CASE REPORT

Correction of a dental arch-width asymmetricdiscrepancy with a slow maxillary contractionappliance

Xianming Hua,a Hui Xiong,b Guangli Han,c and Xiangrong Chengd

Wuhan, China

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A boy, aged 12 years 3 months, sought treatment for a complete unilateral Brodie bite. His maxillary dental archwas asymmetric, and his dentition was 10 mmwider than normal values for his age. The transverse discrepancywas his chief complaint because it caused a chewing dysfunction. We used a special slow maxillary contractionappliance, which contains a screw, connectors, and retainers, to contract the maxillary transverse asymmetricdental arch. This was followed by preadjusted fixed appliances to level the teeth and adjust the occlusion. A sym-metric and functional Class I occlusion was achieved. (Am J Orthod Dentofacial Orthop 2012;142:842-53)

ABrodie bite is a type of posterior crossbite thatcauses interocclusal contact between the outeroblique surfaces of the maxillary lingual cusp

and the mandibular buccal cusp.1 With a Brodie bite dis-crepancy, the maxillary dentition is wider or the mandib-ular dentition is narrower than normal, or bothdentitions can be abnormal. A Brodie bite can be unilat-eral or bilateral and occurs in 1.0% to 1.5% of the pop-ulation.2 The techniques for treating a completeunilateral or bilateral Brodie bite with transverse man-dibular deficiency have been reported and includemandibular widening by distraction osteogenesis,3-6

mandibular transverse expansion by using cross-archelastics,2-7 and expansion of the mandibular dentalarch with a Schwarz appliance.8 A transverse skeletal de-ficiency (or narrow dentition) can be treated with man-dibular widening (or dental arch expansion). However,can we treat a complete unilateral Brodie bite by con-stricting the maxillary dental arch if the maxillary asym-metric dentition is wider than normal?

the Department of Orthodontics, School & Hospital of Stomatology,n University, Wuhan, P. R. China.student, Orthodontic graduate program.ciate professor.ciate professor.ssor and chair.uthors report no commercial, proprietary, or financial interest in the prod-r companies described in this article.t requests to: Guangli Han, Department of Orthodontics, School & Hospi-Stomatology, Wuhan University, 237 Luoyu Rd, Wuhan P. R. China; e-mail,55@gmail.com.itted, February 2011; revised and accepted, March 2011.5406/$36.00ight � 2012 by the American Association of Orthodontists./dx.doi.org/10.1016/j.ajodo.2011.03.029

In this case report, we address this question in ourtreatment of a teenaged patient with a complete unilat-eral Brodie bite on the right side. His maxillary asymmet-ric dentition was 10 mm wider than normal for childrenof his age. We successfully corrected his malocclusionwith a slow maxillary contraction appliance followedby fixed appliance treatment.

DIAGNOSIS AND ETIOLOGY

The patient was a boy, aged 12 years 3 months, witha complete unilateral Brodie bite. His chief complaintwas chewing dysfunction. His soft-tissue profile wasconvex, with an open lip closure in resting status. His up-per and lower lips were slightly thicker than normal(Fig 1). His face was asymmetric. He had no signs orsymptoms of a temporomandibular disorder.

Intraorally, he had a dental Class III molar relation-ship and a Class I canine relationship on both sides(Fig 1). His oral hygiene was excellent, and his periodon-tium was in good condition. The mesial margin of themaxillary left central incisor was coincident with the fa-cial midline, but the right one deviated by 1.8 mm(a space between the maxillary incisors) to the right.The mandibular dental midline was the same as the fa-cial midline in centric occlusion. His right lateral occlu-sion was a complete unilateral Brodie bite with anasymmetric maxillary dentition.

Analysis of the dental casts showed a dental Class IIIrelationship (Fig 2). The spaces between the maxillaryright first molar and left first premolar were 15 mm. Awide, severe maxillary transverse process was a problem.The maxillary first molar's cross-arch width (44.40 mm)

Fig 1. A-G, Pretreatment photographs (age, 12 y 3 mo): arrows, unilateral Brodie bite; vertical lines,maxillary right central incisor deviated 1.8 mm (space between the central incisors) to the right of thefacial midline. The maxillary occlusal view shows the asymmetric dental arch and interdental spaces(15 mm); the mandibular occlusal view shows the right second premolars slightly inclined lingually.

