In-vitro orthodontic bond strength testing: A systematic ... - share

SYSTEMATIC REVIEW
In-vitro orthodontic bond strength testing:
A systematic review and meta-analysis
Katrina J. Finnema, a Mutlu Özcan, b Wendy J. Post, c Yijin Ren, d and Pieter U. Dijkstra e
Groningen, The Netherlands, and Zürich, Switzerland
Introduction: The aims of this study were to systematically review the available literature regarding in-vitro
orthodontic shear bond strength testing and to analyze the influence of test conditions on bond strength.
Methods: Our data sources were Embase and Medline. Relevant studies were selected based on predefined
criteria. Study test conditions that might influence in-vitro bond strength were independently assessed by 2
observers. Studies reporting a minimum number of test conditions were included for meta-analysis by
using a multilevel model with 3 levels, with author as the highest level, study as the second level, and
specimens in the study as the lowest level. The primary outcome measure was bond strength. Results: We
identified 121 relevant studies, of which 24 were included in the meta-analysis. Methodologic drawbacks of
the excluded studies were generally related to inadequate reporting of test conditions and specimen
storage. The meta-analysis demonstrated that 3 experimental conditions significantly affect in-vitro bond
strength testing. Although water storage decreased bond strength on average by 10.7 MPa, each second
of photopolymerization time and each millimeter per minute of greater crosshead speed increased bond
strength by 0.077 and 1.3 MPa, respectively. Conclusions: Many studies on in-vitro orthodontic bond
strength fail to report test conditions that could significantly affect their outcomes. (Am J Orthod
Dentofacial Orthop 2010;137:615-22)
Orthodontic bonding of brackets to teeth is a standard
procedure to align teeth with fixed appliances.
Orthodontic treatment with brackets
generally takes approximately 2 years. Bond failure of
brackets during this period retards treatment and is
costly in terms of time, material, and patient inconvenience.
Bracket debonding at the end of the treatment
should not damage the enamel. Hypothetically, in-vivo
testing in controlled trials is the best way to test the
effectiveness of a bonding system and any detrimental
effects on the enamel. However, clinically, it is almost im-
a Postgraduate student, Department of Orthodontics, University Medical Center
Groningen, University of Groningen, Groningen, The Netherlands.
b Professor, University of Zürich, Dental Materials Unit, Center for Dental and
Oral Medicine, Clinic for Fixed and Removable Prosthodontics and Dental Materials
Science, Zürich, Switzerland.
c Statistician, Department of Epidemiology, University Medical Center
Groningen, University of Groningen, Groningen, The Netherlands.
d Professor and chair, Department of Orthodontics, University Medical Center
Groningen, University of Groningen, Groningen, The Netherlands.
e Professor, Center for Rehabilitation, Department of Oral and Maxillofacial Surgery,
School for Health Research, University Medical Center Groningen, University
of Groningen, Groningen, The Netherlands.
The authors report no commercial, proprietary, or financial interest in the products
or companies described in this article.
Reprint requests to: Katrina J. Finnema, Department of Orthodontics, University
Medical Center Groningen, University of Groningen, Hanzeplein 1, PO Box
30.001, 9700 RB Groningen, The Netherlands; e-mail, k.j.finnema@dmo.
umcg.nl.
Submitted, July 2009; revised and accepted, December 2009.
0889-5406/$36.00
Copyright Ó 2010 by the American Association of Orthodontists.
doi:10.1016/j.ajodo.2009.12.021
possible to distinguish the adhesive potential of a specific
bonding system independent of many other variables
that can influence either the quality or the longevity of
bracket bonding to enamel. 1 In addition, the methodologic
quality of in-vivo randomized controlled trials
(RCTs) evaluating debonding and bracket failure is generally
poor. 2 Consequently, it is difficult to draw conclusions
about the effectiveness of specific bonding systems and
their effects on the enamel from in-vivo studies.
In-vitro studies possibly allow for more standardized
procedures for testing a specific bonding system.
However, the various test conditions that are used hamper
the comparison of their results. 3,4 Test conditions
suggested to influence bond strength include enamel
origin (ie, bovine vs human), substrate storage (eg,
physiologic saline solution or water), and pretreatment
of the enamel surface (eg, grinding and means of
cleaning). 5-7 In addition, bond strength testing might
also be influenced by the specific test mode used (eg,
tensile or shear testing). 8 An explanation for the different
outcomes between in-vitro bond strength studies
might therefore be that bond strength is not being tested
but, rather, an unknown combination of mechanical
properties and factors related to the test surfaces. Lately,
more attention has been given to the various test conditions
and their effects on the results. Recent studies have
evaluated the influence of some of these factors on bond
strength, including force location, 9 tooth type, 10-12
crosshead speed variations, 13,14 and loading mode. 8
615

616 Finnema et al American Journal of Orthodontics and Dentofacial Orthopedics
May 2010
At present, there is no overview on bracket bond
strength from which general conclusions can be drawn.
Because of the lack of standardization, the growing
number of in-vitro studies being published can only
be evaluated individually. The aims of this study were
to systematically review the literature regarding invitro
bond strength and failure mode of the most frequently
used clinical bonding systems and to analyze
by meta-regression the influence of test conditions on
the bond strength measured.
MATERIAL AND METHODS
Relevant studies were identified in a literature
search and subsequently selected on the basis of inclusion
criteria. Studies fulfilling the inclusion criteria
were assessed for reporting test conditions that could influence
the results of in-vitro bond strength testing. The
studies reporting a minimal number of test conditions
were included for meta-analysis.
