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Page 1: Clinical effectiveness of Invisalign® orthodontic treatment: a … · 2018. 9. 28. · orthodontic therapy to orthodontic patients of any age treated with this method comparing either

REVIEW Open Access

Clinical effectiveness of Invisalign®orthodontic treatment: a systematic reviewAikaterini Papadimitriou1, Sophia Mousoulea2, Nikolaos Gkantidis3 and Dimitrios Kloukos1,3*

Abstract

Background: Aim was to systematically search the literature and assess the available evidence regarding theclinical effectiveness of the Invisalign® system.

Methods: Electronic database searches of published and unpublished literature were performed. The reference listsof all eligible articles were examined for additional studies. Reporting of this review was based on the PreferredReporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

Results: Three RCTs, 8 prospective, and 11 retrospective studies were included. In general, the level of evidence wasmoderate and the risk of bias ranged from low to high, given the low risk of bias in included RCTs and the moderate(n = 13) or high (n = 6) risk of the other studies. The lack of standardized protocols and the high amount of clinical andmethodological heterogeneity across the studies precluded a valid interpretation of the actual results through pooledestimates. However, there was substantial consistency among studies that the Invisalign® system is a viable alternativeto conventional orthodontic therapy in the correction of mild to moderate malocclusions in non-growing patients thatdo not require extraction. Moreover, Invisalign® aligners can predictably level, tip, and derotate teeth (except forcuspids and premolars). On the other hand, limited efficacy was identified in arch expansion through bodily toothmovement, extraction space closure, corrections of occlusal contacts, and larger antero-posterior and vertical discrepancies.

Conclusions: Although this review included a considerable number of studies, no clear clinical recommendations can bemade, based on solid scientific evidence, apart from non-extraction treatment of mild to moderate malocclusions in non-growing patients. Results should be interpreted with caution due to the high heterogeneity.

Keywords: Orthodontics, Invisalign, Aligner, Clinical efficiency

BackgroundOrthodontic developments, especially during the lastyears, have been accompanied by a significant increasein the esthetic demands of the patients. Patients oftenexpress the need to influence, or even determine, treat-ment aspects or objectives, along with the orthodontist,driven by the effects that orthodontic appliances havein their appearance. Conventional orthodontic methodshave been associated with a general compromise in fa-cial appearance [1] raising a major concern among pa-tients seeking orthodontic treatment [2]. Thus, esthetic

materials and techniques have been introduced in clin-ical practice aiming to overcome these limitations [3].Since its development in 1997, Invisalign® technology

has been established worldwide as an esthetic alternativeto labial fixed appliances [4–7]. CAD/CAM stereolitho-graphic technology has been used to forecast treatmentoutcomes and fabricate a series of custom-made alignersusing a single silicone or digital impression [6]. After itsintroduction, the system has been drastically developedand continually improved in many aspects; different at-tachment designs, new materials, and new auxiliaries,such as “Precision Cuts” and “Power Ridges” were de-signed to enable additional treatment biomechanics.According to the manufacturer, Invisalign® can effect-ively perform major tooth movements, such as bicuspidderotation up to 50° and root movements of upper cen-tral incisors up to 4 mm [8]. Despite the advocated

* Correspondence: [email protected] of Orthodontics and Dentofacial Orthopedics, 251 Hellenic AirForce General Hospital, P. Kanellopoulou 3, 11525 Athens, Greece3Department of Orthodontics and Dentofacial Orthopedics, University ofBern, Freiburgstrasse 7, CH-3010 Bern, SwitzerlandFull list of author information is available at the end of the article

© The Author(s). 2018 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, andreproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link tothe Creative Commons license, and indicate if changes were made.

Papadimitriou et al. Progress in Orthodontics (2018) 19:37 https://doi.org/10.1186/s40510-018-0235-z

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efficiency of the treatment, its clinical potency still re-mains controversial among professionals, with advocatesbeing convinced by the successfully demonstrated treatedcases, as indicated by clinical evidence, in contrast to op-ponents who argue about significant limitations, especiallyin the treatment of complex malocclusions [5, 9–11].Despite the available body of literature pertaining to

Invisalign® technology, its clinical performance has beenanalyzed less thoroughly and a synthesis of the results stillremains vague. Four systematic reviews about clearaligners exist in the literature: the first one was publishedback in 2005 and assessed the treatment effects of Invisa-lign; it included, nevertheless, only two studies [12]. Morerecently, another three reviews have been published. Thefirst one was last updated in June 2014; it included 11studies and evaluated the control of the clear aligners onorthodontic tooth movement [13]. The second one evalu-ated the periodontal health during clear aligner therapyand was published in the same year [14], and the most re-cent one was undertaken in October 2014 and includedfour studies, since it focused on the comparison betweenclear aligners and conventional braces [15].Therefore, the purpose of the present review was to

systematically search the literature and summarize thecurrent available scientific evidence regarding the clin-ical effectiveness of the Invisalign® system as principalorthodontic therapy to orthodontic patients of any agetreated with this method comparing either among themor those with conventional braces and evaluating thelevel of efficacy in various malocclusions.

Materials and methodsTypes of studiesRandomized clinical trials (RCTs), controlled clinical tri-als (CCTs), and prospective and retrospective studieswere considered eligible for inclusion in this review.These studies concerned to the clinical part of treatmentwith Invisalign, with no restrictions in language, age, sta-tus of publication, and cases with teeth extractions.

Types of participantsOrthodontic patients of any age who were treated with Invi-salign® either as the intervention or as the control group.

Types of interventionsInvisalign® therapy. All other aligner systems have beenexcluded.

OutcomeAny effect on clinical efficiency, effectiveness, treatmentoutcomes, movement accuracy, or predicted toothmovement in ClinCheck® of Invisalign® treatment, in-cluding changes in alignment or occlusion, treatment

duration, and completion rate, as primary outcomes. Ad-verse events/unwanted effects have also been recorded.

Search methods for identification of studiesDetailed search strategies were developed and appropri-ately revised for each database, considering the differ-ences in controlled vocabulary and syntax rules. Thefollowing electronic databases were searched: MEDLINE(via Ovid and PubMed, Appendix, from 1946 to August28, 2017), Embase (via Ovid), the Cochrane Oral HealthGroup’s Trials Register, and CENTRAL.Unpublished literature was searched on ClinicalTrials.gov,

the National Research Register, and Pro-Quest DissertationAbstracts and Thesis database.The search attempted to identify all relevant studies ir-

respective of language. The reference lists of all eligiblestudies were examined for additional studies.

Selection of studiesStudy selection was performed independently and in du-plicate by the first two authors of the review, who werenot blinded to the identity of the authors of the studies,their institutions, or the results of their research. Studyselection procedure was comprised of title-reading,abstract-reading, and full-text-reading stages. After ex-clusion of not eligible studies, the full report of publica-tions considered eligible for inclusion by either authorwas obtained and assessed independently. Disagreementswere resolved by discussion and consultation with thethird and the last author. A record of all decisions onstudy identification was kept.

Data extraction and managementThe first two authors performed data extraction inde-pendently and in duplicate. Disagreements were resolvedby discussion or the involvement of two collaborators(third author and last author). Data collection forms wereused to record the desired information. The following datawere collected on a customized data collection form:

� Author/title/year of study� Design/setting of the study� Number/age/gender of participants� Intervention and comparator/treatment duration� Type of clinical outcome� Method of outcome assessment

Measures of treatment effectFor continuous outcomes, descriptive measures, such asmean differences and standard deviations, were used tosummarize the data from each study. For dichotomousdata, number of participants with events and total num-ber of participants in experimental and control groupswere analyzed.

Papadimitriou et al. Progress in Orthodontics (2018) 19:37 Page 2 of 24

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Unit of analysis issuesIn all cases, the unit of analysis was the patient.

Dealing with missing dataWe contacted study authors per e-mail to request miss-ing data where necessary. In case of no response or noprovision of the missing data, only the available reporteddata were analyzed.

Data synthesisA meta-analysis was planned only if there were at leasttwo studies of low or unclear risk of bias, reporting simi-lar comparisons, and similar outcomes at similar timepoints. Otherwise, qualitative synthesis of the includedstudies would be performed.

Quality assessment of included studiesThe risk of bias for RCT studies was assessed by two re-view authors, independently and in duplicate, using theCochrane risk of bias tool [16].Risk of bias was assessed and judged for seven separ-

ate domains.

1. Sequence generation: was the allocation sequenceadequately generated?

2. Allocation concealment: was allocation adequatelyconcealed?

3. Blinding of participants and investigators: wasknowledge of the allocated intervention adequatelyprevented during the study?

4. Blinding of outcome assessors: was knowledge ofthe allocated intervention adequately preventedbefore assessing the outcome?

5. Incomplete outcome data: were incomplete outcomedata adequately addressed?

6. Selective outcome reporting: were reports of the studyfree of suggestion of selective outcome reporting?

7. Other sources of bias: was the study apparently free ofother problems that could put it at a high risk of bias?

Each study received a judgment of low risk, high risk,or unclear risk of bias (indicating either lack of sufficientinformation to make a judgment or uncertainty over therisk of bias) for each of the seven domains. Studies werefinally grouped into the following categories:

– Low risk of bias (plausible bias unlikely to seriouslyalter the results) if all key domains of the study wereat low risk of bias.

– Unclear risk of bias (plausible bias that raises somedoubt about the results) if one or more key domainsof the study were unclear.

– High risk of bias (plausible bias that seriously weakensconfidence in the results) if one or more key domainswere at high risk of bias.

Prospective and retrospective studies were graded as low,moderate, or high risk of bias according to the followingcriteria, adapted from the Bondemark scoring system [17]:

– Low risk of bias (all criteria should be met):� Randomized clinical study or a prospective study

with a well-defined control group.� Defined diagnosis and endpoints.� Diagnostic reliability tests and reproducibility

tests described.� Blinded outcome assessment.

– Moderate risk of bias (all criteria should be met):� Cohort study or retrospective cases series with

defined control or reference group.� Defined diagnosis and endpoints.� Diagnostic reliability tests and reproducibility

tests described.– High risk of bias (one or more of the following

conditions):� Large attrition.� Unclear diagnosis and endpoints.� Poorly defined patient material.

The Grading of Recommendations Assessment,Development and Evaluation (GRADE) [16] was imple-mented to assess the overall quality of evidence for thestudies included in this systematic review, according towhich the overall evidence is rated as high, moderate,low, and very low. The outcomes included in GRADEwere divided into categories regarding the different pa-rameters that had been assessed in the primary studies.

� High quality of evidence implies that the true effectlies close to that of the estimate of the effect

� Moderate quality of evidence implies that the trueeffect is likely to be close to the estimate of theeffect, but there is a possibility that it is substantiallydifferent

� Low quality of evidence implies that our confidencein the effect estimate is limited: the true effect maybe substantially different from the estimate of theeffect

� Very low quality of evidence implies that the trueeffect is likely to be substantially different from theestimate of effect.

ResultsStudy selectionThe electronic search initially identified 227 relevant ar-ticles. One hundred fifty-eight papers remained after

Papadimitriou et al. Progress in Orthodontics (2018) 19:37 Page 3 of 24

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exclusion on the basis of title-reading. Five articles wereadded through hand-searching. After 49 duplicates’ re-moval, 114 papers were assessed for screening, and afterabstract-reading, 85 studies were excluded leaving 29 arti-cles to be read in full-text. After the application of specificinclusion and exclusion criteria, another seven articleswere removed. In total, 22 studies were considered eligiblefor inclusion in the final analysis (Fig. 1).

Study characteristicsThe characteristics of each study are presented in detail inTable 1. Table 2 gives an overview of the results of the in-cluded studies regarding clinical parameters. Three studies[18–20] were RCTs, eight studies were of prospective [5,21–27], and 11 of retrospective design [28–38].

Quality analysisThe quality assessment of the 22 studies is shown inTables 3 and 4.

