3: Definition and Prevalence of Dentofacial Deformities

Definition and Prevalence of Dentofacial Deformities

The term dentofacial deformity refers to significant deviations from normal proportions of the maxillomandibular complex that also negatively affect the relationship of the teeth within each arch and the relationship of the arches with one another (occlusion).2,4,5,8,11,14,15,17,18,21,22,25,27,31,36,37,40,52,54 The affected individual will have varied degrees of compromise in head and neck functions related to breathing, swallowing, speech articulation, chewing, and lip closure/posture. Effects on the temporomandibular joints, the periodontium, and the teeth themselves may also occur.24,25,28,33,34,38,55 The presenting facial disproportion will, in general, have at least some negative effects on psychosocial health.16,39,56,57

Racial variations with regard to the incidence of facial dysmorphology and the resulting malocclusion are also known to occur.59,64 Definitions of acceptable levels of deviation from normal continue to be questioned by both clinicians and patients.7,26,30,32,35,58,61,62 Over the years, the National Center for Health Statistics has collected data and the Research Council has held multidisciplinary conferences to focus attention on these issues.6,12,19,20,29,41-51,53,63

Surgery to reposition the jaws (i.e., an orthognathic procedure) as part of an interdisciplinary approach is often recommended to manage the related skeletal, dental, and soft-tissue dysfunctions and concerns.3,13,23,60,66 Speech therapy, dental work, orthodontics, and surgical procedures alone are generally inadequate as isolated treatment modalities.

A dental clinician who is asked to evaluate the affected individual must ask himself or herself, “Are the problems too severe to be most effectively managed with orthodontics and dentistry alone?” A cosmetic surgeon who evaluates the same patient must ask himself or herself, “Will limited soft-tissue or augmentation procedures alone be sufficient to properly manage the presenting dysmorphology and to address functional aspects?”

If the discrepancy in the size or position of the jaws as they relate to each other and to the upper facial skeleton results in significant facial disproportion and also negatively affects certain head and neck functions (e.g., speech, swallowing, chewing, lip closure and posture, breathing), then it should not be ignored. It would be misguided to consider orthodontics alone to alter the occlusion without fully informing the patient and his or her family of the preferred biologic approach to management (i.e., orthodontics and jaw surgery). Likewise, it would be avoiding the obvious for the cosmetic surgeon to recommend either soft-tissue aesthetic or skeletal contour procedures without discussion of the presenting malocclusion, airway dysfunction, and overall facial disproportion. The treatment recommended to the patient and his or her family should not be limited by the skill set of the initial consulting clinician.

Facial disproportion observed in a child may at times be self-correcting. For example, apparent mandibular deficiency that is present before the pubertal growth spurt may normalize. In some cases, the maxilla or mandible may be induced to grow a few millimeters, more or less, through dentofacial orthopedics. However, major transformation of the jaws with the use of growth-modification techniques cannot be expected. Proffit has pointed out that, even with the well-intended aim of dentofacial orthopedics to alter jaw growth, as a result of anchorage requirements and biologic realities coupled with the practical desire of the orthodontist to “correct the occlusion,” the treatment generally results in the displacement of the teeth in the direction of correcting the occlusion rather than the jaw relationships.53 The term dental compensation for the skeletal discrepancy is universally understood to explain this treatment approach. Orthodontic-introduced dental compensation for the occlusion will hinder the eventual skeletal (orthognathic) correction if this is later required or requested.

Informed consent from the patient or his or her family is strongly recommended before embarking on a compromised treatment plan. For example, if a child is recognized to have an underdeveloped mandible with a Class II malocclusion and standard growth modification is attempted, it may be difficult for the orthodontist to prevent at least some retraction of the upper incisors and the forward displacement of the lower teeth. This may result in an “improved” occlusion, but it may also potentially involve long-term negative effects on periodontal health (e.g., labial cortical bone stripping), the airway (e.g., retroglossal obstruction), and facial aesthetics (e.g., a weak profile).39,56,57 It also compromises the option of an orthognathic correction with the need to first “undo” the dental compensations through “redo” orthodontics (Fig. 3-1).

In the growing child who presents with a Class II malocclusion pattern, an active treatment approach is often offered by the orthodontist. This approach may attempt to alter jaw growth and to correct the occlusion by means of the following: (1) functional appliance use (e.g., Frankel, Twinblocks) to stimulate sagittal growth of the mandible; (2) the possible extraction of maxillary premolars with orthodontic incisor retraction; (3) the use of headgear to restrain maxillary sagittal growth; and (4) the orthodontic forward displacement of the lower anterior teeth (Fig. 3-2). With the use of this approach, favorable facial results will be seen in only a very specific patient subgroup that includes those patients with true maxillary dental protrusion and a limited degree of mandibular retrusion. In these cases, the extraction of maxillary premolars with the retraction of the incisors to a corrected inclination in combination with the minimal forward displacement of the lower teeth may result in both favorable occlusion and acceptable facial aesthetics.

For the experienced surgeon and orthodontist, the accurate diagnosis of a dentofacial deformity will usually be clear after the initial examination and a review of standard records. A favorable correction through the effective orthodontic alignment of the teeth in combination with the surgical repositioning of the jaw(s) will be the preferred approach.

Prevalence of Jaw Deformities and Malocclusion

U.S. Population Survey

As part of a large-scale evaluation of the health of the U.S. population, a National Health and Nutrition Examination Survey (NHANES III) was carried out between 1989 and 1994.53 Starting with a sampling of 14,000 individuals, estimates of the incidence of malocclusion and its severity were made. The sample of individuals was carefully selected to provide weighted estimates for an approximate 150,000,000 people between the ages of 8 and 50 years who were members of black, white, and Latino American racial and ethnic groups. Those individuals outside of that age range (i.e., those younger than 8 years and older than 50 years), Native Americans, those living on military reservations, and some other specific population groups were excluded from this study. Data collected included the following:

The Horizontal/Sagittal Dimension

This study provides useful information about preadolescent children (8 to 11 years old), adolescents (12 to 17 years old), and adults (18 to 50 years old) with reference to how the teeth fit together and, by inference, the prevalence of dentofacial deformities. When interpreting the data collected for the NHANES III study, it is important to consider that at least some degree of dental compensation for an existing jaw deformity normally occurs during growth and is expected to have been present at the time that the study measurements were taken. Therefore, it is unlikely that either the moderate or greater values of positive overjet or the mild to moderate values of negative overjet measured in the NHANES III study were found in individuals with “normal” jaw relationships. It would be safe to assume that any individual in the study with more than 7 mm of positive overjet has a jaw discrepancy that is characterized by mandibular deficiency (see Chapter 19). In addition, those with 2 mm or more of reverse overjet are assumed to have elements of maxillary deficiency in combination with relative mandibular excess (see Chapter 20).

The NHANES III study documents that extreme positive overjet is more frequent among children and that reverse overjet becomes more common among adults (i.e., after growth completion). This data confirms that, in some children, a late mandibular growth spurt not only corrects the excess positive overjet but actually causes it to become negative. Fortunately, in at least some of the children with an excess overjet, “catch-up” mandibular growth corrects the occlusion without overshooting the mark. The NHANES III study also documents that significant reverse overjet is more prevalent among blacks and Latino Americans as compared with whites. This confirms the more frequent dentofacial deformity growth pattern of maxillary deficiency in combination with relative mandibular excess that is seen among blacks and Latinos as compared with whites.

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Jan 1, 2015 | Posted by in Orthodontics | Comments Off on 3: Definition and Prevalence of Dentofacial Deformities
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