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Immediate effects of rapid maxillary expansionwith Haas-type and hyrax-type expanders:

A randomized clinical trial

Andre Weissheimer,a Luciane Macedo de Menezes,b Mauricio Mezomo,a Daniela Marchiori Dias,a

Eduardo Martinelli Santayana de Lima,b and Susana Maria Deon Rizzattoc

Porto Alegre, Rio Grande do Sul, Brazil

Introduction: The purposes of this study were to evaluate and compare the immediate effects of rapid maxillary

expansion (RME) in the transverse plane with Haas-type and hyrax-type expanders by using cone-beam

computed tomography. Methods: A sample of 33 subjects (mean age, 10.7 years; range, 7.2-14.5 years)

with transverse maxillary deficiency were randomly divided into 2 groups: Haas (n 5 18) and hyrax (n 5 15).

All patients had RME with an initial activation of 4 quarter turns followed by 2 quarter turns per day until the

expansion reached 8 mm. Cone-beam computed tomography scans were taken before expansion and at the

end of the RME phase. Maxillary transversal measurements were compared by using the mixed analysis of

variance (ANOVA) model and the Tukey-Kramer method. Results: RME increased all maxillary transverse

dimensions (P\0.0001). There was less expansion at skeletal than dental levels. The hyrax group had greater

statistically significant orthopedic effects and less tipping tendency of the maxillary first molars compared with

the Haas group. Conclusions: Both appliances were efficient in correcting a transverse maxillary deficiency.

The pure skeletal expansion was greater than actual dental expansion. The hyrax-type expander produced

greater orthopedic effects than did the Haas-type expander, but this effect was less than 0.5 mm per side and

might not be clinically significant. (Am J Orthod Dentofacial Orthop 2011;140:366-76)

R

apid maxillary expansion (RME) is an important

method used to correct a transverse maxillary de-ficiency. It was first described in the literature over

a century ago by Angell,1 and it has been disseminatedand made widely popular by Haas since 1961.2 In

RME, rigid and fixed expanders are used to produceheavy forces to obtain the maximum skeletal response

by opening the midpalatal suture, with minimumorthodontic movement.2-5

Among the appliances used for RME, the tooth-tissueborne (Haas-type) and the tooth-borne (hyrax-type) expanders are the most recognized in the literature.The main difference between them is the acrylic pad that

leans on the lateral walls of the palatal vault (Haas-type)

to reinforce the anchorage for greater orthopedic

response and better force distribution during RME.2,4

In the hyrax-type expander, there is no acrylic pad;

therefore, it is more hygienic and prevents soft-tissueirritation caused by food impaction under the acrylicplate.6 Although a cephalometric investigation has notdemonstrated any differences between Haas-type andhyrax-type expanders,7 there is no consensus in the lit-erature regarding the differences in the immediate

RME effects produced by these appliances.Several investigations have analyzed the effects of

RME through 2-dimensional cephalometric radiographs,which do not allow accurate identification of dentoske-

letal structures because of the superimposition of manybones in the different planes of space.2,7-9 To overcomethese limitations, computed tomography (CT) for theassessment of the transverse dimensions of themaxilla was introduced by Timms et al10 in the1980s. However, the use of conventional CT scans inorthodontics has been limited because of cost and ra-

diation concerns.11 Cone-beam CT (CBCT) has usheredin a new era in dental diagnostics. This technology wasdesigned for imaging hard tissues of the maxillofacialregion with minimum distortion at a lower cost and

with lower radiation emissions compared with

From the Department of Orthodontics, Pontifical Catholic University of Rio

Grande Do Sul, Porto Alegre, Rio Grande do Sul, Brazil.aPostgraduate student (Ph.D.).bProfessor.cAssistant professor.

The authors report no commercial, proprietary, or financial interest in the prod-

ucts or companies described in this article.

Reprint requests to: Andre Weissheimer, Pontifcia Universidade Catolica do Rio

Grande do Sul, Faculdade de Odontologia, Predio 6, Avenida Ipiranga, 6681, sala

209,Porto Alegre, RS, Brazil, CEP 90619-900; e-mail, [email protected].

Submitted, March 2010; revised and accepted, July 2010.

