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Growth modication of the face: A currentperspective with emphasis on Class III treatment

Hugo J. De Clercka and William R. Proftb

Chapel Hill, NC, and Brussels, Belgium

A summary of the current status of modication of jaw growth indicates the following. 1. Transverse expansion of

the maxilla is easy before adolescence, requires heavy forces to create microfractures during adolescence, and

can be accomplished only with partial or complete surgical osteotomy after adolescence. Transverse expansion

of the mandible or constriction of either jaw requires surgery. 2. Acceleration of mandibular growth in preadoles-

cent or adolescent patients can be achieved, but slower than normal growth afterward reduces or eliminates a

long-term increase in size of the mandible. Restraint of maxillary growth occurs with all types of appliances tocorrect skeletal Class II problems. For short-face Class II patients, increasing the face height during preadoles-

cent or adolescent orthodontic treatment is possible, but it may make the Class II problem worse unless favor-

able anteroposterior growth occurs. For those with a long face, controlling excessive vertical growth during

adolescence is rarely successful. 3. Attempts to restrain mandibular growth in Class III patients with external

forces largely result in downward and backward rotation of the mandible. Moving the maxilla forward with

external force is possible before adolescence; moving it forward and simultaneously restricting forward mandib-

ular growth without rotating the jaw is possible during adolescence with intermaxillary traction to bone anchors.

The amount of skeletal change with this therapy often extends to the midface, and the short-term effects on both

jaws are greater than with previous approaches, but individual variations in the amount of maxillary vs mandib-

ular response occur, and it still is not possible to accurately predict the outcome for a patient. For all types of

growth modication, 3-dimensional imaging to distinguish skeletal changes and better biomarkers or genetic

identication of patient types to indicate likely treatment responses are needed. (Am J Orthod Dentofacial

Orthop 2015;148:37-46)

Although growth modication has been

considered important from the beginning oforthodontics, the concepts underlying its use

and the views of its clinical usefulness have variedgreatly over time. To orthodontists in the late 19thand early 20th centuries, growth modication waseasy because it was assumed that growth was largelycontrolled by environmental factors and was judged

as successful because the dental occlusion improved.

By midcentury, cephalometrics had shown that most

of the changes produced by the treatment methods

of that time were tooth movement, not modiedgrowth. At that point, the American view was that it

was almost impossible to modify growth because oftight genetic control, and that attempts to do so

were rarely indicated. Europeans remained more pos-itive; in the United States, there was increasing accep-tance of European functional appliances and

enthusiasm for growth modication in the last quarter

of the century. There is a somewhat less enthusiasticview of it now, as better data for long-term outcomeshave become available, and genetic inuences once

again are being emphasized.In this article, we had 2 goals: (1) to provide an

overview of growth modication possibilities and limi-tations based on the best current data for the varioustypes of malocclusions, and (2) to discuss in moredetail Class III growth modication with elastics to

bone anchors, the most recent form of growth modi-cation and, in terms of short-term changes, perhaps themost successful.

aAdjunct professor, Department of Orthodontics, School of Dentistry, University

of North Carolina, Chapel Hill, NC; private practice, Brussels, Belgium.bKenan distinguished professor, Department of Orthodontics, School of

Dentistry, University of North Carolina, Chapel Hill, NC.

All authors have completed and submitted the ICMJE Form for Disclosure of Po-

tential Conicts of Interest, and none were reported.

Address correspondence to: Hugo J. De Clerck, Kerkstraat 120, 1150 Brussels,

Belgium; e-mail,[email protected].

Submitted, revised and accepted, April 2015.

0889-5406/$36.00

Copyright 2015 by the American Association of Orthodontists.

http://dx.doi.org/10.1016/j.ajodo.2015.04.017

37

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TRANSVERSE GROWTH MODIFICATION

Transverse growth modication is largely done in the

context of maxillary expansion by opening the midpala-tal suture. Ample clinical evidence now conrms that

opening the suture can be accomplished. In young chil-dren, up to age 8 or 9 years, little force is needed. Up tothat age, a transpalatal lingual arch for dental expansionalso will open the midpalatal suture. A jackscrew deviceis not needed, and rapid expansion is contraindicated

because of the possibility of injury to the nose, involvingdisplacement of the vomer bone.

