Dr. David Sarver
Orthodontic therapy and orthognathic surgery for the correction of moderate to severe dentoskeletal deformity have evolved over the past 15 to 20 years to a very well-defined and researched treatment interaction. The most common objective of presurgical orthodontics is to idealize the position of the teeth relative to the bony bases before orthognathic correction of skeletal dysplasia.
This generally involves the following:
- Decompensation of compensated incisor inclinations– For example, Class II patients often require palatal root torque of the maxillary incisors, and uprighting of the mandibular incisors. Class III patients may require facial root torque of the maxillary incisors and increased proclination of the mandibular incisors.
- Alignment of crowded arches
- Transverse coordination of maxillary and mandibular arches
- Leveling of the curve of Spee
- Protrusion reduction
- Segmental alignment of arches to prepare for segmental osteotomies This includes divergence of roots to allow room for interdental osteotomies.
- Attainment of full-dimension edgewise wires for three-dimensional stabilization of the teeth and osteotomies
Post-operative orthodontic treatment often involves:
- Final occlusal detailing– This most often deals with vertical settling of the bicuspids and molars and is heavily affected by the stability of the surgical result, the type of osteosynthesis used by the surgeon, and the type of surgery performed
- Leveling of the curve of Spee, which is done postoperatively if a treatment goal is to increase the lower facial height
- Control of and compensation for postoperative osteotomy relapse
The general treatment objectives in orthognathic surgery are to achieve occlusal improvement and to improve the esthetic deficiencies that frequently characterize severe dentoskeletal deformity. The objective of orthognathic surgery in obstructive sleep apnea is absolutely straightforward- to improve the patients’ oxygen saturation. Therefore, functional considerations override esthetics considerations in these cases, and the presurgical orthodontic phase of treatment should be directed towards maximizing the forward movements of the jaws.
The surgical treatment of obstructive sleep apnea syndrome (OSAS) presents to the orthodontist a very different type of patient than is normally seen, depending on the makeup of the individual’s clinical practice. Typically, the average orthodontist’s practice consists of adolescent and an increasing number of adult patients.
Orthognathic surgery in the orthodontic practice is used for four general reasons:
- Treatment of malocclusion so severe that they are out of the envelope of discrepancy to be treated by orthodontic means alone.
- Cases in which camouflage or compensation would produce an unacceptable esthetic or functional result.
- Orthodontic treatment would yield an inherently unstable result in which a surgical correction would be much more predictable.
- Correction of malocclusions identified to be etiologic in the dysfunction of the temporomandibular joint, speech mechanisms, mastication, etc.
The magnitude of surgical movements in OSAS patients often far exceeds those normally seen in the average orthognathic practice. A 10mm maxillary advancement is not often seen in the normal orthognathic population, whereas in the OSAS population it is quite common. The magnitude of mandibular advancement and chin advancement is affected by the amount of maxillary advancement.
We have found the most significant differences to the orthodontist in maxillomandibular advancement (MMA) cases are as follows:
- The extreme advancement of the lower facial skeleton (maxilla and mandible) tend to experience more instability. This may be due to increased soft tissue stretch of the face and mandibular musculature or the reduced bony interface for stability.
- The importance of planning the final esthetic facial outcome becomes far less important than the functional requirements of OSAS correction.
- These patients not only represent a different age group on the average, but also tend to have more missing teeth and periodontal problems. Therefore, coordination with surgeons, periodontists, and restorative dentists is essential to successful treatment in these patients.
Depending on the type of OSAS patient classification, different orthognathic procedures may be recommended. The most prevalent procedures are either mandibular advancement (MA) or maxillomandibular advancement (MMA).
The role of the orthodontist in preparing the patient for MA involves orthodontic preparation of the dentition to maximize the distance the mandible may be advanced. Because the objective of MA is to move the inferior border of the mandible and the genial tubercle as far forward as is possible, the orthodontist often is called on to maximize the amount of overjet produced in the preparatory phase of orthodontic therapy. This may be accomplished in several different ways.
