A novel method for treatment of Class III malocclusion in growing patients
Al-Mozany et al. Progress in Orthodontics
A novel method for treatment of Class III malocclusion in growing patients
Saad A. Al-Mozany 1
Oyku Dalci 1
Mohammed Almuzian 0 1 2
Carmen Gonzalez 1
Nour E. Tarraf 1
M. Ali Darendeliler 1
0 Oxford University Hospitals, NHS Foundation Trust , Oxford 0X3 9DU , UK
1 Discipline of Orthodontics, Faculty of Dentistry, University of Sydney , Sydney , Australia
2 Eastman Dental Hospital, UCLH NHS Foundation Trust , London , UK
Background: Management of Class III malocclusion is one of the most challenging treatments in orthodontics, and several methods have been advocated for treatment of this condition. A new treatment protocol involves the use of an alternating rapid maxillary expansion and constriction (Alt-RAMEC) protocol, in conjunction with full-time Class III elastic wear and coupled with the use of temporary anchorage devices (TADs). The aim of this study was to evaluate the dento-skeletal and profile soft tissue effects of this novel protocol in growing participants with retrognathic maxilla. Methods: Fourteen growing participants (7 males and 7 females; 12.05 ± 1.09 years), who displayed Class III malocclusions with retrognathic maxilla, were recruited. Pre-treatment records were taken before commencing treatment (T1). All participants had a hybrid mini-implant-supported rapid maxillary expansion (MARME) appliance that was activated by the Alt-RAMEC protocol for 9 weeks. Full-time bone-anchored Class III elastics, delivering 400 g/side, were then used for maxillary protraction. When positive overjet was achieved, protraction was ceased and posttreatment records were taken (T2). Linear and angular cephalometric variables were blindly measured by one investigator and repeated after 1 month. An error measurement (Dahlberg's formula) study was performed to evaluate the intra-examiner reliability. A paired-sample t test (p < 0.05) was used to compare each variable from T1 to T2. Results: Treatment objectives were achieved in all participants within 8.5 weeks of protraction. The maxilla significantly protracted (SNA 1.87°± 1.06°; Vert.T-A 3.29± 1.54 mm p < 0.001), while the mandibular base significantly redirected posteriorly (SNB −2.03° ± 0.85°, Vert.T-B − 3.43± 4.47 mm, p < 0.001 and p < 0.05 respectively), resulting in a significant improvement in the jaw relationship (ANB 3.95°± 0.57°, p < 0.001; Wits 5.15± 1.51 mm, p < 0.001). The Y-axis angle increased significantly (1.95° ± 1.11°, p < 0.001). The upper incisors were significantly proclined (+ 2.98°± 2.71°, p < 0.01), coupled with a significant retroclination of the lower incisors (− 3.2°± 3.4°, p < 0.05). The combined skeletal and dental effects significantly improved the overjet (5.62± 1.36 mm, p < 0.001) and the soft tissue Harmony angle (2.75° ± 1.8°, p < 0.001). Conclusions: Class III elastics, combined with the Alt-RAMEC activation protocol of the MARPE appliance, is an efficient treatment method for mild/moderate Class III malocclusions. The long-term stability of these changes needs further evaluation.
The incidence of Class III malocclusions ranges from
]. The etiology of Class III malocclusions
can be categorized as either genetic or environmental
in origin [
]. The craniofacial characteristics of the
Class III malocclusion may be attributed to both a
positional and a dimensional disharmony of numerous
components of the craniofacial skeleton involving the
cranial base, the maxilla, and/or the mandible [
Ellis and McNamara [
], in their cephalometric sample
of 302 adult participants with Class III malocclusions,
found that 45.5% of their sample had maxillary
Treatment modalities range from dentofacial
orthopedic treatments using protraction facemasks [
camouflage orthodontic treatments to a combined
orthodontic jaw surgery. The extra-oral protraction face
mask (PFM) is the most efficient appliance for short- to
long-term use [
]. Rapid maxillary expansion (RME),
in conjunction with PFM, has been claimed to disrupt
circummaxillary sutures, which in turn might enhance
the skeletal effects [
]. By contrast, some evidence has
suggested that RME provides no benefit to the outcomes
of PFM [
An elaboration of the RME protocol, in which the
maxilla is alternately expanded and constricted
(AltRAMEC) in a weekly cycle, has been demonstrated to
produce a more pronounced “disarticulation” effect that
allows for a significant amount of maxillary protraction
in a considerably reduced amount of time [
welldesigned randomized clinical trial demonstrated that
PFM combined with the Alt-RAMEC protocol resulted
in significant maxillary protraction (0.93 mm, 95% CI,
− 1.65, − 0.20; p = 0.013) with minimal unwanted
clockwise rotation of the mandible (p < 0.05) when compared
with patients who underwent treatment with
conventional PFM and RME [
]. A case-controlled clinical
trial showed no statistically significant differences in
the cephalometric variables among participants who
had their facemask protraction commenced during an
Alt-RAMEC phase when compared with those whose
maxillary protraction started at the end of the
AltRAMEC cycle [
The modern incorporation of skeletal anchorage into
the discipline of orthodontics has led to its utilization
in the orthopedic treatment of Class III malocclusions.