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was greater than normal (34.69 mm) in children of hisage.9 The maxillary dental arch was asymmetric, withthe right side larger than the left. The mandibular firstmolar's cross-arch width (33.91 mm) was nearly normal(32.50 mm). The mandibular right second premolarswere slightly inclined lingually. Transverse and sagittalmeasurements are shown in Figure 3 and Table I.

The cephalometric analysis showed a skeletal Class I re-lationship, with a slight downward and backward rotationof themandible (Fig 4; Table II). Themaxillary incisors ap-peared to be severely tipped labially. A pretreatment pan-oramic radiograph showed a healthy periodontium, withendodontic treatment of the mandibular right first molar.

The primary problem was the serious maxillary andmandibular transverse discrepancy. The maxillary dentalarch was asymmetric and 10 mm wider than normal forhis age. His parents did not have a similar malocclusion.

TREATMENT OBJECTIVES

The treatment objectives were to (1) maintain theskeletal Class I relationship of the maxilla and the man-dible; (2) establish a dental Class I relationship, correctthe asymmetric maxillary dentition, reduce the maxillary

American Journal of Orthodontics and Dentofacial Orthoped

dental arch width, and maintain the mandibular inter-molar width; (3) close the maxillary dental arch spaceand correct the maxillary and mandibular dental mid-lines; and (4) improve the patient's profile.

TREATMENT ALTERNATIVES

Among the above treatment objectives, it was impor-tant to constrict the asymmetric maxillary dentition onthe side of the Brodie bite. To achieve the main objective,4 possibilities were considered.

The first treatment option was to use intermaxillarycrossbite elastics to tip the maxillary right posterior teethlingually and the mandibular right posterior teeth labially.This would effectively correct the posterior buccal cross-bite.5 This would also constrict the asymmetric maxillarydental arch width. However, for this patient, the inclina-tion of the teeth on the Brodie bite side was normalwith the exception of the mandibular second premolar.So, the effects might have increased the mandibular den-tal arch width and tip the maxillary and mandibular pos-terior teeth on the right side. Meanwhile, intermaxillarycrossbite elastics might promote posterior tooth extru-sion, which would not improve the patient's profile. After

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Fig 3. Landmarks andmeasurements on the cast models.A, Transversemeasurements. Tooth cross-archwidths (dashed lines): the distancebetween thebilateral points located at thegingivalmargin on thelingual contour of themaxillary permanent tooth's long axis; intertoothwidths (solid lines): thewidth froma tooth's tip (or fissure) to the tooth on the other side, and left or right width: the distance from tooth tip (orfissure) to the midpalatine raphe. B, Sagittal measurements. The distances (red lines) from the tip (orfissure) of amaxillary tooth to the line that crosses the incisive papilla, vertically to themidpalatine raphe.

Fig 2. A-E, Pretreatment dental casts.

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we considered the long-term stability and the profile, wedid not select intermaxillary crossbite elastics.

The second option was to use implants. Implants asanchorage devices on the palate could make the maxil-lary posterior teeth move lingually. However, this wouldincrease the risks and the costs. In addition, it is difficultto move a complete unilateral dentition in a parallelfashion. Implants require more skill and a special designwhen used for anchorage.

The third option was to place a hyrax expander in anopen position to produce palatal constriction and nar-row the maxilla bilaterally.5 This technique would

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correct the right unilateral Brodie bite but might alsocreate a left posterior crossbite, because of the asymme-try in the maxillary left and right dentitions.

The fourth option was an adjustable slow maxillarycontraction appliance. Anchorage control was criticalfor this patient. The optimal treatment should reducethe maxillary right posterior dental arch width morethan the left one and move the teeth in parallel fashion.A specially designed slowmaxillary contraction appliancecould achieve this goal of treatment of this malocclusion.

