Definition and Prevalence of Dentofacial Deformities

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Definition and Prevalence of Dentofacial Deformities

Jeffrey C. Posnick, DMD, MD

• Prevalence of Jaw Deformities and Malocclusion

• Orthognathic Procedures Performed on Hospitalized Patients in the United States

• Conclusions

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).

Figure 3-1 A 21-year-old woman with a primary mandibular deficiency growth pattern requested a surgical consultation for a “weak chin.” During her early teenage years, she underwent unsuccessful growth modification in an attempt to stimulate the forward projection of the mandible. This was followed by an orthodontic camouflage approach. The mandibular anterior dentition was flared forward. The history was significant for restless sleeping and a degree of daytime fatigue, which are suggestive of obstructive sleep apnea. Examination confirmed a retrognathic mandible with a Class II malocclusion. The mandibular incisors were crowded and procumbent. The family had hoped that a “chin implant” would be effective to manage the aesthetic effects. A sleep study confirmed obstructive sleep apnea (respiratory disturbance index = 18/hour). An orthognathic approach (Le Fort I, Sagittal splits, Osseous genioplasty) with redo orthodontic treatment including lower bicuspid extractions was recommended as the preferred method to improve the airway, to achieve long-term dental health, and to enhance facial aesthetics. A, Frontal facial and occlusal views. B, Profile facial view and lateral cephalometric radiograph.

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.

Figure 3-2 A 20-year-old man with a primary mandibular deficiency growth pattern requested a surgical consultation for a “weak chin.” During his early teenage years, he underwent unsuccessful growth modification in an attempt to stimulate the forward projection of the mandible. This was followed by an orthodontic camouflage approach that included maxillary first bicuspid extractions to retract the anterior teeth. In addition, the mandibular anterior dentition was flared forward. His history was significant for heavy snoring, restless sleeping, and a degree of daytime fatigue, all of which are suggestive of obstructive sleep apnea. Examination confirmed a retrognathic mandible with a molar Class II deep bite malocclusion. The mandibular incisors were crowded and procumbent. The family had hoped that a “chin implant” would be effective to manage the aesthetic effects. A sleep study was recommended. An orthognathic approach (Le Fort I, Sagittal splits, osseous genioplasty) with redo orthodontic treatment was suggested as the preferred method to improve the airway, to achieve long-term dental health, and to enhance facial aesthetics. A, Frontal facial and occlusal views. B, Profile facial view and lateral cephalometric radiograph.

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 alignment of the incisor teeth

• The horizontal position of the incisors (i.e., overjet or reverse overjet)

• The vertical overlap of the incisors (i.e., deep bite or open bite)

• The presence of posterior crossbite

• The presence of maxillary midline diastema

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.

According to the NHANES III study, only a third of the members of the U.S. population have ideal (horizontal) anteroposterior incisor relationships, and another third of these individuals have a moderate overjet discrepancy (i.e., borderline jaw dysharmony). The remaining third have either a severe positive overjet or a reverse overjet malocclusion. It is reasonable to assume that a significant percentage of this subgroup (i.e., those with a severe positive overjet or a reverse overjet) have a jaw discrepancy that would benefit from orthognathic surgery. In reality, many individuals in this subgroup will be treated with compromised orthodontics (i.e., dental compensation) in an attempt to neutralize the occlusion without the benefit of an orthognathic correction. This will result in suboptimal facial aesthetics and the potential for occlusal instability, long-term periodontal sequela, and compromise of the upper airway.

The Vertical Dimension

According to the NHANES III study, only half of the U.S. population has an ideal vertical relationship of the incisors (i.e., 0- to 2-mm overbite). In the others, a deep bite in combination with mandibular deficiency or maxillomandibular deficiency is more prevalent among whites, and an open bite in combination with bimaxillary dental protrusion is more frequent among blacks. Interestingly, either a severe deep bite (≥5 mm) or a marked open bite (≥2 mm) was present in approximately 20% of children and 13% of adults. The extreme values of open bite that were measured in the study group likely represent either a long face growth pattern (i.e., vertical maxillary excess or mandibular deficiency; see Chapter 21) or bimaxillary dental protrusion (see Chapter 24). Interestingly, significant anterior open bite as part of a long face growth pattern is more prevalent among white Americans. The extreme values of deep bite in the studied individuals are likely to represent either a short face growth pattern (i.e., maxillomandibular deficiency; see Chapter 23) or a primary mandibular deficiency. Significant degrees of vertical discrepancy (deep bite or open bite) at the incisors ideally benefit from orthognathic surgery. When dental compensating orthodontic treatment is instituted rather than orthognathic correction, compromised facial aesthetics, occlusal instability, and periodontal sequela are more likely to occur.

