Do malocclusion and orthodontic treatment impact oral health? A systematic review and meta-analysis

Abstract

Introduction
Currently, there is limited evidence on the effects of malocclusion on oral health and whether the correction of malocclusion results in an improvement in oral health. In this review, we examined the evidence from randomized controlled trials and prospective cohort studies to provide information on any association between malocclusion and oral health and the effects of orthodontic treatment.

Methods
We conducted this review in 2 parts: (1) we looked at the impact of malocclusion on oral health, and (2) we reviewed the evidence on the effect of orthodontic treatment on oral health. We searched for randomized controlled trials and prospective cohort studies. The searches were completed for articles published between January 1, 1990 and October 8, 2018 and covered Medline via Ovid, Embase, and the Cochrane Database of Systematic Reviews. References of included articles and previous systematic reviews were hand-searched. No language restrictions were applied. Two members of the study team assessed the quality of the studies using the Appraisal Tool for Cross-Sectional Studies to appraise the quality of studies in part 1. The assessment was performed at the study level. Two authors assessed each study independently, with a third author consulted when a disagreement occurred. For studies in part 2, we used the Newcastle-Ottawa scale to assess the risk of bias. When studies were included in a Cochrane review, we incorporated the risk of bias assessment. We developed data extraction forms for each area of oral health under investigation (trauma, quality of life, caries, and periodontal disease). Each author piloted the form, and we held discussions to inform any necessary refinements. We extracted data from studies into 2 × 2 tables, which provided a binary analysis of malocclusion vs the outcome of interest. If these data were not available from the published paper, then studies were not included in the meta-analysis. The authors were contacted when possible to request data in this format.

Results
For part 1 of the study, we identified 87 studies. The overall quality was low. We could not include any of the data into an analysis because of a large variation in the nature of the studies, data collected, and outcome measures that were selected. For part 2 of the study, we found 7 studies; however, there were similar deficiencies in the data as in part 1, and thus, we could not reach any strong conclusions.

Conclusions
Overall, there is an absence of published evidence regarding the effects of malocclusion on oral health and the impact of orthodontic treatment on oral health.

Full text

Do malocclusion and orthodontic
treatment impact oral health?
A systematic review and meta-analysis
Richard Macey,
a
Badri Thiruvenkatachari,
a
Kevin O'Brien,
b
and Klaus B. S. L. Batista
c
Manchester, United Kingdom, and Rio de Janeiro, Brazil
Introduction: Currently, there is limited evidence on the effects of malocclusion on oral health and whether the
correction of malocclusion results in an improvement in oral health. In this review, we examined the evidence
from randomized controlled trials and prospective cohort studies to provide information on any association be-
tween malocclusion and oral health and the effects of orthodontic treatment. Methods: We conducted this re-
view in 2 parts: (1) we looked at the impact of malocclusion on oral health, and (2) we reviewed the evidence
on the effect of orthodontic treatment on oral health. We searched for randomized controlled trials and prospec-
tive cohort studies. The searches were completed for articles published between January 1, 1990 and October 8,
2018 and covered Medline via Ovid, Embase, and the Cochrane Database of Systematic Reviews. References
of included articles and previous systematic reviews were hand-searched. No language restrictions were
applied. Two members of the study team assessed the quality of the studies using the Appraisal Tool for
Cross-Sectional Studies to appraise the quality of studies in part 1. The assessment was performed at the
study level. Two authors assessed each study independently, with a third author consulted when a
disagreement occurred. For studies in part 2, we used the Newcastle-Ottawa scale to assess the risk of bias.
When studies were included in a Cochrane review, we incorporated the risk of bias assessment. We
developed data extraction forms for each area of oral health under investigation (trauma, quality of life,
caries, and periodontal disease). Each author piloted the form, and we held discussions to inform any
necessary refinements. We extracted data from studies into 2 32 tables, which provided a binary analysis of
malocclusion vs the outcome of interest. If these data were not available from the published paper, then
studies were not included in the meta-analysis. The authors were contacted when possible to request data in
this format. Results: For part 1 of the study, we identified 87 studies. The overall quality was low. We could
not include any of the data into an analysis because of a large variation in the nature of the studies, data
collected, and outcome measures that were selected. For part 2 of the study, we found 7 studies; however, there
were similar deficiencies in the data as in part 1, and thus, we could not reach any strong conclusions.
Conclusions: Overall, there is an absence of published evidence regarding the effects of malocclusion on
oral health and the impact of orthodontic treatment on oral health. (Am J Orthod Dentofacial Orthop
2020;157:738-44)
Orthodontic treatment aims to correct maloc-
clusion.
1
This type of dental care is widely pro-
vided throughout the world and there is a clear
demand for treatment by patients. For example, in the
United Kingdom, the demand for orthodontics is high,
and waiting lists are long, with an estimated cost of
£275 million to the National Health Service in En-
gland in 2015-2016.
2
There is evidence that ortho-
dontic treatment is successful in the technical
correction of malocclusion.
3
Unfortunately, investiga-
tors have evaluated the effects of orthodontic treat-
ment by measuring normative, morphologic features
a
Faculty of Biology, Medicine and Health, Division of Dentistry, School of Med-
ical Sciences, The University of Manchester, Manchester, United Kingdom.
b
Faculty of Biology, Medicine and Health, Division of Population Health, School
of Medical Sciences, The University of Manchester, Manchester, United Kingdom.
c
Faculty of Dentistry, Department of Preventive and Public Dentistry, Rio de Ja-
neiro State University, Rio de Janeiro, Brazil.
All authors have completed and submitted the ICMJE Form for Disclosure of Po-
tential Conflicts of Interest, and none were reported.
Address correspondence to: Kevin O'Brien, Faculty of Biology, Division of Pop-
ulation Health, School of Medical Sciences, Medicine and Health, The University
of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom; e-mail,
kevinobrien@icloud.com.
Submitted, July 2019; revised and accepted, January 2020.
0889-5406/$36.00
!2020 by the American Association of Orthodontists. All rights reserved.
https://doi.org/10.1016/j.ajodo.2020.01.015
738
SYSTEMATIC REVIEW