The slowmaxillary contraction appliance has a screw,connectors, and retainers and was modified from

Journal of Orthodontics and Dentofacial Orthopedics

Table I. Transverse and sagittal measurements

Pretreatment After SMC Posttreatment Retention

T1-T0 T2-T1 T3-T0 T3-T2T0 (12 y 3 mo) T1 (12 y 10 mo) T2 (14 y 8 mo) T3 (17 y 9 mo)Transverse measurements (mm)Maxillary canine cross-arch width 30.36 26.08 28.35 27.86 �4.28 2.27 �2.50 �0.49Maxillary intercanine width 39.35 34.14 37.23 37.20 �5.21 3.09 �2.15 �0.03

Left 19.15 17.51 18.61 18.60 �1.64 1.10 �0.55 �0.01Right 20.20 16.63 18.62 18.60 �3.57 1.99 �1.60 �0.02

Maxillary first premolar cross-arch width 36.15 30.40 32.21 32.32 �5.75 1.81 �3.83 0.11Maxillary interfirst premolar width 45.06 38.90 40.75 41.94 �6.16 1.85 �3.12 1.19

Left 21.78 20.06 20.37 20.96 �1.72 0.31 �0.82 0.59Right 23.28 18.84 20.38 20.98 �4.44 1.54 �2.30 0.60

Maxillary first molar cross-arch width 44.40 39.13 39.62 39.94 �5.27 0.49 �4.46 0.32Maxillary interfirst molar width 56.09 50.33 50.86 51.78 �5.76 0.53 �4.31 0.92

Left 27.34 25.43 25.56 25.95 �1.91 0.13 �1.39 0.39Right 28.75 24.90 25.30 25.83 �3.85 0.40 �2.92 0.53

Maxillary cross-arch alveolar process width 60.17 56.86 60.32 63.18 �3.31 3.46 3.01 2.86Mandibular interfirst molar width 33.91 35.42 35.48 36.55 1.51 0.06 2.64 1.07

Sagittal measurements (mm)Canine distance

Left 2.87 2.58 �1.28 �0.77 �0.29 �3.86 �3.64 0.51Right 2.86 2.13 �1.10 �0.69 �0.73 �3.23 �3.55 0.41

First premolar distanceLeft 12.34 12.05 7.39 8.02 �0.29 �4.65 �4.32 0.63Right 11.44 10.55 7.61 8.16 �0.89 �2.94 �3.28 0.55

First molar distanceLeft 27.31 27.01 22.38 23.01 �0.30 �4.63 �4.30 0.63Right 30.22 27.95 23.3 23.98 �2.27 �4.65 �6.24 0.68

SMC, Slow maxillary contraction.

Fig 4. A, Pretreatment cephalometric radiograph, and B, tracing (age, 12 y 3 mo).

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a conventional rapid maxillary expansion appliance(Fig 5). Briefly, the screw was put on a fit point accordingto the Brodie bite. To leave the tube for constriction, the2 ends of the screw were embedded with plastic in ad-vance and then rotated to an almost fully open position

American Journal of Orthodontics and Dentofacial Orthoped

before putting the screw on the dental cast model formanufacturing. Retainers were made with artificial plas-tic and covered the entire clinical crowns of the posteriorteeth. We usually expect to have a larger area of connec-tors and retainers to achieve maximum anchorage. The

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Table II. Cephalometric summary

Measurement Mean SD

Pretreatment Posttreatment Retention

T1-T0 T2-T1 T2-T0T0 (12 y 3 mo) T1 (14 y 8 mo) T2 (17 y 9 mo)Skeletal (�)SNA 80.8 4.0 81.2 82.0 81.3 0.8 �0.7 0.1SNB 80.1 3.9 79.4 78.8 79.2 �0.6 0.4 �0.2ANB 2.7 2.0 1.8 3.4 2.1 1.6 �1.3 0.3SN-MeGo 32.5 5.2 35.5 34.1 34.6 �1.4 0.5 �0.9SN-Gn 65.8 4.2 67.0 66.4 66.9 �0.6 0.5 �0.1

Dental (�)U1 to SN 105.7 6.3 119.3 109.5 113.6 �9.8 4.1 �5.7L1 to MeGo 96.9 6.0 94.3 91.1 91.7 �3.2 0.6 �2.6U1 to L1 124.2 8.2 110.0 124.0 120.1 14 �3.9 10.1

S, Midpoint of sella; N, nasion; Me, menton; Go, gonion; Gn, gnathion; U1, maxillary central incisor; L1, mandibular central incisor; SN, sella-nasion line; MeGo, menton-gonion line.

