Intraoral distalizer effects with conventional and ... · Bauru, S~ao Paulo, Brazil Introduction:...

SYSTEMATIC REVIEW

Intraoral distalizer effects with conventional andskeletal anchorage: A meta-analysis

Roberto Henrique da Costa Grec,a Guilherme Janson,b Nuria Castello Branco,a Patr�ıcia Garcia Moura-Grec,c

Mayara Paim Patel,a and Jos�e Fernando Castanha Henriquesb

Bauru, S~ao Paulo, Brazil

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Introduction: The aims of this meta-analysis were to quantify and to compare the amounts of distalization andanchorage loss of conventional and skeletal anchorage methods in the correction of Class II malocclusion withintraoral distalizers.Methods: The literature was searched through 5 electronic databases, and inclusion criteriawere applied. Articles that presented pretreatment and posttreatment cephalometric values were preferred.Quality assessments of the studies were performed. The averages and standard deviations of molar and premo-lar effects were extracted from the studies to perform a meta-analysis. Results: After applying the inclusion andexclusion criteria, 40 studies were included in the systematic review. After the quality analysis, 2 articles wereclassified as high quality, 27 as medium quality, and 11 as low quality. For the meta-analysis, 6 studies wereincluded, and they showed average molar distalization amounts of 3.34 mm with conventional anchorage and5.10 mm with skeletal anchorage. The meta-analysis of premolar movement showed estimates of combinedeffects of 2.30 mm (mesialization) in studies with conventional anchorage and �4.01 mm (distalization) instudies with skeletal anchorage. Conclusions: There was scientific evidence that both anchorage systemsare effective for distalization; however, with skeletal anchorage, there was no anchorage loss when direct an-chorage was used. (Am J Orthod Dentofacial Orthop 2013;143:602-15)

For Class II malocclusion, several forms ofcorrection produce different dental and skeletaleffects depending on the type of treatment.1

When the problems of this malocclusion are predomi-nantly skeletal, it is likely to be corrected by functionalor mechanical orthopedic appliances. However, toachieve satisfactory results, these protocols usuallyrequire patient compliance in using the appliances.2-4

Lack of compliance can increase treatment time andcreate an uneasy relationship between parents, patient,and doctor, thus compromising the final treatmentresult.3 When the problems of Class II malocclusionsare predominantly dental, these malocclusions can becorrected by extractions in at least 1 dental arch,5,6

without extractions by using intermaxillary elastics,7,8

Bauru Dental School, University of S~ao Paulo, Bauru, S~ao Paulo, Brazil.raduate student, Department of Orthodontics.ssor, Department of Orthodontics.raduate student, Department of Public Health.uthors report no commercial, proprietary, or financial interest in thecets or companies described in this article.t requests to: Roberto Henrique da Costa Grec, Department of Orthodon-auru Dental School, University of S~ao Paulo, Alameda Oct�avio Pinheirola 9-75, Bauru, SP 17012-901, Brazil; e-mail, [email protected], June 2012; revised and accepted, November 2012.5406/$36.00ight � 2013 by the American Association of Orthodontists./dx.doi.org/10.1016/j.ajodo.2012.11.024

or by distalizing the maxillary molars to create a Class Irelationship.9

For several years, the extraoral appliance was the mostwidely used distalizing device, but it is no longer estheti-cally acceptable. Also, it is removable and depends on pa-tient compliance, which can compromise the results.2-4

Therefore, as alternatives to compliance-dependentheadgear, many intraoral methods to distalize the maxil-lary molars have been proposed, such as repelling mag-nets,10 distal jet appliance,11 Jones jig appliance,12

nickel-titanium coil springs,13 pendulum and pendex ap-pliances,14,15 Wilson bimetric distalizing arch system(RockyMountain Orthodontics, Denver, Colo),16 first classappliance (Leone, Firenze, Italy),17 and others, givingclinicians a wide variety of treatment options.

Intraoral appliances have proven to be effective formaxillary molar distalization independently of patientcompliance.3 However, distalizers generally use theNance button as anchorage, but it is not enoughto neutralize the side effects of anchorage loss,18

represented by maxillary anterior crowding, maxillaryincisor labial inclination increasing the overjet, andtipping of premolars and canines.19-25

To prevent anchorage loss, mini-implants can beused as an efficient skeletal anchorage unit for molardistalization, decreasing the side effects with more

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http://dx.doi.org/10.1016/j.ajodo.2012.11.024

Table I. PICO format

Population Subjects with Class II malocclusionIntervention Intraoral distalizers with conventional anchorageComparison Intraoral distalizers with skeletal anchorageOutcome Efficiency in the correction of Class II malocclusion

Grec et al 603

predictable results and less treatment time, andconsequently creating a new perspective in intraoraldistalizer appliances.26,27

Previously, 2 systematic reviews on the use ofnoncompliance distalizing intramaxillary applianceswith conventional anchorage and skeletal anchoragewere performed.28,29 However, there is still nocomparison between the efficiency of these 2techniques of anchorage.