To identify studies related to in-vitro bond strength,
a search was performed in the databases of Medline
(1967 to December 2007) and Embase (1950 to December
2007) (Table I). References of identified studies and
relevant review articles were searched for additional
studies missed in the initial search. English was the language
restriction.
Initially, the titles and abstracts of the studies identified
in the literature search were prescreened (by
K.J.F.) for relevance to the topic of this study (in-vitro
orthodontic shear bond strength testing). The full text
of each possibly relevant study was retrieved and assessed
by 2 reviewers (M.Ö., K.J.F.) for inclusion and
detailed assessment of the experimental conditions.
The Figure outlines the algorithm of the study selection
procedure.
Studies regarding bond strength testing were selected
for detailed assessment of the experimental conditions
if they met the following criteria: in-vitro
investigation, with the shear bond strengths of metal
brackets evaluated and expressed in megapascals
(MPa), and the sound buccal enamel of human premolars
used. Case reports, abstracts, letters, and narrative
reviews were excluded.
A list of 27 items was used to assess the experimental
conditions, each reflecting an experimental condition
that influences the results of in-vitro bond strength testing
(Table II). 3,4 Before the assessment of the studies, 2
observers (M.Ö. and K.J.F.) discussed all 27
experimental conditions to reach consensus about
their content. They independently assessed whether
the experimental conditions were reported in the
study. After the assessment, the observers agreed on
Table I. Search strategy in Medline and Embase
Search Literature search strategy
1 Explode "orthodontic-brackets"/MeSH
all subheadings
2 Bracket*
3 Fixed applian*
4 #1or#2or#3
5 Explode "dental-bonding"/MeSH all subheadings
6 Bond*
7 #5 or #6
8 #4 and #7
9 Explode "composite-resins"/MeSH all subheadings
10 Explode "compomers"/MeSH all subheadings
11 Explode "glass-ionomer-cements"/MeSH
all subheadings
12 Composite resin
13 Glass ionomer
14 Compomer
15 #8 and (#9 or #12)
16 #8 and (#10 or #14)
17 #8 and (#11 or #13)
18 #8 and bond strength
19 Search Medline/Embase: #15 or #16 or #17 or #18
#, Search; MeSH, medical subjects heading (a thesaurus word); *, truncation
of a text word.
the reporting of the 27 experimental conditions of
each study in a consensus meeting.
Studies included in the meta-analysis
The 2 observers independently determined the most
relevant experimental conditions for in-vitro bond
strength studies based on the results from previous studies.
In a consensus meeting, agreement was reached on
these required experimental conditions. Studies were
included in the meta-analysis if at least all of the following
experimental conditions were reported: storage
solution of teeth, 15 cleaning of enamel, 16 bracket
type, 17-19 etchant type, 20 etching time, 21 adhesive
type, photopolymerization device, 22 total photopolymerization
time, 23 specimen storage time, 24 crosshead
speed, 9,14 force location on bracket, 13 and blade design
of the jig of the universal testing machine. 25
The 2 observers independently extracted the data.
Consensus was reached after discussion in case of disagreement.
First, for each of the 27 experimental conditions, the
number and percentage of included studies describing
this specific item were calculated (Table II). Subsequently,
for each study included in the meta-analysis,
the following data were presented: thymol storage
solution (yes/no), fluor-free cleaning (yes/no), mesh
brackets (yes/no), phosphoric acid etching (yes/no), etching
time (\30 seconds/$30 seconds), photopolymerization
time (seconds), photopolymerized composite (yes/

American Journal of Orthodontics and Dentofacial Orthopedics Finnema et al 617
Volume 137, Number 5
Potentially relevant studies
identified and screened for
retrieval (n = 918)
Studies retrieved for more
detailed evaluation (n = 166)
Potentially appropriate studies
to be included in the
meta-analysis (n = 121)
Studies included in metaanalysis
(n = 28)
Studies with usable
information, by outcome
(n = 24)
Studies excluded, with
reasons (n = 752)
- not relevant for topic
Studies excluded, with
reasons (n = 45)
- did not meet with
inclusion criteria
Studies excluded, with
reasons (n = 93)
- did not meet threshold
Studies withdrawn, by
outcome, with reasons
(n = 4)
- overlapping data
or missing data
Fig. Algorithm of study selection procedure.
no), halogen light (yes/no), water storage (yes/no), storage
time (hours), thermocycling (yes/no), crosshead
speed (millimeters per minute), force location on the
tooth-bracket interface (yes/no), and shearing blade
(yes/no). Of the latter data, the influence on the main outcome
variable (bond strength in megapascals) was evaluated
in the meta-analysis. Failure mode reported with the
adhesive remnant index (ARI) was also scored when
reported and is presented as the percentage of specimens
with all adhesive left on the enamel. 26
Statistical analysis
Statistical analyses were performed by using the
Statistical Package for the Social Sciences (version
16.0, SPSS, Chicago, Ill). The interobserver agreement
with respect to the reporting of experimental conditions
of the included studies before the consensus meeting
was expressed as the Cohen kappa. For descriptive
statistics, means (standard deviations or medians) and
interquartile ranges in skewed distributions are reported.
