01 - Indications for Orthognathic Surgery

Orthognathic Surgical Procedures

Nature of Orthognathic Surgery

“Orthognathic” literally means “straight jaws,” and orthognathic surgery is surgery to bring the jaws into a correct relationship.

The first orthognathic procedures, to correct mandibular prognathism by moving the mandible back, were done 100 years ago, but this surgery really developed only in the second half of the 20th century, as new methods

• allowed the mandible to be moved forward or back,
• made it possible to reposition the maxilla in all three planes of space and in multiple segments if necessary, and
• were developed for surgical repositioning of the chin and dentoalveolar segments.

In the 21st century, it is possible to surgically move the jaws and teeth in any direction, but the soft tissues limit the amount of movement and make some directions more favorable than others.

Click on the icons for illustrations (from Bell, Proffit, White, Surgical Correction of Dentofacial Deformities) of the different types of mandibular and chin surgery that are commonly done today.

Mandibular deficiency: Skeletal mandibular deficiency, surgical mandibular advancement indicated.	Sagittal split advancement: Sagittal split osteotomy for mandibular advancement, done with intraoral approach—the usual surgical approach.
C-osteotomy for advancement: C-osteotomy for mandibular advancement (requires extraoral approach), shown with lower border osteotomy to further augment the chin.	Subapical osteotomy: Mandibular subapical osteotomy to advance the dentition.
Sagittal split setback: Sagittal split osteotomy for mandibular setback.

Nature of Orthognathic Surgery (cont.)

Click on the icons for illustrations of maxillary and combined maxillary-mandibular-chin surgery that is commonly done today (from Bell, Proffit, White, Surgical Correction of Dentofacial Deformities).

The key development in modern orthognathic surgery for the mandible was the sagittal split osteotomy of the ramus, which gives good bone-to-bone contact for mandibular advancement and setback. For the maxilla, it was the development of the LeFort I osteotomy technique, which allows movement of the maxilla in all three planes of space.

Surgery for the maxilla today is used as frequently as surgery to reposition the mandible, and often maxillary and mandibular surgery are done in the same operation. Because the maxilla can be repositioned without concern about maintaining joint function, in some ways orthognathic surgery for the maxilla is more flexible than mandibular surgery. It is quite feasible now to combine maxillary and mandibular surgery when it is needed to obtain acceptable facial proportions.

In current orthognathic surgery, screws and plates for rigid internal fixation have largely replaced the external wires shown in these illustrations.

Maxilla up: Vertical maxillary excess, indication to move maxilla up.	LeFort I osteotomy: LeFort I osteotomy to move maxilla up: removal of measured amounts of bone from the lateral walls.
Maxilla up, mandible rotates: LeFort I osteotomy, maxilla up: vertical repositioning of maxilla allows mandible to rotate upward and forward.	Segmented maxilla: LeFort I osteotomy with segmentation of the maxilla to allow transverse expansion, closure of premolar extraction space.
2-jaw surgery plus chin: LeFort I, sagittal split and lower border osteotomies combined for correction of long face, mandibular deficiency problem.

Sagittal Split for Repositioning the Mandible

The most frequently used orthognathic procedure now is the sagittal split osteotomy, which can be used for mandibular advancement (illustrations from Proffit, White and Sarver, Contemporary Treatment of Dentofacial Deformity) or setback (see screen 1).

The procedure is done completely intraorally, using an incision in the mandibular vestibule (image 1). A cut is made through the medial cortical bone of the ramus above the lingula and extended diagonally across the front of the ramus to the second molar area, then down to the lower border (image 2).

With the cuts completed, an osteotome is used to split the ramus through medullary bone, so that the inferior alveolar neurovascular bundle is with the tooth-bearing segment (image 3). This allows it to be moved forward and rotated as desired (image 4), so that the teeth are brought into the planned occlusion. Backward movement requires removal of a segment of the bone on the facial side of the split, but everything else is similar whether the mandible is advanced or set back.

The teeth are wired together temporarily so that screws can be placed in the ramus for fixation (image 5). Then the interdental wires are removed and the patient is able to function while bone healing occurs. Rigid internal fixation with screws as shown here, rather than wiring the teeth together for 6 weeks after surgery, has the advantages of improving both postsurgical stability and patient comfort, and has almost completely replaced interdental fixation for orthognathic surgery and treatment of jaw fractures.

Image 1, sagittal split incision: Intraoral incision for sagittal split ramus osteotomy.	Image 2, cuts through cortical bone: Osteotomy through medical cortical bone is extended across the front of the ramus and down to the facial lower border.
Image 3, sagittal split: An osteotome is twisted to separate the tooth-bearing segment from the ramus.	Image 4, dental segment advanced: After the split, the tooth-bearing segment can be advanced to its planned position.
Image 5, rigid internal fixation: Screws are placed (in any desired pattern) to hold the segments while healing occurs, which allows jaw function during healing.

LeFort I Osteotomy to Reposition the Maxilla

The most frequently used surgical procedure to reposition the maxilla is the LeFort I osteotomy. The steps in this surgery are illustrated in this set of images.

Image 1, LeFort 1 incision: The sinus walls are sectioned above the roots of the teeth and the roof of the mouth.	Image 2, sectioning the sinus wall: The sinus walls are sectioned above the roots of the teeth and the roof of the mouth.
Image 3, freeing the pterygoid plates: The maxilla is separated from the pterygoid plates so that it can be rotated down anteriorly.	Image 4, maxilla in down-fractured position: With the maxilla in the down-fractured position so that it can be approached from above, the vertical height of the lateral nasal and sinus walls is reduced.
Image 5, maxilla repositioned: The maxilla then is repositioned vertically and moved forward or back as planned.

The Envelope of Discrepancy

Indications for Orthognathic Surgery

Who needs orthognathic surgery? Patients with a severe skeletal problem or a very severe dentoalveolar problem, too severe for correction with orthodontics alone (image 1).