Normal Decompensatory Nonextraction Orthodontic Therapy
As described previously, dental compensation for Class II skeletal discrepancies is generally characterized by upright maxillary incisors and proclined lower incisors. Therefore, presurgical orthodontic treatment is designed to procline or advance the maxillary incisors and upright or retract the lower incisors. These movements may include increasing the axial inclination of the maxillary incisors. Mechanically, this can be accomplished several ways:
- Full-dimension archwires in preadjusted edgewise brackets, additional palatal root torque added to a rectangular archwire, and the possible use of root torquing auxiliaries are possibilities (Fig 1 and 2).
- Class III elastics, which add force in a labial direction below the center of tooth mass and advance the maxillary incisors. These may be used in conjunction with torquing of the maxillary incisors to move the center of rotation more apically.
- Open space in the maxillary arch if first bicuspids were previously removed for orthodontic reasons (Fig 3). An accepted orthodontic approach in the treatment for skeletal and dental Class II patients is with compensation orthodontics via extraction of bicuspids to improve overjet relations through retraction of the maxillary anterior segment. In patients in whom this sort of approach has been used in adolescence and in whom OSAS develops, reopening of the extraction space and advancement of the anterior teeth is a definite treatment option.
Figure 1. Increased axial inclination of the maxillary incisors can be accomplished with edgewise appliances, torquing auxiliaries, or a combination of both as illustrated here. The torquing auxiliary is the wire superior to the orthodontic brackets.
Figure 2. Decompensation results in a significant increase in overjet.
Figure 3. In cases in which bicuspids have been extracted, the maxillary incisors may be advanced and uprighted by opening the extraction site. In this case, compressed coil springs are used to open space.
Extraction of Mandibular First Bicuspids
Extraction of mandibular first bicuspids is followed by maximum anchorage orthodontic therapy to retract the incisors as much as possible. Maximizing retraction of the mandibular anterior segment may be accomplished by:
- Incorporation of the second molars (and even third molars if erupted and present) into the posterior anchorage units when using closing loop space closure mechanics
- The use of Class III elastics, which not only help retract lower incisors, but result in advancement of the maxillary arch as well
- The use of extraoral anchorage (headgear) in the mandibular arch by using J-hook headgear. Although conceptually this is possible, most apnea patients are of the age in which extraoral orthodontic appliances are not particularly a relishing thought! Headgear wear would be limited to only the most motivated of patients.
Mandibular Subapical Osteotomy
Mandibular subapical osteotomy is performed in order to retract the anterior segment for maximum mandibular advancement. This procedure usually involves the extraction of the mandibular second bicuspids and the 4-4 segment retracted. Presurgical preparation should involve expansion of archwire in the first bicuspid region and constriction of the archform in the molar region. There are several advantages to accomplishing this transverse coordination before surgery:
- The chances of buckling of the soft tissue pedicles to the anterior segment are decreased. This undesirable sequela could cause the blood supply to the anterior segment to be compromised, thereby increasing the potential of necrosis of the osteotomy segment.
- The amount of postoperative orthodontic finishing is reduced. Most combined orthodontic-surgical cases exhibit the psychological characteristics of desiring the end of treatment to come as quickly as possible. Kiyak and associates1 have shown that patient dissatisfaction with orthognathic surgery increases dramatically at 6 months postoperatively. The same characteristic is probably true in the OSAS patient, and the postoperative finishing phase of orthodontic therapy should be as expeditious as possible.
The disadvantages of the mandibular subapical procedure include neurapraxis, the possibility of periodontal defect associated with interdental osteotomy, and the fact that technique is not always usable in patients with proclined lower incisors.
Interproximal Reproximation (Stripping) of the Lower Incisors
Interproximal reproximation (stripping) of the lower incisors is performed to produce space for retraction of the lower incisors. This approach rarely produces a significant retraction of the lower incisor tip, which is required for this type of treatment.