(eg, by using measures such as Andrew's 6 keys of oc-
clusion and the Peer Assessment Rating).
4
As a result,
they identify the correction of the malocclusion from
the clinician's perspective. This approach is then
perceived as a presumed benefittothepatient.
5,6
However, there is limited evidence on whether the
correction of malocclusion results in an improvement
in oral health.
7,8
As a result, there is uncertainty about the effects of
malocclusion on oral health and whether orthodontic
treatment has a positive impact on oral health. This is
relevant when we consider that the F!
ed!
eration Dentaire
Internationale defines oral health as,
The ability to speak, smile, chew, swallow and convey
emotions through facial expressions with confidence
and without pain, discomfort and disease of the
craniofacial complex. Reflecting the physiologic, so-
cial and psychosocial attributes that are essential to
the quality of life.
9
This means that if we want to consider the effects of
malocclusion and orthodontic treatment with relevance
to this definition, we need to gather information not
only on caries, periodontal disease, and trauma but
also on the patient's quality of life.
When we consider the patient's quality of life, we are
uncertain if orthodontic treatment will have an
impact.
10,11
For example, a review conducted over
35 years ago
12
highlighted the lack of evidence of the
benefit to the patient's quality of life. A recent system-
atic review also reached the same conclusion.
13
As a
result, we can only conclude that there may remain sub-
stantial uncertainty on whether any changes in the func-
tional and esthetic components of malocclusion affect
the patient's quality of life.
OBJECTIVES
We designed this review to answer 2 related ques-
tions: (1) What is the impact of malocclusion on oral
health? (2) What is the effect of orthodontic treatment
on oral health?
MATERIAL AND METHODS
We registered the protocol for this review on the in-
ternational prospective register of systematic reviews
(PROSPERO) from the National Institute for Health
Research database (www.crd.york.ac.uk/prospero; pro-
tocol no. CRD42017057516) and followed the PRISMA
statement when we reported our review.
The participants of this study were children (aged
18 years and younger) with malocclusion and/or who
have been treated with orthodontics.
The following inclusion criteria were used for part 1
of the review (ie, What is the impact of malocclusion
on oral health?): (1) any study investigating the associ-
ation between malocclusion and oral health at a single
time point; (2) a comparison group with no-
malocclusion; and (3) a study in which malocclusion is
measured using a verified tool, such as Index of Ortho-
dontic Treatment Need (IOTN), Dental Aesthetic Index
(DAI), or a well-described measurement of overjet. Po-
tential data sources were the baseline records of ran-
domized controlled trials, prospective cohorts with an
untreated control, and cross-sectional studies with a
no-malocclusion control.
The following inclusion criteria were used for part 2
of the review (ie, What is the effect of orthodontic treat-
ment on oral health?): (1) studies that assessed the oral
health of participants before and after an orthodontic
intervention; and (2) a comparison group that received
no orthodontic treatment. Therefore, relevant study de-
signs were randomized controlled trials and prospective
cohorts with 2 time points (before and after treatment)
with an untreated control group.
For both parts of the review, we identified outcomes
that fell into 2 broad categories, which included change
in dental disease state and sociodental impact.
14
We re-
corded the following data: (1) caries outcomes: decayed,
missing, and filled teeth; (2) periodontal outcomes: basic
periodontal examination and loss of attachment; (3) pla-
que; (4) incidence of dental trauma; and (5) any oral
health–related quality of life (OHRQOL) outcome.
The following exclusion criteria were used for each
part of review: (1) outcome measures using any radio-
logical measurements, ultrasound measurements, or
bite registrations; (2) any assessments of bonding or
evaluations of the adherence or techniques surrounding
the implementation of orthodontic processes; (3) split-
mouth studies; (4) studies assessing compliance of pa-
tients; and (5) orthognathic surgery studies.
We conducted separate searches for parts 1 and 2
(Supplementary Material 1 provides comprehensive
search strategy). The searches were completed for arti-
cles published between January 1, 1990 and October
8, 2018 and covered Medline via Ovid, Embase, and
the Cochrane Database of Systematic Reviews. Refer-
ences of included articles and previous systematic re-
views were hand-searched. No language restrictions
were applied.
All authors piloted a screening proforma on the first
100 studies to ensure consistency of approach during
screening. The form encompassed the agreed inclusion
and exclusion criteria. We used this form to screen the
results of the searches in duplicate.
Macey et al 739
American Journal of Orthodontics and Dentofacial Orthopedics June 2020 !Vol 157 !Issue 6

