Vertical Skeletal Relationship

Marcello M. | January 30, 2025

The vertical relationship between the maxilla and mandible can be assessed using both angular and linear measurements. These measurements help determine facial proportions and potential growth discrepancies.

Angular Measurements

The maxillary-mandibular plane angle (MMPA) is a key parameter for evaluating the vertical relationship of the jaws. It is determined by the angle formed between the maxillary plane (ANS-PNS) and the mandibular plane (Go-Me). The normal MMPA value is 27 ± 5 degrees. A significantly increased MMPA may indicate a vertical growth pattern (long face syndrome), whereas a reduced MMPA suggests a horizontal growth pattern (short face syndrome).

Another commonly used measurement is the Frankfurt-mandibular plane angle (FMPA). The Frankfurt plane is defined by a line passing through Or-Po, and its angle with the mandibular plane should also be 27 ± 5 degrees. This measurement serves as an alternative to the MMPA and helps confirm vertical discrepancies.

Gonial Angle

The gonial angle is a key cephalometric measurement used to evaluate the vertical growth pattern of the mandible. It is formed by the intersection of the mandibular plane and the ramus of the mandible. The normal value for the gonial angle typically ranges between 120° and 130°.

  • Hyperdivergent Growth Pattern: A gonial angle greater than 130° suggests a vertical growth tendency, often associated with a long face, open bite, and increased lower facial height.
  • Hypodivergent Growth Pattern: A gonial angle below 120° indicates a horizontal growth pattern, typically linked to a short face, deep bite, and reduced vertical dimension.

Proper assessment of the gonial angle is essential for determining the patient’s facial growth pattern and planning orthodontic treatment effectively.

Linear Measurements

Linear measurements provide insight into facial height proportions. The relationship between the upper and lower anterior facial heights is crucial for assessing vertical balance.

  • Total Anterior Facial Height (TAFH): Measured from nasion to menton, with an average value of 119 mm.
  • Upper Anterior Facial Height (UAFH): Extends from nasion to ANS, with an average value of 54 mm.
  • Lower Anterior Facial Height (LAFH): Measured from ANS to menton, with an average value of 65 mm.

Facial Proportion

The proportion between the lower and total anterior facial height provides additional insight into vertical jaw relationships. Ideally, the lower anterior facial height (LAFH) should be approximately 55 ± 2% of the total anterior facial height (TAFH) as measured on a cephalometric radiograph.

Clinical Relevance

Abnormal vertical proportions can be associated with skeletal malocclusions:

  • Increased LAFH: Suggests excessive lower facial height, often linked to open bite or vertical maxillary excess.
  • Reduced LAFH: May indicate deep bite tendencies or horizontal growth patterns.

Understanding these vertical measurements is essential for diagnosing and planning orthodontic or surgical interventions to achieve balanced facial aesthetics and function.