Estimate vertical dimension
before mounting.

Enter facial measurements and get VDO estimated across 4 clinical methods with convergence analysis and a verification checklist.

Important clinical warning

This tool provides statistical estimates based on average facial proportions. It does NOT replace direct clinical evaluation. Final vertical dimension of occlusion must be determined clinically using occlusion rims, live phonetic tests, and facial esthetic assessment. Every patient is unique — these formulas are a starting point, not a diagnosis.

Patient measurements

Enter the measurements you have available. The more measurements, the higher the estimation accuracy. All measurements in millimeters.

Subnasion to gnathion with mandible at physiological rest position
mm
Distance from the pupil (center) to the lower edge of the upper lip (stomion)
mm
Trichion (hairline) to gnathion (chin). For cephalometric thirds method.
mm
Subnasion to vermilion border of the upper lip. Complementary proportional method.
mm

Result by method

Mandatory clinical verification

Before cementing or processing, verify these points with occlusion rims or provisionals:

The 4 methods explained

Willis method

Principle: VDO = Resting height - Interocclusal freeway space (2-4mm). The freeway space is the difference between the mandibular rest position and centric occlusion. Willis established this space averages 3mm in adults.

Limitation: Rest position can vary with stress, medication (muscle relaxants), and cervical posture. Measure 3 times and average.

Proportional method

Principle: The pupil-to-stomion distance is approximately equal to VDO. Based on Da Vinci/McGee facial proportions. Also: subnasion-to-gnathion in occlusion should be approximately equal to the pupil-to-commissure distance.

Limitation: Assumes average facial proportions. Less reliable in patients with facial disproportion, severe prognathism, or retrognathism.

Cephalometric method

Principle: The face is divided into 3 equal thirds: trichion-glabella, glabella-subnasion, subnasion-gnathion. The lower third (subnasion-gnathion) in occlusion = 1/3 of total facial height.

Limitation: Requires a visible hairline (trichion). Less accurate in bald patients or those with very high foreheads. Significant racial variability.

Phonetic method

Principle: When pronouncing "S" (sibilant), the closest speaking space is 1-2mm. If VDO is correct, saying "Mississippi" the teeth almost touch without colliding.

Limitation: Subjective — depends on clinician observation. Not precisely quantifiable. Better as a verification method than a primary one.

Document VDO on every case

TrazaLab lets you log facial measurements, photos, and clinical notes per case. Everything accessible from any device.

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Why it matters

Wrong vertical dimension causes pain, wear, and prosthetic failure

The vertical dimension of occlusion (VDO) is the foundation of every full-arch and full-mouth rehabilitation. If VDO is wrong, everything else fails: facial esthetics, phonetics, masticatory function, and prosthesis longevity.

2-4 mm

is the average range of interocclusal freeway space. Outside this range, the patient experiences muscular or prosthetic symptoms

73%

of complete denture failures are linked to errors in the maxillomandibular relationship record, including VDO

3+

estimation methods must converge to consider VDO clinically acceptable. No single method in isolation is reliable

How it works

The 4 methods for estimating vertical dimension

No single method is reliable on its own. Correct VDO is the one confirmed by multiple converging methods.

1

Willis method (facial proportional / Willis gauge)

Measures the distance from pupil to commissure (middle facial third) and compares it to the distance from the base of the nose to the chin (lower third). With correct VDO, both measurements should be approximately equal. It is fast but has significant individual variability.

2

Proportional thirds method

Divides the face into three thirds: trichial (hairline to glabella), nasal (glabella to base of nose), and mental (base of nose to chin). In occlusion, the lower third should be proportional to the other two. If it is significantly shorter, VDO may be decreased.

3

Cephalometric method

Uses a lateral skull radiograph to measure bony angles and distances. It is the most objective but requires radiographic equipment, tracing software, and interpretation experience. Not available in every office and not practical for every patient.

4

Phonetic method (closest speaking space)

Ask the patient to pronounce sibilant sounds ("Mississippi", "sixty-six"). During these sounds, the anterior teeth approach their minimum distance without contact: the closest speaking space. If the space is less than 1 mm or the teeth contact, VDO may be excessive.

Common mistakes

VDO errors that compromise rehabilitation

01 Relying on a single measurement method

Willis alone, phonetics alone, or cephalometry alone: no single method has enough precision on its own. Individual anatomical variability is too high. At least three converging methods within a 2 mm range are needed to consider VDO validated.

02 Not verifying with phonetics

Phonetics is the most accessible verification method and the most underused. If the patient cannot pronounce sibilants clearly or the teeth clash during speech, VDO needs adjustment. Skipping this test means losing the fastest validation available.

03 Increasing VDO excessively

Increasing VDO too much compresses the freeway space, causes muscle fatigue, TMJ pain, speech difficulty, and a strained facial appearance. Any increase greater than 4-5 mm should be evaluated with a trial prosthesis before fabricating the definitive one.

04 Ignoring bone resorption

In long-term edentulous patients, alveolar ridge resorption has progressively reduced facial height. Using VDO from old prostheses as a perpetual reference perpetuates the error, because those prostheses were already at decreased VDO from years of wear.

05 Using old prostheses as the only reference

Prostheses older than 5-10 years have significant occlusal wear. The VDO the patient is "comfortable with" is not necessarily the correct VDO. Comfort is a factor, but biomechanics, esthetics, and phonetics must be validated independently.

Frequently asked questions

Vertical dimension: key questions

There is no absolute number. Increases of 2-4 mm are generally well tolerated in healthy patients without TMJ pathology. Increases greater than 5 mm should be tested with provisional prostheses for 4-6 weeks before fabricating the definitive one. Individual tolerance varies and depends on muscle and joint condition.

Average interocclusal freeway space is 2-4 mm, measured at mandibular rest position. Less than 1 mm suggests excessive VDO; more than 6 mm suggests insufficient VDO. But the average does not apply to everyone: some patients have a naturally wide or narrow freeway space.

Yes. Tooth loss, occlusal wear, and alveolar ridge resorption progressively decrease VDO. In addition, changes in muscle tone and cervical posture affect mandibular rest position. For this reason, VDO must be reassessed with every rehabilitation, not assumed constant.

Ask the patient to count from sixty to sixty-nine. Watch the distance between upper and lower incisal edges during sibilants. There should be 1-2 mm of space without contact. If the teeth contact, VDO is too high. If the space is greater than 3 mm, it may be too low.

Whenever the VDO increase is greater than 4 mm, when the patient has preexisting TMJ symptoms, when previous VDO is unknown (long-term edentulous), or when there is discrepancy between estimation methods. The trial prosthesis is worn for 4-6 weeks and adjusted before fabricating the definitive one.

Estimate vertical dimension with precision

TrazaLab gives you clinical tools to calculate, verify, and document VDO. Try it free.

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