RCTsThe three RCTs [18–20] were judged to be at an overalllow risk of bias, due to the low risk of bias that appliedto each domain based on the Cochrane risk of bias tool[16] (Table 3).

Prospective studiesThree prospective studies [21, 26, 35] were graded asmoderate and five [5, 22, 24, 25, 27] as high risk of bias.Although they were all studies of prospective design, noblinding in relation to outcome assessment was reportedin all except one [27] study, which also lacked control,among other limitations (Table 4).

Retrospective studiesTen out of the 11 identified retrospective studies [28–38]were graded as moderate risk of bias, since all thepre-determined criteria were met. Only one retrospectivestudy [34] was of high risk of bias, because it did not

Fig. 1 Studies’ flow diagram

Papadimitriou et al. Progress in Orthodontics (2018) 19:37 Page 4 of 24

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Table

1Anoverview

oftheinclud

edstud

iesprovidinginform

ationon

theexpe

rimen

tald

esigns

andsettings

Autho

r(year)

Title

Stud

yde

sign

Setting,

treatm

entdu

ratio

nParticipants

(num

ber,sex)

Age

ofpatients

(meanage)

Inclusioncriteria

Interven

tiongrou

pCom

parison

grou

p

Hen

nessy

etal.[18]

(2016)

Arand

omized

clinicaltrial

comparin

gmandibu

lar

incisorproclinationproduced

byfixed

labial

appliances

andclearaligne

rs.

RCT

Setting:

n/a

Treatm

entdu

ratio

n:fixed

appliancegrou

p,11.3mon

ths;

clearalignerg

roup

,10.2mon

ths

44patients

(17M

,27F)

Invisaligngrou

p:29.1±7.5years

Fixedappliance

grou

p:23.7±7.0years

-Age

≥18

years

-Nocariesor

perio

dontal

disease

-Mild

Mncrow

ding

(<4mm)

-Non

-extractionorthod

ontic

treatm

ent

-Anterop

osterio

rskeletal

patternwith

intheaverage

rang

e(ANB1–4°)

22patientstreatedwith

Invisalign

22patients

treatedwith

fixed

appliances

(self-ligating

brackets)

Liet

al.

[19]

(2015)

Theeffectiven

essof

the

Invisalignappliancein

extractio

ncasesusingthe

ABOmodelgradingsystem

:amulticenterrandomized

controlledtrial.

RCT

2orthod

ontic

clinicsat

the

Second

AffiliatedHospital,

Zhejiang

University

Invisaligntreatm

entdu

ratio

nwas

44%

long

erthan

fixed

appliancetreatm

ent

152patients

(62M

,90F)

Invisaligngrou

p:35.2±7.3years

Fixedappliance

grou

p:32.2±8.3years

-Patientsaged

≥18

years

-Extractio

ntreatm

ent

-Patientsconsen

tedto

the

research

proced

ures

and

sign

ed-Availabilityof

pre-

and

post-treatmen

tde

ntalstud

ymod

elsandpano

ramic

filmswith

good

quality

-Classified

asbe

ingsevere

incomplexity

with

ascoreof

25usingthediscrepancy

inde

x(DI)of

theABO

phase

IIIclinicalexam

ination

-Class

Iocclusion

76patientstreatedwith

Invisalign

76patients

treatedwith

fixed

appliances

Bollenet

al.[20]

(2003)

Activationtim

eandmaterial

stiffne

ssof

sequ

ential

removab

leorthod

ontic

appliances.Part

1:Ability

tocompletetreatm

ent

RCT

University

ofWashing

ton

Region

alClinicalDen

tal

Research

Cen

ter

Prim

aryen

dpoint:

completionof

initialaligne

rs’

series

51patients

(15M

,36F)

34years

(rang

e19–55)

-Age

≥18

years

-Abilityto

attend

weekly

appo

intm

entsandto

pay

forservices

-Requ

iremen

tforregu

lar

dentalandpe

riodo

ntal

mainten

ance

prog

ram

incase

ofcariesor

perio

dontaldisease

51patientsrand

omly

assign

edto

4interven

tion

grou

ps;eith

erto

hard/soft

plastic

applianceand

1week/2weeks

activation

time

The4grou

pswere

comparedto

each

othe

r

Solano

-Men

doza

etal.[21]

(2016)

How

effectiveisthe

Invisalign®

system

inexpansionmovem

ent

with

Ex30′aligne

rs?

Prospe

ctive

Privateclinicin

Stuttgart,

Germany

Meantreatm

entdu

ratio

n:657.4±341.4days

116patients

(46M

,70F)

36.57

±11.53

years

-Treatm

entwith

Ex30

aligne

rmaterial

-Expansionof

thepo

sterior

uppe

rteeth(from

canine

to1stup

permolar)

-Presen

ceof

aninitialand

finaldigitalm

odel

-Definition

ofthethird

palatalrug

a-Nopresence

ofattachments

ontheinitialor

finalmod

el-Nomorethan

twomod

els

perpatient

Expansionwith

Invisalign;

4grou

ps:

(a)G1(n=40):expansion

≤1.99

mm

ininterm

olar

cuspid

width

(b)G2(n=45):expansion

≤3.99

mm

(c)G3(n=14):patients

subjectedto

expansion

≤5.99

mm

(d)G4(n=10):expansion

≥6mm.

7patientsun

classified

dueto

curren

tabsenceof

Initialandfinal

virtual3-D

ClinChe

ck®

mod

els

Papadimitriou et al. Progress in Orthodontics (2018) 19:37 Page 5 of 24

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Table

1Anoverview

oftheinclud

edstud

iesprovidinginform

ationon

theexpe

rimen

tald

esigns

andsettings

(Con

tinued)

Autho

r(year)

Title

Stud

yde

sign

Setting,

treatm

entdu

ratio

nParticipants

(num

ber,sex)

Age

ofpatients

(meanage)

Inclusioncriteria

Interven

tiongrou

pCom

parison

grou

p

oneor

both

1stmolars

Buschang

etal.[26]

(2015)

Pred

ictedandactual

end-of-treatmen

tocclusionprod

uced

with

aligne

rtherapy

Prospe

ctive

1privatepractice,Dallas,

Texas,USA

Treatm

entdu

ratio

n:n/a

27patients

(n/a)

n/a

Con

secutivepatients

27consecutivepatients

treatedwith

Invisalign

Finalvirtual

3-DClinChe

ck®

mod

els

Castroflorio

etal.[22]

(2013)

Upp

er-in

cisor

root

control

with

Invisalign

appliances

Prospe

ctive

2private

orthod

ontic

clinicsin

ametropo

litan

area

ofno

rthw

estItaly

Treatm

ent

duratio

n:no

trepo

rted

6patients

(2M,4F)

26.3±10.2years

Nopatient

hadany

record

ofanterio

rcrossbite,anterior

prosthod

ontic

work,

previous

orthod

ontic

treatm

ent,craniofacial

trauma,surgery,TM

D,or

orofacialp

ain

Invisalign

patients

(n=6;9Mx

incisors)

need

ingpalatal

root

torque

aspartof

their

treatm

ent

Initialand

finalvirtual

3-DClin-

Che

ck®

mod

elsfor

each

uppe

rincisor

Pavoni

etal.[23]

(2011)

Self-ligatingversus

Invisalign:analysisof

dento-alveolar

effects

Prospe

ctive

Dep

artm

entof

Ortho

dontics

“Tor

Vergata,”Den

talSchoo

l,University

ofRo

me

Treatm

entdu

ratio

n:Invisalign

grou

p,18

±2mon

ths;self-

ligatinggrou

p,18

±3mon

ths

40patients

(19M

,21F)

wereeq

ually

divide

dinto

2grou

ps:

Invisalign®

grou

p(8M,

12F);self-

ligatinggrou

p(11M

,9F)

Invisaligngrou

p:18.4years

Self-ligating

grou

p:15.6years

-Class

Imalocclusion

-Mild

crow

ding

inMnarch

(mean:4.4±0.8mm)

-Perm

anen

tde

ntition

-Verteb

ralm

aturationmore

advanced

than

CS4

(post-

pube

rtal)

-Noprevious

orthod

ontic

treatm

ent

Invisalign+IPR(n=20)

Fixed

appliances

(self-ligating;

n=20)

Kravitz

etal.[5]

(2009)

How

welld

oesInvisalign

work?

Aprospe

ctive

clinicalstud

yevaluatin

gtheefficacyof

tooth

movem

entwith

Invisalign

Prospe

ctive

Dep

artm

entof

Ortho

dontics

attheUniversity

ofIllinois,

Chicago

Primaryendp

oint:com

pletion

ofinitialaligners’series.The

meannu

mbero

falignersper

treatm

entwas

10Mxand12

Mnwith

each

alignerw

orn

for2

–3weeks

37patients

(14M

,23F)

31years

-Age

≥18

years

-Anteriorcrow

ding

/spacing

<5mm

andadeq

uate

buccalinterdigitatio

n-Patientswith

posterior

eden

tulous

spaces

were

includ

ediftreatm

entdid

noten

tailspaceclosure

(1participant

hadmandibu

lar

incisorextraction)

-Clinicians

wereallowed

torequ

est/refuse

IPR,

proclination,attachmen

ts,

andovercorrectio

nson

ClinChe

ck®

37patients/401anterio

rteeth(198

Mx,203Mn)

treatedwith

Anterior

Invisalign®

Finalvirtual

3-DClinChe

ck®

mod

els

Papadimitriou et al. Progress in Orthodontics (2018) 19:37 Page 6 of 24

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Table

1Anoverview

oftheinclud

edstud

iesprovidinginform

ationon

theexpe

rimen

tald

esigns

andsettings

(Con

tinued)

Autho

r(year)

Title

Stud

yde

sign

Setting,

treatm

entdu

ratio

nParticipants

(num

ber,sex)

Age

ofpatients

(meanage)

Inclusioncriteria

Interven

tiongrou

pCom

parison

grou

p

-OnlyInvisalignattachmen

tscouldbe

used

andthetray

couldno

tbe

alteredwith

scissors/the

rmop

liers

Kravitz

etal.[24]

(2008)

Influen

ceof

attachmen

tsandinterproximalredu

ction

ontheaccuracy

ofcanine

rotationwith

Invisalign

Prospe

ctive

Dep

artm

entof

Ortho

dontics,

University

ofIllinois,Chicago

Meandu

ratio

n:7mon

ths.

Primaryendp

oint:com

pletion

ofinitialaligners’series

31patients

(13M

,18F)

≥18

years

Sameas

Kravitz

etal.[5]

(2009)

31patients/53

canine

s(33

Mx,20

Mn)

treatedwith

anterio

rInvisalign®

were

divide

din

3grou

ps:

(a)attachmen

tson

ly(AO)

(b)interproximal

redu

ctionon

ly(IO

)(c)ne

ither

attachmen

tsno

rinterproximal

redu

ction(N)

Finalvirtual

3-DClinChe

ck®

mod

els

Baldwin

etal.[27]

(2008)

Activationtim

eandmaterial

stiffne

ssof

sequ

ential

removab

leorthod

ontic

appliances.Part

3:Prem

olar

extractio

npa

tients

Prospe

ctive

University

ofWashing

ton

Region

alClinicalDen

tal

Research

Cen

ter

Primaryendp

oint:com

pletion

ofinitialaligners’series

24patients

(6M,18F)

32.8(range18–54)

years

Sameas

Bollenet

al.[20]

(2003)

+at

least1prem

olar

extractio

n

24patientstreatedwith

either

hard/softplastic

applianceand1week/

2weeks

activationtim

e

Nocontrol

grou

p(pretreatm

ent

cond

ition

)

Vlaskalic

andBo

yd[25]

(2002)

Clinicalevolutionof

the

Invisalignappliance

Prospe

ctive

University

ofthePacific

Meantreatm

entdu

ratio

n:grou

p1,20

mon

ths;grou

p2,

27.2mon

ths;grou

p3,

31.5mon

ths

40patients

14–52years

-Fully

erup

tedpe

rmanen

tde

ntition

(excep

tfor3rd

molars)

-Den

talh

ealth

with

noim

med

iate

need

for

restorations

-Availabilityforeven

ing

appo

intm

ents

-Desire

tocomplywith

orthod

ontic

treatm

ent

3Invisaligngrou

psbased

onseverityof

crow

ding

:group1(n=10

mild

cases);

group2(n=15

moderate

cases),andgrou

p3

(n=15

severe

cases)

The3grou

pswere

comparedto

each

othe

r

Guet

al.