By age 9 or 10, there is enough interdigitation ofbone spicules on the edges of the midpalatal suturethat opening the suture requires microfractures, and aheavier force from a jackscrew device is necessary to

do this. The rate of opening the suture with a jackscrew

remains controversial. The original reason for rapidexpansion was that the suture would open too rapidlyfor tooth movement to accompany it, and the amountof skeletal vs dental change would be greater. This istrue in the short term but not in the medium or long

term: after rapid expansion, skeletal relapse is followedby tooth movement, so that a few weeks after the jack-screw is tied off and left in place as a retainer, the skeletaland dental components of the expansion are about 50-50. Approximately the same ratio is found when the

expansion is done slowly, at a rate of about 1 mm perweek.1 Slow expansion, therefore, can be consideredan equally effective and less traumatic way to expandthe maxilla. Additional transverse growth after adoles-cent expansion almost never occurs.2

The suture opens in a Vpattern both transversely

and vertically, with more expansion anteriorly andsome expansion all the way up to the orbits. Extremelyheavy force in late adolescence carries with it the riskof an uncontrolled fracture that extends vertically andcan lead to a signicant injury.

Transverse expansion of the mandible is possible only

with distraction osteogenesis at the symphysis. The ma-jor indication is lack of development of the mandibularmidline structures (Fig 1). Symphysis distraction as a

way to gain space for the alignment of crowded mandib-ular incisors is now judged to have a poor ratio of benetto cost and risk.

Excessive transverse growth is almost totally a prob-lem in the mandible. Mandibular arch width is affected

by tongue size and posture; with a large tongue carriedlow in the mouth, a posterior crossbite is likely to bepresent with normal or even wide maxillary dimensions.

It may be the best clinical judgment to tolerate such acrossbite rather than to attempt an extreme maxillaryexpansion. Narrowing the mandibular arch in such a case

is almost impossible; surgical narrowing by removal ofbone at the symphysis is difcult and potentially unstable.

MODIFYING CLASS II GROWTH

Patients with a Class II growth pattern have some

combination of decient forward mandibular growthand excessive maxillary growth that is more likely to bedownward than forward. The desired growth modica-tion, of course, is stimulation of forward mandibulargrowth and restraint of maxillary growth in both direc-

tions.The orthodontic literature has hundreds of reports of

devices to modify growth in this way and much data foroutcomes of treatments. Functional appliances thatposition the mandible forward are the mainstays oftreatment. Their short-term effects are summarized in

a recent meta-analysis, to which readers are referredfor further information.3 The conclusions relative togrowth modication are that (1) functional appliancescan accelerate the rate of forward mandibular growth

before and during adolescence, (2) there is an elementof restraint of maxillary growth in the response, and

(3) a signicant part of the correction of a Class II maloc-

clusion is due to dental rather than skeletal change.Does acceleration of mandibular growth during

adolescence lead to a larger mandible at the end of thegrowth period? The possibilities are shown inFigure 2;the consistent conclusion is that the period of growthacceleration is followed by diminished growth later, so

that if there is any increase in mandibular length in thelong term, it is quite small. Sometimes the change isevaluated as statistically signicant; sometimes it isnot, but the data do not support the idea that the ortho-

dontist is growing mandibles.

Fig 1. Extreme mandibular deciency:A, sagittaly and

B, transversely, in a patient with congenitally missing

mandibular canines and 3 incisors, and a hypoplastic

tongue but normal facial soft tissues. This made him an

ideal candidate for mandibular distraction osteogenesis

in preparation for eventual surgical mandibular advance-

ment.

