DOCTOR EDUCATION  ·  OCCLUSION CONNECTIONS

How Much Can I Safely Open the Vertical Dimension?

The question every worn dentition eventually forces — and why “how much” is the wrong half of it.

THE INHERITED TOOLBOX

The methods we all learned

None of what follows is a straw man. These are the techniques that built prosthodontics, taught by careful clinicians and used in good faith for nearly a century:

• Physiologic rest minus freeway space. Find the rest position clinically, subtract the 2–4 mm average Niswonger described in 1934⁴.
• The closest speaking space. Silverman’s method — watch the teeth as the patient makes “s” sounds and leave room for speech⁵.
• Phonetics. “Emma.” “Mississippi.” Watch, estimate, record.
• Facial proportion. Equal facial thirds, a Willis gauge, the esthetic eye.
• Tooth-based rules. 18–20 mm from maxillary to mandibular CEJ in the unworn Class I dentition; wax it to the rule.
• The trial run. A splint or provisionals at the new height for some weeks — if nothing hurts, proceed.

Each of these is workable. Each produced restorations that survived. And each one is an estimate — a population average, a rule of thumb, or a subjective judgment, applied to the individual in your chair.

In 2021, Goldstein, Goodacre and MacGregor reviewed the evidence behind all of it for a best-evidence consensus statement² — which notes, among its findings, that the interocclusal “freeway” distance in healthy patients ranges from 1 to 9 millimeters. The 2–4 mm average describes a population; the range describes patients. A 2025 comprehensive review reached the conclusion quoted above: no single method is universally applicable³. A well-known continuing-education series went further and titled its article on the subject “Taking the Voodoo Out of Vertical Dimension.”

The voodoo was never the vertical. The voodoo is the guessing — and none of these methods, by their own authors’ account, replaces the guess with a measurement of this patient’s physiology.

THE HONEST PART

Most of the time, guessing works

Let’s say the quiet part plainly, because it builds more trust than pretending otherwise: most of the time, the guess gets away with it.

The best evidence the adaptation camp has is a 2012 systematic review by Abduo¹, which concluded that a permanent increase in vertical dimension is “safe and predictable,” with negative signs and symptoms that were “self-limiting.” Healthy musculature is adaptable. A modest, well-executed increase on a patient with a healthy stomatognathic system is usually tolerated.

It is worth knowing what that conclusion stands on: the review retrieved 902 studies and found nine that met its criteria¹. Nine studies, mostly small, underwrite the profession’s confidence that patients adapt.

And here is the other honest admission: most dentists are not going to buy measurement instrumentation, train on it, and change how they determine vertical. They will keep estimating the way they were taught, and hoping — and for something like eight cases out of ten, the hoping will work.

But what is the purpose of continued guessing when a patient’s health and life is at stake? The patient is making a huge investment in getting not just the esthetics correct — even more importantly, they want their bite to feel correct. And the verdict does not arrive at the seat appointment: it is after the dentistry is delivered, over the next 2–3 months, that one knows whether the case is successful or not. The guess is graded when the porcelain is already permanent.

If the eighty percent satisfies you, this is a fair place to stop reading. The rest of this article is about the other two.

WHERE THE TEXTBOOK ENDS

The cases the averages already failed

She arrives at your office with a bite that was opened somewhere else. Full-mouth porcelain, three years old. The ceramic keeps chipping — you have read why crowns keep breaking and recognize the pattern. Or the implant restorations keep loosening — that pattern too. Her muscles never settled. Her jaw is tired by afternoon. She may have headaches she never had before the dentistry, a joint that clicks now, or the complaint clinicians dread most because it sounds psychiatric and isn’t: “I can’t find my bite anymore.”

Her fourth full-mouth rehabilitation — the fourth dentist to touch the case, and a neuromuscular-trained one at that. Four verticals, none measured to her physiology. The porcelain was intact; the headaches, jaw pain and bite problems remained — until the vertical was finally measured, not guessed, and the case was resolved.