In MLwin (version 2.02, Centre for Multilevel
Modelling, Bristol, United Kingdom), a 3-level analysis
(random-effects model) was performed. This is a metaregression
analysis. The lowest level corresponded to
the specimen level (specimens in studies), the middle
level with the study, and the highest level corresponded
Table II. Experimental conditions assessed in the 121
articles
Experimental condition
Number (%) of studies
adequately reporting
experimental
condition
1. Substrate origin* 121 (100)
2. Type of teeth* 121 (100)
3. Storage time before bonding 38 (31)
4. Storage temperature before bonding 38 (31)
5. Storage solution before bonding† 108 (89)
6. Cleaning of specimens† 113 (93)
7. Bracket material* 121 (100)
8. Type of bracket† 94 (78)
9. Type of etchant† 111 (92)
10. Time of etching† 109 (90)
11. Adhesive type† 119 (98)
12. Amount of force at bracket placement 18 (15)
13. Light device type† 75 (62)
14. Total polymerization time† 84 (69)
15. Light directions 65 (54)
16. Sample storage time† 109 (90)
17. Sample storage solution 103 (85)
18. Sample storage temperature 97 (80)
19. Thermocycling 26 (22)
20. Testing machine 119 (98)
21. Shear testing as test method 121 (100)
22. Crosshead speed† 117 (97)
23. Force location on bracket† 83 (69)
24. Blade design† 73 (60)
25. ARI 93 (77)
26. Magnification used in determining ARI 70 (58)
27. Bond strength in MPa* 121 (100)
*Studies reporting experimental conditions numbers 1, 2, 7 and 27
were included in the systematic review. †Studies reporting experimental
conditions numbers 5, 6, 8, 9, 10, 11, 13, 14, 16, 22, 23 and 24,
together with those conditions marked *, were selected for metaanalysis.
with the author. In this way, the correlation within authors
between studies was taken into account. Residual
variance was entered in the multilevel model by using
the within-study variance published in each study.
Different models were compared by using the
change in deviance (–2 log likelihood), a likelihood ratio
test (chi-square distributed). In this way, it was also
possible to test the statistical heterogeneity between
authors and between articles by making different assumptions
about (models for) the covariance structure.
Effects with P values smaller than 0.05 were considered
significant.
RESULTS
The searches of Medline and Embase yielded 918
publications. After the first assessment, 166 studies
were judged to be relevant for this systematic review.
We found no additional studies by checking the

618 Finnema et al American Journal of Orthodontics and Dentofacial Orthopedics
May 2010
references of the included studies and relevant review
articles. After we used the specified criteria, 121 of
the 166 studies regarding bond strength testing were included
for detailed assessment of the experimental conditions
(Fig). Interobserver agreement (Cohen kappa)
for reporting the 27 experimental conditions of the included
studies was 0.86. Disagreements were generally
caused by differences in language interpretation and
were resolved in the consensus meeting.
On average, the 121 included studies reported
a mean of 20.4 (SD, 2.8) experimental conditions with
a minimum of 12 27 and a maximum of 26. 28,29 The
most poorly reported item was the experimental
condition of amount of force at bracket placement.
This was reported in 18 (15%) of the 121 studies. The
most relevant experimental conditions for in-vitro
bond strength were reported in the following percentage
of studies: adhesive type, 98%; crosshead speed, 97%;
cleaning of enamel, 93%; etchant type, 92%; etching
time, 90%; specimen storage time, 90%; storage solution
of teeth before bonding, 89%; bracket type, 78%;
total polymerization time, 69%; force location on
bracket, 69%; photopolymerization device, 62%; and
blade design, 60% (Table II).
Studies included for meta-analysis
By using the threshold value, 28 studies were included
in the meta-analysis. In 3 of the 9 studies from
the same authors, overlapping study data were reported.
30-32 These duplicated data were not entered in
the meta-analysis. One other study was excluded from
the meta-analysis because the standard deviation of
the main outcome measure (bond strength in megapascals)
was not reported. 33 As a result, 24 studies were included
in the meta-analysis (Appendix). 28,34-56 From
these studies, data regarding experimental groups with
a photopolymerized adhesive and nonself-ligating
metal brackets were extracted for further analyses.
This yielded 65 experimental groups that tested bond
strength in specimen groups ranging from 5 to 40 premolars
(mean, 14.1; SD, 7.4) (Appendix). Extracted
teeth were stored in distilled water with thymol in 30 experimental
groups. Fluor-free cleaning was explicitly
reported in 32 groups. In 58 groups, a metal bracket
with a mesh base was used. Phosphoric acid etching
was used in 47 groups; in 48 experimental groups, the
etching time was $30 seconds. The total polymerization
times in the 65 groups varied from 2 to 60 seconds
(mean, 25.3; SD, 14.8).
A photopolymerized composite was used in 59
groups, and a halogen polymerization device was used
to cure the adhesives in 48 groups. Water storage was re-
Table III. Multilevel meta-analysis with bond strength
(MPa) as the dependent variable
Independent variable Beta (SE)
Lower
95% CI
Upper
95% CI
Water storage
(no, 0; yes,1)
–10.648 (3.541) –17.730 –3.566
Polymerization time
(per second)
0.077 (0.030) 0.017 0.137
Crosshead speed
(mm/min)
1.302 (0.599) 0.104 2.500
Constant 20.014 (3.452) 13.110 26.918
ported in 57 groups; in 8 experimental groups, artificial
saliva was used for storing the test specimens. 28 The
storage times of the specimens ranged from 0 to 672
hours (median, 24; interquartile range, 0-48). Thermocycling
was explicitly reported in 15 of the 65 groups.