U.K. Population Survey

An Index of Treatment Need was developed by the Swedish Dental Board to classify the severity of dental findings by the worst presenting characteristic.³³ This method tends to downplay the specific alignment of individual teeth. It is a classification system that looks more globally at facial proportions and head and neck function than at isolated dental details. For example, if you have a mild irregularity of the incisors and only a mildly excessive overjet, you are judged to have only a mild problem. In other words, the impact on the individual is not judged to be more severe, because there is a combination of two mild occlusal deviations from normal. Alternatively, if you have a 10-mm overjet, even if the teeth are aligned in each jaw, you are judged to have a severe problem.

Brook and Shaw made modifications to the Swedish classification and developed the Index of Treatment Need for malocclusion to be used as a grading system of dental health and functional indications for treatment.9,10 The first part of their study was derived from the direct examination of occlusion and dental alignment. They defined five grades of treatment need, with Grade 1 representing little or no need for treatment and Grade 5 representing great need for treatment. The authors attempted to establish meaningful values for cutoff points between grades for each occlusal trait and to determine the quantifiable threat to the dentition if no treatment is provided. Grades 4 and 5 have characteristics that can result in a more severe impact on both facial aesthetic and dental aspects. These characteristics include the following:

Grade 5:

• Defects of cleft lip and palate *

• Overjet of more than 9 mm *

• Reverse overjet of more than 3.5 mm with reported masticatory and speech difficulties *

• Extensive hypodontia *

• Impeded eruption of the permanent teeth

• Submerged primary teeth

Grade 4:

• Extreme lateral or anterior open bites (>4 mm)*

• Increased overjet (>6 mm but ≤9 mm)*

• Reverse overjet (>3.5 mm with no masticatory or speech difficulties)*

• Reverse overjet of more than 1 mm with reported masticatory or speech difficulties

• Posterior crossbite with no functional occlusal contacts in one or both buccal segments

• Increased and complete overbite with gingival or palatal trauma

• Anterior or posterior crossbites with more than 2 mm of centric relation/centric occlusion discrepancy

• Severe contact point discrepancy (>4 mm)

• Less extensive hypodontia (e.g., one tooth per quadrant requiring preprosthetic orthodontics)

• Partially erupted teeth that are tipped and impacted against adjacent teeth

• The presence of supernumerary teeth

Individuals with extremes in positive overjet, reverse overjet, crossbite, and open bite as well as those with associated cleft lip and palate are considered to have Grade 4 and 5 conditions and judged to have problems that are severe enough that definitive treatment is needed. By inference, it is likely that a significant number of individuals with Grade 4 and 5 issues would ideally receive both orthodontics and jaw-straightening surgery.

The second part of the authors’ overall assessment of treatment priority was to record the aesthetic impairment contributed by the malocclusion. The authors used the Standard Continuum of Aesthetic Need (SCAN) index as a rating scale.¹⁶ The SCAN scale was constructed with the use of dental photographs from 1000 12-year-old children that were collected as part of a large multidisciplinary survey. Six non-dental judges rated these photographs on a 10-point visual analog scale. Both the aesthetic impairment component and the dental health component were part of the overall study.

The distribution of ratings for the Dental Health Indications Study conducted by Brook and Shaw were obtained from examination subjects (n = 222) who, at minimum, were felt to have a malocclusion to the extent that referral to a regional orthodontic center for advice or treatment was recommended.¹⁰ Each study patient was then examined, and their available radiographs were reviewed by skilled clinicians. Both components of the index (i.e., aesthetic and dental) were applied, and the patients were also asked to give their own rating according to the SCAN scale. Interestingly, there was a high correlation (confirmed by intraexaminer and interexaminer error testing of the findings) between both components (i.e., aesthetic and dental) of the study.