The dentist who treated her was not careless. He used the methods. He subtracted the average freeway space, checked the speaking space, ran provisionals for six weeks. Every rule was followed — and the case still failed, because every rule was an estimate and her physiology declined to match the population average.

Now open any of the textbooks that taught those methods and find the chapter for her. There isn’t one. The method was guess and hope. Both have already run. The teaching that opened her bite has nothing further to say about her.

THE STANDARD REBUTTAL

“It’s central sensitization” — the modern explanation

To be fair to the literature, it does have an answer for these patients. The modern orofacial-pain model attributes chronic non-adaptation to a maladaptive host response — impaired endogenous pain modulation and central sensitization in a susceptible individual — with the occlusion acting as, at most, a “peripheral trigger.” A 2015 review concluded that altering the vertical dimension does not, of itself, produce TMD⁷, and a 2024 Cochrane review found no reliable evidence supporting occlusal interventions for managing it⁸. In that framework, the failed patient’s pain is driven centrally — and the bite is largely exonerated.

Take the model seriously; it explains real things — the widespread tenderness, the comorbid neck pain and headaches, the way chronic pain can outlive its original cause. But before it closes the case, notice three things.

First, buried in that same literature: experimental occlusal interference in animals produced masticatory muscle hyperalgesia lasting a month — and removing the interference after six days did not stop it⁹. The periphery can light the central fire. An unmeasured bite is not exonerated by the observation that the fire eventually feeds itself.

Second, look at what the negative trials actually tested: occlusal changes made the conventional way — to guessed, averaged, manually manipulated positions. The evidence indicts unmeasured occlusal treatment. A trial of physiologically measured positioning is a different experiment — one the literature has not run. And the reviewers concede the ground themselves: the evidence base against the occlusion rests largely on case reports and anecdote, not controlled trials⁷. “No demonstrated correlation” is a statement about absent evidence, not proof of no effect — and absence of measurement is precisely the article’s complaint.

Third, the model has to explain the patient above. Four full-mouth rehabilitations, years of headaches and jaw pain — resolved when the vertical was finally measured to her physiology. If her pain had been purely central, the measurement should not have mattered. It did.

There may even be an anatomical reason why some patients cannot self-correct. The trigeminal mesencephalic nucleus — where muscle-spindle and periodontal signals converge — actively regulates the vertical dimension: lesion those neurons experimentally, and the normal return from an altered vertical fails¹³. The machinery of adaptation is real neural tissue, and in some patients it demonstrably stops working. The non-adapting patient may be neurology, not neurosis.

None of this denies the central nervous system — GNM is built on it. It simply refuses to use “central” as a reason to keep guessing at the periphery. Verify the peripheral input by measurement; if pain persists beyond a verified physiologic foundation, that too is information — honest information a guessed bite can never provide.

A DIFFERENT DEFINITION

What vertical dimension actually is

The traditional methods treat vertical dimension as a tooth measurement — how tall the dentition should be. But teeth do not hold the mandible anywhere. Muscles do. The mandible is a bone suspended in a sling of musculature, and the vertical dimension of the face is the resting length of that musculature, influenced by head posture and the airway behind it.

This is not a fringe observation. In 1981, Rugh and Drago put electromyography on the question — and what they found deserves more than a passing sentence:

The muscles’ idea of rest and the clinician’s idea of rest are different numbers — measured forty-plus years ago, published in the mainstream prosthodontic literature, and quietly stepped past by every method that still starts from the clinical guess.

Modern instrumented work keeps agreeing. Small changes in vertical jaw relation measurably alter motor-unit recruitment in the masseter¹⁰. And 2023 neurophysiology found that the calibration between muscle spindles and periodontal mechanoreceptors — the system that regulates masticatory force — is tuned to the individual’s established vertical: move away from it and force estimation miscalibrates dose-dependently, worsening the further the jaw is taken from its original vertical¹¹. Objective, quantified, and specific to each patient’s own physiology — not an average in sight.