0889-5406/$36.00

Copyright 2011 by the American Association of Orthodontists.

doi:10.1016/j.ajodo.2010.07.025

366

ORIGINAL ARTICLE
mailto:[email protected]:[email protected]

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conventional CT. The high resolution of CBCT imagesis due to the isotropic voxel (equal in all 3 dimensions),

which produces submillimeter resolutions ranging from0.4 mm to as low as 0.125 mm.11 Several investigationshave shown the high accuracy of CBCT images forquantitative and qualitative analyses.12-15 Its use is

recommended in orthodontics for several purposessuch as evaluation of impacted teeth,16,17 evaluation

of bone grafts in cleft regions,18 analysis of alveolarbone before placement of orthodontic temporary an-

chorage devices,19 and evaluation of RME effects onnasomaxillary structures.20

The purposes of this study were to evaluate and com-pare the immediate effects of RME on the transverse

plane with Haas-type and hyrax-type expanders byusing high-resolution CBCT.

Fig 1. A, Haas-type expander and B, hyrax-type expander at the end of the active phase of RME.

Fig 2. Transverse maxillary posterior region evaluation: A and B, preexpansion; C and D, atthe end ofthe active phase of expansion.

Weissheimer et al 367

American Journal of Orthodontics and Dentofacial Orthopedics September 2011 Vol 140 Issue 3

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MATERIAL AND METHODS

This study was approved by the ethical committee ofthe Pontifical Catholic University of Rio Grande do Sul in

Brazil. Informed consent was obtained from the parentsof all patients who agreed to participate in this study. The

sample was selected by examining subjects in need of or-thodontic treatment at the Department of Orthodonticsof the School of Dentistry. The inclusion criteria forthis study were transverse maxillary deficiency, mixeddentition or early permanent dentition, and no surgicalor other treatment that might affect the RME effects

during the expansion period. Patients with congenitalmalformations or periodontal diseases, or above 15 yearsof age were excluded from the study sample.

In this prospective study, the sample comprised 33

healthy white children (11 boys, 22 girls) with a meanchronologic age of 10.7 years (range, 7.2-14.5 years)

and a mean skeletal age of 10.9 years (range, 6.8-15years). These patients were randomly divided into 2groups: Haas (n 5 18) and hyrax (n 5 15). In the Haasgroup, the Haas-type expander, with 4 bands (first perma-

nent molars and first premolars or first deciduous molars)and buccal and lingual stainless steel bars of 1.0-mmdiameter was used (Fig 1, A). In the hyrax group, thehyrax-type expander, with 4 bands, buccal and lingualstainless steel bars of 1.0-mm diameter and a jackscrew

with 1.4-mm stainless steel extensions soldered to the lin-

gual surfaces of each pair of bands, was used (Fig 1, B).Both appliances had expansion jackscrews with acti-

vations of a quarter turn equivalent to a 0.2-mm expan-sion. All patients in the Haas and hyrax groups had RME,

with initial activations of 4 quarter turns (0.8 mm)

followed by 2 quarter turns per day (0.4 mm) until theexpansion screw reached 8 mm.

The i-CAT (Imaging Sciences International, Hatfield,Pa) was used to obtain CBCT images before RME (T1)and at the end of the active expansion phase (T2). TheCBCT scans were performed at 120 kV, 8 mA, scan

time of 40 seconds, and 0.3-mm voxel dimension. Thedata for each patient were reconstructed with 0.3-mmslice thickness, and the digital imaging and communica-

tions in medicine (DICOM) images were assessed by us-ing the EFILM workstation software program (version2.1.2, Merge Healthcare, Milwaukee, Wis). All linearand angular measurements were made by a blinded ex-aminer (M.M.), who had no access to the data or the clin-ical consultations of the patients in this sample.

For transverse maxillary posterior region evaluation,

the DICOMfiles with CBCT images at T1 and T2 were im-ported into EFILM and visualized as axial imagesarranged side by side. To obtain standardized axial andcoronal slices and thus allow the comparisons betweenT1 and T2, the following references were used. In the

Fig 3. Landmarks used in the evaluation of the maxillary posterior region.

368 Weissheimer et al

September 2011 Vol 140 Issue 3 American Journal of Orthodontics and Dentofacial Orthopedics

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axial slices, the images that displayed the root canal in

the most apical region of the palatal root of maxillaryfirst permanent molars were selected. By using the Mul-tiPlanar Reformation tool, the MultiPlanar Reformationline was positioned at the root canal in the most apical

region of the palatal root of the maxillaryfirst perma-nent molars on the right and left sides. From these ref-erences, standardized coronal images were produced,and the measurements were made (Fig 2). The landmarksused for evaluation of the maxillary posterior region areshown in Figure 3 and described in Table I.

