Introduction

Vertical dimension of occlusion (VDO) represents the distance between two facial landmarks when the teeth are in maximum intercuspation. Changes in vertical dimension profoundly affect facial appearance, function, and comfort. Loss of vertical dimension from dental wear, tooth loss, or bone resorption creates a collapsed appearance with pronounced facial wrinkles and reduced lower facial height. Understanding vertical dimension assessment, the consequences of its loss, and restoration techniques is essential for comprehensive prosthodontic treatment planning.

Definition and Anatomy

Vertical Dimension of Occlusion

Vertical dimension of occlusion is the distance between a fixed point on the maxilla and a fixed point on the mandible when the teeth are in centric occlusion. This is typically measured as the distance between the tip of the nose and the tip of the chin, or between the lower border of the orbit and the lower border of the mandible. In a normal adult, lower facial height typically comprises approximately 40 to 45% of total facial height.

Vertical Dimension of Rest

Vertical dimension of rest (VDR), also called vertical dimension of the resting position, is the distance between the same facial landmarks when the mandible is in its resting position with the lips at rest and no muscular tension. The difference between VDO and VDR is the freeway spaceโ€”typically 2 to 4 millimeters.

Freeway Space

Freeway space is the distance between the maxillary and mandibular teeth when the mandible is in its physiologic resting position. Adequate freeway space is essential for neuromuscular comfort and functional mandibular movement. Freeway space is lost when vertical dimension is reduced below normal levels.

Causes of Vertical Dimension Loss

Dental Wear and Attrition

Progressive wear of the occlusal surfaces of teeth gradually reduces the distance between the maxilla and mandible. Patients with severe bruxism, clenching, or aggressive chewing habits experience accelerated tooth wear. Over many years, this wear can reduce vertical dimension by several millimeters.

Patients with abrasive diets, acidic beverages leading to erosion, or parafunctional habits lose vertical dimension progressively. Once vertical dimension is lost, restoration requires prosthodontic intervention.

Tooth Loss and Alveolar Bone Resorption

Loss of teeth is followed by progressive resorption of the alveolar bone that previously supported the tooth roots. After tooth extraction, the bone resorbs rapidly in the first six months, then more slowly over subsequent years. Complete resorption of a tooth socket can reduce vertical dimension by 1 to 2 millimeters per missing tooth.

Patients with multiple missing teeth or complete dentures experience significant vertical dimension loss. The extent of resorption varies among patients; some experience rapid substantial resorption while others resorb more slowly. Systemic factors including age, bone quality, and estrogen status influence resorption rates.

Fixed Prosthetic Failures

Older fixed prostheses including crowns and bridges may have been constructed with inadequate vertical dimension. Repair or replacement of these restorations with proper vertical dimension is often necessary.

Root Resorption and Periodontal Disease

Severe periodontal disease with progressive alveolar bone loss reduces the distance between the teeth and the alveolar crest. Combined with tooth wear, significant vertical dimension reduction can occur.

Consequences of Vertical Dimension Loss

Facial Esthetic Changes

Reduced vertical dimension creates a collapsed facial appearance with pronounced vertical facial wrinkles, particularly around the mouth. The naso-labial folds deepen, the marionette lines become more prominent, and the corners of the mouth droop. These changes create a prematurely aged appearance.

The lower facial third becomes proportionally reduced. Rather than comprising 40 to 45% of total facial height, it may be reduced to 35% or less. This imbalance creates an esthetically displeasing facial proportion.

The lips may appear thinner as the lower lip becomes more closely approximated to the chin. Lip competence may be affected, with possible lip incompetence and anterior open bite.

Functional Consequences

Loss of freeway space removes the neuromuscular space for comfortable mandibular rest position. Patients with significantly reduced freeway space report discomfort, jaw fatigue, or temporomandibular joint (TMJ) pain.

Chewing efficiency may be compromised due to reduced jaw opening space and altered occlusal forces. Mastication may be less efficient, placing burden on the patient's ability to adequately prepare food for swallowing.

Speech and Phonetic Changes

Some patients notice subtle changes in speech when vertical dimension is significantly reduced, particularly in sibilant sounds. Restoration of proper vertical dimension usually normalizes speech.

Psychological and Social Impact

The aged appearance resulting from vertical dimension loss can profoundly affect patient confidence and social interaction. Some patients report feeling significantly older due to the premature aging appearance.

Assessment of Vertical Dimension

Photographic Assessment

Obtain frontal facial photographs and measure the ratio of lower facial height to total facial height. In a normal face, this ratio is approximately 40 to 45%. A ratio significantly below this suggests reduced vertical dimension.

Compare facial photographs of the patient taken years earlier, if available. Progressive facial collapse is evident when comparing older and recent photographs.

Clinical Examination

Observe the patient's facial proportions with the lips at rest. Excessive deepening of the naso-labial fold or marionette lines suggests vertical dimension loss. Examine the freeway space by observing the patient's resting position.