Torquing Auxiliaries in the Mandibular Arch
Torquing auxiliaries in the mandibular arch is performed to upright the lower incisors. This approach has little or no significant effect on retraction of the mandibular incisors.
Case Illustration of Mandibular Advancement
This 45-year-old woman (Fig 4) was evaluated for a moderate OSAS problem. Her chief complaint consisted of snoring and mild OSAS. Her sleep study revealed 77 apneic events, 28 of which were obstructive. Skeletally, she exhibited a Class II mandibular deficiency that had been esthetically camouflaged with a chin implant. Her maxillary incisor angulations were characterized by upright maxillary incisors and mildly proclined lower incisors (Fig 5 and 6). Her posterior occlusion was virtually Class I (Fig 7 and 8), but the dental compensation was fairly marked. The sleep team recommended the patient consider surgical mandibular advancement, removal of the chin implant, and advancement of the chin via inferior border osteotomy to advance the genial tubercles.
Figure 4. This patient was mandibular retrognathic and had OSAS. The profile had been camouflaged with a chin implant.
Figure 5. The pretreatment cephalogram illustrates dental compensation characterized by upright maxillary incisors and proclined lower incisors.
Figure 6. The dental alignment was good, but with moderate upright upper incisors.
Figure 7. The left buccal occlusion was virtually Class I.
Figure 8. The right buccal occlusion was end-on Class II.
Several orthodontic options were considered, all of which were listed in the previous section. Nonextraction decompensation orthodontic therapy was selected as the mode of treatment. Fixed edgewise appliances were used and presurgical treatment progressed to a full dimension archwire in the maxillary arch to provide maximum torque, while using Class III elastics to upright the lower incisor and help advance the upper incisors. Interproximal reproximation was also used in the lower arch, not so much to retract the lower incisors, but to prevent their increased proclination. The amount of dental decompensation achieved is illustrated (Fig 9-11).
Figure 9. Overjet is increased after decompensation via torque of the upper incisors and Class III elastics to advance the upper arch while maintaining lower incisor position.
Figure 10. The left buccal occlusion progressed to Class II.
Figure 11. The right buccal occlusion also progressed to Class II.
Mandibular advancement of 5mm and advancement genioplasty of 6mm was accomplished surgically with advancement of the genioglossus and the anterior digastric muscles (Fig 12). Finishing orthodontics required 3 months (Fig 13-15).
Figure 12. Cephalometric superimposition reflecting the surgical mandibular advancement.
Figure 13. Post-treatment profile.
Figure 14. Post-treatment dental relations-frontal.
Figure 15. Post-treatment dental relations-buccal occlusion.
The final cephalometric tracing is illustrated (Fig 16). The patient’s posterior airway measurement increased from a preoperative measurement of 4mm to a posttreatment measurement of 12mm.
Figure 16. Final cephalometric tracing.
The orthodontic goals in MMA patients are generally the same as for MA patients. Bear in mind that the object of presurgical orthodontics in OSAS patients is almost always to maximize the amount of MA, even when maxillary advancement is necessary. Of course, clinical judgement is always exercised in each individual case, with the primary goal being to maximize presurgical overjet.
Case Illustration of Maxillomandibular Advancement
A 30-year-old man presented with severe sleep apnea problems. Skeletally, he had a markedly deficient mandible (Fig 17) with severe dental compensation- very upright maxillary incisors (Fig 18) and a 100% deep overbite. Dentally, he had a Class I posterior occlusion (Fig 19), but with significant crowding in both arches. Dental compensation was characterized cephalometrically by very upright and recumbent maxillary incisors(Fig 20).
Figure 17. This patient, severely affected with OSAS, presented with a very retrognathic profile.
Figure 18. The dentition was markedly compensated with detorqued incisors.
Figure 19. The posterior occlusion was Class I.
Figure 20. The cephalometric tracing reflected bimaxillary retrusion and upright incisor angulations.
