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ORIGINAL ARTICLE

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Int linicallon treatedex combpla r by fiMe comp16 hes abu ce theTh 9 yea20 d moat hangegroups with respect to the CTRL. Results: Treatment with an RME-only or an RME-Sz followed by fixedappliances produced significant short-term and long-term increases in maxillary arch widths compared with theCTRL. The RME-Sz led to significantly more favorable results than the RME-only protocol: (1) significantly greaterinc(2)waint3.7incmmfav

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20reases in the transverse width of the mandibular arch and mandibular arch perimeter in the long term, anduprighting of the mandibular posterior teeth buccally, thus allowing for an amount of maxillary expansion thats clinically effective for the correction of moderate tooth size-arch size discrepancies. In the overall observationerval, the significant increases in maxillary and mandibular arch perimeters in the RME-Sz group were 3.8 andmm, respectively, when compared with the CTRL. The RME-only protocol produced modest long-term

reases in maxillary arch perimeter (2.6 mm); the average long-term increase in mandibular arch perimeter (2.0) in the RME-only group was not statistically significant.Conclusions: The RME-Sz led to significantly moreorable results than the RME-only protocol. (Am J Orthod Dentofacial Orthop 2006;130:202-13)

Extract or expand? Over the last 100 years, theintellectual pendulum has swung back and forthbetween nonextraction and extraction treat-ments in patients with tooth size-arch size discrepan-cies. For patients with mild (3 mm) or severe (6mm) crowding, deciding whether to extract teeth togain space is not difficult.1 For patients with moderatecrowding, however, the choice is less clear.

A typical appliance for the treatment of patientswith borderline amounts of crowding and also needingexpansion in both arches is the acrylic splint rapidmaxillary expander.1 An ongoing prospective clinicaltrial (Michigan Expansion Study [MES]) has the goalof evaluating the short-term and long-term effective-ness of rapid maxillary expansion (RME) with abonded appliance in the mixed dentition followed byfixed appliances in the permanent dentition in correct-ing maxillary constriction and relieving tooth size-archsize discrepancies. An article by Spillane and Mc-Namara2 first described the treatment effects and thshort-term stability produced by the acrylic splint

aduate Orthodontic Program, University of Michigan, Ann Arbor; privatectice, Grand Rapids, Mich.omas M. and Doris Graber Endowed Professor of Dentistry, Department ofhodontics and Pediatric Dentistry, School of Dentistry; professor of Anat-y and Cell Biology, School of Medicine; research professor, Center for

an Growth and Development, University of Michigan, Ann Arbor; privatectice, Ann Arbor, Mich.sistant professor, Department of Orthodontics, University of Florence,rence, Italy; Thomas M. Graber Visiting Scholar, Department of Orthodon-and Pediatric Dentistry, School of Dentistry, University of Michigan, Annor.search associate, Department of Orthodontics, University of Florence,rence, Italy; Thomas M. Graber Visiting Scholar, Department of Orthodon-and Pediatric Dentistry, School of Dentistry, University of Michigan, Annor.ported in part by 2 grants from the American Association of Orthodontistsndation and by funds from the Thomas M. and Doris Graber Endowedfessorship, Department of Orthodontics and Pediatric Dentistry, University

ichigan.rint requests to: Dr James A. McNamara, Department of Orthodontics andiatric Dentistry, School of Dentistry, University of Michigan, Ann Arbor,48109-1078; e-mail, [email protected], October 2004; revised and accepted, December 2004.9-5406/$32.00yright 2006 by the American Association of Orthodontists.

:10.1016/j.ajodo.2004.12.023

2long-term evaluationchwarz appliance andxpander in early mixedul W. OGrady,a James A. McNamara, Jr,b Tiziano Bn Arbor and Grand Rapids, Mich, and Florence, Italy

roduction: The aim of this prospective longitudinal cg-term changes in dental-arch dimensions in patientspander alone (RME-only) or a rapid maxillary expanderte (RME-Sz) in the early mixed dentition, followed latethods: The dental casts of 27 RME-only patients wereuntreated controls (CTRL) with constricted maxillary arct before fixed appliance therapy (T2), after fixed appliane mean ages for the treated groups were approximatelyyears at T4. Arch width, arch depth, arch perimeter, anall observation times. T1-T2, T2-T3, T3-T4, and T1-T4 cthe mandibularacrylic splint

entition patientstti,c and Lorenzo Franchid

study was to evaluate the short-term andwith either an acrylic splint rapid maxillary

ined with a mandibular removable Schwarzxed appliances in the permanent dentition.ared with those of 23 RME-Sz patients andt 4 times: pretreatment (T1), after expansionrapy (T3), and at long-term observation (T4).rs at T1, 12 years at T2, 14 years at T3, andlar angulation were assessed in all subjectss were compared statistically in the treated

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American Journal of Orthodontics and Dentofacial OrthopedicsVolume 130, Number 2

OGrady et al 203pander used in the early mixed dentition. Serialntal casts of 162 patients were analyzed to measureh dimensions before expansion, immediately postex-

nsion, and yearly until the eruption of the firstmolars. The average residual increase in transpalatal

dth was 5 to 6 mm. After the postexpansion obser-tion period (2.4 years), 80% of the original expansionthe first permanent molars remained.Brust and McNamara3 examined a larger sample of

tients from the same study group. Changes in archdth, arch perimeter, and molar angulation werealuated immediately postexpansion, at the time ofst premolar eruption, and before comprehensive orth-ontic treatment. The changes were compared withse over a similar time interval in a control group ofuntreated subjects from the University of Michigan

owth Study. A significant amount of stable expan-n was achieved in the maxillary arch, whereasanges in the mandibular arch were less stable.