Ask the patient to open and close the mouth, observing the amount of opening space and the comfort of opening and closing motions.

Closest Speaking Space Method

The closest speaking space method (CSS) measures the vertical distance between the teeth when the patient speaks. Have the patient repeat words or phrases with sibilant sounds (such as "s"), which brings the teeth closer together than normal speaking position. The distance between the teeth during sibilant pronunciation represents the closest speaking space, typically 1 to 2 millimeters.

The vertical dimension of occlusion can be estimated by adding the measured CSS to the freeway space (typically 2 to 4 millimeters). This method provides a functional estimate of appropriate vertical dimension.

Cephalometric Analysis

Lateral cephalometric radiographs can be analyzed to measure facial heights. The anterior facial height (measured from nasion to menton) and posterior facial height (from sella to gonion) can be measured. A posterior-to-anterior facial height ratio of approximately 0.65 to 0.75 is considered normal.

Comparison of current cephalometric radiographs to radiographs taken years earlier, if available, can demonstrate progressive vertical dimension loss.

Phonetic Assessment

The patient can be asked to pronounce specific words or sounds that require particular vertical dimensions. The "M" sound requires the lips to be touching with teeth slightly apart. The "S" sound requires the teeth to be very close together. Observation of these phonetic positions provides functional information about appropriate vertical dimension.

Functional Considerations in Vertical Dimension Restoration

Freeway Space Restoration

When restoring lost vertical dimension, establish appropriate freeway space, typically 2 to 4 millimeters. Inadequate freeway space (< 1 mm) creates TMJ discomfort and muscle tension. Excessive freeway space (> 5 mm) may create an abnormal appearance and poor lip seal.

Adaptation to Increased Vertical Dimension

If vertical dimension has been lost significantly and must be restored substantially, the change should ideally be made gradually. Some prosthodontists recommend restoring lost vertical dimension in stagesโ€”first with restorative treatment, then reassessing after several months before completing final restorations.

Large immediate increases in vertical dimension (> 4 to 5 mm) may create initial discomfort and require adaptation. Most patients adapt to moderate increases (2 to 3 mm) within several weeks. Neuromuscular adaptation occurs as the patient's jaw muscles adjust to the new vertical dimension.

Vertical Dimension Restoration Methods

Edentulous Patients with Complete Dentures

Patients with severe vertical dimension loss due to complete tooth loss require denture construction with proper vertical dimension. Measure the closest speaking space to estimate appropriate vertical dimension, then construct dentures with this dimension.

If the patient has worn dentures with inadequate vertical dimension, they may initially feel uncomfortable with properly restored vertical dimension. Explain that adaptation will occur over several weeks and that improved function and appearance will result.

Dentate Patients Requiring Restorations

Patients with remaining teeth requiring crowns, fixed bridges, or implant-supported restorations should have these restorations constructed with proper vertical dimension. If multiple restorations are needed, they should be coordinated to establish consistent and appropriate vertical dimension.

Partial Edentulous Patients

Patients with some remaining teeth and missing teeth may require a combination of fixed restorations (crowns, fixed bridges, implants) and removable partial dentures. All restorations should be constructed to achieve consistent vertical dimension.

Combined Esthetic and Functional Restoration

Integrated Treatment Planning

Comprehensive restoration of lost vertical dimension often requires multiple components. Restorative dentistry (crowns, implants), prosthodontics (dentures, implant prosthesis), and possibly periodontal or surgical treatment may be needed to achieve optimal results.

Soft Tissue Esthetics

Restoration of vertical dimension improves facial proportions and reduces wrinkles, but may not completely eliminate facial wrinkles in older patients. Some patients may benefit from cosmetic procedures like dermal fillers or botulinum toxin injection to enhance the esthetic results of vertical dimension restoration.

Patient Communication and Expectations

Before and After Analysis

Show the patient photographs and images demonstrating how restoration of vertical dimension will improve facial proportions. Digital smile design software can be used to preview the esthetic changes anticipated from vertical dimension restoration.

Realistic Expectations

Discuss with the patient that while vertical dimension restoration will improve esthetic and functional outcomes, it will not eliminate all facial aging signs. Proper esthetic outcomes depend on appropriate vertical dimension, but other factors including soft tissue characteristics also influence facial esthetics.

Conclusion

Vertical dimension of occlusion fundamentally affects facial esthetics, function, and patient comfort. Loss of vertical dimension from dental wear, tooth loss, or other causes creates an aged, collapsed facial appearance and functional limitations. Assessment of vertical dimension using photographic, clinical, phonetic, and cephalometric methods allows accurate diagnosis of vertical dimension loss. Comprehensive restoration of lost vertical dimension through prosthodontic treatment planning improves facial proportions, restores function, and enhances patient appearance and confidence. Proper understanding of vertical dimension principles is essential for comprehensive dental treatment planning.