The analyses of the transversal changes in the maxil-lary anterior region were performed in a similar way tothose of the posterior region. In the axial slices, imagesat T1 and T2 were selected with the root canals in the

most apical region of the roots of the maxillary perma-nent canines visualized. After that, the MultiPlanar

Reformation line was positioned at the root canal inthe most apical region of the maxillary permanentcanine root on the right and left sides. From theses ref-erences, standardized coronal images were produced,

and the measurements were made (Fig 4). The landmarks

used to evaluate the RME effects in the anterior region ofmaxilla are shown in Figure 5 and described in Table I.

Statistical analysis

Intraexaminer reliability of the measurements wasdetermined by intraclass correlation coefficients. Double

assessments of each parameter at T1 and T2 (10 daysapart) of 15 randomly selected patients from bothgroups were compared (Table II). The data obtainedfrom all measurements were processed with SAS soft-

ware (version 9.0.2, SAS, Cary, NC). Means and standarderrors for each parameter were calculated, and data at T1

Table I. Landmarks for transverse maxillary evaluation

Skeletal

Line 1-2 Posterior baseline Line formed by the 2 lower points at the inferior inner contour of the

posterior nasal cavity on the right and left sides, respectively.

Line 13-14 Anterior baseline Line formed by the 2 lower points at the inferior inner contour of the anteriornasal cavity on the right and left sides, respectively.

Distance 5-6 Posterior apical base width Distance between points 5 and 6 (points formed by the intersection of the

line 1-2 with buccal contour of maxilla on the right and left sides,

respectively).

Distance 11-12 Posterior midpa latal suture width Distance between points 11 and 12 (lower points at medial limits of maxillary

palatine processes, on the right and left sides, respectively), representing

the midpalatal suture.

Distance 15-16 Anterior apical base width (inferior) Distance between points 15 and 16 (points formed by the intersection of line

13-14 with buccal contour of maxilla on the right and left sides,

respectively).

Distance 17-18 Anterior apical base width (superior) Distance between points 17 and 18 (intersection of the straight line, which is

parallel and 5 mm superior to line 13-14, with buccal contour of maxilla

on the right and left sides, respectively).

Distance 21-22 Anterior mid-palatal suture width Distance between points 21 and 22 (lower points at medial limits of maxillary

palatine processes, on the right and left sides, respectively), representingthe midpalatal suture in the anterior region.

Alveolar

Distance 3-4 Posterior width at the alveolar crest level Distance between points 3 and 4 (coronal-most points of the maxillary

buccal alveolar processes, on the right and left sides, respectively).

Distance 19-20 Anterior width at midalveolar level Distance between points 19 and 20 (intersection of the straight line, which is

parallel and 5 mm inferior to line 13-14, with buccalcontour of maxilla on

the right and left sides, respectively).

Dental

Distance 7-8 Intermolar width at occlusal surface Distance between points 7 and 8 (points formed by the intersection of

a straight line, that superimpose the long axis of the root canal offirst

permanent molar palatine root, with the occlusal surface on the right and

left sides, respectively).

Distance 9-10 Intermolar width at palatal root apices Distance between points 9 and 10 (apices of palatine root of permanent first

molars, on the right and left sides, respectively).

Angle 1MD Right first molar angulation Angle formed by the straight line from point 7 and that superimposes the

long axis of the root canal of permanent first molar palatine root, on the

right side, with line 1-2.

Angle 1ME Left first molar angulation Angle formed by the straight line from point 8 and that superimposes the

long axis of the root canal of permanent first molar palatine root, on the

left side, with the line 1-2.



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and T2 were compared by using the mixed analysis ofvariance (ANOVA) model and the Tukey-Kramer method

at a significance level of 5%.

RESULTS

The overall immediate effects of RME on the trans-

verse plane are shown in Table III. There were signifi-cant increases in maxillary width at the skeletal,alveolar, and dental levels for both the Haas (TableIV) and the hyrax (Table V) groups in all parameters

(P\0.05). There was less expansion at the skeletalthan at the dental level, just as the increase in the max-illary apical base was smaller in the posterior region(distances 5-6 and 11-12) compared with the anterior(distances 15-16, 21-22) (Tables III-V). The hyraxgroup had greater statistically significant increases in

the maxillary transverse dimensions at the skeletallevel than did the Haas group in both posterior(distances 5-6 and 11-12) and anterior (distance 21-22) regions (Table VI). There was no significant differ-

ence between the groups for the buccal inclination ofthe maxillary first permanent molars, except for the

linear measure (distance 9-10), which indicated greater

inclination of these teeth in the Haas group than in thehyrax group (Table VI).