The use of surgical plates has eliminated the need for
the cumbersome part-time extra-oral headgear
appliance, and the protraction is maintained full-time. A
recent systematic review suggested that maxillary
protraction anchored with a bone-anchorage device
induces more maxillary advancement with minimal
dental side effects when compared with tooth-anchored
]. Although efficient protraction of the
maxilla has been confirmed following the use of
surgical plates coupled with intermaxillary Class III elastics,
their insertion is undertaken under general anesthesia,
unlike temporary anchorage devices (TADs), which are
usually placed under local anesthesia [
No previous study has investigated the effectiveness
of the use of the Alt-RAMEC protocol in conjunction
with TAD-supported Class III elastic wear for
protraction of the maxilla. The aim of this study was to test
the null hypothesis that this new treatment protocol
will provide no statistically significant dento-skeletal
and profile soft tissue changes.
The study was registered with the Australia New Zealand
(ANZ) Clinical Trial Registry (ACTRN:12610000220066,
Ethical approval Number: X10-010). All participants from
the treatment waiting list of the Orthodontic Department
at Sydney Dental Hospital were screened. Initially, 42
growing participants were identified with Class III
malocclusions. Of these 42 selected participants, 14 (7 males and
7 females; 12.05 ± 1.09 years) met the inclusion criteria. As
the study is a case series analytical study, no sample size
calculation was undertaken. The inclusion criteria were:
Participants at Cervical Vertebral Maturational
(CVM) Stage 2 or 3 and
Participants with clinically diagnosed retrognathic or
hypoplastic maxilla, anterior crossbite, and dental
Class III molars and canines.
Participants with previous orthodontic/orthopedic
treatment or congenital abnormalities were excluded.
All records (T1) were taken in the centric relation
(CR) before commencing the intervention. A senior
clinician (OD) re-examined the participants to confirm
the inclusion criteria. Written informed consent was
obtained from the parents or guardians.
Appliance setup phase
Each participant had four TADs inserted under local
anesthesia (2% lignocaine with 1:80,000 adrenalin); two
were para-medial palatal TADs and two were
mandibular TADs that were inserted between the canine
and the lateral incisor (Fig. 1a). Before placement of
the TADs, the prospective implant site was swabbed
with 0.12% chlorhexidine solution.
In the lower arch, self-drilling 1.6 × 6 mm Aarhus™
(MediconeG, American Orthodontics) TADs were
placed at an approximately 30° apical angle. Insertion was
complete when the head of the TAD was flush with the
labial mucosa. The TADs chosen for the palatal placement
were 2 × 9 mm Mondeal™ (GAC) TADs. The area of the
palatal TAD placement was marked with a periodontal
probe. Pilot 1.5-mm holes were then created using a
surgical hand-piece (speed 800 rpm) under sodium chloride
irrigation until engagement was achieved. The palatal TADs
were then placed using a contra-angle handpiece (torque
setting of 35 Ncm, speed 30 rpm). A minimum clearance
of 5 mm between the two palatal TADs was chosen to
enable the placement of the impression caps. Healing caps
were then placed on the palatal TADs, and a 0.12%
chlorhexidine mouth rinse was prescribed for daily use
(Savacol, alcohol-free, Colgate).