The aims of this meta-analysis were to quantify andto compare the amounts of molar distalization andanchorage loss of conventional and skeletal anchoragemethods in the correction of Class II malocclusion withintraoral distalizers.

MATERIAL AND METHODS

This systematic review/meta-analysis was based onthe PRISMA guidelines, and the main question wasdefined with the PICO format (Table I).30 Usingthe main terms distalizers, distalization appliance,orthodontic distalization, noncompliance appliances,first molar distalization, upper molar distalization,and maxillary molar distalization, an electronic searchwas conducted from 1970 to September 2010 in thefollowing databases: PubMed, Embase, Web of Science,Scopus, and Cochrane Library (Table II).

To identify potential articles, the initial search wasperformed by title and abstract. Initially, the selectedarticles were preferred to have the following inclusioncriteria: published in English, human clinical trial, re-garding the correction of Class II malocclusion with non-compliance molar distalization appliances, no reviews oropinion articles, no annals, and no theses. Duplicatestudies were eliminated. The selection process wasindependently conducted by 2 researchers (R.H.C.G.and M.P.P.), and their results were compared to identifydiscrepancies.

When the abstract did not provide enough informa-tion to make a decision, the article was completelyanalyzed. Interexaminer conflicts were resolved bydiscussion of each article to reach a consensus regardingall selection criteria. Furthermore, hand searches of thereference lists of the selected articles were conducted.

At this stage, the previously selected articles wererescreened according to the following additionalinclusion criteria: correction of Class II malocclusionwith a noncompliance molar distalization appliancewithout concomitant use of other appliances, descrip-tion of measurable pretreatment and posttreatmentcephalometric variables, measurement of the amountof first or second premolar anchorage loss (mesialmovement), minimum of 10 patients in each samplegroup, no case reports, and growing patients.

American Journal of Orthodontics and Dentofacial Orthoped

The quality of each article was scored by using anadapted version of 3 methods previously used by Fudalejand Antoszewska,29 Cozza et al,31 and Chen et al.32 Thefollowing characteristics were evaluated: study design,sample size, sample description, error analysis, andstatistical analysis. Each characteristic received a scoreaccording to the criteria described in Table III. Thequality of each study was categorized as high (7-9points), medium (4-6 points), or low (0-3 points).

The data from the selected articles were divided into 2groups according to the type of anchorage used:conventional or skeletal. There was no distinctionbetween the different types of distalizers.

A meta-analysis was performed according toa method proposed by Antonarakis and Kiliaridis28 andPerillo et al.33 Data from each group (conventional andskeletal anchorage) were individually compared witha control group in which the average was zero. Amonguntreated subjects, these variables are about zerobecause of the short time of distalization.28 The standarddeviation is equal to the method error in the correspond-ing study. In studies that did not mention the methoderror, the mean error from studies that gave the datawas used. Only articles of medium and high qualitywere included in the meta-analysis. The averages andstandard deviations of molar and premolar movementswere extracted from the articles and subsequentlyentered into RevMan software (version 5.0 for Windows;Nordic Cochrane Centre, Copenhagen, Denmark) toperform the meta-analysis.

Heterogeneity was assessed by calculating the I2

index. If there was evidence of heterogeneity, therandom effects model should be used.33-35 Forest plotswere drawn, mean and confidence interval values werecalculated (95% confidence interval), and significancetests were carried out (to calculate P values).

RESULTS

After the electronic database search, 947 studies wereretrieved from PubMed, 138 from Embase, 151 fromWeb of Science, and 185 from Scopus. No studies wereidentified from the Cochrane Library (Fig 1). After appli-cation of the initial inclusion and exclusion criteria andelimination of studies indexed in more than 1 database,178 were retrieved. The full texts were accessed, and allarticles with adult patients (age,$18 years), sample size

ics May 2013 � Vol 143 � Issue 5

Table II. Search strategy

Database Key words LimitsPubMed Distalizers OR distalization appliance OR orthodontic distalization

OR noncompliance appliances OR first molar distalization ORupper molar distalization OR maxillary molar distalization

English language; humans, 1970 to September2010

Embase Distalizers OR distalization appliance OR orthodontic distalizationOR noncompliance appliances OR first molar distalization ORupper molar distalization OR maxillary molar distalization

Only English; humans, 1970 to September 2010

Web of Science Distalizers OR distalization appliance OR orthodontic distalizationOR noncompliance appliances OR first molar distalization ORupper molar distalization OR maxillary molar distalization

English language; only articles (not reviews, letters,abstracts, meetings, and editorials);1970 toSeptember 2010

Scopus Distalizers OR distalization appliance OR orthodontic distalizationOR noncompliance appliances OR first molar distalization ORupper molar distalization OR maxillary molar distalization

English language; only articles (not reviews, letters,abstracts, meetings, and editorials);1970 toSeptember 2010

Cochrane Library Distalizers; distalization and appliance; orthodontic anddistalization; noncompliance and appliances, first and molar anddistalization; upper and molar and distalization; maxillary andmolar and distalization