The crosshead speeds when removing the bracket varied
from 0.1 to 5.0 mm per minute (median, 0.5; interquartile
range, 0.5-1.0). In 23 studies, the force location was
at the bracket-enamel interface. In 50 groups, a shearing
blade was used for debonding the brackets. In the remaining
15 groups, a wire loop was used for the same
purpose. Based on the diversity in reported test conditions,
we concluded that there was considerable clinical
heterogeneity in these studies. Bond strengths ranged
from 3.5 to 27.8 MPa (mean, 13.4; SD, 5.7). ARI scores
were reported in 57 experimental groups. Specimens
with all adhesive left on the enamel after bond strength
testing varied from 0% to 90%.
Meta-analysis
Table III summarizes the results of the metaanalysis.
Heterogeneity between authors and studies
was still significant after entering the predictor variables
(P \0.05). The results of bond strength testing were
negatively influenced when the teeth were stored in water.
Water storage on average decreased bond strength
by 10.7 MPa, assuming that the other predictors remain
constant. Analogously, each second of photopolymerization
time increased the bond strength by 0.077 MPa;
when crosshead speed increased by 1 mm per minute,
bond strength increased by 1.3 MPa.
DISCUSSION
There was great diversity in the experimental conditions
of studies reporting bond strength testing in orthodontics.
The results from the meta-analysis in this
systematic review indicate that the experimental conditions
of water storage, photopolymerization time, and
crosshead speed significantly influenced the results of
in-vitro bond strength testing.

American Journal of Orthodontics and Dentofacial Orthopedics Finnema et al 619
Volume 137, Number 5
As previously shown in 2 other reviews evaluating
orthodontic bond strength studies, there is still great diversity
in test protocols and quality of these studies. 3,4
The observed heterogeneity between the studies in
this meta-analysis was clinically and statistically large.
Not one study described all 27 experimental conditions.
This finding might relate to the fact that some experimental
conditions—eg, the ARI and thermocycling—
were not used in all studies. However, when evaluating
the 121 studies for the most relevant experimental conditions,
only 28 fulfilled the threshold value. This finding
indicates that most of these in-vitro studies did not
properly report important confounding factors that affect
bond strength outcomes. When we finally included
24 of these 28 studies in a meta-analysis, water storage
of the bonded specimens, photopolymerization time,
and crosshead speed were shown to be the variables
that primarily affected the bond strength outcomes.
Water storage decreased bond strength on average
by 10.7 MPa. Although this was the most pronounced
effect of an experimental condition on in-vitro bond
strength outcomes, this finding was mainly influenced
by 1 relatively large study sample in which artificial saliva
was used as a storage medium for specimens. 28
Most in-vitro bond strength studies used distilled water
for storing the specimens, but 11% of the studies did not
report the storage medium. It was previously reported
that specimen storage in artificial saliva reduces bond
strength similarly to the effect of water degradation. 57
Although our study indicates that distilled water has
a different effect on bond strength than artificial saliva,
future research on the effects of different storage media
on bond strength is needed.
The second experimental condition that we found to
significantly affect in-vitro bond strength was photopolymerization
time. Each additional second of photopolymerization
increased bond strength by 0.077 MPa. It was
previously suggested that photopolymerization time has
a greater influence on in-vitro bond strength than the
type of photopolymerization device. 23,58 The studies in
this meta-analysis showed considerable variations in
photopolymerization time: from 2 to 50 seconds. Moreover,
31% of the included studies did not even report
polymerization time (Appendix). Most remaining studies
used 40 seconds for polymerizing the adhesive; this
corresponds to the routine clinical standard. The fact
that the majority of these studies used a halogen device
for polymerizing the adhesive most likely explains
why this polymerization time was used. The results
from our meta-analysis, however, suggest that a longer
polymerization time yields higher bond strengths,
although the most optimal time for polymerizing the
adhesive cannot be deduced from our results.
The third experimental condition shown to significantly
affect outcomes of bond strength testing was
crosshead speed. An increase in crosshead speed of 1
mm per minute yielded an increase in average bond
strength of 1.3 MPa. The opposite effect was demonstrated
in 2 previous studies in which increases in crosshead
speed from 0.5 to 5.0 mm per minute and from 1 to
200 mm per minute, respectively, were associated with
significant decreases of in-vitro bond strength. 14,59 This
phenomenon was suggested to relate to the induction of
a stiff body response and the elimination of the
viscoelastic properties of the adhesive. 59 In another
study, no effect was observed on bond strength with
crosshead speed variations between 0.1 and 5 mm per
minute. 9 In the studies included in this meta-analysis,
crosshead speeds ranged from 0.1 to 5 mm per minute
with most using a speed of 0.5 mm per minute
(Appendix). We have no obvious explanation for the
discrepancy of our results with those of previous studies;
unknown confounders might be responsible.
Bond strength values reported in the 24 studies in
this meta-analysis ranged from 3.5 to 27.8 MPa. Clinical
implications of in-vitro bond strength values are
generally based on the recommendation in a review article
from 1975 60 ; a ‘‘clinically acceptable’’ value was
defined as an in-vitro bond strength of 6 to 8 MPa. According
to this criterion, 53 of the 65 experimental
groups from our meta-analysis should be considered
to have clinically acceptable bond strength values. Because
it has never actually been tested whether 6 to 8
MPa is a sufficient in-vitro bond strength for clinical
use, the use of this reference value has been criticized
before. 4,61 Since the publication of this reference
value, various materials have been used, and the
effects of various test conditions (eg, pH and
temperature variations) have been implicated in the
aging of composite resins. 61 This implies that interpretation
of bond strength data should be limited to the relative
effectiveness of the adhesives used in a study.