The orthodontic treatment plan was designed to upright and advance the maxillary incisors, decompensate the mandibular incisors, decrowd the arches, and create maximum overjet. Presurgical orthodontic treatment included maximizing incisor torque and progression to full-dimension archwires (Fig 21). The surgical treatment planned was maxillomandibular advancement. Superimposition of the pretreatment and presurgical cephalometric radiographs (Fig 22) illustrates the orthodontic movements achieved in the presurgical orthodontic phase of treatment, with both maxillary and mandibular incisors being advanced.
Figure 21. Maxillary incisors decompensated with full dimension edgewise appliances and wires.
Figure 22. Superimposition of the pretreatment and presurgical cephalograms illustrating the orthodontic movements to maximize the overjet by flaring the upper incisors.
The orthognathic procedure consisted of a 1cm MA, an 8mm MA, and a 1cm chin advancement (Fig 23). Postsurgical and finishing orthodontic treatment was completed in 8 months (Fig 24 and 25), and the dramatic increase in airway space is cephalometrically evident (Fig 26 and 27).
Figure 23. Cephalometric superimposition of the surgical procedures performed-Maxillomandibular advancement and advancement genioplasty.
Figure 24. The posttreatment profile.
Figure 25. The final dental relations.
Figure 26. The pretreatment posterior airway.
Figure 27. The posttreatment posterior airway reflecting the increase in distance between the posterior pharyngeal wall and the tongue mass.
The finalization of the occlusal relations in OSAS is not very different from normal orthognathic patients with the exception of the extreme MMA. As mentioned earlier, OSAS patients exhibit more postoperative instability and require more elastic control than do other types of patients. The type of fixation chosen by the surgical team is very influential when considering postoperative orthodontic movements. Rigid fixation osteosynthesis is critical to the stability of these patients, but also presents the orthodontist with a less plastic and therefore less modifiable postoperative situation. We recommend as little posterior open bite in the surgical occlusal setup as is possible. Vertical finishing is more difficult in the rigid fixation environment, so the less interocclusal distance put into the surgically directed occlusal result, the better. This, of course, places more demand on the surgeon for accuracy of condylar placement.
We have tried to systematically describe the orthodontist’s role in the care of patients suffering from obstructive sleep apnea. The variety of apnea patients is as numerous as the types of orthodontic patients that we see in our practices. The goals of orthodontic treatment tend to be quite different from the gals of orthodontic and/or orthognathic treatment plans, in particular, esthetics takes a back seat to the medical needs of the patient. These patients also tend to be older and more periodontally compromised, and ideal occlusal relationships are often difficult to attain. The orthodontist should strive for all parameters of case to be ideal, but must be willing to accept compromised results much as the cancer surgeon may be forced to mar the patient’s face in order to save the patient’s life. In many cases, however, all the treatment goals come together and improved esthetics and function simultaneously result. It has been our experience that OSAS patients represent a challenging and rewarding pare of orthodontic practice.
The author acknowledges the assistance of Dr. Mark W. Johnston, Atlanta, GA, in the research and preparation of this text.
DAVID M. SARVER, DMD, MS
Dr. Sarver received his DMD from The University of Alabama School of Dentistry in 1977 , selected by ODK as the Outstanding Student in the Medical Center. He subsequently received his certificate and M.S. in Orthodontics from the University of North Carolina in 1979. He is a Diplomate of the American Board of Orthodontics, a member of the Edward H. Angle Society of Orthodontists, and a Fellow in both the International and American Colleges of Dentists. In addition to his private practice in Vestavia Hills, Alabama, he is an Adjunct Professor in the University of North Carolina Department of Orthodontics. Dr. Sarver has authored or co-authored over 30 scientific articles, 7 book chapters, and his book, “Esthetics in Orthodontics and Orthognathic Surgery” (C.V. Mosby Co., St Louis, MO) was published in September, 1998. He has given more than 100 professional presentations in the United States, Europe, Australia and the Middle and Far East. David’s wife, Valerie, worked 22 years as a Systems engineer with IBM, and they live in Vestavia Hills with their three children Dave(17), Leigh(13), and Suzanne(10).