[28]

(2017)

Evaluatio

nof

Invisalign

treatm

enteffectiven

ess

andefficiencycompared

with

conven

tionalfixed

appliances

usingthePeer

Assessm

entRatin

ginde

x

Retrospe

ctive

Setting:D

ivision

ofOrth

odontics

atOhioStateUniversity

College

ofDentistry

Treatm

entdu

ratio

n:Invisaligngrou

p,13.35mon

ths;fixed

appliancegrou

p:19.1mon

ths

96patients

(34M

;62F)

Invisaligngrou

p:26

±9.7years

Fixedappliances

grou

p:22.1±7.9years

-Availablepre-

and

posttreatm

ent

records—

age≥16

years

-Noauxiliary

appliances

othe

rthan

elastics

-Non

-extractionpatients

-Noorthog

nathicsurgeryor

synd

romicpatients

-Fullpe

rmanen

tde

ntition

except

third

molars

Invisalign(n=48)

Fixed

appliances

(straigh

t-wire

edge

wise

appliances;

n=48)

Khosravi

etal.[29]

(2017)

Managem

entof

overbite

with

theInvisalignappliance

Retrospe

ctive

Setting:

3privateorthod

ontic

offices;2

locatedinthegreater

Seattle

area,W

ashand1in

Vancou

ver,British

Columbia

Treatm

entdu

ratio

n:n/a

120patients

(36M

;84F)

33years

(interquartile

rang

e:17)

-Age

≥18

years

-11

to40

aligne

rsused

for

each

arch

-Amax

useof

3revision

sets

ofaligne

rs-Non

-extractiontreatm

ent

plan

Invisalign;stratifiedstud

ysampleas

follows:68

patientsintheno

rmal

overbite

grou

p,40

patients

inthedeep-b

itegrou

p,and12

patientsinthe

open-bite

grou

p

The3grou

pswerecompared

with

each

other

Papadimitriou et al. Progress in Orthodontics (2018) 19:37 Page 7 of 24

Page 8: Clinical effectiveness of Invisalign® orthodontic treatment: a … · 2018. 9. 28. · orthodontic therapy to orthodontic patients of any age treated with this method comparing either

Table

1Anoverview

oftheinclud

edstud

iesprovidinginform

ationon

theexpe

rimen

tald

esigns

andsettings

(Con

tinued)

Autho

r(year)

Title

Stud

yde

sign

Setting,

treatm

entdu

ratio

nParticipants

(num

ber,sex)

Age

ofpatients

(meanage)

Inclusioncriteria

Interven

tiongrou

pCom

parison

grou

p

-NoclassIIto

classIocclusio

nchange

-Not

sign

ificantlychange

dpo

sterior-transverse

relatio

nships

-Nofixed

appliances

-Goo

d-qu

ality

pre-

andpo

st-

treatm

entceph

alom

etric

radiog

raph

s

Hou

leet

al.[30]

(2016)

Thepred

ictabilityof

transverse

change

swith

Invisalign

Retrospe

ctive

Setting:

Dep

artm

entof

Preven

tiveDen

talScien

ce,

Divisionof

Ortho

dontics,

Scho

olof

Dentistry,University

ofManito

ba-O

rtho

dontic

practiceinAdelaide,Australia

Treatm

entdu

ratio

n:56

weeks

64patients

(23M

,41F)

31.2years

(range18–61

years)

-Age

≥18

years

-Non

-extractiontreatm

ent

with

outanyauxiliariesother

than

Invisalignattachments

Invisalign(n=64)

Initialandfinal

virtual3-D

ClinChe

ck®

mod

els

Ravera

etal.[31]

(2016)

Maxillarymolardistalization

with

aligne

rsin

adult

patie

nts:amulticen

ter

retrospe

ctivestud

y.

Retrospe

ctive

Ortho

donticprivatepractices

locatedin

Torin

o(Italy)and

Vancou

ver(Canada)

Treatm

entdu

ratio

n:24.3±4.2mon

ths

20patients

(9M,11F)

29.73±6.89

years

-Age

≥18

yearsold

-SkeletalclassIo

rIIanda

bilateralend

-to-en

dmolar

relatio

nship

-Normod

iverge

nceon

the

verticalplane

(SN-GoG

nangle<37°)

-Mild

crow

ding

intheup

per

arch

(≤4mm)

-Absen

ceof

mesialrotation

oftheup

per1stmolar

-Standardized

treatm

ent

protocol,

-Goo

dcompliance

(wearin

galigne

rtim

e,≥20

hpe

rday)

-Absen

ceor

previous

extractio

nof

theup

per3rd

molars

-Goo

dqu

ality

radiog

raph

s

Invisalign(n=20)

Nocontrol

grou

p

Dun

canet

al.[32]

(2015)

Chang

esin

mandibu

lar

incisorpo

sitio

nandarch

form

resulting

from

Invisaligncorrectio

nof

thecrow

dedde

ntition

treatedno

nextraction

Retrospe

ctive

Sing

leorthod

ontic

practice

Treatm

entdu

ratio

n:1stgrou

p,53.6±21.1weeks;

2ndgrou

p,63.7±20.7weeks;

3rdgrou

p:71.7±16.3weeks

61patients

(17M

,44F)

Adu

ltpatients

(age

n/a)

-Non

extractio

ncaseswith

orwith

outIPR

3interven

tiongrou

psaccordingto

pre-

treatm

entcrow

ding

oflower

dentition

(Carey’sanalysis):(a)

20mild

(2.0–3.9mm),

(b)22

mod

erate

(4.0–5.9mm),and(c)

19severe

(>6.0mm)cases

The3grou

pswerecompared

toeach

other

Papadimitriou et al. Progress in Orthodontics (2018) 19:37 Page 8 of 24

Page 9: Clinical effectiveness of Invisalign® orthodontic treatment: a … · 2018. 9. 28. · orthodontic therapy to orthodontic patients of any age treated with this method comparing either

Table

1Anoverview

oftheinclud

edstud

iesprovidinginform

ationon

theexpe

rimen

tald

esigns

andsettings

(Con

tinued)

Autho

r(year)

Title

Stud

yde

sign

Setting,

treatm

entdu

ratio

nParticipants

(num

ber,sex)

Age

ofpatients

(meanage)

Inclusioncriteria

Interven

tiongrou

pCom

parison

grou

p

Grünh

eid

etal.[33]

(2015)

Effect

ofclearaligne

rtherapyon

thebuccolingual

inclinationofmandibular

caninesandtheintercanine

distance

Retrospe

ctive

University

ofMinne

sota

Meantreatm

entdu

ratio

n:Invisaligngrou

p,13.4±6.8mon

ths;fixed

appliancegrou

p:20.2±5.3mon

ths

60patients(30

ineach

grou

p;8M

,22F)

Invisaligngrou

p:25

±11.8years;

fixed

appliance

grou

p:26.3±13.5years

-Fully

erup

tedpe

rmanen

tde

ntition

includ

ingincisors,

canine

s,prem

olars,and1st

molars

-Ang

leclassIm

alocclusion

with

norm

alinterarchmolar

relatio

n-Nope

riodo

ntalattachmen

tloss

-Non

-extractionorthod

ontic

treatm

ent

-Pre-

andpo

sttreatm

entfull-

field

ofview

CBC

Tscans

-Bo

thmandibu

larcanine

sclearly

visiblein

theCBC

Tscans

Invisalign(n=30)

Fixed

appliances

(n=30)

Simon

etal.[34]

(2014)

Treatm

entou

tcom

eand

efficacyof

analigne

rtechniqu

e–regarding

incisortorque,p

remolar

derotatio

nandmolar

distalization

Retrospe

ctive

Privateorthod

ontic

practice

inColog

ne,G

ermany

Treatm

entdu

ratio

n:n/a

30patients

(11M

,19F)

initially,b

ut4

drop

pedou

t(n=26)

32.9±16.3years

Range13–72years

-Health

ypatients

-1of

the3followingtooth

movem

entsrequ

ired:

(1)Upp

ermed

ialincisor

torque

>10°

(2)Prem

olar

derotatio

n>10°

(3)Molar

distalizationof

anup

permolar

>1.5mm

3Invisaligngrou

ps:

(a)Incisortorque

>10°

(b)Prem

olar

derotatio

n>

10°

(c)Molar

distalization>

1.5mm.

Thegrou

pswere

subd

ivided

:inthe1st

subg

roup

,movem

ents

weresupp

ortedwith

anattachmen

t,whilein

the

2ndsubg

roup

noauxiliarieswereused

(excep

tincisortorque,in

which

Power

Ridg

eswere

used

)

Initialandfinal

virtual3-D

ClinChe

ck®

mod

els

Kriege

ret

al.[35]

(2012)

Invisalign®

treatm

entin

theanterio

rregion

.Were

thepred

ictedtooth

movem

entsachieved

?

Retrospe

ctive

Settingandtreatm

ent

duratio

n:no

trepo

rted

50patients

(16M

,34F)

33±11.2years

Fron

talM

xand/or

Mn

crow

ding

accordingto

Little’sinde

xof

irreg

ularity

Invisalign(n=50)

Initialandfinal

virtual3-D

ClinChe

ck®

mod

els

Kriege

ret

al.[36]

(2011)

Accuracyof

Invisalign®

treatm

entsin

theanterio

rtoothregion

.Firstresults

Retrospe

ctive

Settingandtreatm

ent

duratio

n:n/a

35patients

(11M

,24F)

33(rang

e15–59)

years

-Ortho

dontictreatm

ent

exclusivelywith

Invisalign

-Con

secutivepo

st-treatmen

tmod

elsandpatient

documen

tatio

n-Presen

ceof

low-m

oderate

Mxand/or

Mncrow

ding

Ortho

dontictreatm

ent

exclusivelywith

Invisalign

(n=35)

Initialandfinal

virtual3-D

ClinChe

ck®

mod

els

Papadimitriou et al. Progress in Orthodontics (2018) 19:37 Page 9 of 24

Page 10: Clinical effectiveness of Invisalign® orthodontic treatment: a … · 2018. 9. 28. · orthodontic therapy to orthodontic patients of any age treated with this method comparing either

Table

1Anoverview

oftheinclud

edstud

iesprovidinginform

ationon

theexpe

rimen

tald

esigns

andsettings

(Con

tinued)

Autho

r(year)

Title

Stud

yde

sign

Setting,

treatm

entdu

ratio

nParticipants

(num

ber,sex)

Age

ofpatients

(meanage)

Inclusioncriteria

Interven

tiongrou

pCom

parison

grou

p

Kuncio

etal.[37]

(2007)

Invisalignandtradition

alorthod

ontic

treatm

ent

postretentionou

tcom

escomparedusingthe

American

Boardof

Ortho

donticsObjective

Grading

System

Retrospe

ctive

Privatepracticein

New

York

City

Treatm

entdu

ratio

n:Invisaligngrou

p,1.7±0.8years;fixed

appliancegrou

p:2.3±0.8years

22patients

(11in

each

grou

p;1M

,10F)

34yearsin

the

Invisaligngrou

p26

yearsin

the

fixed

applaince

grou

p

Non

-extractioncases

Invisalign(n=11)

Fixed

appliances

(n=11)

Djeuet

al.