Extrapolation of absolute values and comparing them
with a supposedly ‘‘clinically acceptable’’ reference
value should be avoided. 62
Since shear bond strength testing is the most commonly
used method for debonding brackets, only studies
that used this method were included in our review.
With respect to shear bond strength testing, there are
also some variations in blade design. Most studies
used a shearing blade for debonding the brackets,
whereas in some studies a wire loop was used. 40-43,45-47
Debonding brackets with a wire loop is not a true
form of shear bond strength testing, since it also
incorporates a component of tensile stress. Although
blade design could not be identified as an

620 Finnema et al American Journal of Orthodontics and Dentofacial Orthopedics
May 2010
experimental condition that significantly affected invitro
bond strength results in this meta-analysis, different
shearing blades could have an effect. This should be
substantiated by additional studies.
Theoretically, in-vitro studies determine the true
strength of a given bonding system to the enamel substrate.
Unfortunately, in-vitro studies have not been successful
in predicting in-vivo effectiveness. 63,64 An
accurate simulation of the clinical situation seems
necessary to obtain clinically relevant results from invitro
experiments. 4 However, because of the many conditions
involved in the in-vivo situation, an accurate
simulation is at present an unrealistic goal. Although
in-vitro bond strength testing is valuable for initial
screening and selection of materials, it cannot be regarded
as a substitute for in-vivo testing. Orthodontic
materials that perform well in in-vitro experiments
should always be tested with in-vivo RCTs.
Although we systematically reviewed the current
literature on in-vitro shear bond strength testing, our
study has some possible limitations. Selection bias
could have resulted in inappropriate inclusion or exclusion
of studies based on factors other than the inclusion
criteria. This chance was minimized by having 2 observers
independently assess the articles. Another shortcoming
might have been our language restriction.
Moreover, only 2 databases were searched. Some relevant
studies might have been missed by doing so. However,
we believe that our conclusion of poor descriptions
of test conditions in most in-vitro bond strength studies
would not be altered by studies that were possibly
missed because of language and database restrictions.
This is substantiated, since 93 (77%) of the 121 potentially
appropriate studies were excluded from the
meta-analysis because test conditions were not adequately
reported. Finally, this is a systematic review
concerning in-vitro observational studies. Conclusions
in systematic reviews and meta-analyses are preferably
based on results from RCTs. No RCTs were available
for the topic of this systematic review and metaanalysis.
Selection bias, information bias, and unknown
confounders threatened the validity of each study that
we evaluated. In future in-vitro studies, bracket debonding
should be evaluated more carefully by considering
the items studied in this review. With this approach,
the most dominant factor affecting bracket adhesion in
vitro might also be identified and correlated with the
clinical situation.
CONCLUSIONS
In this systematic review and meta-analysis, a summary
of factors is given that can affect the in-vitro bond
strength of orthodontic brackets. Experimental conditions
that significantly influence in-vitro bond strength
are water storage of the bonded specimens, photopolymerization
time, and crosshead speed. Based on the results
from this systematic review, we concluded that
many studies did not properly report test conditions
that could have significantly affected the outcomes. Because
of developments in adhesive dentistry and the increasing
numbers of bond strength studies, uniform
guidelines for standardization of the experimental conditions
of in-vitro bond strength research is clearly
indicated.
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28. Chang WG, Lim BS, Yoon TH, Lee YK, Kim CW. Effects of
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29. Tecco S, Traini T, Caputi S, Festa F, de Luca V, D’Attilio M. A
new one-step dental flowable composite for orthodontic use: an
in-vitro bond strength study. Angle Orthod 2005;75:672-7.
30. Vicente A, Bravo LA, Romero M, Ortız AJ, Canteras M. Bond
strength of brackets bonded with an adhesion promoter. Br Dent
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31. Vicente A, Bravo LA, Romero M, Ortız AJ, Canteras M. Effects
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32. Vicente A, Bravo LA, Romero M. Self-etching primer and a nonrinse
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33. Aljubouri YD, Millett DT, Gilmour WH. Laboratory evaluation of
a self-etching primer for orthodontic bonding. Eur J Orthod 2003;
25:411-5.
34. Buyukyilmaz T, Usumez S, Karaman AI. Effect of self-etching
primers on bond strength—are they reliable? Angle Orthod
2003;73:64-70.
35. Kim MJ, Lim BS, Chang WG, Lee YK, Rhee SH, Yang HC. Phosphoric
acid incorporated with acidulated phosphate fluoride gel
etchant effects on bracket bonding. Angle Orthod 2005;75:
678-84.
36. Klocke A, Korbmacher HM, Huck LG, Kahl-Nieke B. Plasma arc
curing lights for orthodontic bonding. Am J Orthod Dentofacial
Orthop 2002;122:643-8.
37. Martin S, Garcia-Godoy F. Shear bond strength of orthodontic
brackets cemented with a zinc oxide-polyvinyl cement. Am J Orthod
Dentofacial Orthop 1994;106:615-20.
38. McCourt JW, Cooley RL, Barnwell S. Bond strength of light-cure
fluoride-releasing base-liners as orthodontic bracket adhesives.
Am J Orthod Dentofacial Orthop 1991;100:47-52.
39. Northrup RG, Berzins DW, Bradley TG, Schuckit W. Shear bond
strength comparison between two orthodontic adhesives and
self-ligating and conventional brackets. Angle Orthod 2007;77:
701-6.
40. Romano FL, Tavares SW, Nouer DF, Consani S, Borges de Araújo
Magnani MB. Shear bond strength of metallic orthodontic
brackets bonded to enamel prepared with self-etching primer. Angle
Orthod 2005;75:849-53.
