Assessment of in Vivo Bond Strength Studies of The Orthodontic Bracket Adhesive System: A Systematic Review
Assessment of in Vivo Bond Strength Studies of The Orthodontic Bracket Adhesive System: A Systematic Review
Assessment of in Vivo Bond Strength Studies of The Orthodontic Bracket Adhesive System: A Systematic Review
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European Journal of Dentistry • Volume 12 • Issue 4 • October-December 2018 • Pages ***-***
Review Article
Assessment of in vivo bond strength studies of the
orthodontic bracket‑adhesive system: A systematic
review
Tamzid Ahmed1, Norma Ab Rahman1, Mohammad Khursheed Alam2
1
Orthodontics Unit, School of Dental
Sciences (PPSG), Universiti Sains Malaysia,
Kota Bharu, Kelantan, Malaysia,
Correspondence: Dr. Norma Ab Rahman 2
Department of Orthodontics, College of Dentistry,
Email: drnorma@usm.my Jouf University, Sakaka, Kingdom of Saudi Arabia
ABSTRACT
The aim of this study was to systematically review the available studies measuring the bond strength of orthodontic bracket‑adhesive
system under different experimental conditions in vivo. Literature search was performed in four different databases: PubMed,
Web of Science, Cochrane, and Scopus using the keywords – bond strength, orthodontic brackets, bracket‑adhesive, and in vivo.
A total of six full‑text articles were selected based on the inclusion and exclusion criteria of our study after a careful assessment
by the two independent reviewers. Data selection was performed by following PRISMA 2009 guidelines. Five of the selected
studies were clinical trials; one study was a randomized clinical trial. From each of the selected articles, the following data were
extracted – number of samples, with the type of tooth involved materials under experiment methods of measurement, the time
interval between bonding and debonding orthodontic brackets, mode of force application, and the bond strength results with the
overall outcome. The methodological quality assessment of each article was done by the modified Downs and Black checklist
method. The qualitative analyses were done by two independent reviewers. Conflicting issues were resolved in a consensus meeting
by consulting the third reviewer (MKA). Meta‑analysis could not be performed due to the lack of homogenous study results. The
review reached no real conclusion apart from the lack of efforts to clinically evaluate the bonding efficiency of a wide range of
orthodontic bracket‑adhesive systems in terms of debonding force compared to laboratory‑based in vitro and ex vivo studies.
Website:
How to cite this article: Ahmed T, Rahman NA, Alam MK. Assessment
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of in vivo bond strength studies of the orthodontic bracket-adhesive
system: A systematic review. Eur J Dent 2018;12:602-9.
DOI: 10.4103/ejd.ejd_22_18
say that in vivo bond strength tests are more precise initial search. The search strategy of the database
to experiment the efficacy of orthodontic bonding is presented in Table 1. The following criteria were
materials. Few researchers innovated the way to constructed a priori to select the articles for inclusion in
measure the bond strength of orthodontic brackets this review. The inclusion criteria of this review consist
inside the oral environment with a custom‑made of (1) in vivo clinical trials and case–control studies
instrument equipped with a measuring device. that debonded and measured the bond strength of
orthodontic brackets with a suitable experimental
The main PICO question of this study is: how are the device, (2) all age and sex, (3) all languages, and (4) no
accuracy, reliability, and the efficiency of different sample size restrictions. The exclusion criteria were
techniques measuring the bond strength of orthodontic as follows: (1) longitudinal clinical studies or clinical
brackets with the influence of variables in vivo? and trials of in vivo bracket‑failure rates and survival rates,
what are the potential research gaps in comparison ex vivo clinical trials where the orthodontic brackets
to the in vitro and ex vivo studies? were debonded and the bond strength measured
extraorally after temporarily exposing them to the oral
Therefore, the aim of this study is to systematically environment, (2) any conference abstracts and case
review the in vivo clinical studies available in reports, and (3) editorials and opinions. The titles and
the literature measuring the debonding force of abstracts of all the included studies were downloaded
orthodontic brackets to find the answer to our (PICO) in Endnote software version X7 (Thomson, Reuters,
question by assessing and comparing the accuracy Carlsbad, California, USA) cross‑referenced and the
and reliability of different methods, measurement duplicate studies were excluded after the careful
techniques, and the influence of variable parameters assessment and comparison of the study titles,
on the study results. author names, sample sizes, interventions, and the
outcomes by one reviewer (TA). The full‑text articles
MATERIALS AND METHODS were assessed by the two independent reviewers
(TA and NAR) for eligibility. The quality assessment
The review is not registered under any organization. (risk of bias) of the selected studies was also assessed
The review was performed by following the by the same reviewers (TA and NAR) according
Preferred Reporting Items for Systemic Reviews to the modified Downs and Black checklist.[1] The
and Meta‑Analyses (PRISMA) 2009 statements criteria for assessing each study were grouped into
(http://www.prisma‑statement.org). An independent five principal segments: reporting, external validity,
literature search was made by two review authors internal validity‑bias, internal validity‑confounding,
(TA and NAR) in four different databases: and power. Items were given 1 point if the respective
PubMed (last date of search February 18, 2017), Web criteria were fulfilled. Missing or unable to determine
of Science (last date of search February 21, 2017), any criteria was assessed by giving 0 points. In the
Scopus (last date of search February 23, 2017), and power domain, instead of assessing the power of the
Cochrane (last date of search February 23, 2017) studies to detect the clinically important effect on