Recently, Geran et al4 conducted an investigation toess the long-term stability of dental-arch changesuced by the acrylic splint rapid maxillary expanderthe early mixed dentition and followed later by

mprehensive orthodontic treatment (phase II). Notive expansion of the mandibular dental arch wasdertaken in the mixed dentition. The final evaluationthe patients occurred at an average of 6 years afterase II, or approximately 10 years after the comple-n of RME. Serial dental casts of the maxillary andndibular arches were compared with a control groupuntreated subjects. According to the results of thisdy, therapy with an acrylic splint expander in the

rly mixed dentition followed by fixed appliances inpermanent dentition is an effective treatment ap-

ach to correct transverse deficiencies in both archesen evaluated in the long term. This treatment proto-

l also is an option to relieve modest tooth size-arche discrepancies. Geran et al4 reported that approxi-tely 4 mm of long-term relative increase in maxillaryh perimeter and 2.5 mm additional maintenance ofndibular arch perimeter were observed in RME

tients when compared with untreated subjects.The only other long-term controlled study concern-the effects of RME on arch perimeter is that of

cNamara et al,5 who evaluated arch-dimensionanges after Haas-type REM and fixed appliancerapy through the age of 20 years. Treatment withE and fixed appliances induced stable favorable

reases in the width of the dental arches and in archpth. Approximately 6 mm of long-term increase in

xillary arch perimeter (80% of initial deficiency) andmm in mandibular arch perimeter (full correction of

I tprotial deficiency) were observed in patients whenmpared with untreated subjects.

An alternative treatment protocol for patients withderate crowding and also needing expansion in bothhes is the combination of the acrylic splint rapidxillary expander and the removable mandibularhwarz expansion appliance (REM-Sz).1 The protocolgins with an initial phase in which the Schwarzpliance is activated once a week for approximately 5nths. Mandibular expansion is followed immedi-ly by RME. Dentoalveolar decompensation of thendible with the Schwarz appliance establishes aference mandibular arch width to which the max-ry teeth can be expanded.6Wendling et al7 compared cephalometrically the

ort-term skeletal and dentoalveolar effects in a grouppatients from the MES who received either theE-Sz or the RME-only protocol beginning in the

xed dentition. The mandibular Schwarz appliancepeared to prevent the mesial movement of the man-ular first molars, whereas the RME-only protocolto a 0.6-mm mesial movement of these teeth. The

hwarz appliance, therefore, had a slight space main-ner effect on the mandibular arch.The purpose of this study was to evaluate theg-term treatment effects of RME-only and RME-Szrapy in the mixed dentition followed later by com-hensive orthodontic treatment. The treatment effectsre compared with longitudinal records of an un-ated control group (CTRL) with similar amounts ofnstriction of the dental arches and crowding at thetial observation. Of special interest is the long-termbility of these types of expansion and their effects onh perimeter and the extraction or nonextraction

cision.

TIENTS AND METHODS

The patients examined were part of the MES, aspective clinical investigation of mixed-dentition

tients who had undergone RME. A focus of the MESs short-term and long-term treatment effects of RMEth an acrylic splint expander in the mixed dentitionlowed by fixed appliances in the permanent denti-n. This study compared the long-term effects of 2atments with 2 phases (RME-only and RME-Szlowed by comprehensive orthodontic treatment)th a well-matched untreated group.The sample comprised consecutively treated pa-

nts from a private group faculty practice; all patientsre treated jointly by the 3 practitioners. Thesenicians intended to provide a short phase of phase

reatment (9-14 months, depending on the treatment

tocol), followed by an interim period of simple

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American Journal of Orthodontics and Dentofacial OrthopedicsAugust 2006

204 OGrady et alention until the eruption of the permanent teethcluding the second and third molars) was com-ted. A period of fixed appliance therapy then was

ed to finely detail the occlusion. The decision toe an expansion protocol was based on at least 1 ofse preexisting criteria: crowding, lingual cross-e, esthetics, and tendency toward Class II maloc-sion.1Of the 50 patients included in this investigation (20

le, 30 female), 27 patients (11 male, 16 female)derwent RME-only treatment with bonded appli-ces (Fig 1) in the mixed dentition, and 23 patientsle, 14 female) had RME-Sz treatment (Fig 2) fed by a bonded maxillary expander.1 Both groups

re treated with the expansion protocol in the mixedntition and were on average 6 years out of phase IIatment at the long-term observation. Additionally,

patients in both treatment groups had consistentaracteristics. Before treatment, the following teethre present: erupted maxillary and mandibular firstrmanent molars; erupted maxillary and mandibularrmanent central incisors; and deciduous second mo-s. Dental casts were obtained for all patients at 4es: before treatment (T1), after expansion and be-e phase II treatment (T2), after phase II treatment3), and at least 3 years after the T3 records (T4). Thean ages of the 2 treatment groups at the 4 times andmean durations of observation intervals are given in

bles I-IV.Serial dental casts of 16 untreated subjects (9 male,

emale) were obtained from the longitudinal recordstrhe University of Michigan Elementary and Second-

School Growth Study as the CTRL. The dental

Fig 1. Acrylic splint rapid maxillary expander.sts were selected to resemble the treated groups atch time that records were taken. The criteria for

traofection at T1 were based on dental developmentrly mixed dentition) and dental cast measurementsTRL subjects had similar amounts of arch constric-n as the treated patients), at T2 on dental develop-nt and homogeneity of observation interval, and atand T4 on chronological age of 16 years 6 months

older, and a minimum interval between T3 and T4 ofyears. The mean ages of the CTRL group at theferent times and the mean durations of observationervals are shown in Tables V and VI.

eatment protocols

Twenty-seven patients (RME-only group) under-nt RME with bonded acrylic splints (Fig 1) thvered the maxillary first and second deciduous mo-s as well as the maxillary permanent first molar1e midline expansion screw was attached to thepliance with a heavy (.045 in) wire framework ands expanded routinely, once per day, until a buccalssbite was approached. The transverse molar rela-nship obtained in most instances involved contacttween the lingual cusps of the maxillary posteriorth and the facial cusps of the mandibular posteriorth.After expansion (average, 7-8 mm), the bonded

pliance usually remained in place for an additionalmonths, followed by stabilization with a simplelatal plate with ball clasps between the first andond deciduous molars and between the second

ciduous and first permanent molars. The plateically was worn full-time for at least 12 months

d then only at night; in a few patients, however, thete was discontinued after 1 year of retention. A

Fig 2. Removable mandibular Schwarz appliance.nspalatal arch typically was placed before the lossthe second deciduous molars. In addition, over