One week later, molar bands were fitted around the
lower first molars, and alginate impressions were then
taken to construct a modified lingual arch (MLA). At
the same visit, the palatal healing caps were removed
and transfer impression copings were placed onto
them for the subsequent transfer-coping
polyvinylsiloxane (PVS) maxillary impressions. A medium-bodied
PVS impression was injected around the transfer
abutments, whereas the impression tray was filled with a
heavy-bodied PVS. An impression of the maxillary arch
was taken with the transfer abutments in place. After
impression-taking, the laboratory mini-implant
analogues were positioned on the impression transfer
abutments. The three-dimensional relationships of the
TADs in the oral cavity were thus duplicated on the
A hybrid mini-implant-assisted rapid maxillary expander
(Hybrid MARPE), using a Hyrax-screw that produces
0.25 mm per quarter turn, was then constructed. Ball
clasps (Romanium, Dentaurum) were embedded at the
region of the first premolars and first molars (Fig. 2a).
The Hybrid MARME was cemented with a glass
ionomer cement (GIC) on day 28 of the TAD insertion.
The MLA was constructed from 1 mm romanium wire
(Dentaurum, Australia) and cemented with GIC on day
28 after the TAD insertion. The lingual cleats that
extended from the MLA were bonded onto the lingual
surfaces of the anterior teeth with a composite resin to hold
the lower arch as one unit (Fig. 2b).
Fig. 2 a Hybrid MARPE and b MLA appliance design
The participant was instructed to expand the hybrid
MARME by 1 mm/day for 7 days (2 turns in the morning
and 2 turns in the evening). One week later, all
participants presented for expansion assessment; if satisfactory,
the participant was then instructed to constrict the maxilla
by unwinding the hybrid MARME by 1 mm/day (2 turns
in the morning and 2 turns in the evening) for 7 days. This
cycle was repeated until week 9. After 9 weeks of
alternating expansion and contraction, the mobility of the maxilla
was subjectively and manually assessed. This was done by
supporting the forehead and bridge of the participant’s
nose with one hand and holding the maxillary incisors
with the other. The maxilla was then moved in an anterior
and posterior direction to detect the mobility of the
maxilla. When sufficient mobility “disarticulation” was
achieved, the second phase (the protraction phase) of
Maxillary protraction phase
A 0.019″ × 0.025″ stainless steel (SS) wire was bent to fit
passively into the crossheads of the lower TADs on both
sides and was secured with a flowable composite to the
labial surface of the lower incisors. Two full-time heavy
intra-oral elastics per side, producing a total of 400 g/side,
were prescribed. The participant was instructed to change
the elastics once a day. One of these elastics ran in the
long-closing Class III configuration, from the posterior
ball clasps on the hybrid MARPE to the “S” hook. The
other one ran in the short-closing Class III configuration,
from the anterior hook on the hybrid MARPE to the
MLA (Fig. 1b). This configuration was adopted to prevent
counterclockwise rotation of the maxilla.
The participants were then assessed at 2-week
intervals until a + 2-mm overjet was achieved. Once the
overjet was corrected, the appliances were removed, and
post-treatment records were then taken (T2).
One investigator blindly traced all the cephalograms
using the Dolphin software. In addition to measuring
the overjet changes as a primary outcome, the secondary
outcomes included skeletal, dental, and soft tissue
cephalometric measurements, as well as some of the recently
described stable basicranial linear horizontal
] (Fig. 3 and table 1). The intra-examiner
reliability was assessed by repeating all the cephalometric
measurements after 1 month.
The cephalometric data were analyzed statistically using
the Statistical Package for Social Sciences (SPSS, ver.
17.0, SPSS Inc., Chicago, Illinois). The sample was
normally distributed for most parameters, as determined
using the Kolmogorov Smirnov test; hence, a
pairedsample t test (p < 0.05) was used to compare each
variable from T1 to T2. An error measurement (Dahlberg’s
formula) study was performed to evaluate the
One mandibular TAD was lost but was replaced during
the Alt-RAMEC phase. Another participant fractured the
buccal attachment on the MLA, but this was repaired
during elastic loading. Regardless, the aims of the treatment
intervention were achieved in all participants over a period
of 8.5 weeks of protraction (range 8–9 weeks) (Fig. 4).
Method errors were not statistically significant (p > 0.05),
for both linear and angular measurements, at 0.98 mm
and 0.87°, respectively. The pre-expansion (T1) and
postprotraction (T2) cephalometric measurements are
summarized in Table 1.