DISCUSSION

After Broadbent21 introduced the cephalostat in

1931, several investigations have analyzed the effectsof RME through cephalometry in 2-dimensional radio-graphs.3,8,22 The major problem associated withcephalometry is projection errors, which have an effect

on linear and angular measurements, caused bymagnification and distortion and are compounded byincorrect patient positioning.23,24 To overcome theselimitations, we evaluated and compared, using high-resolution CBCT, the immediate effects of RME on thetransverse planes with Haas-type and hyrax-type ex-

panders. CBCT was used because it is a suitable exami-nation for imaging craniofacial areas, with minimumdistortion, at a lower cost and with lower radiation dos-ages than conventional CT.11,25,26 In addition, CBCT isan accurate and reliable method for assessing changesassociated with RME on nasomaxillary structures.20

Fig 4. Transverse maxillary anterior region evaluation: A and B, preexpansion; C and D, at the end of

the active phase of expansion.



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Regarding previous reports that used CT images toevaluate RME, our study had an adequate sample size(33 subjects).10,20,27-33 Furthermore, this study designhad some important features: (1) it was a prospectivestudy; (2) the patients were randomly divided betweenthe groups; (3) the methodology was highly

standardized in terms of appliance fabrication, and rateand amount of expansion; and (4) it used high-resolution CBCT. In this study, since the active expansionphase lasted only 19 days, there was no need to use

a control group without treatment since normal growthwas not an influencing factor in this short time. In this

study, the overall effects of RME produced a significantskeletal increase in the transverse maxillary dimension,confirming previous reports.2-5,20,28,30,34,35 The skeletal

expansion amounts were greater in the anteriorregion2.82 mm (distance 17-18), 3.48 mm (distance15-16), and 4 mm (distance 21-22)compared withthe posterior2.64 mm (distance 5-6) and 2.88 mm(distance 11-12) (Table III). In agreement with previous

authors, the expansion pattern was triangular witha wider base at the anterior portion of maxilla.20,29,35

The greater expansion in the anterior region could be

explained by the resistance of the medial and lateralpterygoid plates of the sphenoid bone to the maxillarytip movement during the RME.35 Another feasible expla-nation would be through maxillary expansion biome-

chanics: ie, the direction of the expansion forceproduced by the expanders would be located anteriorto the center of resistance of each maxillary half.36

The hyrax-type expander produced greater skeletalexpansion3.14 mm (distance 11-12) and 4.37 mm(distance 21-22)than did the Haas-type expander2.62 mm (distance 11-12) and 3.63 mm (distance21-22) (Table VI). The skeletal gain in the hyrax groupaccounted for 38.5% to 39.2% (posterior region) and37.5% to 54.7% (anterior region) of the total expansion

(8 mm). In the Haas group, the increases were smaller,ranging from 27.2% to 32.7% in the posterior region

Fig 5. Landmarks used in the evaluation of the maxillary anterior region.

Table II. Intraclass correlation coefficients of the mea-surements

Measurement ICC

Distance 5-6 0.98

Distance 11-12 0.94

Distance 15-16 0.96

Distance 17-18 0.95

Distance 21-22 0.61

Distance 3-4 0.98

Distance 19-20 0.96

Distance 7-8 0.95

Distance 9-10 0.97

Angle 1MD 0.93

Angle 1ME 0.74



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and 32.7% to 45.2% in the anterior region. These

comparison results between the appliances differ fromprevious reports.7,28,37 Siqueira et al7 compared the

Haas-type and hyrax-type expanders through frontalcephalometric radiographs and found no differences

between them. Garib et al28 also found no differences

between these 2 expanders using spiral CT. This phe-nomenon could be explained by the small study sample(n 5 8), which reduced the power of the t test to showstatistically significant differences. When significantdifferences are demonstrated in such situations, they

clearly exist and most likely have clinical importance.However, the absence of significant differences does

not necessarily indicate that they do not exist. In addi-tion, the RME changes were analyzed 3 months afterthe active expansion phase, unlike our study, with theimmediate effects of RME on 33 patients evaluated. In

disagreement with the present study, Oliveira et al37

found that the Haas-type expander achieved expansionwith a greater component of orthopedic movementthan the hyrax-type expander. However, the comparison

between the 2 kinds of expanders was performed on

study models and anteroposterior cephalograms.The main difference between Haas-type and hyrax-

type expanders is the acrylic pad close to the palate in

the Haas-type appliance. According to Haas,4 a purpose

of the acrylic pad is to reinforce the anchorage forgreater orthopedic response during RME. However,the results of our study did not support this theory,at least regarding the immediate effects of expansion.