How severe does a malocclusion have to be before it is too severe to be corrected by orthodontics alone? Guidelines for this are provided by the “envelope of discrepancy” (image 2).

Consider the distance that incisor teeth can be repositioned orthodontically. In the diagram in image 2, the ideal position of the incisal edge of the central incisor is in the center, and the dimensions of the envelope around that position (dotted line) indicate the distance that this tooth can be moved forward, back, up, or down to correct a malocclusion. Note that the envelope for the upper and lower arch is different and that the dimensions vary by direction. The diagram suggests that upper incisors can be retracted 7 mm to correct maxillary dental protrusion but can moved forward only 2 mm in most circumstances. They can be elongated 4 mm but intruded only 2 mm. For the lower incisor, the distances of possible movement are different for retraction (3 mm) and forward movement (5 mm) but are identical for elongation (4 mm) and intrusion (2 mm).

Obviously, these numbers are guidelines. Could you move the teeth farther? Probably. Could you get them to stay in a more extreme position? That’s more difficult—probably not. Stability is increasingly unlikely as the envelope is stretched further and further.

Image 1, who needs surgery?	Image 2, envelope for tooth movement: Possible distances of a-p and vertical tooth movement.

Envelope of Discrepancy: Tooth Movement

Three important points about tooth movement:

1. Remember, the envelope reflects bodily movement and also takes long-term stability into account. For example, it is possible to intrude an incisor more than 2 mm but difficult to maintain more than that amount of intrusion long-term.
2. If teeth are severely tipped, it may be possible to move the crown more than the envelope implies. For instance, in a patient with Class II, division 2 malocclusion, the crowns of the lingually tipped maxillary central incisors can be brought forward more than the 2-mm limitation.
3. Guidelines, after all, are just that—not rigid rules. For some patients, the distances in the guidelines can be exceeded, and for some, you would be hard pressed to move the teeth that far. When someone shows you a case with tooth movement outside the guidelines, remember: The improbable isn’t impossible, it just doesn’t happen very often.

Envelope of Discrepancy: Growth Modification

A second envelope, the envelope of growth modification (yellow), surrounds the tooth movement envelope. It reflects the amount of change in tooth positions that can be achieved by changing the growth of the jaws.

This envelope differs from tooth movement. The drawings show growth modification wrapped around tooth movement for both the upper and lower dental arches, but that’s potentially misleading. There is only one growth modification envelope. It is drawn to show the possible change in jaw relationship. So the approximate limit of growth change to improve a skeletal Class II relationship is about 5 mm. It makes little difference whether that is achieved primarily by restraining growth of the maxilla or stimulating growth of the mandible. Either way, a 5-mm change in the jaw relationship is about the limit of growth modification for Class II patients. Tooth movement, of course, can be added to obtain greater correction of the malocclusion.

Note that the growth modification possibility for skeletal Class III patients (3-mm improvement from differential growth) is smaller than for skeletal Class II patients. It is difficult to restrain excessive mandibular growth, so this 3 mm is primarily from forward growth of the maxilla.

Does that mean more Class II than Class III problems can be treated without surgery? Yes.

Envelope of Discrepancy: Surgery

A third envelope, the envelope of surgical change, wraps around the other two envelopes. Surgical changes in the position of each jaw can be achieved independently.

In some directions, the possible magnitude of surgical correction is much greater than the potential of growth modification plus tooth movement. For example, surgery can set the mandible back a long way if necessary—much further than the maximum correction from orthodontic treatment based on a combination of tooth movement and growth modification.

In other directions, the difference is not so great. Note that surgery to advance the mandible adds only a few millimeters to the maximum of growth modification plus tooth movement.

Vertical changes in the position of one jaw, of course, affect the other jaw as well. Particularly, repositioning the maxilla vertically requires rotation of the mandible to a new position. So the limits of vertical change are the same for the two jaws—but surgery can change vertical positions by a centimeter or more.

Image 1, mandible: The surgical envelope for the mandible.	Image 2, maxilla: The surgical envelope for the maxilla.
Image 3, both: Envelopes of surgical change.

Envelope of Discrepancy: Effect of Age

What’s the indication for orthognathic surgery? Obviously, having a malocclusion too severe to correct with orthodontics alone. That means it’s outside the combined tooth movement and growth modification envelopes. The envelopes suggest, for instance, that if you have more than 5-mm reverse overjet at any age, surgery will be required to correct it satisfactorily. As long as growth modification is possible and the tooth movement would not damage the patient’s facial appearance, correction of overjet as large as 12 mm is within the reach of nonsurgical treatment.

But of course the growth modification envelope disappears as growth is completed. Its maximum dimension still is available at the beginning of the adolescent growth spurt, then this envelope shrinks until it totally disappears in adults.

Does that mean some malocclusions that could have been corrected with orthodontics if treated earlier would require surgery after growth is completed? Yes, it means exactly that. With orthodontic treatment, you can’t reduce overjet as much in a nongrowing patient as you could in one who is growing. After the adolescent growth spurt, you’re outside the range of orthodontic treatment if you’re outside the tooth movement envelope.

Indications for Surgical Treatment: Health

For any type of elective surgery, the patient must be in acceptable health. For orthognathic surgery, that means that any pathologic conditions must be under control—but the patient does not have to be in perfect health.

As an example, orthognathic surgery for a hemophiliac patient is entirely feasible, and in fact may be the best way to correct some severe malocclusions in such patients. The missing clotting factors must be replaced before the surgery. Then the quicker treatment that surgery makes possible may actually reduce the risk versus more prolonged orthodontic treatment.

Smoking is not a good idea from a health point of view for many reasons. One that you may not have thought of is the reduction in capillary blood flow produced by nicotine. This has a direct effect on bone healing. Because smokers do not heal as well after orthognathic surgery, most surgeons will not consider this treatment until smoking has been discontinued for a few months.