[38]

(2005)

Outcomeassessmen

tof

Invisalignandtradition

alorthod

ontic

treatm

ent

comparedwith

the

American

Boardof

Ortho

donticsob

jective

gradingsystem

Retrospe

ctive

Privatepracticein

New

York

City

Treatm

entdu

ratio

n:1.4years

fortheInvisalign®

grou

p;1.7yearsforthefixed

appliancegrou

p

96patients

(gen

dern/a)

Invisalign®:33.6

±11.8years

Fixedappliances:

23.7±11.0years

Non

-extractioncases

Invisalign(n=48)

Fixed

appliances

(n=48)

Mmale,

Ffemale,

m.a

meanag

e,Mxmaxillary,Mnman

dibu

lar,IPRinterproximal

redu

ction,

CBCT

cone

-beam

compu

tedtomog

raph

y,n/ano

tavailable

Papadimitriou et al. Progress in Orthodontics (2018) 19:37 Page 10 of 24

Page 11: Clinical effectiveness of Invisalign® orthodontic treatment: a … · 2018. 9. 28. · orthodontic therapy to orthodontic patients of any age treated with this method comparing either

Table

2Overview

oftheresults,outcomes,and

conclusion

sof

theinclud

edstud

ies

Autho

r,year,

design

Title

Subject

grou

pOutcomeassessed

Metho

dof

outcom

eassessmen

tResults

Con

clusions

Hen

nessyet

al.

[18]

(2016)

RCT

Arand

omized

clinical

trialcomparingmandibular

incisorproclination

prod

uced

byfixed

labial

appliances

andclear

aligne

rs

Invisalign

vs.fixed

appliances

Mandibu

larincisorproclination

prod

uced

byfixed

appliances

and

Invisalign®

aligne

rswhe

ntreatin

gpatientswith

mild

mandibu

lar

crow

ding

Com

parison

ofpre-treatm

ent

andne

ar-end

treatm

entlateral

ceph

alog

rams;themainou

tcom

ewas

theceph

alom

etric

change

inmandibu

larincisorinclinationto

themandibu

larplaneat

theen

dof

treatm

ent

-Mnincisorproclination:

fixed

appliances,5.3±4.3°;

Invisalign®:3.4±3.2°

(P>0.05)

Nodifferencein

theam

ount

ofMnincisorp

roclinationprod

uced

byInvisalign®

andfixed

labial

appliances

inmild

crow

ding

cases

Liet

al.[19]

(2015)

RCT

Theeffectiven

essof

the

Invisalignappliancein

extractio

ncasesusing

thetheABO

mod

elgradingsystem

:amulticen

terrand

omized

controlledtrial

Invisalign

vs.fixed

appliances

Treatm

entou

tcom

esof

the

Invisalign®

system

bycomparin

gtheresults

ofInvisalign®

treatm

entwith

that

offixed

appliances

inclassIadu

ltextractio

ncases

TheDIw

asused

toanalyze

pretreatmen

trecords(study

casts

andlateralcep

halogram

s)to

controlfor

initialseverityof

malocclusion.TheABO

-OGSwas

used

tosystem

aticallygradebo

thpre-

andpo

st-treatmen

trecords

-Im

proved

totalm

eanscores

oftheOGScatego

riesafter

treatm

entforbo

thgrou

psin

term

sof

alignm

ent,marginal

ridge

s,occlusalrelatio

ns,overjet,

inter-proxim

alcontacts,and

root

angu

latio

n-Invisalign®

scores

weresig

nificantly

lower

than

fixed

appliance

scores

forb-linclinationand

occlusalcontacts

-Invisalign®

hadlong

ertreatm

ent

duratio

n(31.5mon

ths)

comparedto

fixed

appliances

(22mon

ths)

Both

Invisalign®

andfixed

appliances

weresuccessful

intreatin

gclassIadu

ltextractio

ncases,thou

ghInvisalign®

requ

iredmoretim

eandshow

edworse

perfo

rmance

incertain

fields

Bollenet

al.[20]

(2003)

RCT

Activationtim

eand

materialstiffnessof

sequ

entialrem

ovable

orthod

ontic

appliances.

Part1:Abilityto

completetreatm

ent

Invisalign

grou

psEffectsof

activationtim

eand

materialstiffnesson

theability

tocompletetheinitialseriesof

aligne

rs,d

esigne

dto

fully

correct

each

subject’s

malocclusion

InitialPA

Rscores

calculation,

clinicalevaluatio

nandorthod

ontic

records(progressstud

ymod

els

andph

otog

raph

s)every4mon

ths

-15/51completed

theinitial

regimen

ofaligne

rs-2weeks

activationintervalmore

likelyto

lead

tocompletionthan

1week(37%

vs21%)

-Nosubstantiald

ifferen

ces

betw

eensoft-andhard

appliancein

completionrate

(27%

vs32%)

-Highe

stcompletionrate

(46%

)forno

n-extractio

nandinitial

PARscore<15

-Lowestcompletionrate

(0%)in

patientswith

≥2extractio

ns

Greater

likelihoo

dfor

completionof

theinitialsetof

aligne

rsforsubjectswith

ano

n-extractio

n,2weeks

activation

regimen

andlow

initialPA

Rscores

Solano

-Men

doza

etal.[21](2016)

Prospe

ct.

How

effectiveisthe

Invisalign®

system

inexpansionmovem

ent

with

Ex30′aligne

rs?

Accuracy

Ane

wmetho

dformeasurin

gthe

predictabilityof

expansionob

tained

byInvisalign®

treatmentand

differences

betweenthepredicted

(ClinCh

eck®

mod

els)andactual

expansionattheendof

treatment

InitialandfinalClinChe

ck®virtual

modelsmeasuredwith

ToothM

easure®

compa

redto

initialandfin

alactual3D

mod

elsmeasuredwith

Nem

oCast®

forevaluatio

nof

the

followingvariables:canineging

ival

width,1stprem

olarging

ivalwidth,

2ndprem

olarging

ivalwidth,1st

molarging

ivalwidth,canine

cuspidwidth,1stprem

olarcuspid

width,2nd

prem

olarcuspidwidth,

1stmolarcuspidwidth,canine

-Non

-significantdifferences

be-

tweentheinitial3D

mod

elsand

ClinChe

ck®forallvariables

ex-

cept

for1stmolar

cuspid

width

andarch

depth

-Statisticallysign

ificant

differences

betw

eenthefinal3D

andClinChe

ck®mod

elsfor

canine

ging

ivalwidth,1st

prem

olar

ging

ivalwidth,2nd

prem

olar

ging

ivalwidth,1st

molar

ging

ivalwidth,canine

-Differen

cesbe

tweenthefinal

3DandClinChe

ck®mod

els

show

edthat

planne

dexpansionat

theen

dof

treatm

entisno

tpred

ictable

Papadimitriou et al. Progress in Orthodontics (2018) 19:37 Page 11 of 24

Page 12: Clinical effectiveness of Invisalign® orthodontic treatment: a … · 2018. 9. 28. · orthodontic therapy to orthodontic patients of any age treated with this method comparing either

Table

2Overview

oftheresults,outcomes,and

conclusion

sof

theinclud

edstud

ies(Con

tinued)

Autho

r,year,

design

Title

Subject

grou

pOutcomeassessed

Metho

dof

outcom

eassessmen

tResults

Con

clusions

depth,arch

depth,1stmolar

rotatio

n,1strig

htandleftmolar

rotatio

n,and1stmolarinclination

cuspidwidth,1stprem

olarcuspid

width,2nd

prem

olarcuspid

width,1stmolarcuspidwidth

Buschang

etal.

[26]

(2015)

Prospe

ct.

Predictedandactualend-

of-treatm

ento

cclusio

nprod

uced

with

aligner

therapy

Accuracy

Differen

cesbe

tweenfinalactual

mod

elsfro

mthefinalvirtual

ClinChe

ck®mod

elsafter

treatm

entwith

Invisalign

FinalC

linChe

ck®virtualm

odels

comparedto

finalactual3D

mod

elsmeasuredwith

MeshLab

V1.30softwareforevaluatio

nof

theAmerican

Boardof

Ortho

dontics(ABO

)Objective

Grading

System

(OGS)

FinalvirtualC

linChe

ckmod

els

show

edsign

ificantlyfewer

overall

OGSpo

intde

ductions

compared

tofinalactualmod

els(15vs

24).

Differen

cesweremainlyob

served

inalignm

ent(1

vs4de

ductions),

buccolingu

alinclinations

(3vs

4de

ductions),occlusalcontacts

(2vs

3de

ductions),andocclusal

relatio

ns(2

vs4de

ductions)

-ThefinalvirtualC

linChe

ckmod

elsdo

notaccurately

reflect

thepatients’final

occlusion,as

measuredby

the

OGS,at

theen

dof

active

treatm

ent

Castroflorio

etal.

[22]

(2013)

Prospe

ct.

Upp

er-IncisorRootC

ontro

lwith

Invisalign®

Appliances

Accuracy

Efficiencyof

AlignTechno

logy’s

Power

Ridg

ein

controlling

theb-l

inclinationof

uppe

rincisors

ClinChe

ck®initialandfinalvirtual

setups

foreach

uppe

rincisor

from

therig

htandleftde

fault

view

scomparedto

measuremen

tson

3D-scans

ofactualde

ntalmod

els

-Meantorque

values

forthe9

uppe

rincisorsat

T0:20.9°

onthevirtualsetup

sand21.1°on

thescanne

dcasts

-AtT1,the

torque

values

were

10.5°and10.5°,respectively,and

represen

tedthetorque

prescriptio

n(10.4°)

-Invisalign®

controlswellthe

uppe

r-incisorroot

torque,

whe

natorque

correctio

nof

abou

t10°isrequ

ired

Pavoni

etal.[23]

(2011)

Prospe

ct.

Self-ligatingversus

Invisalign:analysisof

dento-alveolar

effects

Invisalign

vs.fixed

appliances

Dentoalveolar

effectsoftheInvisalign®

system

andof

self-ligating

bracketstreatm

entin

relatio

nto

transverse

dimen

sion

,arch

perim

eter

andarch

depthon

Mx

jaw

Measuremen

tson

pre-

andpo

st-

treatm

entmaxillaryde

ntalcasts

(intercanine-,interprem

olar-,and

interm

olar

width,archde

pth,and

arch

perim

eter)

-Nosign

ificant

differences

intreatm

entdu

ratio

n.-Sign

ificant

differences

betw

een

the2grou

pswith

self-ligating

causingfurthe

rincreasesin

the

followingvariables

ascompared

toInvisalign:intercaninewidth

(cusp),2.6mm;firstprem

olar

width

(fossa),3.3mm;first

prem

olar

width

(gingiva),

2.3mm;secon

dprem

olar

width

(fossa),2.0mm;secon

dprem

olar

width

(gingiva),

1.8mm;archpe

rimeter,1.3mm

-Class

Imild

crow

ding

canbe

treatedby

Invisalign®

and

self-ligatingbracketsat

the

sametreatm

entdu

ratio

n-Invisalign®

caneasilytip

crow

nsbu

tno

troots

Kravitz

etal.[5]

(2009)

Prospe

ct.

How

welld

oesInvisalign

work?Aprospective

clinical

stud

yevaluatin

gthe

efficacyof

tooth

movem

entw

ithInvisalign

Accuracy

Differen

cesbe

tweenactual

mod

elsandvirtualC

linChe

ck®

mod

elsin

theanterio

rteeth,after

treatm

entwith

Invisalign

DIscores(overjet,overbite,

anterio

rop

enbite,and

crow

ding

)usingamod

ified

ABO

-OGSon

pretreatmen

tdigitalm

odels.