Better results in the immediate skeletal response wereobtained by the hyrax-type expander vs the Haas-type. This fact can be explained by differences in appli-ance design: more specifically, in the connection mech-anism of the jackscrew to the bands of the anchorageteeth. In the hyrax-type appliance design, the jackscrew

was directly connected to the bands by a rigid stainlesssteel framework (1.4 mm), unlike the Haas-type appli-

ance design, where the acrylic was responsible for con-necting the stainless steel framework (1.0 mm) to the

jackscrew. According to a previous study about the bio-mechanics of RME, appliance designs that use an

acrylic interface with the teeth are far less stiff thanthose constructed solely of soldered stainless steel

wire, as in the case of the hyrax-type expander.36 How-ever, the acrylic pad against the palate would be impor-tant, especially during the retention period, when it

would prevent the bone from moving through theteeth, thus averting an orthopedic relapse of the ex-

panded maxilla.4,5,20

Table III. Immediate changes in the maxillary transverse plane with RME

Variable

T1 T2 Change

PMean SE Mean SE Mean SE

SkeletalDistance 5-6 (mm)

Posterior apical base width 60.29 0.64 62.93 0.64 2.64 0.11 \0.0001*

Distance 11-12 (mm)

Posterior midpalatal suture width 00.00 0.08 02.86 0.08 2.88 0.09 \0.0001*

Distance 15-16 (mm)

Anterior apical base width (inferior) 38.37 0.61 41.85 0.61 3.48 0.23 \0.0001*

Distance 17-18 (mm)

Anterior apical base width (superior) 38.96 0.83 41.78 0.83 2.82 0.23 \0.0001*

Distance 21-22 (mm)

Anterior midpalatal suture width 00.00 0.10 04.00 0.11 4.00 0.13 \0.0001*

Alveolar

Distance 3-4 (mm)

Posterior width at alveolar crest level 51.65 0.51 57.28 0.51 5.63 0.16 \0.0001*

Distance 19-20 (mm)

Anterior width at midalveolar level 40.06 0.58 44.46 0.58 4.40 0.22 \0.0001*

Dental

Distance 7-8 (mm)

Intermolar width at occlusal surface 43.51 0.44 51.31 0.44 7.80 0.15 \0.0001*

Distance 9-10 (mm)

Intermolar width at palatal root apices 29.90 0.52 32.55 0.52 2.65 0.14 \0.0001*

Angle 1MD ()

Right first molar angulation 110.6 1.4 118.1 1.4 7.53 0.74 \0.0001*

Angle 1ME ()

Left first molar angulation 117.7 1.2 123.8 1.2 6.17 0.68 \0.0001*

*Statistically significant (P\0.05).



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In the hyrax group, the transverse expansion at thesuture gradually decreased from the anterior, by 4.37mm (distance 21-22), to the posterior, by 3.14 mm

(distance 11-12) (Table V). This sutural orthopedic sep-aration accounted for 54.7% and 39.2% of the totalexpansion (8 mm) at distances 21-22 and 11-12,

Table IV. Immediate changes in the maxillary transverse plane with RME in the Haas group

Variable

T1 T2 Change

PMean (mm) SE (mm) Mean (mm) SE (mm) Mean (mm) SE (mm)

SkeletalDistance 5-6


Distance 11-12


Distance 15-16


Distance 17-18


Distance 21-22


Alveolar

Distance 3-4


Distance 19-20

Anterior width at midalveolar level 40.56 0.79 44.59 0.79 4.03 0.30 \0.0001*

Dental

Distance 7-8


Distance 9-10



Table V. Immediate changes in the maxillary transverse plane with RME in the hyrax group

Variable

T1 T2 Change

PMean (mm) SE (mm) Mean (mm) SE (mm) Mean (mm) SE (mm)

Skeletal

Distance 5-6


Distance 11-12


Distance 15-16


Distance 17-18


Distance 21-22


Alveolar

Distance 3-4


Distance 19-20Anterior width at midalveolar level 39.58 0.83 44.34 0.83 4.76 0.34 \0.0001*

Dental

Distance 7-8


Distance 9-10





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respectively. These findings endorse a previous report inwhich, of the total expansion achieved, the hyrax-typeexpander produced 55% of the suture expansion in theanterior and 38% in the posterior regions.20 However,

the RME changes were analyzed 3 months after theactive expansion phase, unlike our study, where the

immediate effects of RME were evaluated.This investigation showed a more significant skele-

tal response compared with other studies.29,30 Ina study by Lione et al,29 the RME was performed

with a modified hyrax-type expander (bands on thefirst permanent molars only), and less sutural expan-sion was obtained in both the anterior (2.17 mm)and the posterior (1.15 mm) regions. This small ortho-pedic effect could be explained by (1) the use of a mod-ified hyrax-type expander, which had less anchorage;