41. Sayinsu K, Isik F, Sezen S, Aydemir B. New protective polish effects
on shear bond strength of brackets. Angle Orthod 2006;76:
306-9.
42. Sayinsu K, Isik F, Sezen S, Aydemir B. Light curing the primer—
beneficial when working in problem areas? Angle Orthod 2006;
76:310-3.
43. Schaneveldt S, Foley TF. Bond strength comparison of moistureinsensitive
primers. Am J Orthod Dentofacial Orthop 2002;122:
267-73.
44. Scougall Vilchis RJ, Yamamoto S, Kitai N, Hotta M,
Yamamoto K. Shear bond strength of a new fluoride-releasing orthodontic
adhesive. Dent Mater J 2007;26:45-51.
45. Signorelli MD, Kao E, Ngan PW, Gladwin MA. Comparison of
bond strength between orthodontic brackets bonded with halogen
and plasma arc curing lights: an in-vitro and in-vivo study. Am
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46. Sunna S, Rock WP. An ex vivo investigation into the bond
strength of orthodontic brackets and adhesive systems. Br J Orthod
1999;26:47-50.
47. Tecco S, Traini T, Caputi S, Festa F, de Luca V, D’Attilio M. A
new one-step dental flowable composite for orthodontic use: an
in-vitro bond strength study. Angle Orthod 2005;75:672-7.
48. Usxümez S, Büyükyilmaz T, Karaman AI. Effect of light-emitting
diode on bond strength of orthodontic brackets. Angle Orthod
2004;74:259-63.
49. Uysal T, Basciftci FA, Usxümez S, Sari Z, Buyukerkmen A. Can
previously bleached teeth be bonded safely? Am J Orthod Dentofacial
Orthop 2003;123:628-32.
50. Vicente A, Bravo LA, Romero M, Ortiz AJ, Canteras M. Adhesion
promoters: effects on the bond strength of brackets. Am
J Dent 2005;18:323-6.
51. Vicente A, Bravo LA, Romero M, Ortız AJ, Canteras M. Shear
bond strength of orthodontic brackets bonded with self-etching
primers. Am J Dent 2005;18:256-60.
52. Vicente A, Bravo LA, Romero M. Influence of a nonrinse conditioner
on the bond strength of brackets bonded with a resin adhesive
system. Angle Orthod 2005;75:400-5.
53. Vicente A, Bravo LA, Romero M, Ortiz AJ, Canteras M. A
comparison of the shear bond strength of a resin cement and
two orthodontic resin adhesive systems. Angle Orthod 2005;
75:109-13.
54. Vicente A, Navarro R, Mena A, Bravo LA. Effect of surface treatments
on the bond strength of brackets bonded with a compomer.
Am J Dent 2006;19:271-4.
55. Vicente A, Bravo LA. Direct bonding with precoated brackets and
self-etching primers. Am J Dent 2006;19:241-4.
56. Wendl B, Droschl H. A comparative in-vitro study of the strength
of directly bonded brackets using different curing techniques. Eur
J Orthod 2004;26:535-44.

622 Finnema et al American Journal of Orthodontics and Dentofacial Orthopedics
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American Journal of Orthodontics and Dentofacial Orthopedics Finnema et al 622.e1
Volume 137, Number 5
APPENDIX REFERENCES
1. Buyukyilmaz T, Usumez S, Karaman AI. Effect of self-etching
primers on bond strength—are they reliable? Angle Orthod
2003;73:64-70.
2. Chang WG, Lim BS, Yoon TH, Lee YK, Kim CW. Effects of
salicylic-lactic acid conditioner on the shear bond strength of
brackets and enamel surfaces. J Oral Rehabil 2005;32:287-95.
3. Kim MJ, Lim BS, Chang WG, Lee YK, Rhee SH, Yang HC. Phosphoric
acid incorporated with acidulated phosphate fluoride gel
etchant effects on bracket bonding. Angle Orthod 2005;75:678-84.
4. Klocke A, Korbmacher HM, Huck LG, Kahl-Nieke B. Plasma arc
curing lights for orthodontic bonding. Am J Orthod Dentofacial
Orthop 2002;122:643-8.
5. Martin S, Garcia-Godoy F. Shear bond strength of orthodontic
brackets cemented with a zinc oxide-polyvinyl cement. Am
J Orthod Dentofacial Orthop 1994;106:615-20.
6. McCourt JW, Cooley RL, Barnwell S. Bond strength of light-cure
fluoride-releasing base-liners as orthodontic bracket adhesives.
Am J Orthod Dentofacial Orthop 1991;100:47-52.
7. Northrup RG, Berzins DW, Bradley TG, Schuckit W. Shear bond
strength comparison between two orthodontic adhesives and selfligating
and conventional brackets. Angle Orthod 2007;77:701-6.
8. Romano FL, Tavares SW, Nouer DF, Consani S, Borges de Araújo
Magnani MB. Shear bond strength of metallic orthodontic
brackets bonded to enamel prepared with self-etching primer.
Angle Orthod 2005;75:849-53.
9. Sayinsu K, Isik F, Sezen S, Aydemir B. New protective polish effects
on shear bond strength of brackets. Angle Orthod 2006;76:306-9.
10. Sayinsu K, Isik F, Sezen S, Aydemir B. Light curing the primer–
beneficial when working in problem areas? Angle Orthod 2006;
76:310-3.