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OGrady et al 205lf of the patients had their maxillary incisorscketed for alignment. These so-called temporaryces were worn for approximately 6 months; theainer used to stabilize the maxilla typically did notlude a labial wire, so that the incisors wereowed to drift after bracket removal.After eruption of the permanent teeth, the pa-

nts underwent comprehensive nonextraction orth-ontic treatment with a preadjusted edgewise appli-ce (phase II). The transpalatal arch was left ince for the duration of treatment in most patients;some patients, the palatal bar of the transpalatalh was cut and removed toward the end of treat-nt. After phase II, a positioner usually was used toely detail the dentition for 2 to 3 weeks. Thenpressions for invisible retainers1 typically wereen; the patients were instructed to wear theainers full-time for a year. They also were advisedwear the invisible retainers at night for an addi-

ble I. Descriptive statistics for RME-only group at 4 ti

E-only group (n 27)T1

Mean SD

e (y) 8.5 1.3asure (mm)

axillary arch width (centroid)Intercanine 28.2 1.8Interpremolar (first) 32.2 1.9Interpremolar (second) 37.3 1.9Intermolar (first) 42.0 2.1axillary arch width (lingual)Intercanine 23.4 1.8Interpremolar (first) 25.5 1.8Interpremolar (second) 28.7 2.0Intermolar (first) 32.5 2.1andibular arch width (centroid)Intercanine 23.7 1.5Interpremolar (first) 28.8 1.8Interpremolar (second) 34.6 1.7Intermolar (first) 40.0 1.8andibular arch width (lingual)Intercanine 19.3 1.6Interpremolar (first) 23.6 1.9Interpremolar (second) 27.2 1.7Intermolar (first) 31.2 1.9axillary arch depthFirst molar 28.9 1.7andibular arch depthFirst molar 24.1 1.3axillary arch perimeter 75.6 4.1andibular arch perimeter 67.8 3.1axillary molar angulation () 177.3 9.8andibular molar angulation () 206.7 12.3nal year, after which they were encouraged tontinue to wear them intermittently at night. Most

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detients were no longer wearing their retainers at therecords.The first part of the treatment for the 23 patients

the RME-Sz group was the full-time wearing of aovable mandibular Schwarz appliance (Fig 2)

ich is a horseshoe-shaped acrylic appliance thatalong the lingual border of the mandibular

ntition, extending to the distal aspect of the per-nent first molars.1 The inferior border of the

rylic was below the gingival margin and contactedgingival tissues. The Schwarz applicance typi-

lly was used in patients who had mandibularisor crowding or lingually inclined mandibularsterior teeth. Thus, the midline expansion screws activated one-quarter turn per week (0.2 mm);s resulted in about 1 mm of expansion per month.The Schwarz expander typically was activatedabout 5 months, until the desired amount of

pansion was achieved. The Schwarz appliance was

riodsT2 T3 T4

SD Mean SD Mean SD

1.1 13.3 1.2 19.3 1.3

1.7 32.2 1.4 31.7 1.61.6 36.9 1.5 36.2 1.51.4 42.0 1.4 41.6 1.52.3 45.9 2.0 46.1 2.0

2.0 26.0 1.5 24.5 1.41.8 27.6 1.4 27.1 1.31.4 32.4 1.3 32.2 1.32.5 35.0 2.0 34.8 2.0

1.0 25.0 0.9 24.5 1.21.2 32.2 1.3 31.5 1.31.2 37.3 1.3 36.8 1.51.7 41.5 1.7 42.0 1.9

1.5 20.5 0.7 19.4 1.01.3 26.6 1.3 25.9 1.41.7 30.2 1.3 29.9 1.42.2 32.3 1.8 32.8 2.0

1.3 26.6 1.4 26.1 1.4

1.6 22.2 1.3 21.5 1.42.9 76.8 3.2 75.8 3.12.9 65.5 2.5 64.2 2.88.8 184.0 7.2 182.8 6.79.1 198.9 7.7 202.5 7.5paT4

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206 OGrady et alw far the clinicians could expand the maxillaryh.6 Then a maxillary acrylic splint expander wanded to widen the maxilla (8-10 mm of expan-n), with the same protocol described previouslythe RME-only group. At that point, the Schwarz

pliance continued to be worn full-time as a passiveainer until the maxillary expander was removed.addition, brackets were placed on the maxillaryisors in patients requiring derotation or spacesure, as described above.When the bonded expander was removed, a

latal plate was placed for retention in the maxillaryh, and the Schwarz appliance was discontinued inmandibular arch. No retainer was worn in the

ndibular arch after the placement of the maxillarybilization plate to the beginning of phase IIatment. As with the RME group, most patients hadnspalatal arches placed before the loss of theond deciduous molars. After phase II treatment,same positioner and retention protocol was used

ble II. Descriptive statistics for change scores in RME

E-only group (n 27)T2-T1

Mean SD

e (y) 3.2 0.1asure (mm)

axillary arch width (centroid)Intercanine 3.9 1.2Interpremolar (first) 3.8 1.8Interpremolar (second) 4.2 1.3Intermolar (first) 5.2 2.5axillary arch width (lingual)Intercanine 2.5 1.9Interpremolar (first) 1.7 2.0Interpremolar (second) 3.4 1.6Intermolar (first) 5.3 3.0andibular arch width (centroid)Intercanine 1.0 1.6Interpremolar (first) 1.8 1.6Interpremolar (second) 1.6 1.1Intermolar (first) 1.9 1.4andibular arch width (lingual)Intercanine 0.1 1.8Interpremolar (first) 1.7 1.8Interpremolar (second) 2.5 1.9Intermolar (first) 2.1 1.8axillary arch depthFirst molar 1.1 1.4andibular arch depthFirst molar 0.8 1.1axillary arch perimeter 2.6 2.7andibular arch perimeter 1.2 2.2axillary molar angulation () 3.8 11.2andibular molar angulation () 7.7 10.5the RME-Sz group. Again, most patients were notaring their retainers at the T4 records.