(2) less total expansion (7 mm); and (3) the sutural ex-pansion evaluated in a more posterior region (posteriornasal spine) than in our study (in the first molar re-gion). In our investigation, the amounts of sutural

expansion (2.88 mm in the posterior and 4 mm inthe anterior regions) were greater than the amounts

reported by Podesser et al30 (1.6 mm in the posteriorand 1.5 mm in the anterior regions). This differencecould be explained by less total expansion (7 mm)and the relapse that might have occurred because of

appliance removal and replacement at the end of theactive phase of RME for CT scan acquisition in their

study. In our investigations, there was no need to re-move the appliances before the CBCT examination atT2 because of the lower level of metal artifacts pro-

duced by CBCT compared with conventional CT.11,38

The greater amounts of expansion at the alveolarlevel (distances 3-4 and 19-20) than the sutural expan-sion (distances 11-12 and 21-22) (Table III) show the

bending of the alveolar processes of the maxilla; this re-sult agrees with previous reports.20,28,30 The expansionat the alveolar level (distance 3-4) accounted for 70%

of the total expansion, 36% of which representssutural expansion and 34% is purely alveolar bendingtoward the buccal aspect.

The great changes in maxillary transverse dimensions

occurred at the dental level, where the expansion ac-counted for 97% (distance 7-8) of the total expansion

Table VI. Comparison between the changes in the maxillary transverse planes in the groups

Variable

Haas group Hyrax group

P

T2-T1 T2-T1

Mean SE Mean SE

Skeletal

Distance 5-6 (mm)

Posterior apical base width 2.19 0.15 3.10 0.17 0.0002*

Distance 11-12 (mm)

Posterior midpalatal suture width 2.62 0.12 3.14 0.14 0.010*

Distance 15-16 (mm)

Anterior apical base width (inferior) 3.29 0.30 3.66 0.34 0.427

Distance 17-18 (mm)

Anterior apical base width (superior) 2.62 0.31 3.00 0.35 0.438

Distance 21-22 (mm)

Anterior midpalatal suture width 3.63 0.17 4.37 0.20 0.007*

Alveolar

Distance 3-4 (mm)

Posterior width at alveolar crest level 5.44 0.25 5.80 0.28 0.342Distance 19-20 (mm)

Anterior width at midalveolar level 4.03 0.30 4.76 0.34 0.119

Dental

Distance 7-8 (mm)

Intermolar width at occlusal surface 7.70 0.20 7.90 0.23 0.526

Distance 9-10 (mm)

Intermolar width at palatal root apices 2.15 0.18 3.14 0.21 0.0008*

Angle 1MD ()

Right first molar angulation 8.25 0.98 6.80 1.11 0.334

Angle 1ME ()

Left first molar angulation 6.14 0.90 6.19 1.02 0.975

*Statistically significant difference (P\0.05).



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(8 mm) (Table III). This greater expansion at the dental

level compared with the skeletal level agrees with previ-ous reports.3,4,20,28,30,34,37 However, the actual dentalexpansion can be found by subtracting the total

expansion at the dental level (distance 7-8) from thesuture and alveolar expansions (distance 3-4). Thus,from 97% (7.8 mm) of the total expansion at the

dental level (distance 7-8), only 27% (2.17 mm)represents actual dental expansion, which was smallercompared with 36% (2.88 mm) of pure skeletalexpansion (distance 11-12) and with 34% (2.75 mm)

of pure alveolar bending. RME produced significantbuccal tipping of the first permanent molars,

accounting for 7.53 (angle 1MD) on the right side

and 6.17 (angle 1ME) on the left side (Table III). Therewere no statistically significant differences between the2 groups in angular measurements. The amounts of buc-cal tipping of the first permanent molars for the Haas

group were 8.25 on the right side (angle 1MD) and6.14 on the left side (angle 1ME), whereas, in the hyraxgroup, the tipping amounts were 6.80 on the right and6.19 on the left sides. However, there was a statisticallysignificant difference between the Haas and hyraxgroups in the linear measurement (distance 9-10), which

represents the distance between the apices of the palatalroots of the first permanent molars. The higher values fordistance 9-10 (nearly 8 mm of expansion) reflecteda small buccal tipping of the first molars. In the hyraxgroup, distance 9-10 increased by 3.14 mm, whereas,

in the Haas group, there was an increase of 2.15 mm,showing greater tipping of the first permanent molars

with that expander (Table VI). Similar results were re-ported in other investigations.28-37 In the study ofGarib et al,28 the Haas-type expander produced greater

buccal tipping of the first permanent molars (3.5)

than did the hyrax-type expander (1.6). Oliveiraet al37 found that the Haas-type expander produced

greater buccal tipping of the first permanent molars(7.12 right side, 6.64 left side) compared with the