Fig 5. Slow maxillary contraction appliance: A, upper occlusal view: the space between the 2 sides ofthe slow maxillary contraction appliance was great (arrows); B, the structure of the slow maxillary con-traction: a screw, connectors, and retainers; the left side area (anchorage) was larger than the right one;C-E, the slow maxillary contraction appliance was placed intraorally.

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width of the maxillary dental arch would constrict whenthe screw was turned.

To improve the patient's profile, we also proposed toextract 4 first premolars. However, the patient and hisparents refused any surgical treatment.

TREATMENT PROGRESS

Orthodontic treatment started by placement of the slowmaxillary contraction appliance. During the treatment pe-riod, the patient was told to keep this appliance on everyday and to turn the screw to keep 90� around the axisonce every 2 days. After 7 months, the unilateral Brodie

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bite was corrected (Figs 6 and 7). The slow maxillary con-traction appliance was then used as a retainer for another5 months by placing artificial plastic on the screw. Themain objective of this periodwas to constrict the asymmet-ric maxillary dentition, especially the right side, by usingthe slow maxillary contraction appliance.

After 12 months of treatment with the slow maxillarycontraction appliance, preadjusted fixed appliances(0.022 3 0.028 in) were placed (Fig 8), with a maxillaryfirst molar palatal bar for leveling and alignment. A step-wise treatment through the various round wire sizesfrom 0.014 to 0.018 in was used until the rotationswere corrected and full leveling was achieved. Then

Journal of Orthodontics and Dentofacial Orthopedics

Fig 6. Intraoral photographs after slow maxillary contraction treatment (age, 12 y 10 mo): A, the uppersides of the slow maxillary contraction appliance were closed (arrows); B, the spaces between the ca-nines were closed, and the maxillary dental arch width was contracted greatly; C-E, the unilateral Bro-die bite was corrected (arrows), and no space remained between the maxillary central incisors.

Fig 7. A-E, Dental casts after the slow maxillary contraction treatment (age, 12 y 10 mo).

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0.2153 0.275-in rectangular wires were used to achievethe optimum axial inclinations of the roots of all teeth.During this treatment period, the dental Class III rela-tionship was corrected by Class III elastics, and the max-illary and mandibular dental midlines were adjusted byanterior intermaxillary elastics. The space between the

American Journal of Orthodontics and Dentofacial Orthoped

maxillary right first molar and the left first premolarwas closed with an elastomeric chain. Finally, verticalelastics were used to finish the occlusion. The activetreatment lasted for 17 months. The maxillary and man-dibular removable Hawley retainers were constructed forthe patient.

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Fig 8. A-E, Intraoral photographs during initial fixed appliance therapy.

Fig 9. A-H, Photographs after fixed appliance treatment (age, 14 y 8 mo).

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Fig 10. A-E, Dental casts after fixed appliance treatment (age, 14 y 8 mo).

Fig 11. A, Cephalometric radiograph, and B, tracing after fixed appliance treatment (age, 14 y 8 mo).

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TREATMENT RESULTS

At the end of active orthodontic treatment, a well-aligned dentition was obtained. Lateral excursionsdemonstrated group function-guided occlusion, withno working or balancing interferences. Due to the pa-tient's cooperation with turning the screw and oral hy-giene, the treatment results were excellent. Optimaloverbite and overjet relationships were achieved, andthe patient was satisfied with his teeth and profile aftertreatment (Figs 9 and 10). His oral function was im-proved greatly.

American Journal of Orthodontics and Dentofacial Orthoped

The cephalometric analysis showed that the SNAangle increased by 0.8� and the SNB decreased by0.6� after treatment (Fig 11; Table II). The maxillamoved forward slightly from the slow maxillary con-traction and the Class III elastic treatment. The mandi-ble moved back slightly because of the Class IIImechanics. Anteroposteriorly, the skeletal Class I rela-tionship was maintained. Vertically, the mandiblerotated counterclockwise, since the mandibular planeangle (SN-MeGo) changed from 35.5� to 34.1�

(Table II). These changes were thought to result from

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Fig 12. Panoramic radiographs and cephalometric tracing: A, pretreatment (age, 12 y 3 mo); B, afterslow maxillary contraction treatment (age, 12 y 10 mo); C, after fixed appliance treatment (age, 14 y 8mo); D, retention (age, 17 y 9 mo); E, pretreatment (black lines; age, 12 y 3 mo) and posttreatment (redlines; age, 14 y 8 mo) cephalometric tracings superimposed on SN at sella.