Control of periodontal disease is required before orthognathic surgery, as it is for any treatment involving orthodontics. Some tooth movement cannot be avoided when orthognathic surgery is performed.

Mental as well as physical health must be considered—emotionally disturbed people are not good candidates for any type of elective surgery. It is important for the patient to have realistic expectations of the outcome of treatment and the effect it is likely to have on life adjustment.

Camouflage Limitations

Surgery Indication: Camouflage Impossible

The second major indication for orthognathic surgery is a condition in which a jaw discrepancy is beyond orthodontic camouflage. Camouflage is defined as displacement of the teeth to correct a malocclusion even though the underlying jaw discrepancy is not corrected. The term implies, correctly, that the jaw discrepancy no longer is noticed and is not a problem.

For instance, if protruding maxillary incisors are retracted in a patient whose Class II malocclusion is primarily due to mandibular deficiency, successful camouflage would require that the mandibular deficiency no longer is noticed. The treatment would be unsuccessful if the facial appearance after treatment was unacceptable—no matter how good the dental occlusion was. For an example, see the program To Extract or Not to Extract, part 2, Camouflage.

For a patient with Class III malocclusion and reverse overjet, would successful treatment be possible by tipping the upper incisors tipped facially and retracting the lower incisors? One limit would be how far the teeth could be moved, but there also is a limitation related to facial appearance. Retracting the lower incisors tends to make a prominent chin even more prominent, just the reverse of camouflage, so Class III camouflage can be done only for mild Class III problems.

Vertical problems (long face, for example) can rarely be camouflaged. Elongating teeth in a long face patient, even if the occlusion is corrected, is likely to make the patient look worse, not better. For that reason, surgery may be needed in long face patients even if the dental discrepancy is within the envelope of discrepancy. As we have noted in Level III, skeletal anchorage now makes it possible to intrude maxillary posterior teeth, so that the mandible rotates upward and forward in the same way it does when the maxilla is moved superiorly with a LeFort I osteotomy, but the more severe long face / open bite problems still will require surgery.

Class III Camouflage Failure

Consider the situation for Linda, who was unhappy with the outcome of two years of orthodontic treatment as an adult. She had worn Class III elastics to tip her maxillary incisors facially and upright her mandibular incisors, and the space of an unerupted maxillary left second premolar was closed (producing an asymmetry in the maxillary midline).

On facial examination (images 1, 2), her maxillary deficiency is apparent. Note the lack of support for her upper lip and for the facial tissues adjacent to the nose and the concave profile.

Her malocclusion was corrected reasonably well (images 3-5), but she was unhappy about both her facial and dental appearance.

Is this a camouflage failure? Yes, because she is unhappy with her appearance. Moving the upper incisors forward does nothing to augment the deficient areas adjacent to the nose and can make them even more apparent (in image 1, note the depth of the nasolabial folds). This makes her look older than her 39 years. Moving the lower incisors back does not reduce the prominence of the chin and can make it also more prominent.

The bottom line: If the esthetic outcome isn’t satisfactory, it’s not satisfactory treatment.

Image 1, full face view: Age 39, camouflage failure after 2 years of orthodontics to correct a skeletal Class III malocclusion.	Image 2, profile: Age 39, camouflage failure after 2 years of orthodontics to correct a skeletal Class III malocclusion.
Image 3, frontal view: Reasonably normal occlusion nevertheless is a treatment failure.	Image 4, right lateral: Reasonably normal occlusion nevertheless is a treatment failure.
Image 5, left lateral: Reasonably normal occlusion nevertheless is a treatment failure.

Class III Camouflage Failure: Presurgical Orthodontics

Linda, a high school teacher, sought further consultation after one of her students had orthognathic surgery. Linda thought the result was much better than the outcome of her own treatment—so she was prepared to be told that jaw surgery might be needed in her case.

The initial cephalometric tracing (image 1) confirmed a skeletal Class III jaw relationship, due primarily to maxillary deficiency. Note that the maxilla is behind a perpendicular line dropped from the bridge of the nose, and the mandible is in front of it—just the reverse of the normal relationship.

To prepare her for orthognathic surgery, as the superimposition tracing from pretreatment to presurgery shows (image 2), it was necessary to create reverse overjet, retracting the maxillary incisors and moving the lower incisors forward. Then, when the maxilla was moved forward surgically, reasonably normal dental occlusion still could be achieved. The effect, of course, was to remove the effects of the original orthodontic treatment.

Another problem with ambitious tooth movement for camouflage of jaw discrepancies is that if it doesn’t succeed, you have to re-create the malocclusion as part of the preparation for surgery—not a happy situation for patient or doctor.

Image 1, pre-tx tracing: Cephalometric tracing, after initial orthodontic treatment.	Image 2, progress superimposition: Presurgical orthodontics, with reverse overjet recreated by tipping lower incisors facially and retracting upper incisors.

Class III Camouflage Failure: Surgery

The maxilla was moved forward and rotated slightly to improve the dental midline, which created better support for the facial tissues adjacent to the maxilla. After the retreatment with surgical maxillary advancement, she was pleased with the change in her facial appearance (compare age 39 before treatment to age 41 afterward). Treatment time was 18 months.

Note that the improvement in smile esthetics (image 1) has two components that are obvious in the full face view: The maxillary dental midline is now closer to the midline of her face, and because the paranasal deficiency is improved, the nasolabial folds are not so deep. Examination of the profile photographs (image 2) also reveals the effect of augmenting the paranasal area as well as better support of the upper lip by the incisors. Because the soft tissues are better supported, she looks younger at age 41 than she did at 39.

Interestingly, the dental occlusion after retreatment with maxillary advancement surgery was very similar to the pretreatment occlusion (images 3-5).

The difference, of course, was in the facial appearance. Keep in mind that successful treatment for dentofacial problems requires both acceptable occlusion and acceptable esthetics.