Hyrax-type expander (6.94 right side, 1.21 left side).However, these differences were not considered statisti-

cally significant in either study.We assessed the immediate effects of RME; therefore,

long-term evaluation is necessary for a better under-standing of the differences between Haas-type andhyrax-type expanders, especially during the retentionand postretention phases of RME.

CONCLUSIONS

Based on this clinical trial with CBCT to assess theimmediate effects of RME on the transverse plane with2 kinds of palatal expanders, the following conclusionscan be drawn:

1. RME produced significant increases in all maxil-lary transverse dimensions. The expansion pattern

was triangular, with smaller effects at the skeletal

level than at the dental level. However, the pure

skeletal expansion was greater than actual dentalexpansion. The sutural expansion showed a wedgeshape with the wide base in the anterior maxilla.

2. The opening of the midpalatal suture accountedfor 50% of the total expansion (8 mm) in the

anterior region and 36% in the posterior region(there was a decrease from anterior to posterior).

3. The hyrax-type expander produced greater orthope-dic effects in 3 of the 5 skeletal points measured

compared with the Haas-type expander. However,the effects were less than 0.5 mm per side and might

not be clinically significant.

REFERENCES

1. Angell EH. Treatment of irregularities of the permanent or adult

tooth. Dent Cosmos 1860:540-4, 599-601.

2. Haas AJ.Rapid expansionof themaxillarydentalarch and nasalcav-

ity by opening the midpalatal suture. Angle Orthod 1961;31:73-90.

3. Haas AJ. The treatment of maxillary deficiency by opening the

midpalatal suture. Angle Orthod 1965;35:200-17.

4. Haas AJ. Palatal expansion: just the beginning of dentofacial

orthopedics. Am J Orthod 1970;57:219-55.

5. Haas AJ. Long-term posttreatment evaluation of rapid maxillary

expansion. Angle Orthod 1980;50:189-217.

6. Biederman W. A hygienic appliance for rapid expansion. J Clin

Orthod 1968;2:67-70.7. Siqueira D, Almeida R, HenriquesJ. Frontal cephalometric compar-

ativestudyof dentoskeletal effects producedby three types of max-

illary expanders. Rev Dent Press Ortodon Ortop Facial 2002;7:

27-47.

8. Chung CH, Font B. Skeletal and dental changes in the sagittal,

vertical, and transverse dimensions after rapid palatal expansion.

Am J Orthod Dentofacial Orthop 2004;126:569-75.

9. Sandikciolu M, Hazar S. Skeletal anddental changes after maxillary

expansion in the mixed dentition. Am J Orthod Dentofacial Orthop

1997;111:321-7.

10. Timms DJ, Preston CB, Daly PF. A computed tomographic assess-

ment of maxillary movement induced by rapid expansiona pilot

study. Eur J Orthod 1982;4:123-7.

11. Scarfe WC, Farman AG, Sukovic P. Clinical applications of

cone-beam computed tomography in dental practice. J Can DentAssoc 2006;72:75-80.

12. Lagravere MO, Carey J, Toogood RW, Major PW. Three-dimen-

sional accuracy of measurements made with software on

cone-beam computed tomography images. Am J Orthod Dentofa-

cial Orthop 2008;134:112-6.

13. Mozzo P, Procacci C, Tacconi A, Tinazzi Martini P, Bergamo

Andreis IA.A newvolumetric CT machine for dental imaging based

on the cone-beam technique: preliminary results. EurRadiol1998;

8:1558-64.

14. Hilgers ML, Scarfe WC, Scheetz JP, Farman AG. Accuracy of linear

temporomandibular joint measurements with cone beam com-

puted tomography and digital cephalometric radiography. Am J

Orthod Dentofacial Orthop 2005;128:803-11.



7/30/2019 efectos 6

11/11

15. Misch KA, Yi ES, Sarment DP. Accuracy of cone beam computed

tomography for periodontal defect measurements. J Periodontol

2006;77:1261-6.

16. Nakajima A, Sameshima GT, Arai Y, Homme Y, Shimizu N,

Dougherty H Sr. Two- and three-dimensional orthodontic imaging

using limited cone beam-computed tomography. Angle Orthod2005;75:895-903.