Two members of the study team assessed the qual-
ity of the studies using the Appraisal Tool for Cross-
Sectional Studies to assess the quality of the studies
selected for part 1.
15
This checklist has been designed
for cross-sectional studies. The assessment was per-
formed at the study level. Two authors assessed each
study independently, consulting a third author when
a disagreement occurred. We piloted this approach
on a sample of 10 studies and then compared our re-
sults, which ensured that we were consistent in our
appraisal.
For studies included in part 2, we found that most of
the studies were not randomized. As a result, we used the
Newcastle-Ottawa scale to assess the risk of bias. When
the studies had been included in a Cochrane review, we
incorporated the risk of bias assessment.
We developed data extraction forms for each area of
oral health under investigation (trauma, quality of life,
caries, and periodontal disease). Each author piloted
the form, and we held discussions to inform any neces-
sary refinements.
We extracted the following information for each
study: (1) study design; (2) study methods: method of
allocation to treatment, blinding of participants; (3)
time and setting of the included research; (4) participant
details: age, sex, country, sample size, inclusion and/or
exclusion criteria; (5) interventions: orthodontic treat-
ment, length of treatment, follow up; and (6) outcomes:
as previously listed.
We extracted data from studies into 2 32 tables,
which provided a binary analysis of malocclusion vs
the outcome of interest. If data were not available
from the published paper, then studies were not
included in the meta-analysis. The authors were con-
tacted when possible to request data in this format.
This request required the authors of studies to define a
threshold for malocclusion (ie, overjet .5 mm or point
on a malocclusion scale, such as IOTN or DAI). We ex-
tracted data from the papers to a Microsoft Excel spread-
sheet and then imported those data into RevMan
software (version 5.3; Nordic Cochrane Center, Cochrane
Collaboration, Copenhagen, Denmark) to undertake the
meta-analysis.
Heterogeneity was assessed using the Cochran Q
test (significant at P\0.10), quantified with the I
2
statistic (range from 0% to 100%).
16
If more than
10 studies were available and heterogeneity was sub-
stantial (I
2
.60% or P\0.10 for Q test) we aimed to
explore heterogeneity through sensitivity analysis or
meta-regression according to the baseline year of
study, quality of studies, measurement tools for
malocclusion and outcome measure, and thresholds
applied.
RESULTS
We identified 87 studies that evaluated the associa-
tion between malocclusion and dental disease (Fig 1).
These included 5 longitudinal and 82 cross-sectional
studies. Forty-one studies assessed the quality of life,
39 included trauma, and 9 examined either periodontal
disease or caries. The characteristics of included studies
are presented in Supplementary Tables I-III. Forty-four
of the studies were conducted in Brazil (49%), the
remainder were spread across Europe (13), the Middle
East, India (7), Africa (6), and North America (3). The
most commonly used malocclusion tools were DAI (19)
and IOTN (13), whereas overjet was measured in 38
studies, which primarily investigated the relationship be-
tween malocclusion and dental trauma. The threshold of
5 mm or higher was used in 13 of these trauma studies.
When assessing the quality of life, Child Perceptions
Questionnaire (CPQ) was used in 17 studies with both
the 11-14 and 8-10 scales being adopted, Oral Impacts
on Daily Performance (OIDP) was used in 6 studies,
and Oral Health Impact Profile-14 (OHIP) was used in
5 studies.
The overall quality of the included studies was low
because all studies had at least 1 quality domain that
introduced bias (Supplementary Material 2). The most
common reason for poor quality was the lack of clarity
on participant sampling and the omission of nonre-
sponder and response rate information. In addition,
many failed to report a valid sample size calculation or
lacked transparency in their reporting around ethical
approval and conflicts of interest.
All studies defined their population and measure-
ment techniques, but there was a lack of clarity on
participant selection, and often, the primary data were
not present or interpretable.
When we considered dental trauma, we decided on a
cutoff point for the definition of an increased overjet as
5 mm. We chose this cutoff because it was the most
commonly used cutoff in the literature that we identi-
fied. Of the 39 included trauma studies, 31 reported us-
able data and, of these, 13 provided data at the 5 mm
threshold. We were able to perform a meta-analysis of
these data (Fig 2). The results from these cross-
sectional data, on a sample of 3522 children, suggest
that if a child has an overjet of .5 mm, then the odds
ratio of them suffering trauma to their incisors was
1.98 (95% confidence interval 1.8-2.17). We found
considerable heterogeneity (I
2
584%), a sensitivity
analysis was performed which excluded the outlying
study
17
and resulted in a reduction of I
2
to 40% and
the suggestion that heterogeneity might not be substan-
tial in these studies.
18
740 Macey et al
June 2020 !Vol 157 !Issue 6 American Journal of Orthodontics and Dentofacial Orthopedics