For Linda, more extensive facial change would have required more extensive orthodontic preparation for the surgery, so that the jaw could be moved further without compromising the occlusion too much. Presurgical orthodontics often must focus on making the occlusion worse temporarily, so that it can be better after the jaw is repositioned.

Image 1, change in smile: Smile esthetics, age 39 and 41.	Image 2, change in profile: Profile, age 39 and 41.
Image 3, frontal view l: Dental occlusion age 42, 2 years posttreatment.	Image 4, right lateral: Dental occlusion age 42, 2 years posttreatment.
Image 5, left lateral: Dental occlusion age 42, 2 years posttreatment.

Class II Camouflage

Class II camouflage is built around retracting the maxillary incisors, and almost always requires extraction of maxillary first premolars to provide space for this tooth movement. Typically, in Class II camouflage, the upper incisors are retracted and the lower incisors are moved forward somewhat.

If premolar extractions are done in the mandibular arch, it is to allow use of Class II elastics (from lower molars to upper incisors) (image 1) to help with retraction of the upper teeth, so that the lower molars come forward and the lower incisors are not retracted.

Skeletal Class II malocclusion can include a component of excessive maxillary growth—and if that happens, the problem almost always is too much downward growth of the maxilla. Then the mandible rotates downward and backward unless it grows vertically as much as the maxilla, which rarely occurs. The effect is a long face with a deficient chin, and a tendency toward Class II malocclusion with an anterior open bite.

With that skeletal pattern, Class II elastics (lower molars to upper incisors) can accentuate the vertical problem (image 2), because the elastic force tends to elongate the lower molars, which rotates the mandible down and back even more. The elastics also elongate the upper incisors, which may be desirable in a short face patient but usually not in a long face patient.

What does that mean? Camouflage is more difficult when the patient has both vertical and a-p problems.

Image 1, Class II camouflage diagram: Mandibular extractions in Class II camouflage imply use of Class II elastics.	Image 2, Class II elastics / mandibular rotation: Class II elastics can rotate the mandible down and back.

Class II Camouflage Failure

At age 15, Melissa had had nearly 4 years of orthodontic treatment, with extraction of first premolars—and her Class II open bite problem was not totally corrected (images 1-3).

The residual malocclusion was a problem, but Melissa’s facial appearance (image 4) also was unsatisfactory. She had to strain to bring her lips together, and in the profile photograph, her mandibular deficiency is apparent. Note the poor throat form (short throat length and submandibular fullness), which often is part of the esthetic problem in mandibular deficiency.

The superimposition tracing (image 5) shows the problem: She had almost no mandibular growth during the treatment period, but her maxilla grew downward—so the mandible rotated down and back, and even though the maxillary incisors were retracted and the lower incisors were proclined, the overjet was not corrected and anterior open bite persisted. For a growth pattern like this, Class II elastics make things worse.

When Melissa and her parents were told that surgery was needed at this point, they were angry and said, “Just take the braces off.” So this is the unsatisfactory result of prolonged treatment, a camouflage failure.

Image 1, frontal view: Dental occlusion after nearly 4 years of orthodontic treatment.	Image 2, right lateral: Dental occlusion after nearly 4 years of orthodontic treatment.
Image 3, left lateral: Dental occlusion after nearly 4 years of orthodontic treatment.	Image 4, facial appearance: Melissa, age 15, camouflage failure.
Image 5, superimposition tracing: Superimposition tracing, downward-backward mandibular rotation.

Class II Camouflage Failure: Surgery

After a couple of months, Melissa and her parents changed their mind and decided to go ahead with surgical treatment to correct the problem. A fixed orthodontic appliance was put back on, for stabilization of the teeth during the surgery and for use in postsurgical orthodontics to bring the teeth into their final position. Then (image 1) she had a LeFort I osteotomy to elevate the posterior maxilla so the mandible could rotate upward and forward, and a lower border osteotomy of the mandible to bring her chin forward (which improves both chin prominence and throat form). The upward-forward rotation of the mandible corrected the malocclusion, closing the open bite and correcting the excess overjet (image 2).

In comparing the facial images before and after the orthognathic surgery (images 3, 4), note the

• decrease in face height,
• improved lip form,
• greater prominence of the chin,
• improved relationship of the lips to the chin, and
• improved throat form.

In this case, the skeletal Class II problem was not corrected by lengthening the mandible with ramus surgery. Instead, maxillary surgery to allow the mandible to rotate upward and forward, combined with advancement of the chin, corrected both the malocclusion and the appearance of a long face mandibular deficiency.

Skeletal Class II isn’t always a purely mandibular problem. About 25% of skeletal Class II patients, like Melissa, have excessive maxillary vertical growth. A Class II problem due to rotation of the mandible is very difficult to treat successfully with orthodontic camouflage.

Image 1, superimposition tracing: Superimposition tracing: note the upward/forward rotation of the mandible when the maxila is moved up.	Image 2, posttreatment dentition: Upward/forward mandibular rotation allowed correction of both the open bite and Class II relationship.
Image 3, frontal facial change: Facial appearance before/after surgical treatment.	Image 4, profile change: Facial appearance before/after surgical treatment.

Camouflage vs Surgery

Camouflage vs Surgery

With those camouflage failure cases as background, let’s look at Rita, who was nearly 15 when she was first seen.

She complained that her upper teeth protruded and were ugly (image 1). She had not had any previous orthodontic treatment and now wanted it very much.

She was very aware of her mandibular deficiency and postured her jaw forward most of the time. It was difficult to get a photograph with her jaw in its retruded position—she may be posturing forward a little in this image 2. That is a risk factor for long-term TM dysfunction, but she had no TMD symptoms at this age.

She had a classic Class II division 1 malocclusion, with mild spacing in the maxillary incisor area and a deep bite anteriorly (image 3). In the lateral photographs, she was posturing forward somewhat and did not have her teeth tightly together.