11. Schaneveldt S, Foley TF. Bond strength comparison of moistureinsensitive
primers. Am J Orthod Dentofacial Orthop 2002;122:
267-73.
12. Scougall Vilchis RJ, Yamamoto S, Kitai N, Hotta M,
Yamamoto K. Shear bond strength of a new fluoride-releasing
orthodontic adhesive. Dent Mater J 2007;26:45-51.
13. Signorelli MD, Kao E, Ngan PW, Gladwin MA. Comparison of
bond strength between orthodontic brackets bonded with halogen
and plasma arc curing lights: an in-vitro and in-vivo study. Am
J Orthod Dentofacial Orthop 2006;129:277-82.
14. Sunna S, Rock WP. An ex vivo investigation into the bond
strength of orthodontic brackets and adhesive systems. Br J Orthod
1999;26:47-50.
15. Tecco S, Traini T, Caputi S, Festa F, de Luca V, D’Attilio M. A
new one-step dental flowable composite for orthodontic use: an
in-vitro bond strength study. Angle Orthod 2005;75:672-7.
16. Usxümez S, Büyükyilmaz T, Karaman AI. Effect of light-emitting
diode on bond strength of orthodontic brackets. Angle Orthod
2004;74:259-63.
17. Uysal T, Basciftci FA, Usxümez S, Sari Z, Buyukerkmen A. Can
previously bleached teeth be bonded safely? Am J Orthod Dentofacial
Orthop 2003;123:628-32.
18. Vicente A, Bravo LA, Romero M, Ortiz AJ, Canteras M.
Adhesion promoters: effects on the bond strength of brackets.
Am J Dent 2005;18:323-6.
19. Vicente A, Bravo LA, Romero M, Ortız AJ, Canteras M. Shear
bond strength of orthodontic brackets bonded with self-etching
primers. Am J Dent 2005;18:256-60.
20. Vicente A, Bravo LA, Romero M. Influence of a nonrinse conditioner
on the bond strength of brackets bonded with a resin
adhesive system. Angle Orthod 2005;75:400-5.
21. Vicente A, Bravo LA, Romero M, Ortiz AJ, Canteras M.
A comparison of the shear bond strength of a resin cement
and two orthodontic resin adhesive systems. Angle Orthod
2005;75:109-13.
22. Vicente A, Navarro R, Mena A, Bravo LA. Effect of surface treatments
on the bond strength of brackets bonded with a compomer.
Am J Dent 2006;19:271-4.
23. Vicente A, Bravo LA. Direct bonding with precoated brackets and
self-etching primers. Am J Dent 2006;19:241-4.
24. Wendl B, Droschl H. A comparative in-vitro study of the strength
of directly bonded brackets using different curing techniques.
Eur J Orthod 2004;26:535-44.

622.e2 Finnema et al American Journal of Orthodontics and Dentofacial Orthopedics
May 2010
Appendix table. Overview of the experimental conditions and outcomes of the studies in the meta-analysis
Reference
number of
study
Number
per
group
Thymol
storage
Fluor-free
cleaning
Mesh
base
Phosphoric
acid
etch
Etch
time
$30 s
Polymerization
time (s)
1 20 N N Y Y Y 40 Y
1 20 N N Y N N 40 Y
1 20 N N Y N N 40 Y
1 20 N N Y N Y 40 Y
2 9 Y Y Y Y N 30 Y
2 9 Y Y Y Y N 4 Y
2 9 Y Y Y Y N 50 Y
2 9 Y Y Y Y N 4 Y
2 9 Y Y Y N Y 30 Y
2 9 Y Y Y N Y 4 Y
2 9 Y Y Y N Y 50 Y
2 9 Y Y Y N Y 4 Y
3 10 Y Y Y Y Y 40 Y
3 10 Y Y Y Y Y 40 Y
3 10 Y Y Y Y Y 40 Y
4 15 N N Y Y Y 6 Y
4 15 N N Y Y Y 2 Y
4 15 N N Y Y Y 6 Y
4 15 N N Y Y Y 2 Y
4 15 N N Y Y Y 20 Y
5 10 N N Y Y N 60 Y
6 10 N N Y Y Y 20 Y
6 10 N N Y Y Y 20 Y
6 10 N N Y Y Y 20 N
6 10 N N Y Y Y 20 N
7 20 N N Y Y N 20 Y
8 10 Y Y N Y Y 40 Y
8 10 Y Y N N N 40 Y
8 10 Y Y N N N 40 Y
9 20 N N N Y Y 40 Y
10 15 N N N Y Y 40 Y
10 15 N N N Y Y 40 Y
11 40 Y Y Y Y Y 40 Y
12 35 Y Y Y Y Y 30 Y
12 35 Y Y Y N Y 30 Y
13 15 Y N Y Y Y 20 Y
13 15 Y N Y Y Y 20 Y
13 15 Y N Y Y Y 6 Y
13 15 Y N Y Y Y 6 Y
14 10 N N Y Y Y 20 Y
14 10 N N N Y Y 20 Y
14 10 N N Y Y Y 20 Y
15 15 Y Y Y Y Y 40 Y
16 20 N Y Y Y Y 40 Y
16 20 N Y Y Y Y 10 Y
16 20 N Y Y Y Y 20 Y
16 20 N Y Y Y Y 40 Y
17 20 N Y Y Y Y 20 Y
18 25 Y N Y Y Y 20 Y
19 25 Y N Y N N 20 Y
20 15 Y N Y N N 20 Y
21 25 Y N Y Y Y 30 Y
22 15 Y N Y Y Y 40 Y
22 15 Y N Y N N 40 Y
23 15 Y N Y Y Y 20 Y
23 15 Y N Y N N 20 Y
24 5 N Y Y Y Y 40 Y
24 5 N Y Y Y Y 10 Y
24 5 N Y Y Y Y 2 Y
24 5 N Y Y Y Y 3 Y
24 5 N Y Y Y Y 24 Y
24 5 N Y Y N N 40 N
24 5 N Y Y N N 10 N
24 5 N Y Y N N 6 N
24 5 N Y Y N N 24 N
Light-cured
composite
*On bracket-adhesive interface; †all adhesive remained on enamel; Y, yes; N, no; ?, only mean ARI value given; NR, not reported; SEM, standard
error of the mean.

