Treatment of patients with orthognathic surgery by moving both the maxilla and the mandible became popular in the early part of the 1980s. It was during this time that surgeons and orthodontists recognized the three-dimensional nature of skeletal deformities seen in patients seeking care, and their confidence in performing simultaneous jaw surgery has increased. As documented in Chapter 1 of this text, the skeletal, soft-tissue, and occlusal evaluation of patients continues to require careful examination if patients are to be diagnosed and treated appropriately. Numerous authors have documented the complex nature of skeletal discrepancies that exist in patients with both idiopathic and congenital deformities. This is particularly true when open bite malocclusions are present. In separate papers Ellis and co-workers analyzed groups of patients with Class II and Class III malocclusions. They showed that those with open bites had numerous skeletal discrepancies in multiple planes in space. In a similar fashion, Chaisrisookumporn and colleagues showed that patients with congenital cleft lip and palate have numerous vertical and horizontal abnormalities in both the maxilla and mandible. These findings were confirmed by French surgeons who noted the three-dimensional complexities of patients with a variety of facial clefts and craniosynostosis conditions.
Understanding the complexities of skeletal deformities, several authors have documented that patients could be treated by moving both jaws, achieving improved functional and esthetic results. This trend has continued over the last 20 years. As experience has increased, techniques have become more refined, and treatment planning more precise. Early studies in which wire osteosynthesis was used noted instability of both the maxilla and the mandible. With wire osteosynthesis used to stabilize two-jaw surgery, early investigators noted intrusion of the posterior maxilla. Rigid fixation of both the maxilla and the mandible has increased the stability of both procedures. In addition, the ability to achieve the desired results has improved as technology has progressed.
INDICATIONS
Indications for two-jaw surgery include asymmetry of one or both jaws, marked midline discrepancies, cants in the occlusal plane, excess vertical growth, and functional considerations such as airway compromise. As noted in the papers by the Ellis group, both dental Class II and III patients can have multiple horizontal and vertical issues. These can vary from subtle discrepancies to severe ones. In general, the midline of the maxillary central incisors should be congruent with the midline of the face; however, the ability of professionals and laypersons to detect subtle deviations from normal depends on how symmetric the rest of the face is and how severe the discrepancy is. Cardash and co-workers found that 50% of professionals and laypersons could not detect midline deviations of 2 mm or less. In a similar study Beyer and Lindauer used 120 observers composed of orthodontists, dentists, patients, and parents. They noted that photographs with maxillary midline and/or nose deviations were considered less esthetic by the observers and that the orthodontists and dentists were significantly less tolerant of midline deviations than were the patients. The mean threshold for acceptable dental midline deviation for all of the observers was 2.2 ± 1.5 mm. These studies suggest that discrepancies in the maxillary midline of 2 mm or less may be acceptable. Above this amount, procedures to correct or mask the discrepancy should be considered. In some cases midline discrepancies can be treated by orthodontics; in others they should be treated by surgery. Burstone noted that abnormal and asymmetric axial inclination of teeth may mask an underlying skeletal problem and that orthodontics with extraction of teeth and surgery and extraction can lead to more ideal symmetry.
Variations in vertical face height in patients are well recognized and play an important role in the selection of an individual patient for surgery. Throckmorton and co-workers evaluated morphologic and biomechanical factors that were used in the selection of orthognathic surgery. They found that the most important factors in treatment selection were differences in maxillary and mandibular lengths and differences in anterior and posterior facial height. In general, patients are classified as having long, normal, or low facial height. Janson and co-workers compared three groups of patients whom they classified as having excessive, normal, or short lower anterior face height using the ratio of upper anterior facial height to lower anterior face height. They noted that the largest difference among these three groups was in the dentoalveolar height. Of these, 22% of the variation was explained by the difference in the molar region, whereas 41% was explained by the incisor region. In a separate paper, Ellis analyzed maxillae of individuals who displayed 4 mm or more of central incisor at rest. He compared these with two other groups of individuals who showed less than 1 mm or had 2 mm or more negative overjet. He showed that the vertical position of the maxillary palate was similar for all groups and that the vertical maxillary excess was in the dentoalveolus. Excessive anterior vertical height can result in lip incompetence and excess mouth breathing, with resultant gingival inflammation. In patients with a normal upper lip length and excessive lip incompetence, maxillary impaction corrects this problem.
Asymmetry of the maxilla and mandible can have numerous causes. This chapter discusses stable conditions in which there is not an active cause of the asymmetry. Skeletal Class I, II, and III patients may have asymmetry that causes a cant to the occlusal plane, a cant to the lips, and a cant to the chin. To correct the cant, it is often necessary to move both jaws. Padwa and colleagues studied two groups of patients, one with a documented cant and the other with no cant, with both trained and untrained observers. They noted that cants greater than 4 degrees were detected with 90% frequency by both groups of observers. In a retrospective survey of 1460 patients in a dentofacial center, 34% were found to have clinically apparent facial asymmetry. Of these, 41% had a vertical asymmetry with canting of the occlusal plane, indicating discrepancies in both the mandible and the maxilla.