The cephalometric radiograph (which was obtained in centric relation, the retruded position of the mandible) and tracing (image 4) show that the malocclusion was due almost entirely to mandibular deficiency.

Image 1, full face views: Rita, age 15, prior to treatment.	Image 2, profile: Rita, age 15, prior to treatment.
Image 3, pretreatment dentition: Rita, age 15, prior to treatment.	Image 4, ceph/tracing: Pretreatment ceph and tracing: mandibular deficiency.

Treatment Possibilities

Given Rita’s problem list, there are three possibilities for treatment:

• Class II elastics to pull the teeth together without extraction
• extraction of upper first premolars and retraction of the upper incisors
• surgery to advance the mandible

The first two possibilities, of course, are camouflage. Both of these approaches correct the malocclusion without changing the underlying skeletal problem—and would be successful only if the jaw discrepancy were not noticeable after treatment. Surgery corrects the mandibular deficiency.

It is a great help to both the doctor and patient to predict the outcome of treatment with the various approaches and use the predicted outcome to help select the best approach. It is very difficult to predict growth—but in the absence of growth, treatment changes can be predicted with considerable accuracy.

Class II Elastics for Camouflage?

Cephalometric predictions of possible treatment outcomes, based on manipulation of the ceph tracings, have been used since the 1970s to help decide among treatment options. This cephalometric prediction (image 1) shows the probable result of using Class II elastics, without extractions, to correct Rita’s malocclusion. The prediction tracing is on the left and is superimposed (dashed lines) with the original tracing on the right.

Note that the effect of the elastics would be mostly to bring the lower dentition forward, with some retraction of the upper incisors and downward-backward rotation of the mandible from elongation of the lower molars.

This has two problems: It would be unstable, because pressure from the lower lip would cause uprighting of the lower incisors after treatment, with crowding and return of the deep bite; and it would be unesthetic because of the effect on the lower lip.

Recently it has become possible to superimpose the profile image on the cephalometric tracing, and use algorithms that relate hard tissue to soft tissue changes to change the profile image, so that the prediction is a facial image, not just a tracing.

Image 2 is the computer image prediction of what Rita would look like after orthodontic treatment with Class II elastics. With the profile image linked to the digitized ceph, changes in the tracing alter the profile image, using algorithms to predict various points on the profile. With the image, It is much easier for the patient to understand the esthetic effect of this treatment approach. For Rita, Class II elastics would make the lower lip more prominent relative to the chin, and would not conceal the chin deficiency. Now she and her parents can see that.

Image 1, ceph prediction: Cephalometric prediction, Rita, Class II elastics.	Image 2, computer image prediction: Computer image prediction: left, linked to digitized tracing; right, image prediction.

Extraction for Camouflage?

Image 1 is the cephalometric prediction of the effect of orthodontic treatment for Rita with maxillary premolar extraction. The prediction is on the left, and it is superimposed on the original tracing on the right. Note that the upper incisors have been retracted and intruded. This would be difficult tooth movement but is within the limits established by the envelope of discrepancy for incisor retraction and is right at the limit for intrusion. A small amount of downward-backward rotation of the mandible is predicted, because correction of the overbite solely by intrusion of the upper incisors would not be possible.

After this treatment, the lower dental arch would be in about the same place, so stability of the lower incisors should not be a problem. What about the facial change? Would that be satisfactory, or would lack of support for the upper lip and the residual mandibular deficiency put it into the unsuccessful camouflage category?

Again, using computer imaging to obtain a predicted profile image (image 2) makes it easier to understand the esthetic effect of the “camouflage by extraction” approach. The linked ceph tracing and photograph are shown on the left, the prediction on the right.

This is better than the Class II elastics, from a stability point of view. Does it flatten her upper lip too much, to the point that it leaves her with an unsatisfactory facial appearance?

Image 1, ceph prediction: Cephalometric prediction, Rita, maxillary premolar extractions.	Image 2, computer image prediction: Computer image prediction: left, linked to digitized tracing; right, image prediction.

Mandibular Advancement?

Image 1 is the cephalometric prediction of surgical advancement of the mandible superimposed on the original tracing. This corrects the skeletal mandibular deficiency and gives her a stronger chin.

If the mandible is advanced, the teeth fit together almost perfectly, and because the relationship of the teeth to the tongue and lips is almost unchanged, the result would be expected to be stable (in the absence of surgical relapse, of course—but mandibular advancement surgery is quite stable). What would the esthetic effect be? Computer imaging (image 2) shows the predicted effect on the soft tissue profile.

For the patient, it is particularly interesting to see the predictions side by side (image 3).

The key question is the esthetic effect of the alternative ways to correct the malocclusion. Is it worth it to do the orthognathic surgery to gain the facial change relative to premolar extraction?

So you’re the doctor. How do you decide among these treatment approaches? The answer (image 4) is very simple: You don’t, the patient does.

It is both a moral principle and now a legal requirement that it’s the patient’s decision, not the doctor’s. The doctor’s role is to provide the information so that the patient can make an informed decision. That’s the heart of informed consent to treatment. Computer imaging is a great help to patients in understanding the esthetic impact of a decision to have orthognathic surgery or to accept orthodontic camouflage.

Image 1, ceph prediction: Cephalometric prediction, Rita, surgical mandibular advancement.	Image 2, computer image prediction: Computer image prediction: left, linked to digitized tracing; right, image prediction.
Image 3, side-by-side predictions: Side-by-side image predictions: which is best?	Image 4, who decides?

Surgical Treatment

When Rita and her family came to discuss the plans for her treatment, she said she had thought about it and expected to be told that her lower jaw needed to be lengthened. The predictions confirmed that for her. That definitely was what she and her family wanted.

So that became the plan (image 1). She would have braces put on her teeth to prepare for surgery, then would have a sagittal split osteotomy to advance the mandible, and would have postsurgical orthodontics to bring the teeth to their final position.

