Clinical Techniques for Vertical Dimension and Occlusion Assessment

Methods for Determining Vertical Dimension of Occlusion (VDO)

Willis Bite Rule (Gauge Method)

1. Place the rule in the inferior third of the face and measure the distance from the base of the nose to the base of the chin.
2. Compare this measurement with the distance that extends from the outer corner of the eye to the corner of the lips.

Phonetic Method Using a Compass

1. Mark two arbitrary points on the patient (e.g., tip of the nose and chin) while the occlusion rims are in place.
2. Use a compass and a millimeter ruler to measure the distance between these two arbitrary points.
3. Instruct the patient to speak for five minutes, repeating words containing sibilant sounds (e.g., 'S', 'CH', or words like "mo chichiriviche") to relax the jaw muscles.
4. Re-measure the distance using the millimeter ruler and compass without the occlusion rims (measuring the interocclusal space).

Midline and Arch Width Assessment

Midline Stroke Alignment

The midline stroke allows for the alignment of the two upper central incisors. Reference points used for alignment include:

• Hairline
• Glabella
• Tip of the nose
• Philtrum
• Superior labial frenum
• Menton (chin)

Determination of Bicanine Distance

The bicanine distance indicates the width required for the six upper anterior teeth. This distance is determined when a sharp tool is placed at the corner of the lips, and this point coincides exactly with the distal surface of the canine tooth.

Key Concepts in Occlusion and Jaw Relations

Occlusion and Maximum Intercuspation (MI)

Occlusion refers to the relationship between the maxillary (superior) and mandibular (inferior) teeth.

Maximum Intercuspation (MI) is the tooth-to-tooth relationship determined when the jaw is closed, resulting in the largest number of occlusal contacts between the premolars and molars. The Maximum Intercuspal Position is also known as Centric Occlusion, Usual Centric, or Acquired Centric.

Centric Occlusion vs. Centric Relation

In natural dentition, Centric Occlusion is typically located anteriorly to Centric Relation, usually by an average distance of 0.5 to 1 mm. Since edentulous individuals lack teeth and therefore lack a definitive occlusal relationship, it is necessary to use Centric Relation (CR) as the primary reference position.

Definitions of Centric Relation (CR)

Centric Relation is a complex mandibular position defined by several criteria:

• The mandibular occlusal position that coincides with the average position.
• The mandibular position determined by the neuromuscular reflex acquired when primary teeth are in occlusion.
• The mandibular position that exists when the centers of vertical and lateral motion are in the terminal hinge position.
• The relationship of the mandible to the maxilla when the mandible is braced during swallowing.

Other Mandibular Positions

The following mandibular positions are often considered synonymous:

• Mandibular position synonymous with the Physiological Rest Position.
• Mandibular position synonymous with the position of the mandible during swallowing.