Short Face Growth Patterns: Maxillomandibular Deficiency

Published on 13/06/2015 by admin

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Short Face Growth Patterns

Maxillomandibular Deficiency

Jeffrey C. Posnick, DMD, MD

A frequently seen pattern of facial disharmony has the common denominator of a significant degree of vertical and horizontal (sagittal) deficiency in the maxilla and mandible. Measuring the ratio of the lower facial height (i.e., the subnasion to the menton) to the upper facial height (i.e., the glabella to the subnasion) will confirm that the lower height is diminished. The height of the alveolar process in both jaws is reduced.²³ The visual presentation of the face includes an apparent redundancy of the soft-tissue envelope of the lower face, thereby creating “chubby cheeks” in the adolescent and a prematurely aged look by early adulthood.

Clinical examination of the individual with a short face growth pattern will generally confirm a pseudoprominence of the nose; an acute nasolabial angle; a measurable and visually perceived short lower facial height with a disproportionate facial width-to-height ratio; and either a prominent pogonion (more frequent with a Class I deep bite) or a weak chin (more common with a Class II excess overjet).3,10,11,20,21,35,39,40 Normally, there is a 1 : 2 relationship between the distance from the base of the nose to the upper lip and the distance from the lower lip to the chin. In the individual with a short face growth pattern, the relationship is closer to 1 : 1.^15,42,43,56 The labiomental sulcus is deep and the lower lip is everted, thereby further confirming the degree of mandibular deficiency. The maxillary incisors are often completely covered by the upper lip, which creates an edentulous appearance in repose and an unfavorable “no gingiva” smile. With the teeth in occlusion, the oral aperture appears closed and the upper lip projects forward, often in front of procumbent incisors. Individuals are frequently described as having a sad or unhappy look in repose as a result of the downturned oral commissures and the closed aperture. The reduced lower facial height causes the everted and prominent lips that would otherwise have appropriate shape and volume if the facial height and horizontal projection of the jaws were restored. In the profile view, the nose appears long and prominent. There is often a lateral flaring of the nostrils with a “hanging columella.”

Classically, there is a deep bite with either marked anterior crowding or excessive flaring with less dental crowding.³⁴ There may be a Class II malocclusion with greater than average overjet.^50,51 If so, the mandible has greater deficiency than the maxilla, and the pogonion will lack prominence. Individuals with Class I deep bite without excess overjet are more likely to have a retropositioned A-point as compared with the B-point (i.e., a counterclockwise rotated maxillomandibular complex) and a prominent pogonion. The maxillary and mandibular planes are often nearly horizontal, which results in a “square jaw” facial appearance.

Functional Aspects

• Articulation errors in speech and altered swallowing mechanisms that result from the small jaws, the Class II deep-bite malocclusion, and the limited intraoral volume for the tongue are expected (see Chapter 8).

• Difficulties with chewing and with lateral and protrusive mandibular movements as a result of the Class II deep-bite malocclusion are expected (see Chapter 8).

• A spectrum of upper airway sites of obstruction often exists with the short face growth pattern. This includes obstructions at the intranasal, palatopharyngeal (retropalatal), and glossopharyngeal (retroglossal) locations. The incidence of obstructive sleep apnea is increased in this patient population and should be ruled out (see Chapter 10 & 26).

• Detrimental long-term effects on the dentition and the periodontium as a result of any traumatic malocclusion, the crowding of the teeth in the limited alveolar housing, and previous camouflage orthodontic treatment may be seen (see Chapter 5 & 6).

• A higher incidence of temporomandibular disorders in the form of masticatory muscle discomfort as a result of the short facial height and the deep-bite malocclusion has been reported (see Chapter 9).

Clinical Characteristics

• Absence of maxillary tooth show beneath a relaxed upper lip

• Limited tooth and no gingiva show with broad smile

• Acute nasolabial angle

• Depressed pyriform rims

• An apparent fullness of the cheeks and a squareness of the overall face

• An apparent prominent and elongated nose when viewed in profile

• Procumbent everted lips, turned down corners of the mouth, and a closed aperture

• An excessively deepened and elongated labiomental fold

• Soft-tissue bunching that eventually results in perioral creases (i.e., marionette lines)

• Early and deep jowl formation by middle age

• Premature loss of any semblance of an attractive neck–jaw angle

Dental Findings

• Class II excess overjet malocclusion is common, but a Class I deep bite is also frequent.

• A deep impinging bite with palatal irritation is a frequent finding.

• Dental crowding with flaring of the incisors in each arch is also a frequent finding.

Radiographic Findings

• The total anterior facial height is decreased (i.e., from the nasion to the menton).

• The lower anterior facial height is short (i.e., from the subnasion to the menton).

• Horizontal retrusion is measurable at the A-point and the B-point in both jaws.

• Disproportion in the ratio of the facial width to the facial height is measurable on an anteroposterior cephalometric radiograph or a computed tomography scan.

• Excessive procumbency of the maxillary and mandibular incisors is frequently measurable.

• Excessive flattening (i.e., counterclockwise rotation) of the maxillary and mandibular planes is frequently measurable.

• Decreased alveolar bone height associated with the maxillary incisors is measurable (i.e., the distance from the floor of the nose to the incisal edge).

• Decreased alveolar bone height associated with the mandibular incisors is measurable (i.e., the distance from the short menton to the incisal edge).

Treatment Indications and Objectives

The indications for treatment in a patient with a short face growth pattern may be to improve function (e.g., occlusion, chewing, swallowing, speech, breathing, lip posture), but another compelling aspect is typically the enhancement of facial aesthetics. The visually aesthetic advantages of the surgical lengthening and projection of the short and retrusive lower face toward Euclidian proportions are immediately apparent and do not require quantification.32,33,58

To restore facial proportions and preferred facial aesthetics, there must be both vertical and horizontal expansion of the maxillomandibular complex.⁵⁴ Accomplishing these objectives will eliminate cheek and lip region bunching and distortion and restore a pleasing soft-tissue envelope. When this is done, a youthful oral aperture is restored. The corners of the mouth are no longer downturned, and the lips will be separated when they are at rest. The upper vermillion increases in volume, and the labiomental fold flattens. The maxillary incisors can be seen in repose, and the gingiva is visible with smile. The nose no longer appears excessively prominent, and the nasolabial angle improves. The jowls diminish, and the length-to-width ratio of the face is restored. The shape of the face changes from square to oval with the restoration of the natural contours and attractive ogee curves. The overall facial aesthetic changes from sad and older appearing to younger looking and more attractive (Figs. 23-1 through 23-7).