Treatment time from braces on to braces off was estimated at 12-15 months. How long the treatment takes is determined largely by how much presurgical orthodontics is required to bring the teeth into proper alignment and arch form, and she didn’t need much presurgical change.

Prior to the surgery, heavy rectangular orthodontic arch wires to stabilize the teeth were placed (images 2,3)—it’s important to have braces on when the surgery is done. Hooks on the arch wires were placed to allow the surgeon to wire the jaws together in the operating room while screws were placed to hold the mandible in its new position. Then the intermaxillary fixation wires were removed.

With rigid internal fixation, using bone screws (image 4), the jaw can be allowed to function while it heals because the screws hold the surgical segments together even when the jaw moves. This makes things much more comfortable for the patient and contributes to better stability.

Image 1, tx plan: Rita, treatment plan.	Image 2, presurgery lateral: Rita, age 15, stabilizing arch wires for surgery.
Image 3, presurgery frontal: Rita, age 15, stabilizing arch wires for surgery.	Image 4, postsurg pan: Panoramic radiograph after sagittal split osteomy, screws in place in the ramus for rigid internal fixation.

Postsurgical Orthodontics

For orthognathic surgery patients, the stabilizing arch wires remain in place after surgery until healing is satisfactory and the patient is comfortable functioning into the splint that was used at surgery to establish the jaw relationship. The splint is tied to either the upper or lower orthodontic arch wires after rigid fixation is established. Typically, the splint and the stabilizing arch wires are removed 3-4 weeks postsurgery and lighter working arch wires are placed, as shown here for Rita (images 1, 2).

Like all orthognathic surgery patients, Rita wore light elastics for a few months postsurgery to control jaw movements and guide her into the correct occlusion. The hooks for these elastics are attached to the brackets on the canines and first molar bands (image 2).

The postsurgical orthodontic treatment was completed and the appliance was removed 6 months after surgery—which is typical postsurgical treatment time. At that point, Rita had excellent occlusion (images 3-5) and normal jaw function. Is this a satisfactory outcome?

Remember, you don’t know until you look at the facial appearance.

Image 1, 4 weeks postsurgery, frontal: Rita, age 15-11, 4 weeks postsurgery: splint removed, stabilizing arch wires replaced.	Image 2, 4 weeks postsurgery, lateral: 4 weeks postsurgery, note the hooks for elastics to guide function and bring teeth together.
Image 3, 6 months postsurgery, frontal: Rita, age 16-4, 6 months postsurgery, treatment completed.	Image 4, 6 months postsurg, right lateral: Rita, age 16-4, 6 months postsurgery, treatment completed.
Image 5, 6 months postsurg, left lateral: Rita, age 16-4, 6 months postsurgery, treatment completed.

Facial Effects of Surgical Treatment

Comparison of the pre- and postsurgery facial photographs (images 1-3) shows the facial change that was created.

Rita’s facial appearance didn’t change dramatically. In her case, orthodontic camouflage with premolar extractions would have damaged her facial appearance. To her, that would have been too high a price to pay for a better bite. Sometimes surgery is needed to make patients look better. Sometimes it’s needed to correct a malocclusion without making them look worse, as in Rita’s case.

Remember—if the esthetic outcome isn’t satisfactory, it isn’t satisfactory treatment.

It is interesting to compare the computer image prediction with the actual treatment result (image 4). The computer predictions are not perfectly accurate, but they come quite close. In general, predictions of chin position are accurate, while changes in lower lip position may not be predicted as well.

Research has shown that both outside observers and patients consistently say that the patient looks better than the prediction. This means there is no great risk of setting up unrealistic expectations by showing the predictions to patients. Patients now routinely are shown computer image predictions to help them decide between camouflage and surgery.

Image 1, full face comparison: Rita, presurgery age 15-10 to end of treatment, age 16-4.	Image 2, smile comparison: Rita, presurgery age 15-10 to end of treatment, age 16-4.
Image 3, profile comparison: Rita, presurgery age 15-10 to end of treatment, age 16-4.	Image 4, prediction comparison: Image prediction (at age 14-10), actual profile age 16-4.

Two-Year Recall

On 2-year recall, Rita was away in college. She continued to be pleased with her improved facial appearance (image 1), and had no sign now of her old habit of posturing her mandible forward.

Her dental occlusion was excellent (images 2-4), and the occlusal relationship also was stable.

Research data show that mandibular advancement of this type is a highly predictable and stable procedure, with a >90% probability of an excellent clinical outcome and a 90% chance that the patient will report satisfaction with the result. For patients who are carefully selected for camouflage, equally good results are obtained—but remember that the surgery and camouflage patients are not the same initially. Patients who choose surgery have more severe problems in their own view.

Image 1, facial appearance: Rita, age 18, 2-year recall.	Image 2 ,frontal view: Rita, age 18, 2-year recall.
Image 3, right lateral: Rita, age 18, 2-year recall.	Image 4, left lateral: Rita, age 18, 2-year recall.

Summary

In summary:

• Modern orthognathic surgery allows both jaws, the chin, and dentoalveolar segments to be repositioned in all three planes of space (image 1).
• One major indication for orthognathic surgery is a malocclusion too severe to correct with orthodontics alone—and this changes as growth is completed, so that some problems that could have been corrected with orthodontics during adolescence require surgery later (image 2).
• The other major indication: a jaw discrepancy that cannot be camouflaged satisfactorily with orthodontic tooth movement (image 3).
• Coordinated orthodontic and surgical treatment is necessary for excellent results with orthognathic surgery (image 4): Prior to surgery, orthodontic treatment is used to align the teeth and place them correctly relative to their own supporting bone—which often involves temporarily making the malocclusion worse. At surgery, heavy stabilizing arch wires are used to minimize tooth movement. Postsurgically, lighter working arch wires and interarch elastics are needed to bring the teeth to final position. Like all other orthodontic patients, orthognathic surgery patients require orthodontic retainers.