The literature hesitates over what a weaker, slower, shorter-firing musculature means — adaptation or dysfunction — and admits the question is unresolved. OC does not hesitate. Reduced EMG in function is not just an adaptation; it is a dysfunction. A dysfunction is pathology — unhealth — a biologic system operating below its physiologic optimum in timing, duration and range of motion. The only open question is whether the dentist measures it, or never looks.

Once you see vertical as a musculoskeletal position rather than a tooth height, the traditional question dissolves. “How much can I open?” assumes the answer is a distance. It isn’t. The answer is a position — and positions can be measured.

THE GNM APPROACH

Measured, not averaged

Gneuromuscular dentistry determines vertical the way the rest of medicine determines physiologic values: by measuring the patient.

• Deprogram first. Ultra-low-frequency TENS relaxes the mandibular musculature out of its accommodated, guarded posture — the posture every unmeasured method unknowingly records.
• Measure the true rest position. Computerized jaw tracking (the K7) records where the relaxed musculature actually holds the mandible, and the trajectory it closes along — this patient’s freeway space, not the 1934 average.
• Prove the position before porcelain. The measured bite is tested in a removable orthotic, in the patient’s own musculature, for weeks to months. The porcelain is cut only after the physiology has already accepted the position.

K7 Scan 4/5 — the mandibular rest position and closing trajectory, measured rather than estimated, during an optimized bite registration.

And measured does not mean aggressive. OC teaches conservative openings — unforced, and matched to the patient’s facial proportions. A physiologic vertical harmonizes with the face it lives in — the same golden proportions found throughout human design, which give the clinician an anatomical harmony to respect rather than a blank check to build tall. Oversized, horse-looking anterior teeth are not a vertical dimension strategy; they are the visible sign that space was created for the porcelain rather than found in the physiology.

Nor is vertical a single number. The opening is evaluated at the anterior and at the left and right posterior segments independently — because the mandible relates to the maxilla with six degrees of freedom, and a bite opened purely on an anterior measurement can still be wrong on one side, or both. This is why a vertical “amount” can never describe a mandibular position.

At bottom, this is what OC’s teaching is about: detail and accuracy. The vertical is established from physiologic measurements of the patient — anatomical form and the bio-dynamics of physiologic rest, what GNM regards as true centric relation — and not from what a doctor thinks looks good. When the position is measured right, looking good follows. Esthetics is a result of the method; it is not the method.

Notice what changed. Every traditional method asks the patient to adapt to the restoration. This sequence asks the restoration to conform to the patient — and verifies the conformity before the irreversible step, not after.

Nor is measuring the vertical a novelty. As far back as 1985, Manns and colleagues showed in a controlled trial of dysfunction patients that raising the vertical toward the position of least EMG activity produced significant, sustained reductions in masseter hyperactivity¹². The objective road has been open for forty years. Most of the profession simply hasn’t taken it.

Does this require instrumentation and training most offices don’t have? Yes. That is exactly why eighty percent of dentistry will keep estimating — and why the twenty percent who fail out of that system need somewhere to land.

Step back and the picture is stark. Dentists are trying to restore a pathologic condition — one that is really a comprehensive condition — with less than optimal tools in the toolbox. Why not establish it in one’s thinking, and commit to learning how to measure the unstrained VDO objectively and physiologically — based on science that requires no manual manipulation and no guessing techniques — and do it scientifically, with evidence?

THE CLINICAL QUESTION

When to maintain it — and when to change it

Maintain the vertical when the musculature is comfortable, function is clean, wear is not progressing, and the restorative plan has the room it needs. An asymptomatic, stable patient’s vertical is not a problem to fix.

Question the vertical when you see progressive wear the patient’s age doesn’t explain, collapsed posterior support, a fatigued or symptomatic musculature, forward head posture, airway complaints, or the restorative failures that keep repeating — the broken crowns and loosening implant restorations that brought you to this series.

The earlier fork in the road — wear that age doesn’t explain. This is when the vertical deserves to be questioned, not after the porcelain.