When we evaluated the data derived from studies
concerned with caries and periodontal disease, we could
not include the data for 8 of 9 studies that met our in-
clusion criteria, which was due to the investigators not
recording tooth-level data. The investigators had re-
corded whole-mouth outcomes (ie, decayed, missing,
and filled teeth and Gingival Index); although this is
not relevant to malocclusion when individual compo-
nents such as localized crowding, may influence the out-
comes. It is clear that data should have been recorded on
the teeth associated with the morphologic feature of
malocclusion.
We only found 1 study that evaluated the association
between individual tooth components and dental dis-
ease.
19
They recorded dental irregularity, gingivitis,
and plaque accumulation of 213 children with a mean
age of 12.7 years. Interestingly, they concluded that
there was an association between irregularity and gingi-
vitis. This finding was particularly true for patients with
moderate and poor oral hygiene. However, there was no
association between incisor irregularity and plaque
accumulation. The overall conclusion of the study was
that the crowding of the incisor is directly related to
gingivitis. Nevertheless, this could not be explained by
an effect of crowding on oral hygiene.
We found similar problems with the OHRQOL data. In
29 of the articles that evaluated the quality of life, the
investigators collected composite scores. Unfortunately,
we could not include this information in a meta-analysis
for the following reasons:
(1) The composite scores included data that were not
relevant to a malocclusion—for example, dental
pain.
(2) Many of the authors simply presented the compos-
ite scores and then ran large regression models
evaluating the association of many possible con-
founders. This resulted in an unsystematic
“dredging”of data. Importantly, they did not
Records iden!fied through
database searching
(n = 3741)
ScreeningIncluded Eligibility Identication
Addi!onal records iden!fied
through other sources
(n = 2)
Records a"er duplicates removed
(n = 2124)
Records screened
(n = 2124)
Records excluded
(n =1862 )
Full-text ar!cles assessed
for eligibility
(n = 262)
Full-text ar!cles excluded,
with reasons
(n = 163)
Studies included in
qualita!ve synthesis
(n = 99)
Studies included in
quan!ta!ve synthesis
(meta-analysis)
(n = 20)
Fig 1. PRISMA flow diagram of study selection.
Macey et al 741
American Journal of Orthodontics and Dentofacial Orthopedics June 2020 !Vol 157 !Issue 6

report the data in a manner that allowed the con-
struction of a 2 32 table.
(3) There was no indication of the clinical significance
of the sociodental impact. This was crucial if we
were going to identify any effects of malocclusion.
(4) There was no uniformity in the selection of
outcome measures. For example, 13 teams used
CPQ, 5 used OIDP, 5 used OHIP, 3 used the Early
Childhood Oral Health Impact Scale, and 3 used
an unclear self-esteem measure and “specially de-
signed questionnaires.”This resulted in an unac-
ceptable level of heterogeneity in the study
methods.
(5) Finally, there was variation in the methods of mea-
surement of malocclusion. For example, 13 investi-
gators used the DAI with 4 different cutoff points
to identify malocclusion, 12 used IOTN with 2
different cutoff points, 1 measured the Little's Ir-
regularity Index (incisors only), and 6 recorded
the morphologic features of malocclusion with
limited validity and no uniformity in what consti-
tuted a malocclusion, apart from deviation from
an ideal occlusion.
When we looked at the conclusions of the papers, 8
reported that malocclusion was associated with some so-
ciodental impact, 10 concluded that there was no asso-
ciation, and 11 did not come to clear conclusions.
We identified 7 studies. We classified these into 4
cohort studies and 3 randomized controlled trials. We
obtained data on the treatment of Class II malocclusion
from a Cochrane systematic review,
20
all studies showed
aspects of bias in their methods (Supplementary Tables
IV and V). There were no other systematic reviews report-
ing on the effects of orthodontic treatment.
These data had similar deficiencies as those in part 1.
Unfortunately, investigators did not collect caries and
the periodontal disease data at the tooth level in any
study that we identified. As a result, we could not reach
any conclusions.
When we looked at quality of life, we found 5 articles
and all reported in a way that prevented us from extract-
ing data. For example, they used 4 different sociodental
measures (1 Family Impact Scale, 2 OIDP, 1 Early Child-
hood Oral Health Impact Scale, and 1 OHIP). Therefore, it
was not possible to use these data for meta-analysis.
Importantly, there was no information on the clinically
significant effect size for any of the sociodental mea-
sures that were used. This problem has been previously
highlighted in a similar review of the literature.
21
How-
ever, our inclusion criteria were more stringent.
There was only 1 study that provided us with more
information.
22
This study was a prospective cohort
study. They enrolled 374 young people and followed
them up for 3 years. They recorded CPQ 11-14 and
self-esteem using CHQ-CF87 and IOTN and dental
caries. At the end of 3 years, 258 remained in the study.
At baseline, they found an association between OHR-
QOL and gender, socioeconomic status, self-esteem and
the self-assessed aesthetic component of IOTN. When
Fig 2. Forest plot, dental trauma experienced in children with malocclusion (overjet .5 mm) and no-
malocclusion.
742 Macey et al
June 2020 !Vol 157 !Issue 6 American Journal of Orthodontics and Dentofacial Orthopedics