firsuta collection

The dental casts were measured with a digitalaging system (Bioscan OPTIMAS Imaging System,attle, Wash). This system was developed specifically

the acquisition, measurement, and storage of datatained in an earlier study by Brust and McNamar3ethods for image capture and landmark acquisitionre described extensively in previous articles.2-5,8Arch width was measured at the following teeth:

ciduous or permanent canines, first deciduous molarsfirst premolars, second deciduous molars or secondmolars, and first permanent molars. Arch width wasasured from the lingual point of a given tooth to thee point on its antimere3,4 and between the centroidsa tooth and its antimere, as described by Moyers et9 and Brust and McNamara.3Arch depth was measured as the distance from a

int midway between the facial surfaces of the centralisors to a line tangent to the mesial surfaces of the

group at 4 time intervalsT3-T2 T4-T3 T4-T1

SD Mean SD Mean SD

0.1 6.0 0.1 10.8 0.0

0.9 0.5 0.7 3.5 1.71.3 0.7 0.8 3.9 1.91.2 0.4 0.8 4.3 1.91.2 0.1 1.0 4.0 2.1

1.5 1.6 1.0 1.0 1.71.2 0.5 0.8 1.6 1.81.3 0.2 1.0 3.5 2.12.1 0.3 1.2 2.3 1.9

0.7 0.6 0.7 0.7 1.81.1 0.7 1.0 2.7 1.90.7 0.6 1.1 2.2 1.70.9 0.4 1.3 2.0 1.7

1.2 1.1 0.7 0.1 1.51.0 0.7 1.0 2.4 2.11.2 0.3 1.2 2.7 1.81.3 0.4 1.4 1.6 1.7

1.4 0.4 0.6 2.7 1.8

1.5 0.6 0.9 2.5 1.52.7 1.0 1.2 0.2 3.52.5 1.3 1.4 3.6 3.29.8 1.2 7.5 5.5 9.09.0 3.5 6.8 4.2 13.2s

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OGrady et al 207sial surface of the first molar to the mesial surface of opposite first molar.4Molar angulation was calculated by measuring the

gle of intersecting lines drawn tangent to the mesio-ial and mesiolingual cusp tips of the maxillary andndibular right and left first molars.3,4 Angulations than 180 indicated that the molars were tippedially; values over 180 implied that they were tippedgually.

ror of the method

To verify the reliability of the data collected in thisdy, a double determination of dental casts wasrformed. Records of 10 subjects selected at randomre redigitized for the various arch dimensions oferest. Two analyses were used to measure the reli-ility of the double determination data. First, anraclass correlation coefficient was calculated forch arch parameter measured in both dental arches.

ble III. Descriptive statistics for RME-Sz group at 4 tim

E-Sz group (n 23)T1

Mean SD

e (y) 9.1 0.9asure (mm)

axillary arch width (centroid)Intercanine 28.0 1.4Interpremolar (first) 31.8 1.3Interpremolar (second) 36.9 1.0Intermolar (first) 42.2 1.6axillary arch width (lingual)Intercanine 23.2 1.4Interpremolar (first) 24.8 1.1Interpremolar (second) 28.3 0.9Intermolar (first) 32.8 2.0andibular arch width (centroid)Intercanine 22.4 1.2Interpremolar (first) 27.5 1.2Interpremolar (second) 33.6 1.5Intermolar (first) 39.6 2.0andibular arch width (lingual)Intercanine 18.3 1.3Interpremolar (first) 22.3 1.2Interpremolar (second) 26.4 1.4Intermolar (first) 31.1 1.8axillary arch depthFirst molar 27.8 2.0andibular arch depthFirst molar 23.5 1.9axillary arch perimeter 74.9 3.1andibular arch perimeter 66.1 2.8axillary molar angulation () 174.8 7.5andibular molar angulation () 208.2 11.5cond, Dahlbergs formula10 was used to report andard error for each arch parameter.

Intraclass correlation coefficient values rangedm 0.895 for molar angulation to 0.997 for interpre-lar (first) width in the maxilla, and from 0.932 forlar angulation to 0.995 for interpremolar (first)

dth in the mandible. The values of Dahlbergsmula ranged from 0.09 to 0.35 mm for linearasurements, whereas standard error was 3.36 forlar angulation.

atistical analysis

Comparisons between the 2 treated groups (RME-ly and RME-Sz) and the CTRL were performed withalysis of variance (ANOVA) with the Bonferronist-hoc test (P .016). The following statisticalmparisons were performed:

Comparison of starting forms: RME-only at T1 vRME-Sz at T1 v CTRL at T1.

riodsT2 T3 T4

SD Mean SD Mean SD

1.1 14.4 1.2 21.0 1.6

1.3 32.5 1.5 32.0 1.52.2 37.5 1.6 36.5 1.62.3 42.6 1.9 41.8 1.83.0 46.7 2.5 46.3 2.2

1.9 25.6 1.5 24.7 1.52.0 28.2 1.4 27.4 1.52.4 32.8 1.7 32.5 1.73.7 35.6 2.4 35.2 2.2

1.3 25.3 1.2 24.2 1.32.1 32.4 1.3 31.4 1.42.1 37.9 1.6 36.8 1.62.5 42.8 2.1 42.4 2.0

1.4 20.4 1.0 19.1 1.02.3 26.7 1.1 25.9 1.43.1 30.7 1.4 30.0 1.62.6 33.7 2.0 33.4 1.9

2.3 26.4 1.8 25.9 1.9

2.0 22.2 1.8 21.3 1.94.2 77.3 3.9 76.2 4.03.8 65.9 3.6 64.1 3.4

15.0 181.2 8.0 180.7 8.512.1 203.2 8.7 203.1 7.7fromo

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174.5194.2Evaluation of the effects of expansion: T2-T1changes in RME-only v RME-Sz v CTRL.

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208 OGrady et alEvaluation of the effects of fixed appliances: T3-T2changes in RME-only v RME-Sz v CTRL.Evaluation of posttreatment changes: T4-T3 changesin RME-only v RME-Sz v CTRL.Evaluation of overall changes: T4-T1 changes inRME-only v RME-Sz v CTRL.