Fig 13. Tooth position tracing superimposition on midpa-latine raphe at the incisive papilla before (age, 12 y 3 mo)and after (age, 12 y 10 mo) slow maxillary contraction(SMC) treatment.

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the combined use of the slow maxillary contraction ap-pliance and the Class III elastics. The slow maxillarycontraction moved the maxillary teeth mesially, andthe Class III elastics extruded the maxillary molar. Thefinal panoramic radiograph showed good root parallel-ism and minimal loss of the bony crest in the mandib-ular anterior region (Fig 12, C).

Analysis of the dental casts showed that the maxillarydentition changed dramatically transversely and antero-posteriorly (Table I). Transverse constriction of the max-illary dentition was 5.21 mm in the canine area, 6.16 mmin the first premolar area, and 5.76 mm in the first molararea. Furthermore, the posterior teeth were almost dis-placed parallel to the palatal suture by the plastic re-tainer of the slow maxillary contraction appliance. The

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maxillary first molar cross-arch width and the interfirstmolar width were almost parallel at 5.27 and 5.76 mm,respectively. Similar results were seen for the maxillaryfirst premolars (5.75 and 6.16 mm, respectively). As ex-pected, the maxillary right posterior teeth (Brodie bite)moved to the palatine raphe more than the left ones, be-cause of the anchorage. Surprisingly, the maxillarycross-arch alveolar process width was transversely re-duced by 3.31 mm after the slow maxillary contractiontreatment and relapsed a little after the preadjusted fixedappliance treatment (Table I). The spaces between themaxillary right first molar and the left first premolarwere closed. However, the changes in the anteroposte-rior area were unexpected. The maxillary left and rightposterior teeth movedmesially, and the right side (Brodiebite) moved more than the left. The reason might havebeen the anchorage on the left side. The distances of me-sial movement were the following: canines, 0.29 mm(left) and 0.73 mm (right); first premolars, 0.29 mm(left) and 0.89 mm (right); and first molars, 0.30 mm(left) and 2.27 mm (right). In addition, the maxillary in-cisors inclined labially. Transverse and sagittal superim-positions were drawn (Fig 13) on the time points beforeand after the slow maxillary contraction treatment ac-cording to the dental cast analysis.

During treatment with the preadjusted fixed appli-ance, transversely, the maxillary left and right dentalarch widths changed, as shown in Table I. The mandib-ular first molar cross-arch width increased by 1.51 mm.Anteroposteriorly, in the maxilla, both sides moved me-sially. The maxillary and mandibular incisors wereretracted and uprighted (Fig 12, E).

Journal of Orthodontics and Dentofacial Orthopedics

Fig 14. A-G, Follow-up photographs at 37 months (age, 17 y 9 mo) after fixed appliance therapy. Ametal crown had been placed on the right first molar.

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At the 37-month follow-up, the patient had a stabletransverse occlusion (Figs 14 and 15; Table I). This sta-bility contributed to the good occlusion after orthodon-tic treatment, based on his prepubertal age and 2 yearsof retention. Anteroposteriorly, the SNA and SNB anglesrelapsed to their pretreatment values (Table II) becauseof his growth. Themaxillary incisors tipped labially a littlemore after retention.

DISCUSSION

It has been proposed that correction and adjustmentof asymmetric malocclusions are complicated andchallenging.10 If the malocclusion is moderately severe,treatment should be considered to control and modifyasymmetric growth, because of the patient's activegrowth.11 A true unilateral Brodie bite is relativelyrare.2 Previous reports have presented serious mandibu-lar asymmetric transverse deficiencies, treated withmandibular widening by distraction osteogenesis.5,12

However, treatment of a wider asymmetric maxillarydentition in a Brodie bite has not been published.Skeletal asymmetries are usually treated witha combination of orthodontics and orthognathic

American Journal of Orthodontics and Dentofacial Orthoped

surgery.13 For this patient, the maxillary dental archwas asymmetric and 10 mm wider than the normalvalue for his age. Meanwhile, the maxillary arch's asym-metry primarily resulted from alveolar bone (or hada dental origin). Therefore, we developed a specialslow maxillary contraction appliance to constrict theasymmetric maxillary dentition, especially on the rightside (Brodie bite).