Table III. Methodologic quality scoring protocol(maximum score, 9 points)

Study design3 points: randomized clinical trial2 points: if randomization process was not well described,or if it was a controlled prospective study

1 point: uncontrolled prospective study0 point: retrospective study or not mentioned

Sample size1 point: larger than or equal to 15 subjects or priorestimate of sample size

0 point: less than 15 subjects and no prior estimateof sample size

Sample description2 points: description of all 3 items (age, sex, Class IImalocclusion severity)

1 point: only 2 items described0 point: only 1 item described

Error analysis1 point: error analysis value cited0 point: error analysis value not cited, or error analysis notperformed

Statistical analysis2 points: adequate1 point: partially adequate0 point: no statistical tests conducted

604 Grec et al

less than 10 in at least 1 group, no evaluation of anchor-age loss through premolar mesial movement and oflateral cephalometric radiographs taken immediatelyafter molar distalization, and measurements of onlydental casts were excluded. Therefore, 40 studies fulfill-ing all inclusion and exclusion criteria were included inthis systematic review (Fig 1).

From the remaining articles, we independentlyextracted the following data: author names, year ofpublication, anchorage method, type of distalizingappliances, sample size, mean age of groups, distalizer

May 2013 � Vol 143 � Issue 5 American

treatment time, and amounts of molar and premolardistalization and tipping.

Molar distalization with conventional anchorage wasevaluated in 36 studies, and with skeletal anchorage in 6.Two studies evaluated both types of anchorage and weretherefore subdivided and separately inserted in thetable.36,37 The summarized data of the 40 articlesincluded in the review are shown in Table IV.

Quality assessment

After quality analysis, 2 articles were classified as highquality, 27 as medium quality, and 11 as low quality(Table V).

Among the high-quality articles, only that byPapadopoulos et al9 received a full score. These authorsevaluated the treatment effects of the first classappliance in patients with Class II malocclusion in themixed dentition. The study was a randomized clinicaltrial with a sample of 15 treated children (mean age,9.2 years). Another 11 subjects served as the controlgroup (mean age, 9.7 years). The first class appliancewas placed on the 2 maxillary first molars and the seconddeciduous molars or the second premolars. A modifiedNance butterfly-shaped button was used as anchorage.The mean molar distal movement was 4 mm with distaltipping of 8.56� in 4.01 months. The mean premolar orfirst deciduous molar mesial movement was 1.86 mm(31.84% of anchorage loss) with 1.85� of tipping. Thecontrol group showed distal molar movement of 0.04mm in the same period.9

The other study classified as high quality comparedthe dentoalveolar changes of Class II patients treatedwith the Jones jig and the pendulum appliances.25 FortyClass II malocclusion patients were divided into 2 groupsof 20. Group 1 (11 boys, 9 girls), with a mean

Journal of Orthodontics and Dentofacial Orthopedics

Fig 1. PRISMA flow diagram.

Grec et al 605

pretreatment age of 13.17 years, was treated with theJones jig appliance for 0.91 years, and group 2 com-prised 20 patients (8 boys, 12 girls) with a mean pretreat-ment age of 13.98 years, treated with the pendulumappliance for 1.18 years. The maxillary second premolarsshowed greater mesial tipping and extrusion in the Jonesjig group, indicating more anchorage loss during molardistalization with this appliance. The amounts and themonthly rates of molar distalization were similar inboth groups.

According to each criterion for quality analysis, thefollowing results were obtained.

Study design: only 2 studies were randomized clinicaltrialswith the randomizationprocess described indetail.9,38

Sample size: the authors of 30 studies performedsample-size calculation or had sample sizes larger thanor equal to 15 patients.

Selection description: 7 studies mentioned theseverity of the malocclusions.9,19,23,25,39-41 One article


did not mention the mean age,36 and 2 articles did notmention the sex of the sample.24,42

Error analysis: the authors of 24 studies performedand described the method error results. Some studiesstated that the error of the method was performed butdid not present the results.3,20-22,24,36,38,43-45

Statistical analyses: the authors of 4 studiesperformed only a descriptive analysis.3,18,24,46

Maxillary molar distalization appliances withconventional anchorage

Treatment effects of distalizers with conventionalanchorage were analyzed in 43 groups assessed in 36studies (Table IV).