using the keywords –bond strength, Orthodontic the scale of 1–5 points, the studies that determined
Brackets, Bracket‑Adhesive, and In vivo. There was no sample size using power were given 1 point and
language restriction for the search. In addition, hand 0 points if not. From the total of 27 points, the articles
searching was also performed in the library for any that scored <17 points were judged with the presence
relevant articles. Initially, the titles and abstracts of the of methodological limitation. The following data
resultant articles relevant to our study topic: the bond were extracted from each study included: the sample
strength of orthodontic brackets in vivo were analyzed size with the number and type of teeth involved,
by two review authors (TA and NAR), independently. materials used, type of instrument and measuring
The references of the resultant studies were also device used, the mode and the location of force
searched for any related studies missed during the application, the duration of exposure of the brackets
to the oral environment before debonding, and the rejected because they did not apply their instrument
bond strength results with the overall outcome. Again, to measure the in vivo bond strength of orthodontic
the data were extracted by two independent reviewers brackets. The number of excluded articles with the
(TA and NAR). Resolution of any disagreement was reasons is presented in Table 2. Additional papers
done in a consensus meeting; the consult was also could not be found through hand searching. Among
taken from the third reviewer (MKA). The whole the six included studies, five of them were clinical
process of study selection, data extraction, and the trials[2‑6] and only one study was a randomized clinical
trial.[7] All the articles were published in English,
risk of bias assessment was performed unblinded.
except for one in Portuguese.[5] The Portuguese article
was translated into English with the help of “Google
RESULTS Translator” by TA. The quality assessment result of
each included studies according to modified Downs
The number of studies found by searching through and Black checklist.[1] it is presented in an additional
different databases and the selection procedure is file. According to the assessment, 5 of the studies
detailed in the flow diagram according to PRISMA scored 17 and above and rated as high‑quality,[2‑4,6,7]
2009 guidelines, which is presented below in Figure 1. only one study scored 10 which is rated as lower
From the total of 209 found articles from the databases, quality.[5] The extracted data from each of the study
38 abstracts were retrieved and at last eight full‑text are summarized in Table 3. No studies found to
articles were assessed and analyzed. Two articles were estimate the sample size using the power of the study.
Figure 1: Preferred reporting items for systemic reviews and meta‑analyses flow diagram of the study selection
Table 2: Excluded studies and the reasons for by the visible light for 40 s by two studies, while another
exclusion study attempted polymerization using halogen light
Study Reason for exclusion for 20 s.[2,5,7] One study compared the bond strength
Tonus et al., 2007 In vivo bond strength not measured of orthodontic brackets in two groups after curing
Varlika et al., 2009 In vivo bond failure rate the bonding material with the argon laser for 10 s
Uysal et al., 2010 In vivo demineralization of enamel and conventional visible light for 40 s, respectively,
around orthodontic brackets
and found no difference.[7] All the included studies
Uysal et al., 2010 In vivo enamel demineralization
around orthodontic brackets
characterize the bond strength as average stress in
Uysal et al., 2010 In vivo enamel demineralization megapascal (MPa) units after dividing the debonding
around orthodontic brackets force in newtons (N) by the bracket surface area in
Summers et al., 2004 Bond strength measured square millimeters (mm2). The most common mode of
on extracted teeth
force application was shear/peel loading on the area
Signorelli et al., 2006 In vivo bracket failure rate
between the bracket wings and the base among all the
Shammaa et al., 1999 In vivo bracket survival rate
Rosenbach et al., 2007 Bond strength measured
selected studies. One study emphasized the influence
on extracted teeth of force location on the bond strength of orthodontic
Prietsch et al., 2007 In vivo bond strength not measured brackets.[3] After 10 min of bonding, the time duration
Praxedes‑Neto et al., 2012 In vivo remineralization between the bonding and debonding has no influence
of acid‑etch enamel
on the bond strength in vivo. In comparison to the
Polat et al., 2004 In vivo bracket failure rate
in vitro bond strength values, the in vivo bond strength
Penido et al., 2009 The full‑text article could
not be retrieved of the orthodontic brackets found lower in two studies
Pasquale et al., 2007 In vivo bond failure rate following the similar method of measurement.[2,4] A
Pascotto et al., 2004 In vivo enamel demineralization custom‑made debonding instrument equipped with
around orthodontic brackets digital force gauge was mostly used for debonding
Ozer et al., 2005 In vivo bond failure rate force measurement in vivo.[2,4‑6] Two studies applied
Örtendahl 1998 Ex vivo study
strain gauge to measure the bracket debonding force.[3,7]
Nirupama et al., 2012 Bond strength measured
on extracted teeth Commercially manufactured regular debonding plier
Murray et al., 2003 Bond strength measured was used in only one study.[3]
on extracted teeth
Mullins et al., 2009 In vivo bracket failure rate DISCUSSION
Mirzakouchaki et al., 2016 Bond strength measured
on extracted teeth
Linklater et al., 2003 In vivo bond failure rate
To minimize the possibility of missing any potential
Le et al., 2003 In vivo enamel demineralization study relevant to our search, the inclusion criteria were
around orthodontic brackets lenient. There were no restrictions to the publication
Krishnaswamy et al., 2007 In vivo bond failure rate year, the search was not confined to specific language,
Korbmacher et al., 2006 In vitro bond strength measurement limitations were not also applied for the sample size.