Supe

rimpo

sitio

nof

virtualm

odels

ofthepred

ictedtoothpo

sitio

nover

theachieved

toothpo

sitio

n(Too

thMeasure®).C

omparison

betweenthepredictedandachieved

amou

ntof

toothmovem

ent

(i.e.,expa

nsion,

constrictio

n,intrusion,

extrusion,

mesiodistal

-Invisalign®

meanaccuracy

oftoothmovem

ent,41%

-Mostaccurate

movem

ent:

lingu

alconstrictio

n(47.1%

),least

accurate

movem

ent:extrusion

(29.6%

;18.3%

forMxand24.5%

forMncentralincisors),followed

bymesio-distaltipping

ofthe

Mncanine

s(26.9%

)-Caninerotatio

nsign

ificantlyless

accurate

than

that

ofallo

ther

teeth,except

forthat

oftheMx

-Further

research

isne

eded

toun

derstand

theefficacyand

biom

echanics

oftheInvisalign®

system

-Prescrip

tionby

clinicians

shou

ldbe

madebasedon

thepatient’s

treatm

entne

eds,whiletaking

into

accoun

tthelim

itatio

nsof

theappliance

Papadimitriou et al. Progress in Orthodontics (2018) 19:37 Page 12 of 24

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Table

2Overview

oftheresults,outcomes,and

conclusion

sof

theinclud

edstud

ies(Con

tinued)

Autho

r,year,

design

Title

Subject

grou

pOutcomeassessed

Metho

dof

outcom

eassessmen

tResults

Con

clusions

tip,labiolingu

altip

,and

rotatio

n).

Accuracy(%

)=[(|pred

icted-

achieved

|/|predicted

|)100%

]

lateralincisors,espe

ciallyat

rotatio

nalm

ovem

ents>15°.

-Ling

ualcrowntip

sign

ificantly

moreaccurate

than

labialcrow

ntip

-Nostatisticaldifferencein

accuracy

betw

eenMxandMn

foranymovem

enton

any

specifictooth

Kravitz

etal.[24]

(2008)

Prospe

ct.

Influen

ceof

attachmen

tsandinterproximal

redu

ctionon

the

accuracy

ofcanine

rotatio

nwith

Invisalign

Accuracy

Influen

ceof

attachmen

tsandIPR

oncanine

sun

dergoing

rotatio

nal

movem

entwith

Invisalign®

ToothMeasure®to

compare

the

amou

ntof

canine

rotatio

nspred

ictedwith

theon

esachieved

(inde

grees).A

ccuracy(%)

=[(|pred

icted-achieved

|/|predicted

|)100%

]

-Invisalign®

meanaccuracy

ofcanine

rotatio

nwas

35.8±26.3%

-Nostatisticallysign

ificant

differencein

accuracy

betw

een

the3grou

ps-Nostatisticallysign

ificant

differencein

rotatio

nalaccuracy

forMxandMncanine

sforany

ofthe3grou

ps-Thevertical-ellipsoidwas

the

mostcommon

lyprescribed

at-

tachmen

tshape(70.5%

)

Theeffectiven

essof

the

Invisalign®

system

incanine

derotatio

nislim

itedandno

tsign

ificantlyim

proved

byvertical-ellipsoidattachmen

tsandIPR

Baldwin

etal.

[27]

(2008)

Prospe

ct.

Activationtim

eand

materialstiffnessof

sequ

entialrem

ovable

orthod

ontic

appliances.

Part3:Prem

olar

extractio

npatients

Invisalign

only

Tipp

ingof

teethadjacent

toprem

olar

extractio

nspaces

durin

gspaceclosurewith

aligne

rappliances

Den

talcastsandpano

ramic

radiog

raph

spre-treatm

entandat

theen

dof

Invisaligntreatm

ent

(poten

tially

continuedwith

fixed

appliances)

-Duringtreatm

ent,theaverage

radiog

raph

icchange

sin

interden

talang

lewere21.5°

(P<0.0001;n

=10)in

the

mandibleand16.3°(P<0.0001;

n=19)in

themaxilla.Onthe

mod

els,theaveragechange

swere20.8°(P<0.0001;n

=12)in

themandibleand15.9°(P<

0.0001;n

=20)in

themaxilla

-Nosubjectcompleted

theinitial

seriesof

aligne

rsandon

ly1

ultim

atelycompleted

treatm

ent

with

aligne

rs-Theaveragetim

ein

theinitial

seriesof

aligne

rsbe

fore

failure

was

7(rang

e,1–17)mon

thsand

theaveragetotaltim

ein

aligne

rs16.6(rang

e,6–28)

mon

ths(treatmen

tcontinued

with

fixed

appliances)

-In

prem

olar

extractio

npatients

treatedwith

Invisalign,

sign

ificant

dentaltip

ping

occurs(it

canbe

corrected

with

fixed

appliances)

-Thereisatren

dforgreater

tipping

ofmandibu

larteeth

into

theextractio

nspaceand

arou

ndsecond

prem

olar

extractio

nsitesdu

ring

treatm

entwith

aligne

rs

Vlaskalic

and

Boyd

[25]

(2002)

Prospe

ct.

Clinicalevolutionof

the

Invisalign®

appliance

Invisalign

grou

psClinicalevaluationof

theInvisalign®

system

basedon

afeasibilitystud

ycond

uctedintheUniversity

ofthe

Pacific

in1997

Pre-,p

rogress-,and

post-

treatm

entrecordsinclud

ing

pano

ramicandlateralcephalo

metric

radiog

raph

s,de

ntalcasts,intra-,

andextraoralp

hotograp

hs.

Group

1:aligne

rsne

edto

bewornforat

least10

days

each,

patientstolerate

aligne

rswell,

posteriorop

enbite

occursin

somepatients,overcorrectio

nof

toothpo

sitio

nisne

cessaryin

-The

Invisalignsystem

isaviable

alternativeto

conven

tionalfixed

andremovableappliances

-Patientsin

thepe

rmanen

tde

ntition

with

mild

tomod

eratemalocclusions

may

Papadimitriou et al. Progress in Orthodontics (2018) 19:37 Page 13 of 24

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Table

2Overview

oftheresults,outcomes,and

conclusion

sof

theinclud

edstud

ies(Con

tinued)

Autho

r,year,

design

Title

Subject

grou

pOutcomeassessed

Metho

dof

outcom

eassessmen

tResults

Con

clusions

initial3-Dsetup

Group

2:attachmentsarenecessary

forrotations

ofcylindricalshaped

teeth,intru

sion,extru

sion,bo

dily

toothmovem

ent,extractionof

teethispo

ssible

Group

3:long

vertical

attachmen

tsarene

cessaryfro

mthestartof

treatm

entto

maintain

adeq

uate

root

controlin

extractio

ncases,virtualtoo

thpo

nticsystem

isestheticallyand

mechanically

advantageo

us

begreatly

bene

fited

whe

ntreatm

entisplanne

dcarefully

-Furthe

rinvestigationisne

eded

fortheultim

ateclinical

potentialo

fInvisalign®

Guet

al.[28]

(2017)

Retrosp.

Evaluatio

nof

Invisalign

treatm

enteffectiven

ess

andefficiencycompared

with

conven

tionalfixed

appliances

usingthePeer

Assessm

entRatin

gindex

Invisalign

vs.fixed

appliances

Effectiven

essandefficiencyof

the

Invisalignsystem

comparedwith

conven

tionalfixed

appliances

inmild

tomod

eratemalocclusions

Com

parison

betw

eenpatients

treatedwith

Invisalign®

andfixed

appliances

assessingpo

st-

treatm

entPA

Rscores,p

ost-

treatm

entredu

ctionin

PAR

scores,treatmen

tdu

ratio

n,and

malocclusionim

provem

ent

-Average

pretreatmen

tPA

Rscores:20.81

forInvisalignand

22.79forfixed

appliances

(NS)

-Not

statisticallydifferent

posttreatm

entPA

Rscores

and

PARscoreredu

ctionbe

tween

the2grou

ps.

-Invisalign®

patientsfinishe

d5.7mon

thsfaster

than

those

with

fixed

appliances

(P=0.0040).

-Allpatientsin

both

grou

pshad

>30%

redu

ctionin

PARscores.

-Odd

sof

achieving“great

improvem

ent”in

theInvisalign®

grou

pwere0.33

times

greater

than

thosein

thefixed

appliances

grou

pafter

controlling

forage(P=0.015)

-Bo

thInvisalign®

andfixed

appliances

areableto

improve

mild

tomod

erate

malocclusion

-Fixedappliances

weremore

effectivethan

Invisalignin

providinggreater

improvem

ents

-Treatm

entwith

Invisalignwas

finishe

don

average30%

(5.7mon

ths)faster

than

treatm

entwith

fixed

appliances.

Khosraviet

al.

[29]

(2017)

Retrosp.

Managem

entof

overbite

with

theInvisalign

applian

ceInvisalign

grou

psVerticaldimen

sion

change

sin

patientswith

various

pre-treatm

ent

overbite

relatio

nships

treatedon

lywith

Invisalignandotherd

ental

andskeletalchanges

Pre-

andpo

st-treatmen

tlateral

ceph

alom

etric

radiog

raph

s;ceph

alom

etric

analyses

byDolph

inImaging,Ch

atsw

orth,Calif

-Deepbite

patientshada

med

ianoverbite

open

ingof

1.5mm,w

hereas

theop

enbite

patientshadamed

ian

deep

eningof

1.5mm.The

med

ianchange

fortheno

rmal

overbite

patientswas

0.3mm

-Chang

esin

incisorpo

sitio

nwere

respon

sibleformostof

the

improvem

entsin

thede

epbite

andop

enbite

grou

ps-Minim

alchange

sin

molar

verticalpo

sitio

nandmandibu

lar

planeangle

-Invisalignisrelatively

successful

inmanaging

overbite

-Overbite

ismaintaine

din

patientswith

norm

aloverbite

-Deepbite

improvem

ent

prim

arily

byproclinationof

Mn

incisors

-Invisaligncorrectsmild

tomod

erateanterio

rop

enbites,

prim

arily

throug

hincisor

extrusion

Papadimitriou et al. Progress in Orthodontics (2018) 19:37 Page 14 of 24

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Table

2Overview

oftheresults,outcomes,and

conclusion

sof

theinclud

edstud

ies(Con

tinued)

Autho

r,year,

design

Title

Subject

grou

pOutcomeassessed

Metho

dof

outcom

eassessmen

tResults

Con

clusions

Hou

leet

al.[30]

(2016)

Retrosp.

Thepred

ictabilityof

transverse

change

swith

Invisalign

Accuracy

Differen

cesbe

tweentheinitial

andfinalactualmod

elsfro

mthe

initialandfinalvirtualC

linChe

ck®

modelsaftertreatmentw

ithInvisalign,

whenplanning

transverse

changes

-Com

parison

betw

eenpre-

and

posttreatm

entdigitalm

odels,

(created

from

aniTeroscan)and

digitalm

odelsfro

mClincheck®

(AlignTechno

logy)

-Digitalm

odelsweremeasured

with

Geo

magicQualify

-In

theMx,whe

nde

ntoalveo

lar

expansionwas

planne

dwith

Invisalign®,the

rewas

amean

accuracy

of72.8%:82.9%

atthe

cusp

tipsand62.7%

atthe

ging

ivalmargins,w

ithpredictio

nworsening

towardthepo

sterior

region

ofthearch

-FortheMnarch,the

rewas

anoverallaccuracyof

87.7%:98.9%

forthecusp

tipsand76.4%

for

theging

ivalmargins

-Varianceratio

sforup

perand

lower

arches

weresign

ificantly

different

(P<0.05)

-Clincheck®

pred

ictio

nof

expansioninvolves

more

bodilymovem

entof

theteeth

than

that

achieved

clinically.

Morede

ntaltip

ping

was

observed

-Careful

planning

with

overcorrectio

nandothe

rauxiliary

metho

dsof

expansion

may

help

redu

cetherate

ofmidcourse

correctio

nsand

refinem

ents,especially

inthe

posteriorregion

oftheMx

Ravera

etal.[31]

(2016)

Retrosp.