The study results indicated that 19.2% of the subjects (44 of 222) were considered to have Grade 5 conditions. Interestingly, the distribution of ratings from Grades 1 through 5 that were obtained from the examination of a matched, random, unselected group of schoolchildren (n = 333) indicated that only 5.1% fell in the Grade 5 category. A Grade 5 score indicates severe malocclusion with a high need for treatment to establish dental health. Most of the traits listed as Grade 5 cannot be corrected with orthodontics alone, and orthognathic surgery would likely be recommended or at least considered. The Shaw study indicates that, in the United Kingdom, more than 5% and as high as 19% of children who have been referred to an orthodontist for evaluation are likely to have a malocclusion to the extent that orthodontics alone would not be the first choice for full correction (i.e., there is a need for orthognathic surgery).¹⁰

Orthognathic Procedures Performed on Hospitalized Patients in the United States

Venugoplan and colleagues completed a study with the aim of providing a nationally representative estimate of the number and type of orthognathic procedures performed on hospitalized patients in the United States.⁶⁵ Their data was obtained from the Nationwide Inpatient Sample (NIS) database from 2008 and included all hospitalizations for orthognathic procedures. The procedures were identified via the procedure code listed in the International Classification of Diseases, 9th Revision, Clinical Modification.¹ The NIS database is sponsored by the Agency for Healthcare Research and Quality, a division of the Department of Health and Human Services of the U.S. government. Ten thousand three hundred and forty-five (10,345) hospitalizations for orthognathic procedures were identified as occurring during the 2008 calendar year. The average age of these patients was 26.7 years, and female patients comprised 56.2% of all those who were hospitalized for these procedures. Whites, blacks, Hispanics, Asians, Pacific Islanders, and Native Americans and other races constituted 71.9%, 4.9%, 12.6%, 5.6%, 0.4%, and 4.6% of the hospitalizations, respectively. Private insurance plans were the primary payers (77.3%). Government insurance plans (i.e., Medicare and Medicaid) accounted for 13.4% of the patient mix, whereas 3.5% of patient paid privately (i.e., out of pocket), without the benefit of medical insurance.

Le Fort I osteotomy without segmentation accounted for 15.3% of the procedures; 45.8% of the procedures were Le Fort I with segmentation; and 31.7% of the procedures were ramus osteotomies of the mandible (e.g., sagittal split ramus osteotomies or vertical oblique osteotomies). It was found that 53.3% of the patients underwent one jaw surgery, whereas 36.8% likely underwent bimaxillary osteotomies. It would appear that only 9.2% of the patients underwent combined upper jaw, lower jaw and chin procedures. Only 0.7% underwent additional other simultaneous procedures, including such possibility as septoplasty, inferior turbinate reduction, neck liposuction, and the removal of wisdom teeth.

The pattern of jaw deformity for which the patient underwent orthognathic surgery could to a certain extent be delineated. It would appear that 33.1% of the skeletal patterns were Class III anomalies, whereas 23.8% involved skeletal Class II anomalies. The vast majority of orthognathic procedures were for the correction of routine dentofacial deformities. Approximately 10% of the orthognathic procedures were for the correction of a syndromal form of jaw deformity.

Ninety-six percent of patients were discharged routinely without the need for a “home health care facility” or transfer to either a long-term or acute-care facility. The mean length of hospital stay was 2.95 days, and the mean hospital bill generated costs of $47,348.00. This was assumed to include all costs related to the hospital, operating room, and anesthesia, but it did not include the surgeons’ fees. The hospital bill generated did not necessarily correlate with the amount actually paid by either the third-party insurance company or the self-paying patient. Data regarding the actual payments is not available. From the available data, the total estimated hospitalization charges for orthognathic procedures carried out in the United States during 2008 were estimated to be $466.8 million (not including the surgeons’ fees). Surgeons in “teaching hospitals” performed 67.1% of the procedures, and surgeons in “large-bed hospitals” performed 70% of the procedures. Hospitals in urban areas accounted for 97.4% of the hospital admissions.

It must be understood that the study by Venugoplan and colleagues did not capture those orthognathic procedures carried out either in an outpatient setting (i.e., not requiring admission to hospital) or procedures that were performed exclusively in a “surgicenter.” These parameters were outside of the NIS database. It is estimated that as many as another 20% of orthognathic procedures were likely completed in these outpatient or surgicenter settings during this time period, which could result in 2000 additional patients.