Fourteen distalizers were used: first class, pendu-lum, distal jet, Jones jig, dual force, Keles slider,greenfield, jig appliance modified, pendex, 3-dimensional bimetric maxillary distalizing arch(3D-BMDA), intraoral bodily molar distalizer (IBMD),


Table IV. Characteristics of included studies

Number Study Appliance Anchorage nConventional anchorage1 Papadopoulos et al,9 2010 First class Nance button 152 Acar et al,47 2010 Pendulum Nance button 153 Haq et al,78 2010 Distal jet Nance button 304 Patel et al,25 2009 Jones jig Nance button 205 Patel et al,25 2009 Pendulum Nance button 206 Polat-Ozsoy et al,37 2008 Pendulum Nance button 177 Sch€utze et al,79 2007 Pendulum Nance button 158 €Onca�g et al,36 2007 Pendulum Nance button 159 Angelieri et al,19 2006 Pendulum Nance button 22

10 Fuziy et al,23 2006 Pendulum Nance button 3111 Mavropoulos et al,46 2006 Keles slider Nance button 2012 Sayinsu et al,80 2006 Keles slider Nance button 1713 Chiu et al,22 2005 Pendulum Nance button 3214 Chiu et al,22 2005 Distal jet Nance button 3215 Kinzinger et al,73 2005 Pendulum Nance button 1016 Kinzinger et al,73 2005 Pendulum Nance button 1017 Kinzinger et al,73 2005 Pendulum Nance button 1018 Mavropoulos et al,18 2005 Jones jig Nance button 1019 Ferguson et al,81 2005 Distal jet Enlarged acrylic Nance button 2520 Ferguson et al,81 2005 Greenfield Enlarged acrylic Nance button 2521 Fortini et al,82 2004 First class Modified acrylic Nance button 1722 Papadopoulos et al,40 2004 Jig appliance modified Modified acrylic Nance button 1423 Taner et al,83 2003 Pendex Nance button 1324 Bolla et al,84 2002 Distal jet Nance button 2025 Paul et al,38 2002 Jones jig Nance button 1126 Nishii et al,85 2002 Distal jet Nance button 1527 Chaqu�es-Asensi and Kalra,86 2001 Pendulum Nance button 2628 Ngantung et al,39 2001 Distal jet Nance button 3329 Keles,43 2001 Keles slider Nance button with an anterior bite plane 1530 Toro�glu et al,48 2001 Pendulum Nance button 1431 Toro�glu et al,48 2001 Pendulum Nance button 1632 Bussick and McNamara,21 2000 Pendulum Nance button 10133 €Ucem et al,41 2000 3D-BMDA Intermaxillary elastic system 1434 Brickman et al,20 2000 Jones jig Nance button 7235 Haydar and €Uner,24 2000 Jones jig Nance button 1036 Keles and Sayinsu,3 2000 IBMD Nance button 1537 Bondemark,87 2000 Nickel-titanium coil Nance button 2138 Bondemark,87 2000 Repelling magnets Nance button 2139 Runge et al,45 1999 Jones jig Nance button 1340 Gulati et al,42 1998 Sectional jig assembly Nance button 1041 Byloff and Darendeliler,57 1997 Pendulum Nance button 1342 Byloff et al,88 1997 Pendulum Nance button 2043 Ghosh and Nanda,58 1996 Pendulum Nance button 41Skeletal anchorage1 Kinzinger et al,44 2009 Distal jet 2 mini-implants 102 Oberti et al,51 2009 Dual force 2 mini-implants used in maxillofacial

surgery for osteosynthesis 1 Nance button16

3 Polat-Ozsoy et al,37 2008 Pendulum 1 or 2 mini-implants 1 Nance button 224 €Onca�g et al,36 2007 Pendulum 1 implant 155 Escobar et al,49 2007 Pendulum 2 mini-implants 1 Nance button 156 Kircelli et al,50 2006 Pendulum 1 or 2 mini-implants 1 Nance button 10

606 Grec et al

nickel-titanium coil, magnets, and sectional jigassembly. The pendulum appliance was the mostused (22 articles), followed by the distal jet (7 articles)


and the Jones jig (6 articles). The most used anchoragereinforcement appliance was the Nance button and itsvariations (Table IV).


Table IV. Continued

Average age (y)Distalization

treatment time (mo)Molar

distalization (mm) Molar tipping (�)Premolar

movement (mm)Premolartipping (�)

Conventional anchorage9.2 4.3 �4 �8.56 1.86 1.85

15.0 3 �4.53 �5.13 0.27 2.212.8 7.11 �2.93 �3.41 0.95 7.3313.2 10.92 �3.12 �9.54 2.55 9.2913.9 14.16 �3.51 �10 2.23 2.3713.6 5.1 �2.7 �5.3 2.3 3.812.6 8.46 �3.83 �6.45 1.18 �1.94– 7.25 �5.03 �6 2.16 2.98

14.5 5.85 �2 �9.4 3.6 6.614.6 5.87 �4.6 �18.5 2.65 2.513.1 4.37 �3.1 �4 3.2 6.113.5 – �2.85 �2.56 2 2.2112.5 7 �6.1 �10.7 1.4 �1.712.3 10 �2.8 �5 2.6 0.39.9 6.22 �3.93 �6.35 1.05 0.7