Maxillarymolardistalization

with

aligne

rsin

adult

patie

nts:a

multicen

ter

retrospe

ctivestud

y

Invisalign

grou

pDentoalveolarandskeletalchanges

followingmaxillarymolardistalization

therap

ywith

Invisalignin

adult

patie

nts

Pre-

andpo

st-treatmen

tlateral

ceph

alom

etric

radiog

raph

s-Distalm

ovem

entof

the1st

molar:2.25mm

with

out

sign

ificant

tipping

andvertical

movem

ents

-Distalm

ovem

entof

the2n

dmolar:2.52mm

with

out

sign

ificant

tipping

(P=0.056)

andverticalmovem

ents

-Nosign

ificant

movem

entson

thelower

arch.

-SN

-GoG

nandSPP-GoG

nangles

show

edno

significantdifferences

betweenpre-

andpo

st-treatment

ceph

alog

rams

-Invisalignaligne

rsareeffective

indistalizingMxmolarsin

selected

end-to-end

classII

non-grow

ingsubjectswith

out

sign

ificant

verticalandmesio-

distaltip

ping

movem

ents

-Nochange

sto

thefacial

height

Dun

canet

al.

[32]

(2015)

Retrosp.

Chang

esin

mandibu

lar

incisorpo

sitio

nandarch

form

resulting

from

Invisaligncorrectio

nof

thecrow

dedde

ntition

treatedno

nextraction

Invisalign

grou

psTreatmentoutcomesinnon-extraction

caseswith

loweranteriorcrowding

treated

with

Invisalign®

-Pre-andpo

st-treatmen

trecords

(digitalstudy

mod

elsandlateral

ceph

alom

etric

radiog

raph

s)-Cep

halometric

analysisto

determ

inelower

incisorchange

s-IPRandchange

sin

arch

width

werealso

measured

-In

thesevere

crow

ding

grou

p,therewerestatistically

sign

ificant

change

sin

lower

incisorpo

sitio

nandangu

latio

n-Nosign

ificant

differences

inlower

incisorpo

sitio

nand

angu

latio

nin

thethemild

and

mod

eratecrow

ding

grou

ps-Statisticallysign

ificant

increase

inbu

ccalexpansionin

allthree

grou

ps.

-Nochange

inthelower

incisor

positio

nor

angu

latio

nin

mild

tomod

eratelower

anterio

rcrow

ding

cases

-Inno

n-extractio

nsevere

crow

d-ingcases(>

6mm),thelower

incisorstend

toproclineand

protrude

-BuccalarchexpansionandIPR

areim

portantfactorsin

crow

ding

resolutio

n-In

tercanine,interpremolar,and

interm

olar

widthsdo

notdiffer

amon

gthethreegrou

psat

post-treatmen

t

Grünh

eidet

al.

[33]

(2015)

Retrosp.

Effect

ofclearaligne

rtherapyon

the

buccolingu

alinclination

ofmandibu

larcanine

s

Invisalign

vs.fixed

appliances

Treatm

entchang

esinb-linclination

ofMncaninesandintercaninedis-

tancebetweenpatientstreated

with

Invisalign®

andconventional

Pre-

andpo

st-treatmen

tCBC

Ts-Nosign

ificant

pre-treatm

ent

differencebe

tweenthegrou

psregardingtheb-linclinationof

Mncanine

sandintercanine

Invisalignseem

sto

increase

the

Mnintercaninedistance

with

little

increase

inb-linclination

comparedto

fixed

appliances

Papadimitriou et al. Progress in Orthodontics (2018) 19:37 Page 15 of 24

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Table

2Overview

oftheresults,outcomes,and

conclusion

sof

theinclud

edstud

ies(Con

tinued)

Autho

r,year,

design

Title

Subject

grou

pOutcomeassessed

Metho

dof

outcom

eassessmen

tResults

Con

clusions

andtheintercanine

distance

fixed

appliances

distance

-Po

sitivepre-

andpo

st-treatmen

tb-linclinations

ofMncanine

s(i.e.,theircrow

nswerepo

sitioned

buccalto

theirroo

ts)for

both

grou

ps-Significantlygreaterp

ost-treatment

b-linclinationintheInvisalign

group

-Sign

ificantlyincreased

intercaninedistance

inthe

aligne

rgrou

pat

theen

dof

treatm

ent

Simon

etal.[34]

(2014)

Retrosp.

Treatm

entou

tcom

eand

efficacyof

analigne

rtechniqu

e–regarding

incisortorque,p

remolar

derotatio

nandmolar

distalization

Accuracy

Treatm

entefficacyof

Invisalign®

aligne

rsforthefollowing3

pred

etermined

toothmovem

ents:

incisortorque

>10°,prem

olar

derotatio

n>10°,andmolar

distalization>1.5mm

-Com

parison

betw

eenthe

pred

ictedam

ount

oftooth

movem

entby

ClinChe

ck®and

theam

ount

achieved

after

treatm

ent

-Evaluatio

nof

theinfluen

ceof

auxiliaries(attachm

ents/Pow

erRidg

e),the

staging(m

ovem

ent/

aligne

r),andthepatient’s

compliancewith

treatm

ent

-Overallmeanefficacy:59

±0.2%

-Meanaccuracy

forup

perincisor

torque:42±0.2%

-Prem

olar

derotatio

nshow

edthe

lowestaccuracy

ofapproxim

ately40

±0.3%

-Distalizationof

anup

permolar

was

themosteffective

movem

ent,with

efficacy

approxim

ately87

±0.2%

-Bo

dilytoothmovem

ent(m

olar

distalization)

canbe

effectively

perfo

rmed

usingInvisalign®

aligne

rs-Prem

olar

derotatio

nsign

ificantlyde

pend

son

velocity

andtotalamou

ntof

planed

toothmovem

ent

-Forup

perincisortorque

and

prem

olar

derotatio

n,overcorrectio

ns/case

refinem

entsmay

bene

eded

Kriege

ret

al.[35]

(2012)

Retrosp.

Invisalign®

treatm

entin

theanterio

rregion

.Werethepred

icted

toothmovem

ents

achieved

?

Accuracy

Differen

cesin

theanterio

rregion

betw

eentheinitialandfinal

actualmod

elsfro

mtheinitialand

finalvirtualC

linChe

ck®mod

els

aftertreatm

entwith

Invisalign

-Electron

icdigitalcaliper

for

measuremen

tsin

casts

-Evaluatedparameters:up

per/

lower

anterio

rarch

leng

thand

intercaninedistance,overjet,

overbite,d

entalm

idlineshift,

andLittle’sirreg

ularity

inde

x-ClinChe

ck®was

measuredwith

ToothM

easure®

-Mxanterio

rcrow

ding

:initial,5.4

(rang

e1.5–14.5)mm;final,1.6

(rang

e0.0–4.5)

mm

-Mnanterio

rcrow

ding

:initial,6.0

(rang

e2.0–11.5)mm;final,0.8

(rang

e0.0–2.5)

mm

-Slight

deviations

betw

eenthe

initialactualandvirtual

ClinChe

ck®mod

elsin

overjet

(−0.1±0.3mm),up

peranterio

rarch

leng

th(−

0.3±0.5mm),

lower

anterio

rarch

leng

th(0.0±0.5mm),andin

overbite

(0.7±0.9mm)

-Mod

erateto

severe

anterio

rcrow

ding

canbe

successfully

correctedwith

Invisalign®

-Wellp

redictableresolutio

nof

lower

anterio

rcrow

ding

isachieved

byprotrusion

ofanterio

rteeth(i.e.,

enlargem

entof

theanterio

rarch

leng

th)

-In

gene

ral,theachieved

tooth

movem

entwas

inaccordance

with

thepred

ictedmovem

ent

forallp

aram

eters,except

for

overbite

Kriege

ret

al.[36]

(2011)

Retrosp.

Accuracyof

Invisalign®

treatm

entsin

the

anterio

rtoothregion

.Firstresults

Accuracy

Differen

cesbe

tweentheinitial

andfinalactualmod

elsfro

mthe

initialandfinalvirtualC

linChe

ck®

mod

elsaftertreatm

entwith

Invisalign

-Electron

icde

ntalcaliper

tomeasure

pre-

andpo

st-

treatm

entmod

els

-ToothM

easure®to

measure

the

ClinChe

ck®

-Exam

ined

parameters:overjet,

overbite,and

dentalmidline

shift

-Slight

deviations

inoverjet

(0.1±0.3mm),overbite

(0.3±0.4mm),andde

ntal

midlinede

viation(0.1±0.4mm)

betw

eeninitialactualandvirtual

mod

els

-Larger

deviations

inoverjet

(0.4±0.7mm),overbite

(0.9±0.9mm),andde

ntal

-Accep

tableaccuracy

ofInvisalign®

techno

logy

durin

gcompu

terized

transfer

ofmalaligne

dteethinto

the

ClinChe

ck®presen

tatio

n.-Toothcorrectio

nsin

the

verticalplaneweremore

difficultto

achieve.

-Overcorrectionin

thefinal

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Table

2Overview

oftheresults,outcomes,and

conclusion

sof

theinclud

edstud

ies(Con

tinued)

Autho

r,year,

design

Title

Subject

grou

pOutcomeassessed

Metho

dof

outcom

eassessmen

tResults

Con

clusions

midlineshift

(0.4±0.5mm)

betw

eenfinalactualandvirtual

mod

els

ClinChe

ck®,case

refinem

entat

treatm

enten

dor

additio

nal

measures(e.g.,ho

rizon

tal

beveledattachmen

tsor

verticalelastics)aresugg

ested

tomeetindividu

alized

therapeutic

goals,espe

ciallyin

verticalcorrectio

ns

Kuncio

etal.[37]

(2007)

Retrosp.

InvisalignandTradition

alOrtho

donticTreatm

ent

PostretentionOutcomes

comparedusingthe

American

Boardof

Ortho

donticsObjective

Grading

System

Invisalign

vs.fixed

appliances

(retention)

Post-retentio

ntreatm

entou

tcom

esinpatientstreatedwith

Invisalign

andthosetreatedwith

tradition

alfixed

appliances

-ABO

-OGSanalysison

pano

ramic

radiog

raph

sandde

ntalcasts

-Investigated

parameters:total

alignm

ent,Mxanterio

rand

posterioralignm

ent,Mnanterio

randpo

sterioralignm

ent,

marginalridge

s,b-linclination,

occlusalcontacts,occlusalrelations,

overjet,interproximalcontacts,root

angulations

-Evaluatio

nafterappliance

removal(T1)

andat

apo

st-

retention(T2)

(3yearsafter

applianceremoval).

-Efficacyin

retentionin

comparison

toEssixretainer

afterfixed

appliances

-Po

st-reten

tionworsening

oftotalalignm

entandMnanterio

ralignm

entforbo

thgrou

ps-Highe

rpo

st-reten

tionchange

sin

totalalignm

ent(ABO

-OGS

score)

forInvisalignpatients

(−2.9±1.6)

than

patients

treatedwith

fixed

appliances

(−1.4±1.2)

-Po

st-reten

tionworsening

ofMx

anterioralignm

entintheInvisalign

grou

pon

ly.

Greater

relapsein

theInvisalign®

grou

pforthisob

servation

perio

d(app

roximately3years)

forInvisalignthan

forfixed

appliancegrou

p

Djeuet

al.[38]

(2005)

Retrosp.