At the skeletal level, both angular (Sella-Nasion to
A (SNA) 1.87± 1.06 mm) and linear (Vert.T-A 3.34 ±
1.54 mm) measurements of the anteroposterior position
of the maxilla showed a significant protraction (p < 0.001).
Similarly, the mandible position was significantly
improved (Vert.T-B − 3.43± 4.47 mm, p < 0.05; Sella-Nasion
to B (SNB) − 2.02 ± 0.85, p < 0.001). A marked
improvement was evident in the ANB angle (3.95° ± 0.57°,
p < 0.001) and Wits measurement (5.16± 1.5 mm, p <
0.001). The significant increase in the Y-axis (1.95° ±1.22°,
p < 0.001), coupled with a significant increase in the lower
third (ANS-Me) of 3.19± 2.2 mm (p < 0.001), indicated a
clockwise rotation of the mandible. However, no
significant increase was noted in the middle facial height
(NANS) (0.32± 1.53 mm, p = 0.45).
At the dental level, the upper incisors proclined
significantly (UI-PP = 2.98° ± 2.71°, p < 0.005) coupled with
a significant retroclination of the lower incisors
(LIMP = 3.2°± 3.4°, p < 0.05). The combined dental and
skeletal changes led to a significant improvement in the
overjet and overbite, at 5.62 ± 1.36 mm (p < 0.001) and
− 1.21± 1.89 mm (p < 0.05), respectively.
Furthermore, cephalometric soft tissue profile analysis
showed a significant increase in the H angle, at 2.76± 1.8
(p < 0.001).
The recommended starting age for maxillary protraction
therapy for a good orthopedic effect is the prepubertal
]. Nevertheless, the participants in this
study (aged 12.05 ± 1.09 years) responded positively, with
a mean treatment time of approximately 8.5 weeks.
The Alt-RAMEC protocol was utilized to produce a
more pronounced disarticulation of the maxilla than can
be obtained using conventional maxillary expansion [
The mean maxillary protraction was significantly greater
than the outcomes reported in the previous literature
21, 24, 25
]. This could be attributed to a combination
of the disarticulation effect of the Alt-RAMEC protocol
and/ or the full-time utilization of the heavy Class III
elastics which were partially tooth-bone-anchored.
Similarly, the anteroposterior mandibular position was
significantly improved secondary to the intervention, again
probably due to the full-time utilization of the Class III
elastics. The argument might be made that the changes
in the SNB and therefore ANB were surpassed as a
result of the elimination of mandibular functional
displacement secondary to the intervention however the
main aim of our class III correction was to improve the
maxillary position nevertheless taking records at the
RCP could induce another inherent pseudo-increase in
the facial height.
A posterior rotation of the mandible and an increase in
the anterior facial height are common treatment
biomechanical effects of the PFM treatment [
Similar changes were observed in this study in the form of
significant increases in the lower facial height and Y-axis.
The maxillary protraction protocol partially utilized
the dentition for the transmission of the forces to the
underlying skeletal structures, including the maxilla and
the mandible. This led to the unwanted effects
represented by proclination of the upper incisors and
retroclination of the lower incisors, as reported in other studies
]. Therefore, correction of the malocclusion was
due to the combination of skeletal and dentoalveolar
The skeletal and dentoalveolar changes observed in
our study resulted in an overall normalization of the
unesthetic facial concavity. This was seen as a significant
reduction in the H angle of these participants. For a
clinical demonstration, the treatment records are presented
for one of the participants enrolled in this study (Fig. 5).
Limitations of the study and future research
An argument can be made that the wide standard
deviation of SNA angles could increase the level of
uncertainty. This might be attributed to individual
variations in response to the treatment and/or errors in
One of the aims of using TADs in our treatment
protocol was to reduce the unwanted dentoalveolar side
effects; however, proclination of the upper incisors and
retroclination of the lower incisors were unavoidable.
This could be a result of the inherent flexibility of the
vertical arms that connect the lower TADs to the
mandibular incisors, as this may have allowed wire flexion
under the effect of the heavy inter-maxillary elastics,
thereby allowing for retroclination of the lower incisors.
Similarly, the arms that connect the palatal TADs to the
acrylic pads of the hybrid MARPE may have flexed
under the protractive effect of the Class III elastics,
allowing for proclination of the maxillary incisors.