11.6 4.45 �3.43 �5.05 1.4 �0.412.6 5.95 �4.20 �2.55 0.8 �1.813.2 4.37 �1.9 �6.8 2.08 7.512.5 7.87 �3.4 �3.2 1 3.111.5 10.4 �3.9 �6.5 2.9 0.213.4 2.4 �4.0 �4.6 1.7 2.213.4 4.12 �1.4 �6.8 2.6 8.110.6 7.31 �3.81 �11.77 0.73 4.0812.6 5 �3.2 �3.1 1.3 2.814.8 6 �1.17 �4.56 0.18 –

14.6 6.4 �2.4 �1.9 1.4 –

11.2 6.5 �5.3 �13.06 2.21 4.8412.8 6.7 �2.12 �3.26 2.6 �4.3313.3 6.1 �4.92 �0.89 1.31 1.2513.1 5.7 �5.9 �14.9 4.8 3.912.9 5.03 �4.1 �13.4 6.6 5.912.0 7 �5.7 �10.6 1.8 1.512.2 1.5 �3.5 �1.8 2.1 1.413.7 6.35 �2.51 �7.53 2 4.7610.7 2.5 �2.80 �7.85 3.35 6.0513.5 7.5 �5.23 �1.15 4.33 �2.7314.4 6.5 �2.5 �2.2 1.2 2.113.9 5.8 �2.6 �8.8 1.8 6.714.5 6.5 �2.23 �4 2.23 9.4712-15 4 �2.95 �3.5 1.05 2.611.1 4.15 �3.39 �14.5 1.63 –

13.1 6.81 �4.14 �6.07 2.22 –

12.4 6.2 �3.37 �8.36 2.55 1.29Skeletal anchorage

12.1 6.7 �3.92 �3 0.72 0.7914.3 5 �5.9 �5.68 �4.26 �5.43

13.6 6.8 �4.8 �9.1 �4.1 �9.9– 6.75 �3.95 �12.2 �3.1 �6.795

13.0 7.8 �6.00 �11.31 �4.85 �8.6213.5 7 �6.4 �10.9 �5.4 �16.3

Grec et al 607

The included studies evaluated patients during thegrowth period, and the mean initial chronologic age


ranged from 9.29 to 1547 years. Treatment times were1.50 to 14.16 months.


608 Grec et al

Molars demonstrated distal movements from 1.17 to6.10 mm with conventional anchorage. The pendulumappliance showed the greatest distalization in 7months.22 The least distalization was obtained withthe Jones jig in 6 months.38 The greatest molar distaltipping was 18.5�,23 and the least was 0.89�.43

Anchorage loss could be identified in the studies withconventional anchorage through premolar movement,which showed positive values indicating mesialmovement. These values ranged from 0.27 mm in 3months47 to 6.6 mm in 5 months48 with the pendulumappliance. The greatest premolar mesial tipping was9.47� observed in the study of Runge et al.45

Maxillary molar distalization appliances withskeletal anchorage

In 6 studies, the treatment effects of distalizers withskeletal anchorage were analyzed. Four studies used thependulum appliance to distalize the maxillarymolars,36,37,49,50 one used the distal jet,44 and the otherused the dual force.51 One36,37,50 or 237,44,49,51 implantsor mini-implants were used in the paramedian region ofthe midpalatal suture as anchorage. The screw wasconnected to an acrylic plate37,49-51 except in thestudies of Kinzinger et al44 and €Onca�g et al36 (Table IV).

The mean initial chronologic age ranged from 12.144

to 14.351 years. One study did not report the mean initialage.36 Treatment time ranged from 5.051 to 7.849

months.Themeanmolar distalmovement ranged from3.944 to

6.450mm, and themeanmolar distal tipping ranged from3.0�44 to 12.2�.39 The greatest distalization was obtainedwith the pendulum and the smallest with the distal jet.

Studies with mini-implant anchorage showednegative values for premolar movement (�3.1 to �5.4mm) indicating distal movement of these teeth and noanchorage loss. Only the study of Kinzinger et al44

showed mesial movement (0.72 mm) and mesial tipping(0.79�) of premolars, indicating anchorage loss evenwhen associated with mini-implants.

No article with skeletal anchorage was classified ashigh quality, 4 were classified as medium quality, and2 had low quality (Table V).

Meta-analysis

After we assessed the quality of the 36 studies withconventional anchorage included in the systematicreview, 34 were rejected because of low or mediumquality. Thus, the meta-analysis was conducted with 2high-quality studies with no heterogeneity (I2 5 0%).However, in the group with skeletal anchorage, no studyhad high quality, and 2 articles with low quality were


excluded. The meta-analysis was conducted with 4studies of medium quality, with heterogeneity of I2 of82% in the analysis of molar distalization, and of I2 of69% in the analysis of premolars.

One study with more than 1 group was subdividedaccording to the number of groups and separatelyincluded in the meta-analysis.25 Therefore, 3 itemswere analyzed with conventional anchorage and 4 itemswith skeletal anchorage.

The meta-analysis of molar distal movement hadestimated combined effects of 3.34 mm in studies withconventional anchorage and 5.10 mm in studies withskeletal anchorage (Figs 2 and 3).