they looked at the longitudinal data, the Dental Health
Component of IOTN improved in 35% of the sample,
regardless of whether they had received orthodontic
treatment. There was also a significant improvement in
CPQ 11-14, suggesting that this also improves with
time. Finally, there was no effect on orthodontic treat-
ment on CPQ scores. However, the number of partici-
pants was low (35), and we could not give much
weight to this finding.
The only useful data were those concerning trauma.
We obtained this from a Cochrane systematic review of
the effectiveness of orthodontic treatment for Class II
Division 1 malocclusion.
20
This finding revealed that
correcting prominent incisors resulted in a reduction in
trauma from 31.7% to 19.7%. This was a reduction of
12%. Importantly, the orthodontic treatment did not
eliminate the chance of injury.
DISCUSSION
We found from this review that there was an absence
of evidence on the relationship between malocclusion
and dental health, except for the apparent effect of
increased overjet on the incidence of incisal trauma.
Similarly, when we looked at the impact of orthodontic
treatment, there was limited evidence that orthodontic
treatment influenced oral health. There was also an ef-
fect of treatment on the incidence of trauma.
When we consider these results, we must remember
that an “absence of evidence does not mean that there
is evidence of absence.”As a result, we cannot conclude
that malocclusion and orthodontic treatment do not in-
fluence oral health. This is because most of the research
that has been done has not been designed to address the
questions specifically posed in this review. It appears that
the outcome measures used were either not relevant to
oral health or have been applied inappropriately. Tshlaki
and O'Brien
6
highlighted this issue of orthodontic
outcome measures when they concluded that there are
many and varied outcome measures with no consistency
in the outcomes selected. In effect, the research may
have missed any effects of malocclusion or orthodontic
treatment on oral health. Steps are currently being taken
to develop a condition-specific measure to evaluate the
effect of malocclusion on oral health impact.
23
Never-
theless, this research is still in its early stages and looks
promising.
The only exception to this finding is incisal trauma.
We can conclude with a degree of certainty that
providing orthodontic treatment to correct an overjet
for a young patient will reduce the chance of them expe-
riencing incisal trauma, as highlighted by another
recently published review.
24
Regardless, we also need
to consider that orthodontic treatment will not
completely avoid injury.
There is no doubt that these findings are disap-
pointing. There is an urgent need to conduct studies
that will answer questions on the effects of malocclusion
and orthodontic treatment on oral health. Shaw et al
11
first posed these questions in 1984, and to date, they
remain unanswered.
12
This was a large and challenging review. The main
strengths were that we adopted systematic review
methods, identified the deficiencies and quality of the
included papers, and attempted to perform relevant
meta-analyses. The limitations were concerned with
the need to be critical on the measures that have previ-
ously been used, the use of arbitrary or absent cutoff
points by authors, and a general lack of uniformity in
study design. This meant that we had to reject a large
amount of data that may have been useful. However,
this enabled us to identify significant deficiencies in
the quality of information on this increasingly important
area of dental health care.
Finally, we need to consider the type of investigations
required to address this lack of knowledge of malocclu-
sion and orthodontics. It is clear that studies that eval-
uate the effects of malocclusion should ideally be
directed at the association between the morphologic
features of malocclusion and oral health. For example,
we should be evaluating the relationship between the
crowding of individual teeth and any caries and peri-
odontal disease directly associated with these teeth.
Similarly, when we consider OHRQOL, this can be evalu-
ated by the development of condition-specific instru-
ments or adapting original measures to reflect the
likely consequences of malocclusion. Finally, we should
consider using qualitative measures, as studies using this
methodology are revealing interesting findings from the
patient's viewpoint.
25,26
We could consider that the ideal study design may be
a prospective cohort study using the appropriate
outcome measures. Unfortunately, this may suffer
from a problem with retention of participants, and it is
unlikely to be successful. This means that any longitudi-
nal study will be of short duration, and this may not pro-
vide us with sufficient certainty on the long-term effects
of malocclusion.
An alternative could be a cross-sectional study. How-
ever, the sample of participants should be recruited
consecutively or randomly and the methods should be
clearly reported. Convenience sampling will lead to
inherent selection biases. Furthermore, attention should
be directed toward nonresponders to identify if their
characteristics and reasons for nonparticipation were
different from the responders.
Macey et al 743
American Journal of Orthodontics and Dentofacial Orthopedics June 2020 !Vol 157 !Issue 6

If we want to evaluate the effects of orthodontic
treatment, the ideal study would be a randomized trial
of treatment vs no treatment, but it would not be ethical.
Alternative designs such as cohorts could be considered.
Unfortunately, this will not deal with the confounder of
why some children are treated, and others are not, thus
leading to bias in the study.
CONCLUSIONS
As a result, we can only conclude that, apart from
trauma, there is an absence of evidence on the effects
of malocclusion on oral health and the impact of ortho-
dontic treatment on oral health. Unfortunately, it may
not be possible to answer these questions with the de-
gree of certainty that we are seeking because of the is-
sues that we have discussed.
ACKNOWLEDGMENTS
Richard Macey was funded by Public Health England.
The views expressed are those of the authors and not
necessarily those of Public Health England or the Na-
tional Health Service.
SUPPLEMENTARY DATA
Supplementary data associated with this article can
be found, in the online version, at https://doi.org/10.
1016/j.ajodo.2020.01.015.
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744 Macey et al
June 2020 !Vol 157 !Issue 6 American Journal of Orthodontics and Dentofacial Orthopedics

APPENDIX
Search strategy: MEDLINE Ovid:
1. Orthodontics/
2. exp Malocclusion/ or exp Orthodontics, Corrective/
3. exp Orthondotic Appliances, Functional/ or exp Or-
thodontics, Corrective/ or malocclusion, Angle Class
II/ or Open Bite/
4. Malocclusion.mp.
5. 1 or 2 or 3 or 4
6. exp Therapeutics/
7. exp Methods/is, mt [Instrumentation, Methods]
8. correct$.mp.
9. 6 or 7 or 8
10. 5 and 9
11. dental caries activity tests/ or dental caries/
12. periodontal disease/
13. “Wounds and Injuries”/
14. Exp “Quality of Life”
15. 11 or 12 or 13 or 14
16. 5 and 15
17. Limit 16 to yr “1990-Current”
18. Limit 17 to humans
Macey et al 744.e1
American Journal of Orthodontics and Dentofacial Orthopedics June 2020 !Vol 157 !Issue 6