One of the difficulties in using this treatment
protocol is the delicateness of implant appliance placement,
as the slightest error in appliance
impression/construction makes it difficult to issue the expander with palatal
TADs. An alternative would be to design a new hybrid
MARPE system that would permit the cementation of
the expander with hooks for class III elastic placement
first, followed by insertion of the TADs. Another
drawback of this novel treatment approach is participant
compliance with performing the expansion and
constriction of the maxilla and the daily interchange of the
elastics. Future developments may involve an expander
that expands and contracts itself, as per a particular
protocol, plus the development of intra-oral nickel
titanium springs to minimize the participant’s
compliance. Alternatively, magnets can be used to provide the
The authors acknowledge that the sample size of this
study is too small to comment on the validity of the use
of this novel approach in treating Class III malocclusion
compared to other established methods. A future
direction of the study would be to compare this treatment
modality with other treatment approaches using a
longterm randomized clinical trial.
Bone-anchored Class III protraction using MARPE and
miniscrew supported lower lingual arch and Alt-RAMEC
protocol, is an efficient first phase treatment for Class III
malocclusions. Correction was achieved through a
combination of skeletal, and dentoalveolar effects. However, a
long-term randomized clinical trial with a larger sample
size is recommended for verification.
The authors would like to acknowledge Dr. Peter Petocz (Department of
Mathematical Sciences, Macquarie University) for his support and advice, the
American Orthodontics for their generosity in the donation of materials and
equipment used during the study, and the Australian Society of
Orthodontics Foundation for Research and Education for their continued
support for the study.
SA treated the patients. SA, OD, CG, and NT participated in the design and
coordination of the study, carried out the sample collection, and made
substantial contributions to analysis and interpretation of data. MA made
substantial contributions to the interpretation of data and was involved in
revising the study critically. AD conceived the study, participated in the design
and coordination of the study, and made substantial contributions to analysis
and interpretation of data. All authors drafted the manuscript and read and
approved the final manuscript.
Ethics approval and consent to participate
The study was registered with the Australia New Zealand (ANZ) Clinical Trial
Registry (ACTRN:12610000220066, Ethical approval Number: X10-010).
Consent for publication
Written informed consent was obtained from the patients for publication of
this research and accompanying images.
The authors declare that they have no competing interests.
Springer Nature remains neutral with regard to jurisdictional claims in
published maps and institutional affiliations.
1. Ast DB , Carlos JP , Cons NC . The prevalence and characteristics of malocclusion among senior high school students in upstate New York . Am J Orthod . 1965 ; 51 : 437 - 45 .
2. Krogman WM . The problem of “timing” in facial growth, with special reference to the period of the changing dentition . Am J Orthod . 1951 ; 37 : 253 - 76 .
3. Jacobson A , Evans WG , Preston CB , Sadowsky PL . Mandibular prognathism . Am J Orthod . 1974 ; 66 : 140 - 71 .
4. Guyer EC , Ellis EE , McNamara JA , Behrents RG . Components of Class III malocclusion in juveniles and adolescents . Angle Orthod . 1986 ; 56 : 7 - 30 .
5. Battagel JM . The aeitiological factors in Class III malocclusion . Eur J Orthod . 1993 ; 15 : 347 - 70 .
6. Tollaro I. Class III malocclusions in the deciduous dentition: a morphological and correlation study . Eur J Orthod . 1994 ; 16 : 401 - 8 .
7. Ellis Iii E , McNamara JA Jr. Components of adult Class III malocclusion . J Oral Maxillofac Surg . 1984 ; 42 : 295 - 305 .
8. Baccetti T , McGill JS , Franchi L , McNamara JJA , Tollaro I. Skeletal effects of early treatment of Class III malocclusion with maxillary expansion and face-mask therapy . Am J Orthod Dentofac Orthop . 1998 ; 113 : 333 - 43 .
9. Watkinson S , Harrison JE , Furness S , Worthington HV : Orthodontic treatment for prominent lower front teeth (Class III malocclusion) in children . 2013 .
10. Mandall N , DiBiase A , Littlewood S , Nute S , Stivaros N , McDowall R , Shargill I , Worthington H , Cousley R , Dyer F. Is early class III protraction facemask treatment effective? A multicentre, randomized, controlled trial: 15-month follow-up . J Orthod . 2010 ; 37 : 149 - 61 .