17. Walker L, Enciso R, Mah J. Three-dimensional localization of

maxillary canines with cone-beam computed tomography. Am J


18. Hamada Y, Kondoh T, Noguchi K. Application of limited cone

beam computed tomography to clinical assessment of alveolar

bone grafting: a preliminary report. Cleft Palate Craniofac J

2005;42:128-37.

19. Poggio PM, Incorvati C, VeloS, Carano A. Safe zones: a guide for

miniscrew positioning in the maxillary and mandibular arch. Angle

Orthod 2006;76:191-7.

20. Garrett BJ, Caruso JM, Rungcharassaeng K, Farrage JR, Kim JS,

Taylor GD. Skeletal effects to the maxilla after rapid maxillary

expansion assessed with cone-beam computed tomography. Am

J Orthod Dentofacial Orthop 2008;134:8.e1-11.21. Broadbent BH. A new x-ray technique and its application to ortho-

dontia. Angle Orthod 1931;1:45-66.

22. Sandikciolu M, Hazar S. Skeletal and dental changes after maxil-

lary expansion in the mixed dentition. Am J Orthod Dentofacial

Orthop 1997;111:321-7.

23. Ahlqvist J, Eliasson S, Welander U. The effect of projection errors

on cephalometric length measurements. Eur J Orthod 1986;8:

141-8.

24. Ahlqvist J, Eliasson S, Welander U. The effect of projection errors

on angular measurements in cephalometry. Eur J Orthod 1988;

10:353-61.

25. Hatcher DC, Aboudara CL. Diagnosis goes digital. Am J Orthod

Dentofacial Orthop 2004;125:512-5.

26. Ludlow JB,Ivanovic M. Comparative dosimetry of dentalCBCT de-

vices and 64-slice CT for oral and maxillofacial radiology. Oral Surg

Oral Med Oral Pathol Oral Radiol Endod 2008;106:106-14.

27. Garib DG, Henriques JF, Janson G, de Freitas MR, Fernandes AY.

Periodontal effects of rapid maxillary expansion with

tooth-tissue-borne and tooth-borne expanders: a computed

tomography evaluation. Am J Orthod Dentofacial Orthop 2006;

129:749-58.

28. Garib DG, Henriques JFC, Janson G, Freitas MR, Coelho RA. Rapid

maxillary expansiontooth tissue-borne versus tooth-borne

expanders: a computed tomography evaluation of dentoskeletal

effects. Angle Orthod 2005;75:548-57.29. Lione R, Ballanti F, Franchi L, Baccetti T, Cozza P. Treatment and

posttreatment skeletal effects of rapid maxillary expansion studied

with low-dose computed tomography in growing subjects. Am J


30. Podesser B, Williams S, Crismani AG, Bantleon HP. Evaluation of

the effects of rapid maxillary expansion in growing children using

computer tomography scanning: a pilot study. Eur J Orthod 2007;

29:37-44.

31. Habersack K, Karoglan A, Sommer B, Benner KU. High-resolution

multislice computerized tomography with multiplanar and

3-dimensional reformation imaging in rapid palatal expansion.


32. Ballanti F, Lione R, Fanucci E, Franchi L, Baccetti T, Cozza P. Im-

mediate and post-retention effects of rapid maxillary expansion

investigated by computed tomography in growing patients. AngleOrthod 2009;79:24-9.

33. Rungcharassaeng K, Caruso JM, Kan JYK, Kim J, Taylor G. Factors

affecting buccal bone changes of maxillary posterior teeth after

rapid maxillary expansion. Am J Orthod Dentofacial Orthop

2007;132:428.e1-8.

34. Lagravere MO, Heo G, Major PW, Flores-Mir C. Meta-analysis of

immediate changes with rapid maxillary expansion treatment.

J Am Dent Assoc 2006;137:44-53.

35. Bishara SE, Stanley RN. Maxillary expansion: clinical implications.


36. Braun S, Bottrel JA,Lee KG,Lunazzi JJ,LeganHL. Thebiomechan-

ics of rapid maxillary sutural expansion. Am J Orthod Dentofacial

Orthop 2000;118:257-61.

37. Oliveira NL,Da Silveira AC,Kusnoto B, Viana G. Three-dimensional

assessment of morphologic changes of the maxilla: a comparison

of 2 kinds of palatal expanders. Am J Orthod Dentofacial Orthop

2004;126:354-62.

38. Cohnen M, Kemper J, Mobes O, Pawelzik J, Modder U. Radiation

dose in dental radiology. Eur Radiol 2002;12:634-7.


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