Image 1, 2-jaw surgery: LeFort I, sagittal split and lower border osteotomies combined for correction of long face, mandibular deficiency problem.	Image 2, envelope of discrepancy: Envelopes of discrepancy: tooth movement/growth modification/surgical possibilities.
Image 3, camouflage?: Too severe for camouflage? That’s for the patient to decide.	Image 4, coordinated treatment: Coordinated treatment: stabilization after presurgical orthodontics, postsurgical orthodontic finishing, 2-year recall after retainers discontinued.

Self-Test Referral

The self-test section of this program is designed to help you be sure you have understood the material. Do the assigned reading (*Contemporary Orthodontics, 5th ed., pages 685-709; 4th ed., pages 687-707),*then take the test and use it as a guide for further study and review.

Copyright 2013, UNC Dept. of Orthodontics

Self-Test

Question 1

What is the most frequently used orthognathic surgical procedure at present?

1. Sagittal split, mandibular ramus, advancement ✓
2. Sagittal split, mandibular ramus, setback
3. Mandibular lower border osteotomy, chin augmentation
4. LeFort I osteotomy, maxilla
5. Combined LeFort I osteotomy and sagittal split

Correct

That’s right, the sagittal split mandibular ramus osteotomy for advancement is the most frequently used procedure, simply because mandibular deficiency is the most prevalent problem requiring orthognathic surgery and almost all advancements now are done with a sagittal split. All the other procedures listed here are used routinely at present, however.

Incorrect

No, that’s wrong. The sagittal split mandibular ramus osteotomy for advancement is the most frequently used procedure, simply because mandibular deficiency is the most prevalent problem requiring orthognathic surgery and almost all advancements now are done with a sagittal split. All the other procedures listed here are used routinely at present, however.

Question 2

How far can upper incisors be retracted to correct maxillary dental protrusion?

1. 3 mm
2. 5 mm
3. 7 mm ✓
4. 9 mm
5. 12 mm

Correct

That’s right, the general guideline is that protruding upper incisors can be retracted a maximum of about 7 mm in most circumstances. It’s unrealistic to think they can be retracted a lot more than that, but remember that the envelope of discrepancy provides guidelines. Don’t think that the numbers are precise predictions for individual patients.

Incorrect

No, that’s not the best answer. The general guideline is that protruding upper incisors can be retracted a maximum of about 7 mm in most circumstances. It’s unrealistic to think they can be retracted a lot more than that, but remember that the envelope of discrepancy provides guidelines. Don’t think that the numbers are precise predictions for individual patients. With reasonable orthodontic control, 6-7 mm is entirely possible, so estimates lower than that are unduly pessimistic.

Question 3

One approach to a skeletal Class II problem in early adolescence is growth modification. How much improvement in the jaw relationship can be reasonably expected?

1. 3 mm
2. 5 mm ✓
3. 7 mm
4. 9 mm
5. 12 mm

Correct

That’s right, the best estimate is 5 mm of skeletal change. Since the molar relationship must be changed 7 mm to change a typical Class II relationship to a normal Class I relationship, that means some tooth movement in addition to growth modification almost always is required to correct a skeletal Class II problem. Could you correct a 12-mm overjet with orthodontics alone? Perhaps, but with only 5 mm of skeletal change available, it would require 7-mm movement of the teeth.

Incorrect

No, that’s wrong. The best estimate for skeletal change is 5 mm. Since the molar relationship must be changed 7 mm to change a typical Class II relationship to a normal Class I relationship, that means some tooth movement in addition to growth modification almost always is required to correct a skeletal Class II problem. Could you correct a 12-mm overjet with orthodontics alone? Perhaps, but with only 5 mm of skeletal change available, it would require 7-mm movement of the teeth.

Question 4

(A) The potential for orthodontic treatment of skeletal Class II problems decreases after adolescence because (B) Tooth movement is much less successful in adults than children, so the incisors can’t be retracted as far.

1. A true, B true, A and B related
2. A true, B true, A and B not related
3. A true, B false ✓
4. A false, B true
5. A and B false

Correct

That’s correct, the first statement is true but the second is false. The potential for orthodontic treatment decreases after adolescence because growth modification to significantly improve the jaw relationship is no longer possible. Tooth movement has about the same potential in adults as in younger patients.

Incorrect

No, that’s wrong. The first statement is true but the second is false. The potential for orthodontic treatment decreases after adolescence because growth modification to significantly improve the jaw relationship is no longer possible. Tooth movement has about the same potential in adults as in younger patients.

Question 5

(A) More Class III than Class II patients require orthognathic surgery because (B) The position of the mandible can be changed much more with surgery than orthodontics.

1. A true, B true, A and B related
2. A true, B true, A and B not related ✓
3. A true, B false
4. A false, B true
5. A and B false

Correct

That’s right, both statements are true, but they aren’t related in a cause-and-effect sense. More Class III than Class II patients require surgery, not because surgery can move mandibles further but because both growth modification and tooth movement have less potential to correct Class III problems. Note in the envelopes that the maximum potential of orthodontic treatment for Class II patients is close to the maximum for stable surgical correction. The result: >90% of skeletal Class II patients can be treated with a combination of growth modification and tooth movement if the treatment starts during adolescence. Because the potential for orthodontic Class III treatment is smaller, probably the worst one-third of skeletal Class III patients need surgery for correction.

Incorrect

No, that’s wrong. Both statements are true, but they aren’t related in a cause-and-effect sense, so the right answer is (2). More Class III than Class II patients require surgery, not because surgery can move mandibles further but because both growth modification and tooth movement have less potential to correct Class III problems. Note in the envelopes that the maximum potential of orthodontic treatment for Class II patients is close to the maximum for stable surgical correction. The result: >90% of skeletal Class II patients can be treated with a combination of growth modification and tooth movement if the treatment starts during adolescence. Because the potential for orthodontic Class III treatment is smaller, probably the worst one-third of skeletal Class III patients need surgery.

