these questions depend on.
Two days, 16 CE hours, no prerequisite — and no instrumentation of your own required.
Occlusion Connections — The Center for Gneuromuscular Dentistry and Orthopedic Advancement
6170 W. Desert Inn Rd., Las Vegas, NV 89146
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Email: jane@occlusionconnections.com
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