Epidemiologic surveys demonstrate that a large percentage of the United States’ population has a significant malocclusion.1–3 Very little data describe the exact prevalence of significant skeletal facial deformity. This information can be extrapolated from studies that have evaluated the prevalence of severe malocclusion. The National Health and Nutrition Examination Survey (NHANES III), conducted from 1989 to 1994, obtained a sample of 14,000 individuals ages 8 through 50 years, which roughly approximates the general U.S. population. In this study, information was collected describing overjet and reverse overjet, vertical overlap (deep bite and open bite), and posterior cross-bites.¹ It can be assumed that patients with extreme values in each of these categories have underlying facial deformities (Table 26-1). Because many patients have dental compensations for skeletal growth abnormalities (described later in this chapter), this study likely underestimates the severity of skeletal abnormalities. This type of data, combined with other criteria that clearly define the most severe characteristics of a malocclusion such as overjet versus crowding, can help to estimate more accurately the prevalence of skeletal abnormality that may require surgical correction as part of the treatment for malocclusion.²

It appears that about 2% of the U.S. population has mandibular deficiency, vertical maxillary excess that is severe enough to be considered a handicap, or both.³ Other abnormalities and their percentages of prevalence in the population include mandibular excess, maxillary deficiency, or both, 0.3%; open bite, 0.3%; and asymmetry, 0.1%. Therefore, it appears that approximately 2.7% of the U.S. population may have a dentofacial deformity contributing to malocclusion that will require surgical treatment for correction.

Historically, treatment of malocclusions, even those associated with dentofacial deformities, has been aimed at correction of dental abnormalities, with little attention to the accompanying deformity of the facial skeleton. In the last 60 years, surgical techniques have been developed to allow positioning of the entire midface complex, the mandible, or dentoalveolar segments to any desired position. The combining of surgical and orthodontic procedures for dentofacial deformities has become an integral part of the correction of malocclusions and facial abnormalities.

Malocclusion and associated abnormalities of the skeletal components of the face can occur as a result of a variety of factors, including inherited tendencies, prenatal problems, systemic conditions that occur during growth, trauma, and environmental influences. Although it is not within the scope of this book to present a detailed discussion of facial growth, an understanding of basic principles as they relate to the development of dentofacial deformities is essential. Enlow and Han’s Essentials of Facial Growth should be reviewed for a more complete discussion of the principles of facial growth.4

The development of proper craniofacial form and function is a complex process affected by many factors. In the area of the craniofacial complex, some parts appear to have their own intrinsic growth potential, including the spheno-occipital and sphenoethmoidal synchondroses and the nasal septum. In addition, the majority of growth of the bones of the face occurs in response to adjacent soft tissue and the functional demands placed on underlying bone. These soft tissue influences include the nasal, oral, and hypopharyngeal airway; facial muscles; and muscles of mastication.5

The general direction of normal growth of the face is downward and forward with lateral expansion. The maxilla and the mandible appear to grow by remodeling or differential apposition and resorption of bone, producing changes in three dimensions. Enlow and Hans describe this phenomenon as area relocation, with the maxillary–mandibular complex enlarging in the downward and forward direction as an “expanding pyramid” (Figure 26-1).⁴ The direction and amount of growth characterize an individual’s growth pattern.⁶ Alterations in the pattern of growth or in the rate at which this growth occurs may result in abnormal skeletal morphology of the face and an accompanying malocclusion.

Environmental influences also play a role in the development of dentofacial deformities. As early as the prenatal stage, intrauterine molding of the developing fetal head may result in a severe mandibular deficiency. Abnormal function after birth also may result in altered facial growth because soft tissue and muscular function often influence the position of teeth and growth of the jaws. Abnormal tongue position or size can affect the position and growth of the maxilla and the mandible (Figure 26-2). Respiratory difficulty, mouth breathing, and abnormal tongue and lip postures can adversely influence facial growth.⁷ Trauma to the bones of the face can result in severe abnormalities of the facial skeleton and the occlusion. In addition to the abnormality that occurs as an immediate result of trauma, further effects on the development of facial bones may occur. In the case of temporomandibular joint (TMJ) trauma in a growing child, significant restriction of jaw function may occur as a result of scarring or bony or fibrous ankylosis. Subsequent alteration of growth may result with deficient or asymmetric mandibular growth (Figure 26-3).

Many areas of dental practice, in addition to orthodontics and surgery, must be integrated to address the complex problems of patients with dental deformities. This integrated approach, used throughout the evaluation, presurgical, and postsurgical phases of patient care, provides the best possible results for these patients.8

The most important phase in patient care centers on evaluation of the existing problems and definition of treatment goals. At the initial appointment, a thorough interview should be conducted with the patient to discuss the patient’s perception of the problems and the goals of any possible treatment. The patient’s current health status and any medical or psychological problems that may affect treatment are also discussed at this time.

The involved orthodontist and oral-maxillofacial surgeon should conduct a thorough examination of facial structure, with consideration of frontal and profile esthetics.

Evaluation of facial esthetics in the frontal view should assess the presence of asymmetries and evaluate overall facial balance. The evaluation should include assessment of the position of the forehead, eyes, infraorbital rims, and malar eminences; configuration of the nose, including the width of the alar base; paranasal areas; lip morphology; relationship of the lips to incisors; and overall proportional relationships of the face in the vertical and transverse dimensions. Figure 26-4 demonstrates normal facial proportions. The profile evaluation allows an assessment of the anteroposterior and vertical relationships of all components of the face. The soft tissue configuration of the throat should also be evaluated. Photographic documentation of the pretreatment condition of the patient should be a standard part of the evaluation. Video and digital computerized images have been introduced over the past decade as an additional aid in evaluating facial morphology.

A complete dental examination should include assessment of dental arch form, symmetry, tooth alignment, and occlusal abnormalities in the transverse, anteroposterior, and vertical dimensions. The muscles of mastication and TMJ function should also be evaluated. A screening periodontal examination, including probing, should assess the patient’s hygiene and current periodontal health status. Impressions and a bite registration for dental cast construction and evaluation should also be obtained at this time.

Lateral cephalometric and panoramic radiographs are routinely used in the patient evaluation and are an important part of the initial assessment. The cephalometric radiograph can be evaluated by several techniques to aid in the determination of the nature of the skeletal abnormality (Figure 26-5; Table 26-2).^9,10 An important note, however, is that cephalometric radiographs are only a part of the evaluation process; they are used as adjunctive diagnostic tools in the clinical assessment of the patient’s facial structure and occlusion. Other radiographic images may be helpful in evaluating patients for surgical correction. These may include posteroanterior facial films, TMJ images when indicated, and conventional and cone beam computed tomography (CBCT) (Figure 26-6). In difficult, complex cases, it may be helpful to obtain a stereolithic three-dimensional model constructed from CT data. Computerized digital technology helps integrate cephalometric data with digital images of the face to improve evaluation of the relationship of the underlying facial skeleton and overlying soft tissue. After careful clinical assessment and evaluation of the diagnostic records, a problem list and treatment plan should be developed, combining the opinions of all practitioners participating in the patient’s care, including the orthodontist, oral-maxillofacial surgeon, periodontist, and restorative dentist.