38 De Clerck and Prof t

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Is extraoral force to the maxilla effective in restrainingits forward growth? The answer is yes, andthe amount ofgrowth restraint is greater with headgear than with

functional appliances, but the outcomes of treatmentbetween functional appliances and headgear are remark-ably similar. It appears that an improvement in the ante-roposterior position of the maxilla relative to the

mandible greater than 5 mm is about as much as growthmodication can provide, and that such a favorable result

occurs in not more than two thirds to three quarters ofthe patients treated during adolescence.4

The timing of Class II growth modication treatmentremains controversial despite multiple clinical trials withthe same conclusion: that 2-stage treatment beginning

before the adolescent growth spurt is not moreeffective

than 1-stage treatment during adolescence.

5

The pri-mary indication for preadolescent treatment, therefore,is psychosocial problems caused by teasing and harass-ment about protruding maxillary teeth, not a severemalocclusion.

SHORT-FACE AND LONG-FACE GROWTH

MODIFICATION

Vertical deviations from acceptable facial proportionsare less frequent but not less important than anteropos-terior deviations and can accompany Class II or Class IIIgrowth patterns.

The best description of short-face problems is that

the lower third of the face is short relative to the otherfacial thirds; the graphic way to say it is that the chinis too close to the nose. Patients with this problem usu-

ally have a relatively long ramus, an acute gonial angle,and a low mandibular plane angle: the so-called skeletaldeepbite conguration. If they also are somewhat

mandibular decient, a Class II Division 2 malocclusionmay be present.

In those patients, one would want downward growthof the mandible and would be willing to accept somedownward rotation of the mandible to increase anteriorface height. The problem is that rotating the mandibledown also moves the chin back, so improving the face

height may make the mandibular deciency worse.The most successful approach to growth modica-

tion in these patients is an activator or bionator typeof appliance, with contact of the mandibular incisors

against the palatal portion of the appliance and theacrylic trimmed to allow eruption of the mandibular pos-terior teeth. It may be necessary to tip the maxillary in-cisors facially rst to allow mandibular advancement.A less desirable alternative is cervical headgear becauseit elongates the maxillary posterior teeth and rotates

the occlusal plane down posteriorly. It is better to in-crease both the occlusal plane and the mandibular planeangles during treatment.

Does the deepbite impede forward mandibulargrowth? Occasionally, there is a burst of forward growth

as face height is increased, but this is the exceptionrather than the rule. On the other hand, lengthening

the face is a quite successful form of growth modica-tion.6 For Class II deepbite patients, trauma to thepalatal soft tissues or gingivae facial to the mandibularincisors is an indication for beginning treatment before

adolescence.In contrast, modifying the long-face pattern of

growth and controlling downward and backward rota-tion of the mandible is difcult and, at least untilnow, has been almost impossible. In theory, it should

be possible to impede downward growth of the posterior

maxilla with high-pull headgear and impede eruption ofthe posterior teeth in both arches. In fact, even thecombination of high-pull headgear with a functionalappliance with bite-blocks is not successful in produc-ing the desired skeletal changes.7 It is possible that anadaptation of the technique for intrusion of the maxil-lary posterior teeth to correct open bites after adolescent

growth, or bone plates across the zygomaticomaxillarysuture, can be used to diminish the downward growthof the maxilla that is a key component of long-facedevelopment, but there are as yet no data to conrmthat.8

Fig 2. Diagrammatic representation of the difference be-

tween mandibular growth acceleration and true stimula-tion of mandibular growth. Good evidence shows that

growth in the period after acceleration is slower than ex-

pected growth. The extent of some true stimulation in

the long term is small if not zero. (From Proft WR, Fields

HW Jr, Sarver DM. Contemporary orthodontics. 5th ed.

Philadelphia: Elsevier; 2013. With permission from

Elsevier).

De Clerck and Proft 39

American Journal of Orthodontics and Dentofacial Orthopedics July 2015 Vol 148 Issue 1

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For modication of vertical growth, the conclusions

are the following. Can you producedownward and back-ward rotation of the mandible and increase the faceheight when this is required? Yes. Can you produce up-

ward and forward rotation of the mandible, or evenmaintain its vertical position, in a patient with a long-face pattern? Unfortunately, no, at least not yet.