Moving the maxilla and mandible can have profound effects on the pharyngeal airway. Turnbull and Battagel found significant decreases in the airway space after mandibular setbacks, and conversely a significant increase in airway space after mandibular advancements. Although they did not see any significant changes in snoring after mandibular setback, some of their advancement patients noted a change in sleep quality when there had been signs of an underlying sleep disorder before surgery. Hochban and co-workers evaluated the airway space of 16 patients before and after mandibular setback procedures. Preoperatively all had increased airway space, whereas afterward all showed decrease of the pharyngeal space. Kawakami and colleagues noted that after a mandibular setback there was a significant downward movement of the hyoid bone. Gradually over 1 year the hyoid returned to its original position, resulting in a significant decrease in retrolingual airway dimension. These studies and others suggest that airway space and symptoms of obstruction in the patient be evaluated by involving sleep partners or family members before considering large mandibular setbacks. Alternative treatment strategies of moving both jaws to minimize the amount of mandibular setback so that the posterior airway space is protected should be considered.
STABILITY
ONE- VS. TWO-JAW SURGERY
Stability of two-jaw surgery is related to the direction of movement of each jaw, the type(s) of fixation, and the surgical techniques used to treat either jaw. As noted previously, when wire osteosynthesis was used routinely to stabilize two-jaw surgeries, postsurgical superior movement of the posterior maxilla was noted. Rigid fixation of the maxilla and mandible has alleviated this problem. With regard to individual jaw surgeries, the most stable procedure is maxillary impaction followed by mandibular advancement when anterior facial height is maintained. Ayoub and colleagues studied two groups of patients who were treated with a Le Fort I osteotomy with advancement and/or impaction and a bilateral sagittal split for advancement of the mandible. They noted that in all cases the maxillary surgery was more stable than the mandibular surgery.
Advancement of the maxilla is reasonably stable, but not as stable as impaction of the maxilla. Dowling and co-workers studied 43 patients who underwent a Le Fort I osteotomy advancement and noted that horizontal relapse was associated with the amount of surgical advancement and the degree of inferior repositioning of the anterior maxilla. Mandibular setback is not as stable as mandibular advancement. In two-jaw Class III surgery, the stability of each jaw is initially more stable compared with that seen with isolated maxillary advancement or isolated mandibular setback; however, at 5 years there is less stability. Busby and colleagues showed that 80% of the bimaxillary group showed less than 4 mm of postsurgical change from 1 year to 5 or more years. Costa and colleagues had similar findings when assessing two-jaw maxillary advancement and mandibular setback, noting that the maxillary advancement was more stable than mandibular setback. However, they saw a trend for relapse when the maxilla was advanced greater than 6 mm.
The least stable orthognathic procedure is transverse expansion of the maxilla. Hoppenreijs and colleagues studied 130 patients with vertical maxillary excess treated with either one- or two-jaw surgery in which the maxilla was widened by either orthodontics and a one-piece maxilla or a multisegmented Le Fort I osteotomy. The difference in relapse of the transverse dimension between the two groups was not significant. Surgical assisted rapid palatal expansion is thought of as an alternative to large expansion of the maxilla by a multisegmented maxilla. Although appealing, it is controversial. Swinnen and colleagues studied skeletal and dentoalveolar stability after surgical orthodontic treatment of anterior open bites. When expansion was necessary, surgical assisted rapid palatal expansion was performed at least 9 months before the Le Fort I osteotomy. They showed a high tendency for relapse to occur but concluded that closing open bites by posterior maxillary impaction with or without a bilateral sagittal split had relatively good clinical dental and skeletal stability. Byloff and Mossaz studied skeletal and dental changes seen with tooth-borne appliances for surgical assisted rapid palatal expansion. They noted differences seen in expansion in the region of the dentition versus the palatal bone. They found that expansion occurred by lateral rotation of the two maxillary halves with only minimal horizontal translation. This often results in causing an anterior open bite. This problem may be solved with bone-borne appliances used in conjunction with expansion of the maxilla. The work by Neyt and colleagues shows promising preliminary results on transpalatal expansion in which the two halves of the maxilla have horizontal translation rather than rotation.
Alternative techniques that have been used to minimize relapse of an expanded Le Fort I segmented maxilla include blocks in between the segments, platting across ostectomies, and parasagittal palatal incisions.