And when the vertical does need to change — the amount is not chosen. It is found, it is measured scientifically to physiologic parameters unique to each patient. Found in the patient’s own relaxed musculature, recorded, and proven reversibly before a single tooth is prepared. That is the entire difference between opening a bite and gambling one.

BEFORE THE DAMAGE

The missing link

GNM offices see the failed twenty percent every week — the opened bites that never settled, arriving after the damage, after the porcelain, after everyone else was finished. Rescue is honorable work, and somebody has to know how to do it.

But the measurement that rescues these patients existed before their first crown was cut or before any existing crowns were removed. Nothing about TENS or jaw tracking requires a failure to justify it. Filling the missing link after the damage is rescue. Filling it before is dentistry.

That is the choice the profession quietly makes every time a vertical is set by an average: to find out which group the patient was in — the eighty or the twenty — only after the porcelain is seated.

SOURCES

References

1. Abduo J. Safety of increasing vertical dimension of occlusion: a systematic review. Quintessence Int. 2012;43(5):369–380. PMID 22536588.
2. Goldstein G, Goodacre C, MacGregor K. Occlusal vertical dimension: best evidence consensus statement. J Prosthodont. 2021;30(S1):12–19. PMID 33783090.
3. Fayad MI, Moussa R, Ragheb NA, Ahmed Y, Sultan S, AbdulSalam MR, Ismail HA, Elboraey MO, AbdElaziz MH, Helal MA. Vertical dimension in prosthodontics theory and practice (Part II): a comprehensive review of vertical dimension determination in prosthodontics from classical methods to digital innovation. Cureus. 2025. PMC12501398.
4. Niswonger ME. The rest position of the mandible and centric relation. J Am Dent Assoc. 1934;21:1572–1582.
5. Silverman MM. The speaking method in measuring vertical dimension. J Prosthet Dent. 1953;3:193–199.
6. Rugh JD, Drago CJ. Vertical dimension: a study of clinical rest position and jaw muscle activity. J Prosthet Dent. 1981;45(6):670–675.
7. Moreno-Hay I, Okeson JP. Does altering the occlusal vertical dimension produce temporomandibular disorders? A literature review. J Oral Rehabil. 2015;42(11):875–882. PMID 26140528.
8. Singh BP, Singh N, Jayaraman S, Kirubakaran R, Joseph S, Muthu MS, et al. Occlusal interventions for managing temporomandibular disorders. Cochrane Database Syst Rev. 2024;9(9):CD012850. PMID 39282765.
9. Cao Y, Xie QF, Li K, Light AR, Fu KY. Experimental occlusal interference induces long-term masticatory muscle hyperalgesia in rats. Pain. 2009;144(3):287–293. PMID 19473767.
10. Terebesi S, Giannakopoulos NN, Brüstle F, Hellmann D, Türp JC, Schindler HJ. Small vertical changes in jaw relation affect motor unit recruitment in the masseter. J Oral Rehabil. 2016;43(4):259–268. PMID 26707515.
11. Tanaka Y, Sato H, Toyoda H, Saito M, Maeda Y, Kang Y. The mechanism for regulating the isometric contraction of masseter muscles is involved in determining the vertical dimension of occlusion. J Neurophysiol. 2023;129(1):211–219. PMID 36541608.
12. Manns A, Miralles R, Cumsille F. Influence of vertical dimension on masseter muscle electromyographic activity in patients with mandibular dysfunction. J Prosthet Dent. 1985;53(2):243–247. PMID 3856667.
13. Zhang W, Kobayashi M, Moritani M, Masuda Y, Dong J, Yagi T, et al. An involvement of trigeminal mesencephalic neurons in regulation of occlusal vertical dimension in the guinea pig. J Dent Res. 2003;82(7):565–569. PMID 12821720.

Updated: August 12, 2026

Written by Clayton A. Chan, D.D.S. — Founder and Director, Occlusion Connections  |  Las Vegas, Nevada