SULTS

Descriptive statistics for the CTRL and 2 treatmentups are given in Tables I to VI.At T1, the starting ages of the 3 groups were similar

ME-only, 8.5 years; RME-Sz, 9.1 years; CTRL, 8.0ars). The pretreatment casts for the 3 groups weretistically similar in dental-cast measurements as ault of the ANOVA test.Treatment with RME-only produced significant in-

ments in all variables for maxillary arch widthsables II, VI, and VII), as measured at the centroen compared with the CTRL (eg, 4.1 mm for

ble IV. Descriptive statistics for change scores in RME

E-Sz group

T2-T1

Mean SD

e (y) 3.5 0.2asure (mm)

axillary arch width (centroid)Intercanine 3.4 2.0Interpremolar (first) 3.8 1.7Interpremolar (second) 4.5 1.9Intermolar (first) 5.3 2.5axillary arch width (lingual)Intercanine 1.3 2.7Interpremolar (first) 2.0 1.6Interpremolar (second) 4.0 2.1Intermolar (first) 5.8 3.3andibular arch width (centroid)Intercanine 2.3 1.3Interpremolar (first) 3.4 1.4Interpremolar (second) 2.6 1.6Intermolar (first) 3.7 2.0andibular arch width (lingual)Intercanine 1.5 1.7Interpremolar (first) 3.5 1.6Interpremolar (second) 3.2 2.7Intermolar (first) 3.5 2.1axillary arch depthFirst molar 0.6 1.6andibular arch depthFirst molar 1.3 1.0axillary arch perimeter 2.9 2.8andibular arch perimeter 0.0 2.4axillary molar angulation () 0.3 13.4andibular molar angulation () 14.0 14.9xillary intermolar width). Maxillary arch perimeterhibited significant increases in the RME-only group

wisigen compared with the CTRL (2.3 mm). No signifi-nt increases were recorded for any other measure-nt during RME-only treatment with respect to theRL.Adding a mandibular Schwarz appliance to RME

atment induced significant increments in both max-ry (4.3 mm for intermolar width) and mandibular (3.1

for intermolar width) arch widths when comparedth the CTRL (Tables IV, VI, and VII). The increasesth maxillary and mandibular arch perimeters (2.7 and

mm, respectively) were significant as well. TheE-Sz group also showed significant uprighting ofmandibular first molars (11.0) when compared withCTRL. The comparison between the RME-Sz andE-only groups showed that increases in mandibular

h widths were significantly greater in the former group.Phase II treatment with fixed appliances induced a

nificant decrease in maxillary intermolar width1.7 mm) in the RME-only group when compared

roup at 4 intervals3-T2 T4-T3 T4-T1

SD Mean SD Mean SD

0.1 6.6 0.4 12.0 0.7

1.6 0.5 0.6 4.0 1.51.7 1.0 0.7 4.6 1.31.7 0.8 0.6 4.9 1.52.0 0.4 0.7 4.1 1.5

1.6 0.9 0.8 1.5 1.71.6 0.7 0.7 2.6 1.31.8 0.3 0.8 4.3 1.72.7 0.4 0.7 2.3 1.8

1.1 1.1 0.7 1.8 1.41.7 1.1 0.8 3.9 1.31.3 1.2 0.8 3.2 1.61.8 0.4 0.8 2.8 1.7

1.4 1.3 0.8 0.8 1.51.9 0.8 0.9 3.6 1.42.2 0.7 0.9 3.6 1.82.1 0.3 0.9 2.3 1.4

1.5 0.5 0.7 1.9 1.8

1.2 0.9 0.7 2.2 1.52.7 1.1 1.1 1.3 3.22.4 1.7 1.2 2.0 2.5

14.1 0.6 8.2 5.8 6.210.4 0.1 5.9 5.1 12.7ids

whca

me

CT

treillamm

wibo2.8RMthetheRMarc

sig(

0.40.9

0.8

0.00.50.3

6.79.0th the CTRL (Tables II, VI, and VII). No othernificant difference was found for any measurement

or

linRMan

Ta

su

poIV

wiva

ce

ma

Min(2.an

wicre

sec

V,nd

Ta period

CT Mean

Ag 12.3Me

M30.033.538.443.6

M22.625.029.833.1

M23.530.235.540.4

M18.724.7

M

M

MMMM


OGrady et al 209between-group comparisons, except a significantgual inclination of the mandibular molars in theE-Sz group when compared with both the CTRL

d the RME-only group (10.1 and 9.1, respectively;bles II, IV, VI, and VII).No significant difference was found for any mea-

rement or any between-group comparisons during thesttreatment phase after fixed appliances (Tables I, VI, and VII).When overall changes were considered, treatment

th RME-only produced significant increments in allriables for maxillary arch widths as measured atntroid when compared with the CTRL (2.7 mm forxillary intermolar width) (Tables II, VI, and VII

axillary arch perimeter exhibited significant increasesthe RME-only group when compared with the CTRL6 mm). No significant increases were recorded fory other measurement during RME-only treatmentth respect to the CTRL, except the significant in-

ble V. Descriptive statistics for CTRL group at 4 time

RL group (n 16)T1

Mean SD

e (y) 8.0 0.8asure (mm)

axillary arch width (centroid)Intercanine 28.6 1.6Interpremolar (first) 32.5 1.6Interpremolar (second) 37.5 1.5Intermolar (first) 42.5 1.8axillary arch width (lingual)Intercanine 23.9 1.6Interpremolar (first) 25.7 1.6Interpremolar (second) 28.8 1.4Intermolar (first) 32.6 1.7andibular arch width (centroid)Intercanine 22.7 1.4Interpremolar (first) 28.2 1.5Interpremolar (second) 34.0 1.9Intermolar (first) 39.9 2.1andibular arch width (lingual)Intercanine 18.6 1.6Interpremolar (first) 23.0 1.6Interpremolar (second) 26.7 2.1Intermolar (first) 31.4 1.9axillary arch depthFirst molar 28.3 2.1andibular arch depthFirst molar 24.4 1.8axillary arch perimeter 76.1 3.9andibular arch perimeter 67.4 2.2axillary molar angulation () 180.3 9.3andibular molar angulation () 210.7 11.8ase in mandibular arch width measured between theond premolars (1.8 mm).

un

onRME-Sz treatment induced significant overall in-ments in both maxillary (2.8 mm for intermolardth) and mandibular (2.3 mm for intermolar width)h widths when compared with the CTRL (Tables I, and VII). The increases in both maxillary andibular arch perimeters (3.8 and 3.7 mm, respec-ely) were significant. No significant differences wereorded for the comparison between the RME-Sz andE-only groups.