CLASS III GROWTH MODIFICATION

Class III problems are a combination of possiblecauses: decient maxillary growth forward and down-

ward and excessive mandibular growth forward, or de-cient growth downward. Decient vertical growth allows

upward and forward rotation of the mandible and exac-erbates a Class III problem; downward and backward

rotation alleviates it, but only if excess face height

does not become a problem instead. At present, thereare 3 major treatment methods, which will be discussedseparately.

Chincup effects on the mandible

Attempts to restrain mandibular growth go back to

the beginning of orthodontics and almost always involvea cup or cap on the chin that is attached to the back ofthe head (Fig 3). Although this produces an upward and

backward force, almost always the result is downwardrotation of the mandible, with minimal restraint ofgrowth in length of the mandible. Some data suggest

that chincup restraint is more effective at an early age,but catch-up growth after early treatment tends towipe out any improvement.

If a patient with a large mandible also has a short

face, chincup treatment would be more valuable. Forthat reason, it is widely acknowledged that wearing a

chincup during mandibular growth is more effective inpatients of Asian than of European or African descent,simply because shorter face height is more likely in AsianClass III patients. In contrast, most Americans and Euro-peans with a Class III problem caused by excessive

mandibular growth also have a long face; for them, chin-

cup therapy is not effective.

Facemask effects on the maxilla

Until the pioneering work of Delaire9 with facemasktreatment in young children, orthodontists thoughtthat bringing the maxilla forward was impossible; effortsto do that resulted only in proclination of the maxillary

teeth. It now is well established that protraction of themaxilla can be accomplished with facemask therapy,that skeletal change is more likely in children at age8 years or younger, and that the upper limit for a positiveresult is about age 10.10 Above that age, the outcome

usually is only tooth movement and downward andbackward mandibular rotation.

Disarticulation of the maxillary sutures by rapidpalatal expansion or an alternating expansion-constriction of the midpalatal suture before tractionoften is included in the standard facemask protocol.

However, in a randomized prospective clinical trial,the amount of protraction of the midface was not

affected by rapid palatal expansion.11 The only indica-tion for rapid palatal expansion in facemask patients,therefore, is a severe constriction of the maxilla, sothat a crossbite would not be corrected as the maxilla

moved forward.Some investigators have tried using bone anchors on

the maxilla to decrease tooth movement in the hope thatthis would allow treatment at later ages, but theimprovement in skeletal change was small and inconsis-tent.12 For most patients at any age, downward and

backward rotation of the mandible is part of the

response, which again means that short-face patientsare most likely to respond well.

Below, magnitudes of change with facemask treat-ment are compared with the changes obtained withthe third method, Class III elastics to bone anchors.

Fig 3. Chincup for mandibular restraint circa 1900 (gure

from Angle EH. Treatment of malocclusion of the teeth

and fractures of the maxillae. 7th ed. Philadelphia: SS

White Dental Mfg Co; 1907). Angle was convinced that

it would work if patients really cooperated but acknowl-

edged his disappointment with the usual results.



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Class III elastics to bone plates

The use of skeletal anchorage in Class III orthopedics

has 2 advantages: (1) it can be used to minimize bothdentoalveolar changes and downward and backwardmandibular rotation, and (2) with continuous light forcefrom Class III elastics, there now is evidence that greaterskeletal changes can be created than have been seen pre-

viously, with effects on the maxilla, mandible, andtemporomandibular joint. Because this method is rela-

tively new and has not been as thoroughly examinedas the treatment procedures discussed above, it will bereviewed here in more detail.