11. Anne Mandall N , Cousley R , DiBiase A , Dyer F , Littlewood S , Mattick R , Nute S , Doherty B , Stivaros N , McDowall R . Is early class III protraction facemask treatment effective? A multicentre, randomized, controlled trial: 3-year follow-up . J Orthod . 2012 ; 39 : 176 - 85 .
12. Haas AJ . Palatal expansion: just the beginning of dentofacial orthopedics . Am J Orthod . 1970 ; 57 : 219 - 55 .
13. Vaughn GA , Mason B , Moon H-B , Turley PK . The effects of maxillary protraction therapy with or without rapid palatal expansion: a prospective, randomized clinical trial . Am J Orthod Dentofac Orthop . 2005 ; 128 : 299 - 309 .
14. Liou EJ-W. Effective maxillary orthopaedic protraction for growing Class III patients: a clinical application simulated distraction osteogenesis . Prog Orthod . 2005 ; 6 : 154 - 71 .
15. Liu W , Zhou Y , Wang X , Liu D , Zhou S . Effect of maxillary protraction with alternating rapid palatal expansion and constriction vs expansion alone in maxillary retrusive patients: a single-center, randomized controlled trial . Am J Orthod Dentofac Orthop . 2015 ; 148 : 641 - 51 .
16. Canturk BH , Celikoglu M. Comparison of the effects of face mask treatment started simultaneously and after the completion of the alternate rapid maxillary expansion and constriction procedure . Angle Orthod . 2014 ; 85 : 284 - 91 .
17. Feng X , Li J , Li Y , Zhao Z , Zhao S , Wang J . Effectiveness of TAD-anchored maxillary protraction in late mixed dentition: a systematic review . Angle Orthod . 2012 ; 82 : 1107 - 14 .
18. De Clerck HJ . Orthopaedic traction of the maxilla with miniplates: a new perspective for treatment of midface deficiency . J Oral Maxillofac Surg . 2009 ; 67 : 2123 - 9 .
19. Toffol LD , Pavoni C , Baccetti T , Franchi L , Cozza P. Orthopedic treatment outcomes in Class III malocclusion . Angle Orthod . 2008 ; 78 : 561 - 73 .
20. Cha K-S. Skeletal changes of maxillary protraction in patients exhibiting skeletal Class III malocclusion: a comparison of three skeletal maturation groups . Angle Orthod . 2003 ; 73 : 26 - 35 .
21. Merwin D , Ngan P , Hagg U , Yiu C , SHY W. Timing for effective application of anteriorly directed orthopedic force to the maxilla . Am J Orthod Dentofac Orthop . 1997 ; 112 : 292 - 9 .
22. Baccetti T , Franchi L , McNamara JJA . The cervical vertebral maturation (CVM) method for the assessment of optimal treatment timing in dentofacial orthopedics . Semin Orthod . 2005 ; 11 : 119 - 29 .
23. Melsen B . Palatal growth studied on human autopsy material: a histologic microradiographic study . Am J Orthod . 1975 ; 68 : 42 - 54 .
24. Sung SJ , Baik HS . Assessment of skeletal and dental changes by maxillary protraction . Am J Orthod Dentofac Orthop . 1998 ; 114 : 492 - 502 .
25. Kapust AJ , Sinclair PM , Turley PK . Cephalometric effects of face mask/ expansion therapy in Class III children: a comparison of three age groups . Am J Orthod Dentofac Orthop . 1998 ; 113 : 204 - 12 .
26. Ngan P , Cheung E , Wei SHY . Comparison of protraction facemask response using banded and bonded expansion appliances as anchorage . Semin Orthod . 2007 ; 13 : 175 - 85 .
27. Hata S , Itoh T , Nakagawa M , Kamogashira K , Ichikawa K , Matsumoto M , Chaconas SJ . Biomechanical effects of maxillary protraction on the craniofacial complex . Am J Orthod Dentofac Orthop . 1987 ; 91 : 305 - 11 .
28. Chong Y-H , Ive JC , Artun J . Changes following the use of protraction headgear for early correction of Class III malocclusion . Angle Orthod . 1996 ; 66 : 351 - 62 .
29. Kajiyama K , Murakami T , Suzuki A . Comparison of orthodontic and orthopedic effects of a modified maxillary protractor between deciduous and early mixed dentitions . Am J Orthod Dentofac Orthop . 2004 ; 126 : 23 - 32 .