SCUSSION

The purpose of this long-term prospective clinicalestigation in a private practice setting was to com-

re the modifications in arch dimensions in patientso were treated with 2 early expansion protocols (RME-ly and RME-Sz) followed later by fixed appliances withse observed in an untreated CTRL group.A unique aspect of this study was the nature of theRL. The untreated group used for comparison was

sT2 T3 T4

SD Mean SD Mean SD

1.1 13.4 1.1 19.0 2.5

1.8 30.1 1.5 29.8 1.61.5 33.7 1.5 33.5 1.71.2 38.6 1.4 38.2 1.81.7 44.0 1.7 43.9 1.9

1.5 22.8 1.5 22.2 1.61.4 25.1 1.1 25.2 1.41.2 30.0 1.3 29.9 1.61.4 33.3 1.3 33.3 1.4

1.2 23.3 1.2 23.1 1.51.8 30.1 1.7 30.1 1.82.1 34.7 2.1 34.4 2.32.1 40.5 2.0 40.4 2.3

1.4 18.0 1.4 17.5 1.62.0 24.8 1.7 24.7 1.82.7 28.4 2.3 28.1 2.62.1 31.6 1.9 31.5 2.2

2.3 26.9 2.4 26.3 2.2

2.2 21.9 2.1 21.1 2.13.9 74.8 3.7 73.6 3.83.4 63.1 2.9 61.8 3.39.2 187.4 9.8 192.5 8.9

10.3 206.7 8.0 208.0 8.5I,

).

cre

wiarc

VIma

tivrec

RM

DI

invpawhon

tho

CT

29.231.7

28.0

23.076.364.7

188.9207.7usual in that it matched the 2 treatment groups notly for chronologic age at all time intervals and

duchce

lonun

deimica

RMsev

theintcre

incthatheam

theRMwi

Ta L grou

CT

T

Mean

Ag 1.1Me

M0.10.20.20.4

M0.3

0.10.30.2

M0.1

0.10.1

0.0M

0.60.1

M

M

MMMM


210 OGrady et alrations of observation intervals, but also for occlusalaracteristics at T1. To date, no investigation con-rning the effects of RME has incorporated ag-term observation of the occlusal changes in

treated subjects with initial constriction of thental arches. The nature of our CTRL had anportant effect on the interpretation of some numer-l values reported below.The evaluation of the active treatment effects afterE-only therapy showed significant increases ineral maxillary arch dimensions when compared withCTRL. From T1 to T2, maxillary intermolar and

ercanine widths demonstrated average residual in-ases of 4.1 and 2.4 mm, respectively, whereas therease in maxillary arch perimeter was 2.3 mm moren in the CTRL (Table VII). These values do not refloriginal amount of maxillary expansion but, rather, theount of expansion remaining at the beginning offixed appliance phase of treatment. Retention after

ble VI. Descriptive statistics for change scores in CTR

RL group (n 16)T2-T1

Mean SD

e (y) 4.4 0.3asure (mm)

axillary arch width (centroid)Intercanine 1.4 1.0Interpremolar (first) 1.0 0.9Interpremolar (second) 0.8 0.9Intermolar (first) 1.1 1.1axillary arch width (lingual)Intercanine 1.1 1.5Interpremolar (first) 0.7 1.0Interpremolar (second) 0.9 0.9Intermolar (first) 0.5 1.2andibular arch width (centroid)Intercanine 0.9 1.0Interpremolar (first) 1.8 0.9Interpremolar (second) 0.8 1.1Intermolar (first) 0.6 0.8andibular arch width (lingual)Intercanine 0.2 1.5Interpremolar (first) 1.5 1.1Interpremolar (second) 1.7 1.6Intermolar (first) 0.3 0.8axillary arch depthFirst molar 0.4 1.1andibular arch depthFirst molar 1.5 1.3axillary arch perimeter 0.2 2.3andibular arch perimeter 2.8 2.1axillary molar angulation () 8.6 9.0andibular molar angulation () 3.0 10.8E removal consisted only of a removable palatal platethout a labial wire worn full-time for at least 1 year. In

ofgrost instances, a transpalatal arch also was placed beforeloss of the maxillary second deciduous molars. The

erval between T1 and T2 on average lasted 3 years 2nths. During the period with fixed appliances (T2-T3),ich averaged 18 months in duration, a significant

crease (1.7 mm) in maxillary intermolar width wasorded. The width between the maxillary second pre-lars decreased by only 0.5 mm during the same time

riod. No other significant changes occurred duringher phase II treatment or the posttreatment period3-T4). In the overall observation interval (T1-T4), the

E-only group still showed significant increases inxillary arch widths (2.7 and 2.2 mm at intermolar andercanine widths, respectively) along with a significantrease in maxillary arch perimeter (2.6 mm) withpect to the CTRL. The nonsignificant increase inndibular arch perimeter over the CTRL in the overallservation period was 2.0 mm. This lack of statisticalnificance, however, apparently was related to the nature

p at 4 time intervals3-T2 T4-T3 T4-T1

SD Mean SD Mean SD

0.1 5.5 1.3 11.0 1.7

0.4 0.2 0.5 1.2 2.00.4 0.2 0.9 1.0 1.70.5 0.3 0.8 0.8 1.80.7 0.2 0.6 1.3 1.9

0.8 0.5 0.8 1.7 2.20.5 0.1 0.9 0.6 1.60.7 0.1 0.7 1.1 1.60.7 0.0 0.4 0.7 1.9

0.4 0.3 0.4 0.4 1.20.7 0.1 0.6 1.9 1.10.4 0.3 0.6 0.4 1.50.5 0.1 0.6 0.5 1.5

0.9 0.5 0.8 1.1 1.90.6 0.1 0.7 1.7 1.20.6 0.4 0.8 1.3 1.70.5 0.1 0.6 0.1 1.3

1.0 0.6 0.6 2.0 1.7

1.1 0.8 0.4 3.3 1.61.3 1.2 0.7 2.5 3.11.6 1.3 1.3 5.7 2.35.8 5.1 10.9 12.2 9.87.8 1.3 9.0 2.7 10.4ect

mo

theintmo

whderec

mo

peeit(TRMma

intincres

ma

obsig

0.20.1

1.1

1.11.51.61.51.1the controls rather than to the response of the treatmentup, as will be discussed later.