As for the premolars, themeta-analysis showedaveragemesial movements of 2.30 mm in studies with conven-tional anchorage and 4.01 mm of distal movement instudies with skeletal anchorage (Figs 4 and 5).

DISCUSSION

Since the introduction of intraoral distalizers forClass II malocclusion treatment, studies have beenconducted to evaluate their distalizing effects andanchorage losses with their use.

One systematic review evaluated the effects of intrao-ral distalizers with conventional anchorage28 and theother with skeletal anchorage.29 The purpose of thismeta-analysis was to compare the anchorage loss withthe use of these appliances with both types of anchorage.

There is no standardization regarding evaluation ofanchorage loss, which can be conducted by using thepremolars, incisors, and overjets as references. Becauseanchorage loss can be underestimated by crowding ofthe anterior teeth, the option was to determine loss ofanchorage by means of changes in premolar position.Thus, studies that used the incisors and overjet asreferences were excluded to decrease the variabilityamong the studies.

In a systematic review, it is important to evaluate thequality of the articles and allow inclusion of better-quality articles in the meta-analysis to decrease theheterogeneity among them, with the goal of presentingmore reliable data.52 In health field investigations, whichinvolve patient treatments, significant degrees ofclinical, methodological, and statistical heterogeneityare expected because of the nature of these studiesand the different variables involved, and the entire sys-tematic review project must address this issue.34

Various factors should be considered to explainthis heterogeneity. One is the degree of occlusalseverity of the Class II malocclusions; this has a direct in-fluence on the amounts of distalization andanchorage loss after treatment. In other words, a complete


Table V. Assessment of the study quality

Number StudyStudy

design 0-3Samplesize 0-1

Selectiondescription 0-2

Methoderror

analysis 0-1

Adequacy ofstatistical

analysis 0-1Quality

Score 0-9

Judgedqualitystandard

Conventional anchorage1 Papadopoulos et al,9 2010 3 1 2 1 2 9 High2 Acar et al,47 2010 1 1 1 1 1 5 Medium3 Haq et al,78 2010 0 1 1 1 1 4 Medium4 Patel et al,25 2009 2 1 2 1 2 8 High5 Polat-Ozsoy et al,37 2008* 0 1 1 1 1 4 Medium6 Sch€utze et al,79 2007 0 1 1 1 2 5 Medium7 €Onca�g et al,36 2007* 2 1 0 0 1 4 Medium8 Angelieri et al,19 2006 1 1 2 1 1 6 Medium9 Fuziy et al,23 2006 1 1 2 1 1 6 Medium

10 Mavropoulos et al,46 2006 1 1 1 1 0 4 Medium11 Sayinsu et al,80 2006 1 1 1 1 1 5 Medium12 Chiu et al,22 2005 0 1 1 0 1 3 Low13 Kinzinger et al,73 2005 1 1 1 1 1 5 Medium14 Mavropoulos et al,18 2005 1 0 1 1 0 3 Low15 Ferguson et al,81 2005 0 1 1 1 1 4 Medium16 Fortini et al,82 2004 1 1 1 1 1 5 Medium17 Papadopoulos et al,40 2004 1 0 2 1 2 6 Medium18 Taner et al,83 2003 2 0 1 1 1 5 Medium19 Bolla et al,84 2002 0 1 1 1 1 4 Medium20 Paul et al,38 2002 3 1 1 0 1 6 Medium21 Nishii et al,85 2002 1 1 1 1 1 5 Medium22 Chaqu�es-Asensi and Kalra,86 2001 1 1 1 1 1 5 Medium23 Ngantung et al,39 2001 0 1 2 1 1 5 Medium24 Keles,43 2001 0 1 1 0 1 3 Low25 Toro�glu et al,48 2001 1 1 1 0 1 4 Medium26 Bussick and McNamara,21 2000 0 1 1 0 1 3 Low27 €Ucem et al,41 2000 1 0 2 1 1 5 Medium28 Brickman et al,20 2000 1 1 1 0 1 4 Medium29 Haydar and €Uner,24 2000 2 0 0 0 0 2 Low30 Keles and Sayinsu,3 2000 1 1 1 0 0 3 Low31 Bondemark,87 2000 0 1 1 1 1 4 Medium32 Runge et al,45 1999 0 0 1 0 1 2 Low33 Gulati et al,42 1998 1 0 0 1 1 3 Low34 Byloff and Darendeliler,57 1997 1 0 1 0 1 3 Low35 Byloff et al,88 1997 1 1 1 0 1 4 Medium36 Ghosh and Nanda,58 1996 0 1 1 1 1 4 MediumSkeletal anchorage1 Kinzinger et al,44 2009 1 0 1 0 1 3 Low2 Oberti et al,51 2009 1 1 1 0 1 4 Medium3 Polat-Ozsoy et al,37 2008* 0 1 1 1 1 4 Medium4 €Onca�g et al,36 2007* 2 1 0 0 1 4 Medium5 Escobar et al,49 2007 1 1 1 0 1 4 Medium6 Kircelli et al,50 2006 1 0 1 0 1 3 Low

*Both studies compared the effects of the Pendulum on both anchorage types (conventional and skeletal).