Outcomeassessmen

tof

Invisalignandtradition

alorthod

ontic

treatm

ent

comparedwith

the

American

Boardof

Ortho

donticsob

jective

gradingsystem

Invisalign

vs.fixed

appliances

Treatm

entou

tcom

eof

Invisalign

comparedto

conven

tionalfixed

appliancetreatm

ent

-Pretreatmen

trecords(den

tal

castsandlateralcep

halogram

s)assessed

with

theDI

(measuremen

ts:overjet,

overbite,anteriorop

enbite,

lateralo

penbite,crowding

,occlusion,lingu

alpo

sterior

crossbite,b

uccalp

osterio

rcrossbite,cep

halometrics,and

othe

r)-Po

sttreatm

entrecords(den

tal

castsandpano

ramic

radiog

raph

s)scored

byABO

-OGS(m

easuremen

ts:alignm

ent,

marginalridge

s,b-linclination,

occlusalcontacts,occlusal

relatio

ns,overjet,interproximal

contacts,roo

tangu

latio

n)

-Lower

OGSpassingrate

for

Invisalign®

(27.1%

)than

that

for

fixed

appliances

-Invisalign®

scores

were

sign

ificantlylower

than

fixed

appliancescores

forb-linclin-

ation,occlusalcontacts,occlusal

relatio

nships,and

overjet(P

<0.05)

-Invisalign®

OGSscores

negativelycorrelated

toinitial

overjet,occlusion,andbu

ccal

posteriorcrossibite

-Treatm

entdu

ratio

non

average

4mon

thsshorterwith

Invisalign®

than

with

fixed

appliances

(P<0.05)

-Treatm

entresults

offixed

appliances

aresupe

riorto

thoseof

Invisalign®

(13OGS

pointson

average)

-Redu

cedability

ofInvisalignto

correctlargeA-P

discrepancies

andocclusalcontacts

Prospect.,prospe

ctive,Retrosp.,retrospective,DId

iscrep

ancy

inde

x,AB

OAmerican

Boardof

Ortho

dontics,OGSObjectiv

eGrading

System

,Mxmaxilla(ormaxillary),M

nman

dible(orman

dibu

lar),N

Sno

tstatisticallysign

ificant,

b-lb

uccolingu

al

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Table

3Qualityassessmen

tof

theinclud

edRC

Tstud

ies

Autho

r-year

ofpu

blication

Stud

yde

sign

Sequ

ence

gene

ratio

n(selectio

nbias)

Allocatio

nconcealm

ent

(selectio

nbias)

Blinding

ofparticipants

andpe

rson

nel

(perform

ance

bias)

Blinding

ofou

tcom

eassessors(detectio

nbias)

Incompleteou

tcom

edata

(attritionbias)

Selectiverepo

rting

(repo

rtingbias)

Other

sourcesof

bias

Overall

risk

Hen

nessyet

al.

[18]

(2016)

RCT

Aj:Low

risk

Sfj:Alth

ough

not

explicitlystated

,sequ

ence

gene

ratio

nisvery

likelydu

eto

referenceof

rand

ompicking

upof

sealed

opaque

envelope

s

Aj:Low

risk

Sfj:Sealed

opaque,

envelope

s

Aj:Low

risk

Sfj:Incompleteblinding

,bu

tthereview

authors

judg

ethat

theou

tcom

eisno

tlikelyto

beinfluen

cedby

lack

ofblinding

Aj:Low

risk

Sfj:Noblinding

ofou

tcom

eassessmen

t,bu

tthereview

authorsjudg

ethat

theou

tcom

emeasuremen

tisno

tlikelyto

beinfluen

cedby

lack

ofblinding

Aj:Low

risk

Sfj:Missing

outcom

edata

balanced

innu

mbe

rsacross

interven

tiongrou

ps,

with

similarreason

sfor

missing

data

across

grou

ps

Aj:Low

risk

Sfj:Thestud

yprotocol

isavailableandallo

fthestud

y’spre-

specified

outcom

esthat

areof

interestin

thereview

have

been

repo

rted

inthepre-

specified

way

Aj:Low

risk

Sfj:Thestud

yappe

ars

tobe

freeof

othe

rsourcesof

bias

Low

Liet

al.[19]

(2015)

RCT

Aj:Low

risk

Sfj:Use

ofa

compu

terrand

omnu

mbe

rge

nerator

Aj:Low

risk

Sfj:Sequ

entially

numbe

red,

opaque,sealed

envelope

s

Aj:Low

risk

Sfj:Blinding

ensuredand

unlikelythat

the

blinding

couldhave

been

broken

Aj:Low

risk

Sfj:Blinding

ofou

tcom

eassessmen

ten

suredandun

likely

that

theblinding

couldhave

been

broken

Aj:Low

risk

Sfj:Nomissing

outcom

edata

Aj:Low

risk

Sfj:Thestud

yprotocol

isavailableandallo

fthestud

y’spre-

specified

outcom

esthat

areof

interestin

thereview

have

been

repo

rted

inthepre-

specified

way

Aj:Low

risk

Sfj:Thestud

yappe

ars

tobe

freeof

othe

rsourcesof

bias

Low

Bollenet

al.

[20]

(2003)

RCT

Aj:Low

risk

Sfj:Referenceto

arand

omnu

mbe

rlist

Aj:Low

risk

Sfj:Rand

omization

sche

dulebased

onalistof

rand

omnu

mbe

rspe

rform

edby

acalibrated

investigator,

unaw

areof

the

treatm

entplan

Aj:Low

risk

Sfj:Incompleteblinding

,bu

tthereview

authors

judg

ethat

theou

tcom

eisno

tlikelyto

beinfluen

cedby

lack

ofblinding

Aj:Low

risk

Sfj:Noblinding

ofou

tcom

eassessmen

t,bu

tthereview

authorsjudg

ethat

theou

tcom

emeasuremen

tisno

tlikelyto

beinfluen

cedby

lack

ofblinding

Aj:Low

risk

Sfj:Missing

outcom

edata

balanced

innu

mbe

rsacross

interven

tiongrou

ps,

with

similarreason

sfor

missing

data

across

grou

ps

Aj:Low

risk

Sfj:Thestud

yprotocol

isavailableandallo

fthestud

y’spre-

specified

outcom

esthat

areof

interestin

thereview

have

been

repo

rted

inthepre-

specified

way

Aj:Low

risk

Sfj:Thestud

yappe

ars

tobe

freeof

othe

rsourcesof

bias

Low

Aj:au

thors’judg

men

t,Sfjsup

portforjudg

men

t

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include any diagnostic reliability and reproducibility tests(Table 4).

Qualitative synthesis of the included studiesStudy settingsAn overview of the experimental design of the includedstudies is presented in Table 1. Eight studies [5, 21, 22,24, 30, 34–36] used patients’ virtual ClinCheck® modelsof the predicted tooth movement as control group,aided by ToothMeasure® [5, 21, 22, 24, 34–36] or Geo-magic Qualify [30], in order to investigate the treat-ment’s efficacy. More specifically, the extent that the

initial and final actual models were different from theinitial and final virtual models after treatment was eval-uated. However, two of them had similar samples andoutcomes with two other studies, namely [5] with [24,35] with [36]. We decided not to exclude any of thesestudies, since additional information was provided.Seven studies [18, 19, 23, 28, 33, 37, 38] comparedtreatment outcome of Invisalign® orthodontic treatmentwith that of conventional fixed appliances. At last, fourstudies [20, 25, 29, 32] compared Invisalign® groups toeach other, while one study [31] did not have any con-trol or comparison group.

Table 4 Quality assessment of the included prospective and retrospective studies

Author-year of publication Study design anddefined control group

Adequately definedpatient material

Defined diagnosisand end points

Diagnostic reliability andreproducibility tests

Blinded outcomeassessment

Overallrisk

Solano-Mendoza et al. [21](2016)

+(prospective)

+ + + − Moderate

Buschang et al. [26](2015)

+(prospective)

+ + + − Moderate

Castroflorio et al. [22](2013)

+(prospective)

− − − − High

Pavoni et al. [23](2011)

+(prospective)

+ + + − Moderate

Kravitz et al. [5](2009)

+(prospective)

+ + − − High

Kravitz et al. [24](2008)

+(prospective)

+ + − − High

Baldwin et al. [27](2008)

-(prospective,uncontrolled)

+ − + + High

Vlaskalic and Boyd [25](2002)

+(prospective)

+ − − − High

Gu et al. [28](2017)

+(retrospective)

+ + + + Moderate

Khosravi et al. [29](2017)

+(retrospective)

+ + + − Moderate

Houle et al. [30](2016)

+(retrospective)

+ + + − Moderate

Ravera et al. [31] (2016) +(retrospective)

+ + + + Moderate

Duncan et al. [32](2015)

+(retrospective)

+ + + − Moderate

Grünheid et al. [33](2015)

+(retrospective)

+ + + + Moderate

Simon et al. [34](2014)

+(retrospective)

+ + − − High

Krieger et al. [35](2012)

+(retrospective)

+ + + − Moderate

Krieger et al. [36](2011)

+(retrospective)

+ + + − Moderate

Kuncio et al. [37](2007)

+(retrospective)

+ + + + Moderate

Djeu et al. [38](2005)

+(retrospective)

+ + + − Moderate

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All studies tested mainly non-growing patients, andmost of them included patients of an average age of30 years [5, 19–21, 29–31, 34–38]. Non-extractioncases were used as study samples in nine studies [18,28–33, 37, 38]. Treatment duration differed among andwithin studies, as expected according to malocclusionseverity and the implemented intervention. Six studies[18, 22, 29, 34–36] did not report on treatment dur-ation. Finally, only one study [37] reportedpost-retention treatment outcomes by comparing theinduced changes in patients treated with Invisalign®with those treated with traditional fixed appliances. Theevaluation was conducted at a maximum post-retentiontime of 3 years after appliance removal, with all the pa-tients undergoing at least 1 year of retention.

Clinical findingsTable 2 gives an overview of the results of the includedstudies regarding clinical parameters, grouped in the fol-lowing three subject categories.

A. Accuracy The accuracy of Invisalign® was reportedin nine studies [5, 21, 22, 24, 26, 30, 34–36], where itwas evaluated as the deviation between the achievedand the planned tooth movements. The findings amongstudies were varying ranging from sufficient accuracy inresolving anterior crowding [35, 36] and distalizingmaxillary molars [34] to contradictory findings in upperincisor root control [22, 34] and to inadequacies inbodily expansion of the maxillary posterior teeth [21,26, 30], canine [5, 24] and premolar [34] rotationalmovements, extrusion of maxillary incisors5, and inoverbite control [35, 36].

B. Invisalign® vs traditional fixed appliances Sevenstudies [18, 19, 23, 28, 33, 37, 38] compared Invisa-lign® orthodontic treatment outcomes to that of con-ventional fixed appliances. A recent RCT study [18]found no significant difference in the amount of man-dibular incisor proclination produced by Invisalign®and fixed labial appliances in mild crowding cases,supported by a retrospective study [23], which alsoconcluded that treatment duration in these cases wassimilar for the two methods, though Invisalign wasnot so successful in root alignment. Gu et al. [28] re-ported similar outcomes, but shorter duration withInvisalign, for mild to moderate malocclusions.However, worse performance of Invisalign was notedin more severe cases, a finding also supported byDjeu et al. [38]. In the same line, in a RCT study, Liet al. [19] concluded that both therapeutic approachescan succeed in class I adult extraction cases, thoughInvisalign required more time and was less able to

correct bucco-lingual inclination and occlusal con-tacts. The latter findings are also in agreement withthose of two retrospective studies [33, 38].Differences between the two methods in

post-retention alterations were investigated in oneretrospective moderate risk of bias study [37]. Greaterrelapse was found 1–3 years posttreatment after Invi-salign® treatment compared to conventional orthodon-tic therapy with fixed appliances.

C. Invisalign groups only In an early exploratory study,Vlaskalic and Boyd [25] concluded that Invisalign® maybe more beneficial for patients in the permanent denti-tion with mild to moderate malocclusions after carefultreatment planning. Another early exploratory RCTstudy [20] also concluded that non-extraction treatmentof milder malocclusions has greater chances to be suc-cessfully treated by Invisalign.Three recent retrospective studies also tested vari-

ous Invisalign groups. One showed the moderate abil-ity of Invisalign to manage overbite [29]. Morespecifically, normal overbite was well maintained, butdeep bite was partially corrected, through mandibularincisor proclination. Open bite was also partially cor-rected, but mainly through incisor extrusion. On theother hand, a second study [31] reported the abilityof Invisalign to bodily distalize maxillary molars inadult nonextraction mild class II cases (≤ ½ cusp),with no changes in facial height. Finally, a third study[32] showed the ability of Invisalign to correct mildto moderate crowding nonextraction cases withoutcausing significant changes in the mandibular incisorposition and inclination. On the contrary, suchchanges (protrusion and proclination) were inducedin cases with severe crowding (≥ 6 mm).The Grading of Recommendations Assessment,

Development and Evaluation (GRADE) [16] was im-plemented to assess the overall quality of evidence forthe studies included in this review and for outcomesthat were assessed by two or more studies. GRADEtables illustrate the outcomes that were assessed bytwo or more studies (Additional file 1, 2, and 3).