The technical aspects will be considered rst. Mini-

plates are inserted on the infrazygomatic crest and inthe mandibular canine region and connected by elastics

day and night. In the maxilla, an intraoral incision andreection of a ap are needed to allow placement ofthe bone anchor above the alveolar process and theattachment that projects into the mouth to emerge at

the proper location. To prevent dehiscence of the softtissues, the lower part of the bone anchor should be con-toured so that it is in closecontact with the bone surface

before the ap is sutured.13

To reduce the risk of bacterial inltration, it is impor-tant that the perforation of the soft tissues through

which the intraoral part of the bone anchor enters the

oral cavity is located at the upper extent of the attachedgingiva. Furthermore, the section of the extension perfo-rating the soft tissues should be round to facilitate oralhygiene and good adaptation of the soft tissues aroundthe bone anchor. In the mandible, the plates should be

inserted after eruption of the canines to reduce the risk

of damaging these teeth during xation of the screws.Repeatedly loading the intraoral part of the bone anchor

by tongue or nger pressure should be avoided becauseit may lead to bone loss and increased mobility of thescrews. That is why early loading is advocated toneutralize the adverse effects from discontinuous

muscular forces.The success rate of miniplates is mostly related to

the surgical procedure and the thickness and qualityof the bone, which varies from one location toanother.14 Cone-beam computed tomography (CBCT)images can be helpful to choose the best places for

insertion of the screws. Especially in young children,both the thickness and the density of the bone inthe infrazygomatic crest may be insufcient for goodmechanical retention of the osteosynthesis screws.

For this reason, the best stability of the skeletalanchorage is obtained in children at least 11 years

old. Higher density and thickness of the externalcortical bone in the mandible results in a lower failurerate than in the maxilla. At any age, mandibular boneis more dense than maxillary bone, so 3 screws areneeded to stabilize the maxillary bone plates, but

only 2 are needed in the mandible.A typical sequence of treatment is shown inFigure 4.

If at the start of treatment there is a reverse crossbite ofthe incisors, a biteplate should be used to unlock the oc-clusion and to facilitate forward movement of themaxilla. This biteplate is worn day and night, and also

during eating. At every monthly checkup (needed for

Fig 4. A,Start of intermaxillary bone anchored elastic traction; B, a biteplate to unlock the occlusion;

C-E,distalization mechanics with the xed appliance;F, 4 years out of retention.



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patients treated in this way), interdigitations in the bite-

plate or occlusal interferences should be eliminated.It has always been assumed that higher forces are

needed for moving bones than for moving teeth. How-

ever, better clinical results are obtained with lightbone-anchored intermaxillary traction than with heavyextraoral force from a facemask. More important than

the amount of force seems to be the loading protocol:continuous intraoral forces give a better outcome thanintermittent extraoral traction. This probably is due inpart to better compliance with wearing intraoral elasticsthan an extraoral facemask, but as a general rule, heavyforce is not required for growth modication. This has

been conrmed by both human experience and animal

experiments.15

In a typical treatment, the timing is similar to Class IIgrowth modication: intermaxillary traction is main-tained for 12 months and is followed by treatment

with a xed orthodontic appliance. Because of growthchanges in the maxilla and the mandible, a Class III orClass I molar occlusion is often transformed into a ClassII relationship that will need to be corrected in the xedappliance stage of treatment.

In these maxillary-decient patients, there often is

insufcient space for the eruption of the maxillary ca-nines. Usually some additional space is already obtained

by the protraction of the maxilla, resulting in an increaseof arch length in the molar region. More space can becreated using maxillary miniplates combined with the

xed appliance as anchorage to distalize the maxillarymolars and premolars (Fig 4). This can improve smile es-

thetics and tooth exposure, especially in patients with ahypoplastic midface, and reduce the need for premolarextractions. An alternative would be headgear to supportthe distalization, but bone-anchored distalization me-

chanics depend less on compliance than does headgeartraction, and because the miniplates are inserted below

the zygomaticomaxillary suture, this will not result incompression of the sutures, minimizing what would bean undesired orthopedic effect with headgear.