an

icadimarc ).Frwi4.2CThamm

an

mo

wiinctream

duothpeRMcre

intarc

ninReFrogrope

tre -cre

thegrosig

al

Ta ANOdif

Me T2T1

MaI 4.2I 3.7I 2.9I 2.0

MaI 3.1I 1.9I 1.6I 1.4

MaF 0.2

MaF 0.2

Ma 2.7Ma 2.8Ma 8.9Ma 11.0

*Si


OGrady et al 211The addition of a removable lower Schwarz appli-ce to the bonded expander protocol produced signif-nt increases in all maxillary and mandibular archensions when compared with the CTRL, except

h depth and maxillary molar angulation (Table VIIom T1 to T2, maxillary intermolar and intercaninedths demonstrated significant residual increases of

and 2.0 mm, respectively, compared with theRL. Mandibular intermolar and intercanine widths

d significant increases over the CTRL of 3.1 and 1.4, respectively. The significant increases in maxillary

d mandibular arch perimeters were 2.7 and 2.8 mmre than in the CTRL, respectively. Patients treated

th the RME-Sz protocol showed a significant buccallination of the mandibular molars during activeatment compared with the CTRL (11.0). Thisount of buccal tipping rebounded almost completelyring the period with fixed appliances (10.1). Noer significant change was assessed during either this

riod or the posttreatment period. From T1 to T4, theE-Sz group still showed significant residual in-

ases in maxillary arch widths (both intermolar andercanine widths increased 2.8 mm) and mandibularh widths (2.3 and 1.4 mm at intermolar and interca-e widths, respectively) with respect to the CTRL.sidual increases in the premolar regions were similar.m T1 to T4, the significant increase of the RME-Sz

ble VII. Statistical comparisons between groups byferences in change scores with their significance)

RME-only v CTRL

asure (mm) T2T1 T3T2 T4T3 T4T1

xillary arch width (centroid)ntermolar 4.1* 1.7* 0.3 2.8*nterpremolar (second) 3.3* 0.5 0.1 3.5*nterpremolar (first) 2.9* 1.1 0.5 2.8*ntercanine 2.4* 0.0 0.3 2.2*ndibular arch width (centroid)ntermolar 1.4 0.3 0.5 1.5nterpremolar (second) 0.9 1.1 0.3 1.8*nterpremolar (first) 0.0 1.4 0.6 0.8ntercanine 0.0 0.5 0.3 0.3xillary arch depthirst molar 0.8 0.1 0.2 0.7ndibular arch depthirst molar 0.6 0.0 0.1 0.8xillary arch perimeter 2.3* 0.1 0.2 2.6*ndibular arch perimeter 1.6 0.5 0.0 2.0xillary molar angulation () 5.2 4.5 6.3 6.7ndibular molar angulation () 4.7 1.0 2.2 1.5gnificant comparison.up over the CTRL was 3.8 mm in maxillary archrimeter and 3.7 mm in mandibular arch perimeter.

ac

difWhen analyzing the comparison between the 2ated groups (Table VII), significantly greater inases in all mandibular arch widths were recorded inRME-Sz group when compared with the RME-onlyup (differences ranged from 1.0 to 1.7 mm). Anificant lingual inclination of the mandibular molarss observed during the phase with fixed appliances inRME-Sz group (9.1).Our results confirm data from our earlier study9

out the physiologic decrease in arch perimeters intreated growing subjects observed from the earlyxed dentition, also as described by Geran et al.4 Inntrast with this previous investigation, however, ourRL subjects had constricted arches at T1. The

erall decrease in maxillary arch perimeter in ourdy was smaller than that reported by Geran et 42.4 and 3.8 mm, respectively), whereas theounts of decrease in mandibular arch perimeter in

2 studies were similar (5.7 and 6.2 mm,pectively).A direct comparison of our outcomes can be made

th the results of 2 previous longitudinal controlleddies: Geran et al4 and McNamara et al.5 However, investigation by McNamara et al5 described theatment effects of a protocol that included a tooth/sue-borne device for RME (the Haas expander),ereas this study and that of Geran et al4 used an

VA and Bonferroni post-hoc test (between-group

RME-Sz v CTRL RME-Sz v RME-only

T3T2 T4T3 T4T1 T2T1 T3T2 T4T3 T4T1

* 1.2 0.2 2.8* 0.1 0.5 0.5 0.1* 0.8 0.4 4.1* 0.4 0.3 0.3 0.6* 1.6 0.8 3.6* 0.0 0.5 0.3 0.8* 0.4 0.3 2.8* 0.4 0.4 0.0 0.6

* 0.5 0.3 2.3* 1.7* 0.2 0.8 0.8* 1.1 0.9 2.7* 1.0* 0.0 0.6 0.9* 1.2 1.0 2.0* 1.6* 0.2 0.4 1.2* 0.6 0.8 1.4* 1.4* 0.1 0.5 1.1

0.2 0.1 0.1 0.6 0.3 0.1 0.8

1.0 0.1 1.1 0.4 1.0 0.2 0.3* 1.0 0.0 3.8* 0.4 1.1 0.2 1.2* 1.3 0.5 3.7* 1.2 0.8 0.5 1.7

5.7 8.2 6.4 4.1 3.7 0.6 0.3* 10.1* 1.4 2.4 6.3 9.1* 3.6 0.9wa

the

abun

mico

CTov

stu(am

theres

wistuthetretiswhrylic splint expander bonded to the teeth.1 Anotherference is that both our study and that of Geran et al4

an

RMbytheadma

chof co

CTtrapregelon

thecre

mm

theon alincou

(abapthe

thilonasc

treim1.5co

of

allallgroincwa

inon

inton

ov

arc

intva

thistuco

ter

grorec

bymm

theRMal4 inthestuma

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RMdibofulaofgroofSclespeideco

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212 OGrady et alalyzed long-term treatment outcomes produced byE in the early mixed dentition, whereas, in the study

McNamara et al, 5 the patients received expansion inlate mixed and early permanent dentitions. The

vantages of the earlier orthopedic expansion of thexilla performed in the MES include greater skeletal

anges,11 the possibility for spontaneous improvementClass II occlusal relationships,1,7 and an effective

rrection of posterior crossbites.12-14 The nature of theRL also was different in our study (subjects withnsverse deficiency of the dental arches) than in thevious investigations4,5 in which untreated subjects

nerally with more normal occlusions were followedgitudinally.In the studies by Geran et al4 and McNamara et al,5treated group showed mean overall residual in-

ases in maxillary intermolar width of 3.5 and 4.0, respectivelyvalues that are slightly greater than2.8-mm increase in our study for both the RME-

ly and RME-Sz groups (Table VII). The residureases in maxillary intercanine width in both previ-s studies were similar to the increase reported hereout 2.5 mm).4,5 RME followed by fixed appliances

pears to be an effective treatment option to increasewidth of the maxillary arch.Interestingly, the slightly less favorable results of