Grec et al 609

Class II molar relationship requires greater molar distaliza-tion and produces greater side effects on the anchorageunit than does a quarter Class II molar relationship.8,53,54

Among the 40 studies included in the systematicreview, only 7 presented data regarding the initial occlu-sal severity of the Class II malocclusions.9,19,23,25,39-41

Uc€em et al41 included only patients with a complete ClassII molar relationship; Papadopoulos et al40 included onlypatients with over a half Class II molar relationship; and


Ngantung et al39 included only Class II up to 3 to 4mmofmolar relationship discrepancy. The other articles in-cluded patients with various severities.9,19,23,25,41 Itwould be ideal if all investigators had selected patientswith a similar occlusal malocclusion severity, since itwould have allowed better comparisons among thestudies. However, obtaining sufficient numbers ofpatients with the same characteristics in a clinical studyis difficult.55


Fig 2. Forest plots representing molar distalization with conventional anchorage.

Fig 3. Forest plots representing molar distalization with skeletal anchorage.

610 Grec et al

Another factor related to heterogeneity is the use ofdifferent cephalometric reference points.28 Some studieshave used the buccal cusps of the maxillary teeth, whichare difficult to locate because of image superimposition;these teeth move excessively with accentuatedangulation and do not reflect actual molar and premolarmovements.56 Other studies were based on the center ofthe clinical crown and the centroid point, which betterrepresent changes during treatment.20,39,45,57,58

Part of this heterogeneity is also related to thedifferent study designs (randomized clinical trials, casecontrol studies, and retrospective studies), lack of erroranalyses, and different sample calculations withconsequent great variability in the numbers of patientsin the studies. In orthodontics, it is difficult to conducta randomized clinical trial on certain topics.31,59

Because there were only 2 randomized clinical trials,we thought that other study designs that disclosedimportant results on the effects of distalizers withdifferent anchorage systems should be included in thissystematic review. Therefore, quality assessment was


used instead of a risk of bias assessment, which ismore rigid and specific for randomized clinical trials.The number of patients in the sample is important tobe able to represent part of a population; therefore, itwas 1 criterion for quality analysis.60

Another important criterion is a statistical analysis ofthe data because it provides a mathematic interpretationof the data.61 In this systematic review, the quality of 4articles was compromised because the authors gave onlydescriptive analyses.3,18,24,46

In all the evaluated studies, the patients were inthe growth stage, in which natural skeletal and dentoal-veolar changes must be differentiated from theappliance-induced effects.62 The mean initial chrono-logic ages ranged from 9.29 to 1547 years. However,craniofacial growth does not significantly interferewhen 2 distalization modalities are compared becausedistalization time is short.

The different types of distalizers used was alsoa methodologic variable that must be considered. Theseappliances have an active unit that applies a distalizing


Fig 4. Forest plots representing premolar movement with conventional anchorage.

Fig 5. Forest plots representing premolar movement with skeletal anchorage.

Grec et al 611

force with various mechanisms. Because the intentionwas to compare the changes in the 2 types of anchorage,these differences would not play a significant role, sincethe anchorage units were similar (a Nance buttonsupported on the premolars), except for Kinzingeret al,63 who used the deciduous molars for conventionalanchorage. In the skeletal type, the anchorage unit wasa mini-implant37,44,49-51 or an implant.36

These methodologic limitations were the reason forconsidering 11 studies to be low quality, 29 mediumquality, and only 2 high quality. Of these 2 studies,only one obtained the maximum score possible.9 Ofthe 11 low-quality studies, 7 were published over 10years ago. The 2 studies considered to be high qualitywere from 2009 and 2010, indicating greater concernwith quality because of increasingly demandingscientific methodologic criteria.

In this review, we observed that the most frequentlyused distalizer was the pendulum and its variations.


This might be explained because this distalizer hasa low cost and is easy to fabricate, whereas with otherdistalizers (distal jet, Jones jig, first class), one needs tobuy a kit that requires more complex laboratoryfabrication.15 As anchorage, all used a Nance button,except for €Ucem et al,41 who used intermaxillary elasticsas recommended for the 3D-BMDA appliance.64,65

The great variation in distalization time (1.50-14.16months) in the studies might be the result of variationsin the amount of force applied by each type of applianceand the different Class II malocclusion occlusal severitiesof the samples, which demanded different amounts ofdistalization (�1.17 to �6.10 mm).