Maxillary dental arch constriction can be corrected byseveral techniques.14-16 For example, maxillary dentalarch broadness can be treated by contracting themaxillary arch to some extent with a removableappliance.17 For this patient, to reduce the maxillaryright posterior dental arch width more than the leftone and to move teeth in a parallel manner, it was im-portant to strengthen the maxillary left anchorage andmove the teeth on the right. Therefore, the slow maxil-lary contraction device was specially designed for cor-recting the unilateral Brodie bite. We used variousdental measurements on the dental casts to demonstratea nearly parallel constriction of the alveolar bone (dentalarch width) (Table I). The optimal treatment outcomes ofmaxillary expansion are that the posterior teeth are

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Fig 15. A-E, Follow-up dental casts at 37 months (age, 17 y 9 mo) after fixed appliance therapy.

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displaced bodily, with minor or no buccal tipping of theanchorage teeth, and no root and bone resorption.18

Thus, we concluded that satisfactory results were ob-tained to meet these requirements.

Placing constricting screws at different locationsresulted in different effects. Force is characterizedby magnitude and vector, which are determined by lo-cation and orientation. Similar to the transpalatal dis-tractor on the transverse maxillary deficiency, theplacement point and the angulations of the screwwere vital.19 In this case, the screw was placed at thelevel of the second premolar, and the right teeth (Brodiebite) were moved more forward to the midpalatine ra-phe rather than to the left side (anchorage) after theslow maxillary contraction treatment. Greater constric-tion occurred in the anterior part of the maxilla thanin the posterior part, with minor or no lingual tiltingof teeth. In this slow maxillary contraction appliance,the left plastic part, which extended to the right canine,was larger than the right one. Thus, the forces on the 2sides were different, and this was the rationale that theright posterior teeth move more to the midpalatal raphethan to the left.

Valuable experience gained from this case raisesseveral questions. (1) Can an asymmetric maxillary den-tition be constricted by slow maxillary contraction uni-laterally? (2) If yes, how and where is the screwplaced? (3) Is the alveolar process or the basal bone con-stricted? (4) Is the maxillary dental arch stable after slowmaxillary contraction treatment? We demonstrated that

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an asymmetric maxillary dental arch can be adjusted andcorrected unilaterally by designing sufficient anchorage.This supports the concept of segmental unilateral trans-palatal distractor.20 The maxillary alveolar process couldbe constricted during slow maxillary contraction treat-ment with minor relapse after the fixed appliance wasplaced and remained stable after active treatment. On1 hand, the maxillary bone was compacted, and resorp-tion occurred during slow maxillary contraction treat-ment. On the other hand, the period of treatment waslonger (7 months with the slowmaxillary contraction ap-pliance), so the stability of the slowmaxillary contractiontreatment was different from rapid maxillary expansiontreatment. At the 37-month follow-up, the patient hada stable transverse occlusion. However, we could notverify whether the basal bone was constricted, althoughthe maxillary cross-arch alveolar process width wasreduced by 3.31 mm. To further explore this issue, addi-tional research is needed.

CONCLUSIONS

A specially designed slow maxillary contraction ap-pliance can provide powerful anchorage for treatinga unilateral Brodie bite with significant maxillary andmandibular transverse discrepancies. In this uniquecase, the maxillary dentition was constricted, particularlyon the side of Brodie bite. The posterior teeth on bothsides moved mesially, and the maxillary alveolar processwas compacted during treatment with the slowmaxillarycontraction appliance. The transverse occlusion was

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stable after retention. Slow maxillary contraction is aninexpensive and effective way to treat a transversemaxillary asymmetry.

We thank Peng Liu for improving the language of themanuscript andMedjaden Bioscience Limited for editingand proofreading.

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