s study compared with previous ones4,5 in terms ofg-term increase in maxillary intermolar width can beribed to the different behavior of our CTRL. Un-ated subjects with constricted dental arches showedprovement in maxillary intermolar width of about

mm in the overall observation period, whereas thentrols in the other investigations had improvementsonly 0.4 to 0.8 mm.4,5Mandibular intermolar width showed similar over-

increases in the treatment groups over the controls in3 studies, ranging from 1.5 mm (our RME-onlyup) to 2.5 mm (McNamara et al5). In our study, therease over the CTRL in mandibular intermolar widths significant in the RME-Sz group (2.3 mm), but notthe RME-only group (1.5 mm). All 3 studies agreedthe approximately 1.5-mm increase in mandibular

ercanine width in the long term, except our RME-ly group, which showed an increase of only 0.3 mmer the CTRL. The 2.3-mm increase in mandibularh width in the RME-Sz group, however, can beerpreted as a favorable result because of the actuallue shown by the CTRL for the long-term change ins measurement (0.8 mm more than the controls in thedy by Geran et al4 and 1.7 mm more than thentrols in the study by McNamara et al5).As for the measurement of maxillary arch perime-, in this study, the overall increase in the RME-only

2ofup over the TRL was 2.6 mm, a smaller value thanorded in the RME-Sz group (3.8 mm) in the studies Geran et al4 (3.8 mm) and McNamara et al5 (6.0

). The relatively smaller amount of increase overCTRL in maxillary arch perimeter observed in ourE-only group with respect to the study by Geran et

is explained by the different nature of the controls2 studies. Although the untreated subjects in the

dy by Geran et al4 had an overall decrease inxillary arch perimeter of3.8 mm, our CTRL group

owed a decrease of only 2.4 mm. The RME-Szproved the amount of increase over the CTRL inxillary arch perimeter by 1.2 mm on average, with aal overall increase over the CTRL of 3.8 mm.The greater amount of maxillary expansion in theE-Sz patients occurred presumably because the man-

ular appliance created a new reference for the widththe maxillary dental arch after uprighting the mandib-r posterior teeth.1,6 The amounts of actual activationthe RME screw were 7 to 8 mm for the RME-onlyup and 8 to 10 mm for the RME-Sz group becausethe buccal inclination of 11.0 induced by the

hwarz appliance at the mandibular molars. Neverthe-s, the increase over the CTRL in maxillary archrimeter in the RME-Sz group (3.8 mm), althoughntical to that reported by Geran et al,4 still was

nsiderably smaller when compared with the 6.0-mmrease described by McNamara et al.5 In this regard,specifics of phase II treatment with fixed appliances

the different studies could have played an importante in maintaining or even improving the gain in archrimeter from phase I treatment with RME. A specific

of fixed appliance therapy in the treatment group of study by McNamara et al5 was the control of theittal position of the maxillary first molars in the

panded dental arch. This is evidenced by the consid-bly greater amount of long-term increase over the

ntrols in maxillary arch depth in the treated samplescribed by McNamara et al5 (3.0 mm) when com-red with the RME-Sz sample of our study (0.1 mm).e increased maxillary arch depth can account for thepplementary increase of about 2.0 mm in maxillaryh perimeter during the overall treatment period in treated sample described by McNamara et al5 withpect to the RME-Sz group reported here, thusducing an increase over the CTRL in maxillary arch

rimeter of 6.0 mm.Mandibular arch perimeter exhibited consistent de-

ases throughout the treatment and posttreatmentriods; this resulted in decreases in the overall obser-tion period of 3.6 mm in the RME-only group and

.0 mm in the RME-Sz group. In reality, the amountdecrease in mandibular arch perimeter in the un-

treated group of this study during the overall observa-tion period (5.7 mm) was much greater than that ofthe control group in the study by McNamara et al5(3.0 mm). This differential decrease produced in-creases over the CTRL of 2.0 mm for the RME-onlygrogroM eov

un

obma

ye(mNa

fropreofac

rec

scr

mo

terrefma

tiotre10ma

apbuthe

CO

mm) enables the correction of moderate tooth size-arch size discrepancies; the RME-only protocol pro-duces smaller long-term increases in arch perimeterfor the correction of more modest (3 mm) toothsize-arch size discrepancies.

im

RE

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

13.

14.


OGrady et al 213up and, more significantly, 3.7 mm in the RME-Szupa value that is similar to that reported by

cNamara et al5 (4.5 mm). The different values for therall decrease in mandibular arch perimeter in thetreated groups were related to the time of firstservation, which was before the exfoliation of thendibular second deciduous molars (mean age, 8-9

ars) in this study, and during the late mixed dentitionean age, 11 years 6 months) in the study by Mc-mara et al.5A useful clinical implication that can be derived

m the various studies comprising the MES and thevious study by McNamara et al5 is that, regardlesstransverse occlusal relationships in each subject, an

tivation of the RME screw of at least 10 mm can beommended in most instances. Smaller amounts ofew activation (7-8 mm) appear to produce onlydest long-term increases in maxillary arch perime-. The use of the RME-Sz can create a more adequateerence for the amount of expansion needed in thexillary arch. The Schwarz-induced buccal inclina-n of the mandibular molars (11.0) during the activeatment period allows the clinician to reach easily themm activation of the screw during expansion of thexilla. Moreover, the use of the mandibular Schwarz

pliance has the advantage of avoiding a completeccal crossbite at the end of aggressive expansion of

maxilla.

NCLUSIONSThe RME-Sz protocol is as effective as the RME-only protocol in increasing the width of the maxillaryarch, whereas it can induce a significantly morefavorable increase in the transverse width of themandibular arch.The mandibular Schwarz plate can decompensate themandibular posterior teeth buccally; this allows foran amount of maxillary expansion (at least 10 mm ofactivation of the expansion screw) that is clinicallyfavorable for the increase in arch perimeter.The long-term increase in maxillary and mandibulararch perimeters by using the RME-Sz protocol (3.8We thank Elvis L. Evans for modifying the digitalaging system for use in this study.

FERENCES

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A long-term evaluation of the mandibular Schwarz appliance and the acrylic splint expander in early mixed dentition patientsPATIENTS AND METHODSTreatment protocolsData collectionError of the methodStatistical analysis

RESULTSDISCUSSIONACKNOWLEDGMENTREFERENCES

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