After debonding, some relapse of the Class III growth

can still occur. In that case, additional intermaxillaryelastics may be needed for some time to maintain thenal occlusion. Therefore, the miniplates should beremoved only after stabilization of growth.

Next, we consider facial changes. Extra forwardgrowth of the zygomaticomaxillary complex and re-straint of the forward displacement of the bony chin

can result in an important reduction of the soft tissueconcavity and improvement of the overall expressionof the face. The upper lip is most affected by the protrac-tion; the tip of the nose usually is slightly moved upwardand forward, whereas the chin becomes less prominent.

Exposure of the maxillary dentition typically improves.

All these changes take place over a long period.Cranial base superimpositions of CBCT images allow

a much better understanding of the changes produced

by treatment of this type. When there is considerablevariability in the treatment outcomes, the percentageof various types of change in a series of consecutive pa-

tients provides a better understanding than statisticsbased on the normal distribution. Figure 5 is a frontalview of soft tissue changes in 25 consecutive patients,all treated by the rst author and analyzed by colleaguesat the University of North Carolina.16,17

As shown inFigure 5, in the majority of the patients,the midface and the maxilla, not just the maxilla, were

moved forward. This included forward movement ofthe infraorbital area, the zygomatic arches, and thenose. The mean advancement of the zygomatic arch

was 3.7 6 1.7 mm; for the maxillary incisor, it was

4.3 6 1.7 mm. The large standard deviations suggesthigh variability, andFigure 5shows that there were mid-face advancements of 4 to 5 mm in 8 of the 25 patients(32%) and 2 to 3 mm in 12 patients (48%). The nasal tipmoved upward by 1 to 2 mm as well as forward in those

who had midface advancement. But there was essen-

tially no maxillary or midface advancement (0-1 mm)in 20% of the patients.

There also was an effect on the mandible in almostevery patient, with 4 to 5 mm of distal movement ofthe chin in 3 patients (12%) and 2 to 3 mm in 5 patients

(20%). Distal movement of the chin in monkeys who hada continuous force against the chin was reported in early

animal experiments but had not been seen in humanspreviously. This would be possible, of course, only ifthere was remodeling or relocation of the condylar fossaand distal movement of the condyles, and this was

observed in the CBCT superimpositions in most patients.Although the patients were growing during the treat-

ment period, the chin moved forward in only 5 (20%),so there was some degree of growth restraint in 80%,and in many patients there was an increase in the lengthof the mandible without forward movement of the chin.

These skeletal effects underlying the soft tissue changesare discussed in more detail below.

There were effects on the maxilla and the midface.The maxilla is connected by sutures to the surrounding

bones. Animal experiments have clearly shown by histol-ogy that traction across the posterior sutures of themaxilla leads to increased boneformation and forward

displacement of the maxilla.18 Resistance againstseparation of sutures depends on the total surface ofthe suture and the complexity of the interdigitations,and that is why the zygomaticomaxillary suture hasa much higher resistance to separation than the



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zygomaticotemporal and the zygomaticofrontal sutures.This explains why not only the maxilla and the teeth but

also the zygomatic bone often move forward as 1 unit.For the same reason, much larger separations are

observed all along the transverse palatine suture thanat the level of the tight junction between the pyramidal

process of the palatine bone and the pterygoid plates ofthe sphenoid bone. In contrast to the zygoma, the pala-tine bone seems not to be affected much by the forwardtraction.

The center of resistance of the maxilla has been hy-pothetically dened as at the buttress.19 Since the lineof force connecting both bone anchors is at a clear dis-

tance below the buttress, counterclockwise rotation ofthe maxilla was initially expected. During protraction,however, only a small amount of rotation occurs. There-fore, the center of resistance of the zygomaticomaxillarycomplex must be located close to the line of force with

intraoral traction, and more backward and downwardthan the theoretical center of resistance of the maxilla.

Thanks to the pure skeletal anchorage, almost no den-toalveolar compensations are observed at the level ofthe maxillary incisors.