SAGITTAL SPLIT VS. TRANSORAL VERTICAL RAMUS OSTEOTOMY
Performing a bilateral sagittal split versus a transoral vertical ramus osteotomy (TOVRO) for two-jaw surgery in which the mandible is set back is dependant on the complexity of the move and surgeon-patient preference. Large asymmetric moves are more easily accomplished with a TOVRO but in general commit the patient to a period of intermaxillary fixation. Stability of the jaw is very different after the two procedures. With rigid fixation of a BSSO setback, whether one- or two-jaw surgery is done, the mandible tends to come forward, whereas with an intraoral vertical ramus osteotomy the mandible tends to rotate posteriorly and inferiorly, pivoting on the molar occlusion. Ueki and colleagues suggested that an intraoral vertical ramus osteotomy may improve disk position and temporomandibular joint symptoms. Injury to the inferior alveolar nerve occurs more frequently with a bilateral sagittal split than with an intraoral vertical ramus osteotomy. However, the ability to use rigid fixation more easily with a sagittal split and subsequent postsurgical function has been suggested as its greatest advantage over an intraoral vertical ramus osteotomy. In addition, as will be discussed further, using a TOVRO limits the sequence of two-jaw surgery to doing the maxilla first. Readers seeking more information about a bilateral sagittal split osteotomy and a TOVRO are referred to other chapters in this textbook.
STABILITY
ONE- VS. TWO-JAW SURGERY
Stability of two-jaw surgery is related to the direction of movement of each jaw, the type(s) of fixation, and the surgical techniques used to treat either jaw. As noted previously, when wire osteosynthesis was used routinely to stabilize two-jaw surgeries, postsurgical superior movement of the posterior maxilla was noted. Rigid fixation of the maxilla and mandible has alleviated this problem. With regard to individual jaw surgeries, the most stable procedure is maxillary impaction followed by mandibular advancement when anterior facial height is maintained. Ayoub and colleagues studied two groups of patients who were treated with a Le Fort I osteotomy with advancement and/or impaction and a bilateral sagittal split for advancement of the mandible. They noted that in all cases the maxillary surgery was more stable than the mandibular surgery.
Advancement of the maxilla is reasonably stable, but not as stable as impaction of the maxilla. Dowling and co-workers studied 43 patients who underwent a Le Fort I osteotomy advancement and noted that horizontal relapse was associated with the amount of surgical advancement and the degree of inferior repositioning of the anterior maxilla. Mandibular setback is not as stable as mandibular advancement. In two-jaw Class III surgery, the stability of each jaw is initially more stable compared with that seen with isolated maxillary advancement or isolated mandibular setback; however, at 5 years there is less stability. Busby and colleagues showed that 80% of the bimaxillary group showed less than 4 mm of postsurgical change from 1 year to 5 or more years. Costa and colleagues had similar findings when assessing two-jaw maxillary advancement and mandibular setback, noting that the maxillary advancement was more stable than mandibular setback. However, they saw a trend for relapse when the maxilla was advanced greater than 6 mm.
The least stable orthognathic procedure is transverse expansion of the maxilla. Hoppenreijs and colleagues studied 130 patients with vertical maxillary excess treated with either one- or two-jaw surgery in which the maxilla was widened by either orthodontics and a one-piece maxilla or a multisegmented Le Fort I osteotomy. The difference in relapse of the transverse dimension between the two groups was not significant. Surgical assisted rapid palatal expansion is thought of as an alternative to large expansion of the maxilla by a multisegmented maxilla. Although appealing, it is controversial. Swinnen and colleagues studied skeletal and dentoalveolar stability after surgical orthodontic treatment of anterior open bites. When expansion was necessary, surgical assisted rapid palatal expansion was performed at least 9 months before the Le Fort I osteotomy. They showed a high tendency for relapse to occur but concluded that closing open bites by posterior maxillary impaction with or without a bilateral sagittal split had relatively good clinical dental and skeletal stability. Byloff and Mossaz studied skeletal and dental changes seen with tooth-borne appliances for surgical assisted rapid palatal expansion. They noted differences seen in expansion in the region of the dentition versus the palatal bone. They found that expansion occurred by lateral rotation of the two maxillary halves with only minimal horizontal translation. This often results in causing an anterior open bite. This problem may be solved with bone-borne appliances used in conjunction with expansion of the maxilla. The work by Neyt and colleagues shows promising preliminary results on transpalatal expansion in which the two halves of the maxilla have horizontal translation rather than rotation.
Alternative techniques that have been used to minimize relapse of an expanded Le Fort I segmented maxilla include blocks in between the segments, platting across ostectomies, and parasagittal palatal incisions.
SAGITTAL SPLIT VS. TRANSORAL VERTICAL RAMUS OSTEOTOMY
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