Question 6

Which of the following are contraindications for orthognathic surgery?

a. diabetes mellitus

b. severe periodontal disease

c. hemophilia

d. paranoid schizophrenia

1. all
2. a, c, and d
3. b, c, and d
4. c and d
5. none if controlled ✓

Correct

That’s right, patients with any of these pathologic conditions can have orthognathic surgery if the underlying condition has been brought under control by adequate treatment. Uncontrolled disease is a contraindication; controlled disease is not. Even hemophiliacs can have orthognathic surgery if the missing clotting factors are replaced, and for some hemophiliacs surgery under those controlled conditions is better patient management than prolonged orthodontic treatment.

Incorrect

No, that’s incorrect. Patients with any of these pathologic conditions can have orthognathic surgery if the underlying condition has been brought under control by adequate treatment. Uncontrolled disease is a contraindication; controlled disease is not. Even hemophiliacs can have orthognathic surgery if the missing clotting factors are replaced, and for some hemophiliacs surgery under those controlled conditions is better patient management than prolonged orthodontic treatment.

Question 7

How do you determine whether orthodontic camouflage was successful?

1. Quantify the quality of the occlusion with PAR scores or a similar occlusal index
2. Evaluate TM joint function with Helkimo’s index or a similar quantitative method
3. Obtain scores on the psychological MMPI test
4. Ask the patient what he or she thinks ✓

Correct

That’s correct. What the patient thinks is the determinant of whether orthodontic camouflage was successful. If the patient thinks things look acceptable, psychosocial problems related to dental and facial appearance will largely disappear, and if the patient doesn’t think they look acceptable, there’s still a problem no matter how good the scores are for occlusion and TM joint function. Scores on psychological tests might provide details of what the psychosocial problem is, but that kind of testing is not necessary to know whether a problem still exists. The primary goal of treatment, after all, was to solve the patient’s problems.

Incorrect

No, that’s wrong. What the patient thinks is the determinant of whether orthodontic camouflage was successful. If the patient thinks things look acceptable, psychosocial problems related to dental and facial appearance will largely disappear—and if the patient doesn’t think they look acceptable, there’s still a problem no matter how good the scores are for occlusion and TM joint function. Scores on psychological tests might provide details of what the psychosocial problem is, but that kind of testing is not necessary to know whether a problem still exists. The primary goal of treatment, after all, was to solve the patient’s problems.

Question 8

Which of the following is not an appropriate surgical approach to a skeletal Class II patient with mandibular deficiency?

1. Surgical retraction of the upper anterior teeth ✓
2. Mandibular advancement
3. Upward movement of the maxilla
4. Simultaneous combination of 2 and 3

Correct

That’s right, retracting the protruding teeth (surgery to do the same thing that orthodontic tooth movement would have accomplished) is not an appropriate surgical approach because it would probably result in a camouflage failure. Mandibular advancement is the solution to deficient mandibular growth. Moving the maxilla up allows the mandible to rotate upward and forward. This improves a skeletal Class II jaw relationship and is indicated, alone or in combination with mandibular advancement, in patients who had too much vertical maxillary growth. If necessary, simultaneous maxillary and mandibular surgery is quite feasible.

Incorrect

No, that’s incorrect. Retracting the protruding teeth (surgery to do the same thing that orthodontic tooth movement would have accomplished) is not an appropriate surgical approach because it would probably result in a camouflage failure. Mandibular advancement is the solution to deficient mandibular growth. Moving the maxilla up allows the mandible to rotate upward and forward. This improves a skeletal Class II jaw relationship and is indicated, alone or in combination with mandibular advancement, in patients who had too much vertical maxillary growth. If necessary, simultaneous maxillary and mandibular surgery is quite feasible.

Question 9

(A) Computer image prediction is more successful in predicting the probable outcome of growth modification than surgery because (B) Facial changes accompanying growth are inherently more predictable than surgical movement of the jaws.

1. A true, B true, A and B related
2. A true, B true, A and B not related
3. A true, B false
4. A false, B true
5. A and B false ✓

Correct

That’s correct, both of these statements are false. The truth is just the opposite. Computer image predictions of surgical change are clinically useful, but they can be quite misleading for growing children because growth changes remain largely unpredictable. The effects of treatment in the absence of growth are predictable, and orthognathic surgery is done only after major growth changes are no longer likely.

Incorrect

No, that’s wrong. both of these statements are false. The truth is just the opposite. Computer image predictions of surgical change are clinically useful, but they can be quite misleading for growing children because growth changes remain largely unpredictable. The effects of treatment in the absence of growth are predictable, and orthognathic surgery is done only after major growth changes are no longer likely.

Question 10

(A) Correcting a malocclusion may require surgery to keep from making a reasonably satisfactory pretreatment facial appearance unsatisfactory because (B) Tooth movement alone to correct the occlusion can make dental and facial esthetics worse.

1. A true, B true, A and B related ✓
2. A true, B true, A and B not related
3. A true, B false
4. A false, B true
5. A and B false

Correct

That’s correct. Some patients with an underlying jaw discrepancy don’t have an unacceptable facial appearance before treatment, but they would be moved into the unacceptable category if the incisors were repositioned to bring them into proper occlusion. This girl’s facial appearance would have been damaged by retracting her upper incisors. Computer slide predictions can help patients understand the esthetic implications of treatment choices.

Incorrect

No, that’s wrong. Some patients with an underlying jaw discrepancy don’t have an unacceptable facial appearance before treatment, but they would be moved into the unacceptable category if the incisors were repositioned to bring them into proper occlusion. This girl’s facial appearance would have been damaged by retracting her upper incisors. Computer slide predictions can help patients understand the esthetic implications of treatment choices.