In the same way as in conventional anchorage, thependulum appliance was the most used in the studiesthat used skeletal anchorage. Associated with skeletalanchorage, most also opted for the Nance button. Useof the Nance button might be a way to reduce possiblemovement of the mini-implants.66


612 Grec et al

Studies that associated intraoral distalizers withskeletal anchorage in the palate used devices withvarious diameters and lengths. However, these factorsdo not interfere with the stability or the effectivenessof the mini-implant to increase anchorage.67,68 Alldevices used had diameters greater than 1.0 mm,because thinner mini-implants can have considerablefailure rates.69

The majority of the studies used 1 or 2 mini-implantsinserted in the paramedian region; this is consideredbetter for mini-implants in growing patients becausethe midpalatal suture consists of connective tissue,and insertion in this suture could compromise reten-tion.70-72

Differently from conventional anchorage, there werefewer variations in treatment times (5.0-7.8 months),amounts of distalization (�3.9 to �6.4 mm), andanchorage loss (�3.1 to�5.4 mm). Although the studieswith skeletal anchorage did not mention the anteropos-terior occlusal severity of the malocclusion, it is believedthat there is a tendency to select patients with greaterseverity for treatment with this type of anchorage.

Mini-implants can be used as direct or indirectanchorage. In direct skeletal anchorage, mini-implantsdirectly receive the force of reaction resulting frommovement, whereas in indirect anchorage, the force isreceived on the anchor teeth that are supported by themini-implants.73 Of the 6 studies included in the system-atic review, 5 that used direct anchorage showedspontaneous distal movement of the premolars,probably due to stretching of the interseptalfibers.36,37,49-51 In the study that used indirectanchorage, loss of anchorage, although small, wasshown.44 This is because the reaction force, in conjunc-tion with other factors, such as movement of themini-implants due to absence of osseointegration orbone elasticity, flexibility of the premolar–mini-implantconnecting wire, or insufficient contact of the wirewith the mini-implant and the periodontal ligament,might result in mesialization of premolars even whenassociated with mini-implants.49,70

Kinzinger et al44 used the distal jet associatedwith mini-implants in the palate, including the 2 firstpremolars instead of the second premolars. Afterdistalization of the molars, the second premolarsunderwent spontaneous distalization of 1.87 mm;however, there was no reduction in anterior crowding,because the first premolars that had indirect anchorageshowed mesialization of 0.72 mm.

To enable a meta-analysis, careful selection wasmade, and only 2 studies in the group with conventionalanchorage were included because they were of highquality. However, since there were no high-quality


articles in the group with skeletal anchorage, themeta-analysis was performed with medium-qualityarticles; this resulted in high heterogeneity.

When there is heterogeneity, alternative analysessuch as meta-analysis in subgroups and meta-regression could be considered to explain the variabilityamong the groups; however, these types of analysesrequire many studies.52 When this is not the case, therandom-effects model is recommended.74 This canalso be used when the researcher combines variousstudies with the same objective that were not conductedin the same manner.34,74 This justifies its use in thisstudy.

The clinical success of molar distalization and Class IImalocclusion correction was observed in both groups(conventional and skeletal anchorage) evaluated in thisstudy. However, the meta-analysis showed a greatermean distalization in the skeletal anchorage group,similar to the results of Polat-Ozsoy et al.37 Thedifference between the groups was 1.76 mm. The greaterdistalization in the group with skeletal anchorage mighthave been due to the tendency to include patients withmore severe Class II malocclusions, when greateranchorage is desired.

The use of intraoral distalizing appliances withconventional anchorage has shown anchorage loss,which was confirmed in this meta-analysis.70,71,75 Thisis because the Nance button and the anterior teethcannot resist the opposing forces of distalizationwithout moving in the opposite direction.36,44

Consequently, associating intraoral distalizers withskeletal anchorage has been an approach to achieve totalanchorage during distalization.36,37,44,49-51,66,70 The 4studies included in the meta-analysis used directanchorage, which explains the net distal movement ofthe premolars.

Direct skeletal anchorage produces fewer side effectsresulting from distalization mechanics, due to sponta-neous distal migration of the premolars; thisreduced anterior crowding, facilitating the fixedappliance treatment phase and decreased treatmenttime.36,49,50,71

Even though the studies with direct anchorageshowed no anchorage loss, side effects of anteriormovement of mini-implants can occur, caused by thereaction force from the molars.36,49 Skeletal anchoragedoes not eliminate the reaction force duringorthodontic treatment but transfers it to the bone,which has plasticity when subjected to forces and thusallows movement of mini-implants.76,77

The efficiency of intraoral distalizers in clinicalapplications depends on a stable anchorage unit.75

Anchorage is a decisive factor for successful


Grec et al 613

orthodontic treatment with these appliance types andmust be an initial concern of orthodontists in this typeof treatment.

CONCLUSIONS

Molar distalization was shown to be effective withboth anchorage systems. The amounts of distal molarmovement were 3.34 mm with conventional anchorageand 5.10 mm with the skeletal anchorage system.

The conventional anchorage system showed anchor-age loss, represented by premolar mesial movement of4.01 mm. The skeletal anchorage system showed noanchorage loss and spontaneous distal premolarmovement of 2.30 mm when direct anchorage wasused. Therefore, intraoral distalizers associated withdirect skeletal anchorage seem to be a viable methodto minimize the effects of anchorage loss in thetreatment of Class II malocclusions.

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