Supplementary Table I. Trauma studies
Study, year Location Setting Male (%) Age (y) Recruited/reported (n) Malocclusion tool
Malocclusion
threshold (mm)
Trauma
measure Trauma reporting
Abidoye, 1993
1
Nigeria School 51 12-12 574/574 Class I, II, III Garcia Godoy
Aldrigui, 2011
2
Brazil Preschool 53 2-5 305/260 TDI $3.1 mm Glendor Presence/absence
Altun, 2009
3
Turkey School 52 6-12 4956/472
Antunes, 2015
4
Brazil Preschool 319 2-6 606/606 Overjet $3 mm WHO
classification
No trauma (0), treated (1),
enamel fracture (2),
dentine fracture (3), pulp
(4), missing tooth because
of trauma (5), other
damage (6)
Artun, 2005
5
Kuwait School 50 13-14 1583/1572 Overjet #3.5, 4-6 mm,
6.5-9 mm
National Institute
of Dental
Research Index
Presence/absence,
assumed .3.5 for overjet
in data extraction
Baldava, 2007
6
India School 14-16 386/370 Overjet #3.5, 4-6 mm,
6.5-9 mm
Sgan-Cohen
method
No trauma (0), enamel (1),
dentin (2), pulp (3),
treated (4), discolor (5),
avulsed (6)
Bendo, 2010
7
Brazil School 11-14 1870/1612 Overjet .5 mm
Bendgude, 2012
8
India School 0 11-17 2045/2045 Overjet #3.5, 4-6 mm,
6.5-9 mm
Ellis & Dovey
Bonini, 2009
9
Brazil Health center 51 0-1 1265/1265 Overjet Not reported Ellis
Bonini, 2012
10
Brazil Health center 49 3-4 380/376 Overjet .3 mm Andreasen
Borzabadi-Farahani,
2010
11
Iran School 49 11-14 502/502 ICON $44 No trauma (0), enamel (1),
dentin (2), pulp (3),
treated (4), discolor (5),
avulsed (6)
Burden, 1995
12
UK School 48 11-12 1137/1107 Overjet & IOTN #3.5, 4-6 mm,
6.5-9 mm
Presence/absence
Cavalcanti, 2009
13
Brazil School 51 7-12 448/448 Overjet .3 mm Presence/absence
Cortes, 2001
14
Brazil School 47 9-14 3817/3702 Overjet .5 mm UK CDH Survey
Feldens, 2010
15
Brazil Nursery 51 3-5 888/888 Not reported .2 mm Andreasen
Francisco, 2013
16
Brazil School 41 9-14 850/765 Overjet .3 mm O'Brien .0
Freire-Maia, 2015
17
Brazil School 8-10 1201/0 Overjet .4 mm Andreasen
Hamdan, 1995
18
Jordan School 49 10-12 459/459 Overjet .5 mm Ellis Classification
Hunter, 1990
19
UK School 46 11-12 1018/936 Overjet .5 mm Fractures
Kania, 1996
20
U.S. School 7-12 4393/3396 Overjet Sweet classification
Kumar, 2011
21
India School 50 12-15 963/963 Overjet .3 mm Enamel,
dentine, pulp,
luxation
Livny, 2010
22
Israel School 49 11-12 804/804 Overjet .5 mm UK CDH Survey
Malikaew, 2006
23
Thailand School 11-13 4720/2725 Overjet .5 mm Cortes Classification Presence/absence
Marcenes, 1999
24
Syria School 59 9-12 1087/1087 Overjet, lip coverage .5 mm UK CDH Survey Yes/no
744.e2 Macey et al
June 2020 !Vol 157 !Issue 6 American Journal of Orthodontics and Dentofacial Orthopedics

Supplementary Table I. Continued
Study, year Location Setting Male (%) Age (y) Recruited/reported (n) Malocclusion tool
Malocclusion
threshold (mm)
Trauma
measure Trauma reporting
Marcenes, 2000
25
Brazil School 53 12-12 476/476 Overjet, lip coverage .5 mm UK CDH Survey Yes/no
Marcenes, 2001
26
UK School 48 14-14 2684/2242 Overjet, lip coverage .5 mm UK CDH Survey Yes/no
Marcenes, 2001a
27
Brazil School 50 12-12 652/652 Overjet, lip coverage .5 mm UK CDH Survey Yes/no
Martins, 2012
28
Brazil School 46 7-14 590/590 Overjet .3 mm UK CDH Survey Yes/no
Otuyemi, 1994
29
Nigeria School 53 12-12 1016/1016 Overjet, lip coverage Any trauma
Petti, 1996
30
Italy School 6-11 824/824 Overjet, lip coverage #3 mm
(overjet)
Garcia Godoy Any trauma
Rajab, 2013
31
Jordan School 47 12-12 2560/2560 Overjet, lip coverage .3 mm WHO Classification Yes/no
Ravishankar, 2010
32
India School 51 12-12 1020/1020 Overjet, lip coverage .5.5 WHO Classification
Schatz, 2013
33
Switz School 53 6-13 1900/1898 Overjet .6 mm NIDR
Sgan Cohen, 2005
34
Israel School 50 9-13 1195/1195 Overjet, lip coverage .7 mm No (1); mild: enamel (2);
severe: dentine, pulp (3)
Sgan Cohen, 2008
35
Israel School 60 10-12 480/453 Overjet, lip coverage .4 mm
(overjet)
No (1); mild: enamel (2);
severe: dentine, pulp (3)
Soriano, 2004
36
Brazil School 52 12-12 1150/116 Overjet, lip coverage .5 mm Andreasen
Taiwo, 2011
37
Nigeria School 57 12-12 719/719 Overjet .6 mm WHO Classification Yes/no
Traebert, 2003
38
Brazil School 52 11-13 2493/2260 Overjet, lip coverage .5 mm Yes/no
Traebert, 2006
39
Brazil School 12-12 297/260 Overjet, lip coverage .5 mm UK CDH Survey
Note. Empty spaces within the table mean that the data were not reported. TDI, traumatic dental injury; WHO, World Health Organization; ICON, index of complexity, outcome, and need; UK, United
Kingdom; CDH, Children's Dental Health; NIDR, National Institute of Dental Research.
Macey et al 744.e3
American Journal of Orthodontics and Dentofacial Orthopedics June 2020 !Vol 157 !Issue 6