American Journal of Orthodontics and Dentofacial Orthopedics Finnema et al 622.e3
Volume 137, Number 5
Appendix table. (Continued)
Halogen
light
Water
storage
Storage
time (h) Thermocycling
Crosshead speed
(mm/min)
Force
location*
Shear
blade
ARI†
(%)
Bond strength
(MPa) SEM
Y Y 24 N 0.5 Y Y 85 13.10 0.69
Y Y 24 N 0.5 Y Y 75 16.00 1.01
Y Y 24 N 0.5 Y Y 0 11.50 0.74
Y Y 24 N 0.5 Y Y 0 9.90 0.89
Y N 72 Y 0.5 Y Y 11 24.40 1.84
N N 72 Y 0.5 Y Y 11 18.21 1.34
Y N 72 Y 0.5 Y Y 11 27.76 1.03
N N 72 Y 0.5 Y Y 11 25.09 1.24
Y N 72 Y 0.5 Y Y 0 23.44 1.94
N N 72 Y 0.5 Y Y 0 21.23 1.37
Y N 72 Y 0.5 Y Y 0 22.89 1.19
N N 72 Y 0.5 Y Y 0 16.24 1.05
Y Y 1 N 1.0 Y Y 22 14.05 1.03
Y Y 24 N 1.0 Y Y 30 20.94 0.79
Y Y 0 Y 1.0 Y Y 10 18.03 0.84
N Y 48 N 1.0 N Y 0 12.09 0.89
N Y 48 N 1.0 N Y 0 7.66 0.41
Y Y 48 N 1.0 N Y 7 11.24 0.92
Y Y 48 N 1.0 N Y 0 6.41 0.57
Y Y 48 N 1.0 N Y 7 11.85 1.13
Y Y 24 Y 0.5 Y Y NR 19.60 3.04
Y Y 24 N 0.5 N Y NR 11.35 0.93
Y Y 672 N 0.5 N Y NR 9.19 1.20
Y Y 24 N 0.5 N Y NR 11.58 0.95
Y Y 672 N 0.5 N Y NR 5.39 0.75
N Y 40 N 0.1 N Y 90 15.20 1.01
Y Y 24 N 0.5 N N 80 6.43 0.59
Y Y 24 N 0.5 N N 50 4.61 0.28
Y Y 24 N 0.5 N N 0 4.74 0.4
Y Y 72 N 3.0 N N NR 13.03 0.54
Y Y 72 N 3.0 N N NR 14.45 0.61
Y Y 72 N 3.0 N N NR 14.17 0.54
Y Y 72 Y 2.0 N N 17.5 14.82 0.41
Y Y 360 Y 5.0 Y Y 29 18.10 0.93
Y Y 360 Y 5.0 Y Y 29 12.70 0.56
Y Y 0.5 N 1.0 N N ? 13.6 0.98
Y Y 1 Y 1.0 N N ? 16.1 0.93
N Y 0.5 N 1.0 N N ? 14.2 1.19
N Y 1 Y 1.0 N N ? 18.2 1.19
Y Y 24 N 5.0 N N 0 21.56 1.05
Y Y 24 N 5.0 N N 0 22.32 0.51
Y Y 24 N 5.0 N N 0 17.82 0.5
Y Y 72 N 1.0 N N 65 23.23 1.34
Y Y 24 N 0.5 Y Y 85 13.10 0.69
N Y 24 N 0.5 Y Y 50 9.10 0.69
N Y 24 N 0.5 Y Y 55 13.90 1.07
N Y 24 N 0.5 Y Y 55 12.70 1.16
Y Y 24 N 0.5 Y Y 80 12.90 0.76
Y Y 24 N 1.0 N Y 0 12.27 1.00
Y Y 24 N 1.0 N Y 0 12.20 0.85
Y Y 24 N 1.0 N Y 0 10.45 1.06
Y Y 24 N 1.0 N Y 0 14.93 0.95
Y Y 24 N 1.0 N Y 0 7.19 0.73
Y Y 24 N 1.0 N Y 0 8.34 0.51
Y Y 24 N 1.0 N Y 0 14.13 2.27
Y Y 24 N 1.0 N Y 0 14.28 2.74
Y Y 1 N 0.5 N Y 0 9.50 0.72
Y Y 1 N 0.5 N Y 0 5.80 0.58
N Y 1 N 0.5 N Y 0 3.50 0.49
N Y 1 N 0.5 N Y 0 5.20 0.31
N Y 1 N 0.5 N Y 0 5.80 0.72
Y Y 1 N 0.5 N Y 0 8.20 0.80
Y Y 1 N 0.5 N Y 0 7.50 0.63
N Y 1 N 0.5 N Y 0 9.40 0.85
N Y 1 N 0.5 N Y 0 8.00 0.67