Since mild transverse crossbites are spontaneously

eliminated during the orthopedic correction as themaxilla is brought forward, rapid maxillary expansionis indicated for intermaxillary traction patients only

with severe transverse discrepancies between the 2 jaws.There are signicant differences between both the

timing and the outcome of facemask protraction and in-termaxillary traction. It is well known that interdigitation

of sutures increases with age, so protraction of the mid-face can be obtained more easily in young patients. Forthis reason, treatment with a facemask has always beenadvocated before the age of 9 years. However, other pa-rameters such as skeletal maturation and staging of the

Fig 5. Cranial base superimpositions from before to after 1 year (11-13 months) of intermaxillary trac-tion for 25 consecutive maxillary-decient Class III adolescents.Redshows forward movement relative

to the cranial base;blueshows backward movement relative to the cranial base. (From Nguyen et al,16

with permission from Elsevier).



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interdigitation of sutures on CBCT images may better

predict the orthopedic outcome in the future.Despite being older (because bone anchors are less

stable at earlier ages), patients treated with bone-

anchored orthopedics without rapid maxillary expansionat a mean age of 12 years showed about twice as muchmaxillary forward displacement compared with a group

treated about 4 years earlierwith a facemask precededby rapid palatal expansion.20 However, there was highvariability in the amount of protraction observed withboth protocols. Downward and backward rotation ofthe mandible occurred in many facemask patients; this

was not observed in the intermaxillary traction patients.There are effects on the mandible and temporoman-

dibular joint. Because facemask treatment is more suc-cessful than chincup therapy, the adaptability of thesutures to external factors has been considered greaterthan the adaptability of condylar cartilage, and Class

III orthopedics have been focused mostly on stimulationof maxillary growth. However, the forces generated by

bone-anchored elastics also pull the chin backwardand upward. This is in contrast to the more horizontalreaction forces of the facemask applied to the chin.That is why no posterior rotation of the mandible and

no increase of the vertical dimension of the face arecommonly observed with intermaxillary traction. Clock-

wise rotation of the mandible results in increased facialconvexity and is often wrongly interpreted as a restraintof mandibular growth.

The increases in length of the ramus and the body ofthe mandible in patients treated with intermaxillary trac-

tion are not signicantly different from those of a con-trol group. However, the distance between the condyleand the chin (condylion-gnathion) increases signi-cantly less in a treated group than in the controls. This

is explained by a reduction of the gonial angle in thetreated group, vs its slight increase in the control group.

One would think that a reduction of the gonial anglewould project the bony chin more forward, but incontrast to the control group, the gonial landmarksmoved posteriorly in the treated group. This swing-

backmovement of the ramus is an important cause ofrestriction of forward projection of the chin. The combi-nation of a slight closure of the gonial angle and theswing-back of the ramus explains why, despite similarlengthening of the ramus and the body of the mandiblein treated patients and untreated controls, the chin pro-

jection is restrained without an increase of the mandib-

ular plane angle. The shape rather than the size of themandible is affected by the elastic traction.

Superimposition on the cranial base of the CBCT im-ages before and after bone-anchored elastic tractionalso shows posterior displacement of the condyles in

about half of our treated patients. A high correlation

was found between the amount of displacement of theanterior and posterior surfaces of the condyles and theamount of apposition at the anterior eminence and

resorption at the posterior wall of the glenoid fossa (un-published data, in preparation). This reects a moderaterelocation of the articular fossa; this also has been

observed as a response to Herbst appliance treatment,but in the opposite direction.21,22

It also is true that the direction of condylar growthcould be modied by the force application. Similar tothe method of superimposition on metal markers of

Bjork and Skieller,23 a method for superimposition onstable internal structures in the chin has been developed

(unpublished data, in preparation), and soon this willgive us better insight into whether the direction ofcondylar growth is related to and can be inuenced bythe direction of the elastic traction.