Supplementary Table II. Quality of life studies
Study, year Location Setting Male (%) Age (y) Recruited/reported
Malocclusion
tool Malocclusion threshold
QOL
measure QOL reporting
Dann, 1995
40
US Secondary 51 9.3-11.4 104/104 Irregularity index Not clear Self concept
Peres, 2009
41
Brazil School 54 6-12 359/339 DAI Multiple features of
malocclusion
OIDP
Abanto, 2014
42
Brazil Other 53 1-4 1215/1215 Morph feature ECOHIS Continuous
Abreu, 2015
43
Brazil Secondary-
ortho dept
49 11-12 125/123 DAI 1 (\25), 2 (26-30), 3 (31-
35), 4 (.36)
FIS Continuous (0-56), low
impact (0-3), greater
impact (4-26)
Anosike, 2010
44
Nigeria School 49 12-16 805/0 DAI None (\25), elective (26-
30), desirable (31-35),
mandatory (.35)
OHIP 14 No impact (#14), impact
($15)
Araki, 2017
45
Mongolia School 47 10-16 420/420 Overjet, overbite,
IOTN, DHC
IOTN 4 or 5, overjet .6mm CPQ 11-14 Mean and SD reported
Barbosa, 2013
46
Brazil School 49 8-12 150/150 DAI 1 (\25), 2 (26-30), 3 (31-
35), 4 (.36)
CPQ 11-14 All domains
Barbosa, 2016
47
Brazil School 29 8-14 550/167 DAI 13-25, 26-31, 32-35, .36 CPQ 8-10
Bernab!
e, 2009
48
UK School 52 11-12 1126/1034 IOTN, DHC No need (0-3), need (4-5) OIDP-CS Identified impact relevant to
mal
De Oliveira, 2003
49
Brazil School 724 15-16 1675/1675 IOTN No need (1-2), moderate
need (3), great need (4-5)
OIDP Dichotomous into 0 or any
larger value 5impact
De Oliveira, 2004
50
Brazil School 724 15-16 1675/1675 IOTN OIDP
De Paula, 2013
51
Brazil School 12-12 286/267 DAI No need (\31), need (.31) CPQ 11-14 Continuous
Dimberg, 2016
52
Sweden Secondary 46 9-13 277/257 IOTN Need/no need CPQ 11-14 Dichotomous using medians
Dos Santos, 2017
53
Brazil School 44 12-12 240/248 IOTN AC & DHC Malocclusion (3-5), No (1-2) CPQ 11-14 Overall score
Duarte-Rodrigues,
2017
54
Brazil School 39 300/300 DAI Malocclusion present (.26) CPQ 8-10 and
child OIDP
Mean and SD reported
across domains and total
scores
Freire-Maia, 2015
17
Brazil School 45 8-10 1201/1201 Morph Features Overjet (\3), overbite (\2),
crowding (\2)
CPQ 8-10 Divided by conglomerates
Gomes, 2017
55
Brazil Preschool 52 5-0 769/769 None just
presence
of conditions
Increased overbite (.2 mm),
increased overjet
(.2 mm), AOB, anterior
crossbite, and posterior
crossbite
SOHO-5
and SOC-13
Heravi, 2010
56
Iran School 100 14-17 120/120 ICON Acceptable (.31), moderate
(31-43), definite (.43)
CPQ 11-14
Kaur, 2017
57
India School 43 10-17 1784/1140 IOTN AC & DHC Standard groups RSES Score 10-40
Kok, 2004
58
UK School 44 10-12 208/170 IOTN AC AC .6 CPQ 11-14 All domains
Locker, 2007
59
Canada School 56 11-14 370/370 IOTN AC 1-4, 5-7, 8-10 CPQ 11-14 Dichotomize at 80%
Machry, 2018
60
Brazil School 1134/0 DAI “Presence of malocclusion”
(moderate, severe, or
disabling)
744.e4 Macey et al
June 2020 !Vol 157 !Issue 6 American Journal of Orthodontics and Dentofacial Orthopedics