Quantitative synthesis of the included studiesThe lack of standardized protocols impeded a validinterpretation of the actual results through pooled es-timates. Substantial differences in the implementedinterventions, participants’ characteristics (age andgender distribution), treatment duration, and investi-gated outcomes indicated significant methodologicalheterogeneity. Therefore, a meta-analysis was notfeasible.

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DiscussionIn order to successfully deliver orthodontic treatment,clinicians need to carefully plan an appropriate thera-peutic approach based on the current scientific evi-dence. Although this is not the only determiningfactor for the final decision, as clinical experience andpatient’s opinion also play an important role, thisinformation needs to be taken into consideration toassess the possibilities and limitations of each treat-ment modality.With regard to Invisalign®, to date, there are four sys-

tematic reviews available, pertaining to clinical effectsof the system [12–15], with one of them [14] evaluatingperiodontal health issues. Given the limited availableevidence in certain earlier attempts [12, 15] and theevaluation of the effectiveness of Invisalign® under thewider spectrum of clear aligners [13, 15], strong con-clusions regarding the investigated clinical efficiency ofthe Invisalign® system were not feasible. This ambientobscurity on a highly increasing treatment approachwas the reason to perform a systematic search of theliterature and assess the available scientific evidencewith respect to the clinical outcomes of the Invisalign®orthodontic treatment. Due to the relatively unexploredtopic, an attempt was made to conduct the presentsystematic review to a high standard, in order tominimize any chance of bias, but also include all theavailable information.Indeed, a considerable number of studies were

included in this review, though only three of themwere RCTs [18–20], with low risk of bias. From theremaining 19 studies, 8 were of prospective [5, 21–27] and 11 of retrospective design [28–38] with mod-erate [21, 23, 26, 28–38] or high [5, 22, 24, 25, 27,34] risk of bias. Thus, since it was difficult to assessthe outcomes and reach safe results and conclusions,a strict methodology in both the data extraction andquality analysis was attempted. The methodologicalquality of the retrieved studies was thoroughly evalu-ated and a qualitative synthesis of the results wasperformed.Considerable differences in participants’ characteris-

tics, types of interventions, reporting of clinical out-comes, and treatment’s duration was evident, thus,preventing the implementation of a meta-analysis.More specifically, the number of patients recruitedranged from 6 [22] to 152 [19], which indicates astrong methodological difference among the studyprotocols and in strength of the stated results.Concerning the age of the patients that underwenttreatment with Invisalign®, it varied between 13 [34]and 61 [30] years, with all studies primarily includingnon-growing patients, most of them having an aver-age age of 30 years [5, 19–21, 29–31, 34–38], and

most of them with moderate [21, 29–31, 35–38] andhigh [5, 34] risk of bias. This reveals a strong lack ofinformation for growing individuals and indicates thatInvisalign® is at present a preferred treatment optionfor late adolescent and adult patients, who usuallyhave higher esthetic demands.With regard to the outcome measures, measure-

ments in pre- and post-treatment records were made.The records included the following: actual or/anddigital dental casts [5, 19–23, 25, 28, 30, 32, 35–38],panoramic radiographs [25, 37, 38], lateral cephalo-grams [18, 19, 25, 29, 31, 32, 38], CBCTs [33], andphotographs [19, 20, 25, 38]. The discrepancy index(DI) and the peer assessment rating index (PAR) wereused in the pre-treatment records to assess the initialseverity of malocclusion [5, 19, 28, 38]. The AmericanBoard of Orthodontics – Objective-grading system(ABO-OGS) was used in three studies [5, 19, 38] tosystematically grade both pre- and post-treatment re-cords evaluating various clinical parameters. Tooth-Measure®, which is the Invisalign®’s proprietarysuperimposition software, was also used to make mea-surements on 3D dental models, including the initialand final ClinCheck® virtual models [5, 24, 35, 36].As for the overall treatment duration, there were

different completion criteria and varying outcomesamong and within studies. When compared to con-ventional appliances, the Invisalign® system showedsignificantly shorter treatment duration in three stud-ies [28, 33, 38], while no difference was reported inanother study [23]. All these studies evaluated nonex-traction treatment of mild to moderate malocclusionsand scored as moderate risk of bias. On the contrary,one study on extraction treatment reported longerduration for Invisalign treatment [19], with low riskof bias. Thus, it seems that Invisalign might treatfaster mild nonextraction cases, but it requires moretime than fixed appliance treatment for more com-plex cases.Substantial variation in the investigated clinical out-

comes was noted among studies. The majority ofthem focused on the accuracy of Invisalign® or itscomparison to conventional fixed appliances. The firstwas found sufficient when certain malocclusion fea-tures, such as overjet or anterior arch length discrep-ancy, were tested [35, 36] or for maxillary molardistalization [34]. The efficacy on maxillary molar dis-talization (≤½ cusp) was also supported by anotherclinical study [31]. However, important limitationswere reported for bodily expansion of the maxillaryposterior teeth [21, 30], canine [5, 24] and premolar[34] rotational movements, extrusion of maxillary in-cisors 5, and in overbite control [35, 36]. All of thesereferred studies scored as moderate according to

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Bondemark scoring system [17]. Based on these find-ings, the use of additional attachments or overcorrec-tions was commonly suggested in the literature forthese types of movement. As for the comparison tofixed appliances, from studies with moderate [23, 28]to low [18] risk of bias, it seems that Invisalign per-forms well in mild to moderate non-extraction cases[18, 23, 28], but it cannot equally succeed in moredifficult cases, including extraction cases [19, 27, 28,33, 38]. Teeth inclinations and occlusal contacts seemto be among the major limitations of Invisalign [19,33, 38], most of them judged as moderate [23, 33, 38]risk of bias and only two with low [18, 19]. Theresults from studies that included only different Invi-salign groups are in agreement with the abovemen-tioned findings [20, 25, 29, 32].In addition, only one study [37], graded as moder-

ate, included a post-treatment observational periodinvestigating the stability of treatment outcomes withInvisalign®, indicating a general lack of informationwith regard to retention. Although the amount ofevidence is limited, this study showed more relapse inthe Invisalign cases, as compared to fixed appliancetreatment, that might be attributed to the inadequa-cies in obtaining certain bodily movements and solidocclusal contacts.Overall, evidence was of moderate quality. Apart

from the three RCTs [18–20], where a low risk of biaswas considered, the remaining prospective and retro-spective studies were graded as moderate [21, 23, 26,28–38] or high [5, 22, 24, 25, 27, 34] risk of bias. Thestudies’ review showed high amount of heterogeneity interms of methodology and outcome reporting thatimpeded a valid interpretation of the actual resultsthrough pooled estimates. However, there was substan-tial consistency among researchers that the Invisalign®system is a viable alternative to conventional ortho-dontic therapy in correcting mild to moderate maloc-clusions, without extractions. Moreover, when thetreatment is carefully planned, Invisalign® aligners cansafely straighten dental arches in terms of leveling andderotating the teeth, except for canines and premolars.Finally, crown tipping can be easily performed. On theother hand, important limitations include arch expan-sion through bodily tooth movements, extraction spaceclosure, corrections of occlusal contacts, and largerantero-posterior and vertical discrepancies.All things considered, it is evident that more

high-quality research of prospective design with re-spect to the clinical outcomes of Invisalign® needs tobe carried out in the future. A standardized method-ology including control samples would be valuable inobtaining comparative results with conventional ap-proaches. Furthermore, though more than half of the

studies included in the present review have been pub-lished in the last 5 years (range 2012–2017), the find-ings of the review should be interpreted with somecaution; the continuous improvement of the Invisalignsystem (especially in 2013 with SmartTrack® material)[39] may not allow for direct synthesis and validcomparisons between older studies with the most re-cent ones, as the inclusion of data from different iter-ations of Invisalign material may become a factor ofbias. This is, of course, a major consideration whensynthesis of studies’ results for clinical evidence isconcerned, in an era that software, scanners, and 3Dprinter costs are more affordable and potentialin-house printing of aligners is rapidly growing. Lastbut not least, the long-term effectiveness pertainingto retention outcomes also needs further investigation,whereas complete lack of evidence is evident forgrowing patients.

ConclusionsDespite the fact that orthodontic treatment with Invisa-lign® is a widely used treatment option, apart fromnon-extraction treatment of mild to moderate malocclu-sions of non-growing patients, no clear recommenda-tions about other indications of the system can be made,based on solid scientific evidence.Although this review included a considerable num-

ber of studies, treatment outcomes need to be inter-preted with caution due to the high heterogeneity.Further research with parallel arm RCTs or well-designedprospective trials are needed to form robust clinical rec-ommendations for a wide spectrum of malocclusions andfor growing patients.Albeit the existing limitations, the following conclu-

sions were made, based on the available evidence:

� Invisalign might treat faster mild non-extractioncases, but it requires more time than fixed appliancetreatment for more complex cases.

� Invisalign® aligners can safely straighten dentalarches in terms of leveling and derotating the teeth(except for canines and premolars, where a smallinadequacy was reported). Crown tipping can beeasily performed.

� Teeth inclinations and occlusal contacts seem to beamong the limitations of Invisalign®, when accuracyof planned movements achieved with aligners isconcerned.

� Use of additional-novel attachments might be moreeffective for various types of movement, such asbodily expansion of the maxillary posterior teeth,canine and premolar rotational movements, extrusionof maxillary incisors, and in overbite control.

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Additional files

Additional file 1: GRADE Working Group grades of evidence. Summaryof findings: Invisalign compared in groups of different treatmentmodalities or divergent severity of crowding. (DOCX 16 kb)

Additional file 2: GRADE Working Group grades of evidence. Summaryof findings: Accuracy of treatment result. (DOCX 16 kb)

Additional file 3: GRADE Working Group grades of evidence. Summary offindings: Invisalign compared to fixed appliances in adults. (DOCX 16 kb)

AbbreviationsABO-OGS: American Board of Orthodontics – Objective-grading system;GRADE: Grading of Recommendations Assessment, Development andEvaluation; RCT: Randomized clinical trial

Protocol and registrationThe protocol was not registered prior to the study. This study was notregistered in any publicly assessable database.

Availability of data and materialsAll data generated or analyzed during this study are included in this publishedarticle [and its supplementary information files].

Authors’ contributionsThe first two authors (AP and SM) performed data extraction independentlyand in duplicate. Disagreements were resolved by discussion or the involvementof two collaborators (third author and last author: NG and DK). All authors readand approved the final manuscript.

Ethics approval and consent to participateEthical approval was not required.

Consent for publicationNot applicable.

Competing interestsThe authors declare that they have no competing interest.

Publisher’s NoteSpringer Nature remains neutral with regard to jurisdictional claims inpublished maps and institutional affiliations.

Author details1Department of Orthodontics and Dentofacial Orthopedics, 251 Hellenic AirForce General Hospital, P. Kanellopoulou 3, 11525 Athens, Greece.2Department of Orthodontics, University Hospital Ghent P8, University of

Ghent, C. Heymanslaan 10, B-9000 Ghent, Belgium. 3Department ofOrthodontics and Dentofacial Orthopedics, University of Bern, Freiburgstrasse7, CH-3010 Bern, Switzerland.

Received: 29 June 2018 Accepted: 27 July 2018

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5. ortho caps 5

6. orthocaps 1

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8. removable AND aligner 33

9. esthetic AND splint AND orthodont* 75

10. transparent* AND orthodont* 63

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