Although almost no dentoalveolar changes areobserved in the maxilla, in nearly all intermaxillary trac-tion patients a spontaneous decompensation of the up-right mandibular incisors occurs. Why this occurs is not

yet clear. It could be explained by increased pressure bythe tongue and perhaps by reduced muscular force from

the lower lip. This repositioning of the mandibular inci-sors, however, commonly results in a spontaneousreduction of incisor crowding.

In comparison with chincup treatment, bone-anchored traction does not produce downward and

backward rotation of the mandible but does produce ef-fects on the shape of the mandible that have not been

observed in chincup patients. Would 3D studies of chin-cup patients show changes at the condyles or mandib-ular shape in those who do have a positive response totreatment? Perhaps, but it appears that intermaxillary

traction produces much more predictable and greaterchanges.

There are also effects in patients with cleft lip andpalate. In addition to the total bone surface and inter-digitation of sutures, stretching of the intraoral and ex-traoral soft tissue envelopes may contribute to the limits

of protraction of the midface. The impact of the soft tis-sues on the resistance to the forward traction of themaxilla is not known yet. Is there a maximum amountof stretching? How much does it inuence relapse, andhow could it eventually be modied by external factors?In cleft patients, scar tissues from the surgical closure ofthe lips and soft and hard palates further restrict the for-

ward movement. The location and the amount of thesescar tissues certainly affect the amount of protraction ofthe midface. It has not yet been established whether in-termaxillary traction can overcome the restriction in for-

ward growth of the maxilla that frequently results from



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cleft lip and palate correction. Three-dimensional imag-

ing data now being collected and analyzed will clarifythis possible use of the method.

Regarding intraoral traction vs orthognathic surgery,

do the changes during intermaxillary traction make adifference in the need for later surgical repositioningof the maxilla or both jaws? Although good data for

long-term outcomes with intermaxillary traction arenot yet available, several advantages are possible evenif the treatment effects are partially lost as the originalgrowth pattern continues after treatment. Improvementof facial esthetics in teenagers instead of postponing asurgical approach until completion of growth mayhave a favorable effect on self-esteem and psychosocial

development of these young people during puberty.Treated patients can more easily adapt to these relativelyslow changes than to the sometimes drastic facial trans-formation obtained immediately after orthognathic sur-

gery, and the magnitude of surgical change needed afterintermaxillary traction would be expected to be less thanin patients who had no growth modication. Sincegrowth modication with intermaxillary traction iscompleted at an older age than facemask treatment,posttreatment changes also should be less than after

facemask treatment. Because of the high variabilityand the lack of objective criteria for prediction of theoutcome, however, patients and parents should always

be told that orthopedic treatment never can exclude asurgical approach after growth.

CONCLUSIONS

More than a century of research has shown that in

contrast to tooth movement, growth modication ofthe face is hard to obtain. Many attempts have been

made to change proportional relationships during skel-etal growth and to limit unwanted dental compensa-tions. It appears that for the large part, this occursonly within limits of average change of a few millimeters.Although larger changes are seen in some patients, it is

difcult to be sure that much of this is not a growth

change that would have occurred without treatment.Recently in Class III growth, miniplate anchoragecombined with light forces from continuous intermaxil-lary elastic traction has shown a better outcome thantooth-supported appliances for maxillary protraction

or chincup restraint of the mandible, achieving greaterskeletal changes with less displacement of the dentition.Three-dimensional imaging with accurate and repro-ducible registrations on the anterior cranial base andthe mandibular symphysis make it possible now to studymuch better the real effects on the growth of the jaws,

distinguishing this growth from dental and overall facial

changes. There is no doubt that within certain limits, at

least in the short term, some modication of growth ofthe different components of the midface can be ob-tained with intermaxillary traction. In some cases, this

may be suf

cient to avoid orthognathic surgery or atleast reduce the severity of the surgical correctionneeded after completion of growth. Individual variations

in treatment outcomes, however, are high. For all typesof growth modication, better biomarkers are neededto predict the outcome and to dene guidelines andindications for an orthopedic approach in growingchildren.

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