Supplementary Table II. Continued
Study, year Location Setting Male (%) Age (y) Recruited/reported
Malocclusion
tool Malocclusion threshold
QOL
measure QOL reporting
Manjith, 2012
61
India Secondary care 50 200/0 IOTN DHC Little or no need, borderline,
required
OHIP 14 No summary score
Marquez, 2009
62
Brazil School 35 14-18 448/403 DAI No treatment (#25), definite
treatment (.25)
OIDP With impact 1
O'Brien, 2007
63
UK Secondary care 43 11-14 147/0 IOTN DHC No need (1-2), moderate
need (3), great need (4-5)
CPQ 11-14 Medians
Onyeaso, 2007
64
Nigeria School 48 12-17 274/274 ICON Need (.43), easy (\29),
mild (29-50), moderate
(51-63), difficuly (67-77),
very difficult (.77)
OHIP 14 No impact (0-1), impact (2-
4)
Paula, 2009
65
Brazil School 42 13-20 301/301 DAI 1 (\25), 2 (26-30), 3 (31-
35), 4 (.36)
OHIP Overall score
Paula, 2012
66
Brazil School 12-12 0/515 DAI No need (\31), need (.31) CPQ 11-14
Scarpelli, 2013
67
Brazil School 5-5 1632/1412 Morph features Any feature 5malocclusion B-ECOHIS Continuous
Schuch, 2015
68
Brazil School 8-10 1086/750 DAI CPQ 8-10 All domains
Silva, 2016
69
Brazil School 12-15 1050/1015 DAI \25 no need Angles class: normal, Class I,
Class II
OHIP 14 No impact (0-9), impact (10-
28)
Sousa, 2014
70
Brazil School 3-5 732/732 Morph features ECOHIS Continuous
Tessarollo, 2012
71
Brazil School 53 12-13 704/704 DAI-quartiles #20, 21-24, 25-28, $29 Specially
designed Qs
Appearance, self-perception
of speech and mastication
Tomazoni, 2014
72
Brazil School 46 12-12 1134/0 DAI Not described CPQ 11-14 0-64
Vedovello, 2016
73
Brazil School 47 7-10 1256/0 Overjet .2,
cross bite \2,
overbite .2
Class I, II, III CPQ Division at median
Feu, 2013
74
Brazil 12-15 0/318 IOTN Mean measures OHIP 14 Overall score
Kramer, 2013
75
Brazil School 52 2-5 1380/1036 Overjet, AOB Present or absent ECOHIS FIS and CIS
Sun, 2017
76
Hong Kong School 52 12 668/589 IOTN No need (1-2), borderline
need (3), definite need (4-
5)
CPQ 11-14 Mean
Sun, 2018
77
Hong Kong School 51 15 668/364 IOTN No need (1-2), borderline
need (3), definite need (4-
5)
CPQ 11-14 Mean
Traebert, 2018
78
Brazil School 40 4-5 389/389 DAI Normal (\25), mild (26-30),
severe (31-35), very severe
malocclusion ($36)
OIDP All domains
Note. Empty spaces within the table mean that the data were not reported. ECOHIS, Early Childhood Oral Health Impact Scale; FIS, Family Impact Scale; DHC, Dental Health Component; SD, standard
deviation; UK, United Kingdom; AC, aesthetic component; SOHO-5, Scale of Oral Health Outcomes for Five-Year-Old Children; SOC-13, Sence of Coherence Scale; ICON, index of complexity,
outcome, and need; RSES, Rosenberg self-esteem scale; CS,condition-specific; AOB, anterior open bite; CIS, Child Impact Section.
Macey et al 744.e5
American Journal of Orthodontics and Dentofacial Orthopedics June 2020 !Vol 157 !Issue 6

Supplementary Table III. Caries and periodontal studies
Study, year Location Setting Male (%) Age (y)
Recruited/
reported (n) Malocclusion tool
Malocclusion
threshold Outcome measure Outcome reporting
Buczkowska-
Radlinska, 2012
79
Poland 3.5-19 Caries DMFT
Ashley, 1998
80
UK School 57 12.7 201/201 Irregularity of incisors Overlap and space
requirement
Plaque Silness & Loe
Davies, 1991
81
UK School 417/0 Crowding Plaque
Eismann, 1990
82
Germany Secondary care 60 9-9 30/0 Gingival health
Mtya, 2009
83
Tanzania School 40 12-14 1601/0 Overjet, AOB,
open bite,
crowding
Bjork & Bjork WHO criteria DMFT
Singh, 2011
84
India School 52 12-12 945/927 DAI Caries DMFT
Jord~
ao, 2015
85
Brazil School 12-12 2962/2075 DAI Perio CPI
Felden, 2015
86
Brazil School 11-14 509/509 DAI Caries DMFT
Zhang, 2017
87
Hong Kong School 53 4-5 538/495 Cross bite/open bite Caries DMFT
Note. Empty spaces within the table mean that the data were not reported. DMFT, decayed, missing, and filled teeth; UK, United Kingdom; AOB, anterior open bite; WHO,WorldHealthOrganization;
CPI, Community Peridontal Index.
Supplementary Table IV. Newcastle-Ottawa risk of
bias assessments for phase 2 studies
Study,
year Study design Selection Comparability Exposure
Dann,
1995
40
Case control ** ** **
Benson,
2015
88
Nonrandomized
cohort
**** ** ***
Thomson,
2002
89
Nonrandomized
cohort
**** ** *
Feu, 2013
74
Nonrandomized
cohort
**** * ***
744.e6 Macey et al
June 2020 !Vol 157 !Issue 6 American Journal of Orthodontics and Dentofacial Orthopedics

Supplementary Table V. Cochrane risk of bias for phase 2 studies
Study, year Design
Random
sequence
generation
Allocation
concealment
Blinding of outcome
assessment
Incomplete
outcome data
Selective
reporting Other biases
Chen, 2011 RCT High risk Unclear risk Low risk High risk Low risk Low risk
Tesco, 2010 RCT High risk Unclear risk High risk Low risk Low risk High risk
O'Brien, 2009 RCT Low risk Low risk Low risk Low risk Low risk Low risk
RCT, randomized control trial.
Macey et al 744.e7
American Journal of Orthodontics and Dentofacial Orthopedics June 2020 !Vol 157 !Issue 6

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