The upper jaw, or maxilla, is a complex bone structure that forms the central part of the face, supporting the upper teeth, the floor of the nasal cavity, and the eye sockets. Maxillary hyperplasia (MH) is a condition characterized by the overgrowth of this structure, resulting in a disproportionately large upper jaw relative to the rest of the facial skeleton. This condition disrupts the balance between the upper and lower jaws, leading to functional and aesthetic concerns. MH is often referred to as Vertical Maxillary Excess (VME), which emphasizes the dimension of overgrowth that most affects facial appearance and bite alignment.
Defining Maxillary Hyperplasia
Maxillary hyperplasia denotes an excessive increase in the size or volume of the maxilla, which is typically due to an overgrowth of the bone and the surrounding dentoalveolar tissues. The term “hyperplasia” itself is a biological descriptor meaning the enlargement of tissue caused by an increase in the reproduction rate of its cells. In the context of the upper jaw, this cellular overgrowth leads to an abnormally increased dimension, most commonly in the vertical plane.
The disproportionate size of the maxilla creates a skeletal malocclusion, meaning the upper and lower teeth do not align properly when the jaw is closed. The increased size of the upper jaw alters the facial profile, often resulting in a convex appearance and a longer midface region. Functionally, the excessive dimension can interfere with biting, chewing, and speaking.
Recognizable Signs and Symptoms
Patients with maxillary hyperplasia often present with a combination of highly observable features. One of the most frequently noted signs is excessive gingival display, commonly known as a “gummy smile,” where more than two to three millimeters of gum tissue is visible above the upper teeth when smiling. This excessive visibility occurs because the maxilla has grown too far downward, carrying the teeth and gums with it.
The overgrowth contributes to a noticeable elongation of the midface, giving the lower third of the face a lengthened appearance. The excessive vertical dimension makes it difficult for the lips to meet naturally without conscious effort, a condition called lip incompetence. Facial proportions may also be affected by asymmetry.
The improper skeletal relationship often results in a specific type of malocclusion, such as an anterior open bite, where the front upper and lower teeth do not touch when the back teeth are closed. This issue, along with increased overjet (horizontal overlap of the front teeth), can compromise the ability to incise food effectively.
Underlying Causes and Contributing Factors
The development of maxillary hyperplasia stems from a complex interplay of genetic, developmental, and environmental influences. Genetic predisposition plays a substantial role, as a family history of facial imbalances or a long-face pattern can increase the likelihood of the condition developing. Certain rare genetic or syndromic conditions are also known to include MH as a feature.
The condition can arise from developmental anomalies during the active growth phases of childhood and adolescence. A significant acquired factor is chronic mouth breathing, often caused by nasal airway obstructions like enlarged adenoids or tonsils. Mouth breathing alters the resting posture of the tongue, which normally acts as a brace against the palate, helping to regulate the proper growth of the maxilla.
When the tongue posture is habitually lowered, the maxilla loses this internal support, and the buccinator muscles on the cheeks apply an imbalanced pressure. This altered environment can lead to the excessive vertical growth of the upper jaw, contributing to the long-face appearance. Despite these known contributors, the exact cause remains idiopathic in many cases.
Corrective Treatment Pathways
Addressing maxillary hyperplasia requires a comprehensive, multidisciplinary approach that involves close collaboration between an orthodontist and an oral and maxillofacial surgeon. The choice of treatment pathway depends heavily on the severity of the skeletal discrepancy and whether the patient is still growing. For less severe cases in younger patients, orthodontic management can sometimes be used to control minor skeletal adjustments and guide tooth movement.
However, for adult patients or those with severe skeletal excess, surgical correction is the definitive treatment method. The standard procedure is the Le Fort I osteotomy, a versatile orthognathic surgery designed to reposition the entire tooth-bearing segment of the maxilla. During this procedure, the surgeon makes a horizontal cut across the maxilla to separate it from the rest of the facial skeleton.
To correct the vertical excess, the mobilized maxilla is moved upward, a process known as impaction, and the excess bone is carefully removed from the upper part of the jaw. The repositioned maxilla is then secured in its new, higher position using small titanium plates and screws. This surgical correction simultaneously reduces the excessive gum display, shortens the elongated midface, and establishes a stable, functional bite, typically followed by a period of post-surgical orthodontic finishing to refine the tooth alignment.