Ireland et al., 2003 In vivo bond failure rate Despite all the measures, the number of studies eligible
Hammad et al., 2013 Bond strength measured
on extracted teeth
for inclusion is only six. Lack of regular turnover of
Grover et al., 2012 In vivo bond failure rate the patients receiving fixed orthodontic therapy,
Ghiz et al., 2009 In vivo enamel demineralization dimension, and the limitation of the instruments
around orthodontic brackets with a measuring device in terms of access, safety,
de Moura et al., 2006 In vivo enamel demineralization and efficacy may be the attributing factors that the
around orthodontic brackets
researchers are more focused on laboratory‑based
Chatzistavrou et al., 2009 Bond strength measured
on extracted teeth bond strength measurement. Studies that are titled as
Cal‑Neto et al., 2006 Bond strength measured on the in vivo bond strength of orthodontic brackets, but
extracted teeth actually measured the bond strength on the teeth that
are already planned for extraction after exposing them
Premolar teeth were predominantly used as a sample to the oral environment for certain period are excluded.
to measure the bond strength. For enamel surface In these cases, the brackets and the adhesives may
preparation before bonding orthodontic brackets, get exposure to the oral environment, but these are
self‑etching primer, and 37% phosphoric acid was practically ex vivo studies because the bond strength
used predominantly.[2,5‑7] Two studies did not mention is measured outside preferably in a laboratory by a
the enamel surface preparation technique.[3,4] In vivo mechanical testing device. Transbond XT (3M Unitek,
polymerization of the orthodontic adhesives was done Monrovia, California, USA) light‑cured composite
606
Authors, Sample size Materials Device used Debonding Type and Bond strength (Mpa), mean±SD Result
year of to measure time area of force
publication bond strength application
Pickett, 8 patients, 37% phosphoric Modified Average 23 Sheer/peel 5.47±2.18 Mean bond strength in vivo after
et al., 2001 64 premolar acid + Victory twin debonding months force, area comprehensive orthodontic treatment
teeth metal brackets device with between is significantly lower than in vitro
precoated with the digital bracket base
Transbond XT force gauge and wings
Composite
Brosh, 50 patients, Transbond XT Orthodontic 24±3 Base method: Wings method Debonding force in the base method
et al., 2005 720 teeth composite + debonding months Wedging Maxilla of bracket removal is significantly
from central stainless‑steel plier (model: force at the Central incisors: 12.8±5.8 higher than in Wings method. Half
incisor to brackets 804‑728, 3 bracket‑enamel Lateral incisors: 12.3±6.5 of the bracket failure occurs at
second M Unitek, interface. Canines: 10.5±4.4 the enamel‑adhesive interface
premolar of Monrovia, Wings method: First premolars: 8.7±6.1
both upper CA, USA) Shear/peel Second premolars: 8.7±6.5
and lower jaw equipped with force at the Mandible
strain gauge area between Central incisors: 11.1±8.7
bracket base Lateral incisors: 11.7±7.7
and wings Canines: 13.6±6.8
First premolars: 9.9±5.3
Second premolars: 10.5±6.8
Base method
Maxilla
Central incisors: 17.8±7.6
Lateral incisors: 20.1±7.0
Canines: 18.1±6.2
First premolars: 17±6.8
Second premolars: 16.9±6.0
Mandible
Central incisors: 14.6±6.0 Lateral
Incisors: 14.4±6.1 Canines:
17.6±5.8 First premolars: 17.5±5.3
Second premolars: 15.4±5.8
Hajrassie 22 volunteers, Transbond XT Modified 10 min Sheer/peel 5.24±1.08 There are no significant differences of
and Khier 60 premolar composite + debonding 24 h force, area 601±1.08 in vivo mean bond strength values within
Ahmed, et al.: Bond strength of orthodontic brackets in vivo
2007 teeth mini twin metal device with 1 week between 5.49±1.17 the four experimental time periods
brackets the digital 4 weeks bracket base 5.92±1.44
force gauge and wings
Hildebrand 23 patients, Self‑etching Orthodontic 14 days Sheer/peel Maxilla No significant difference of in vivo
et al., 2007 92 premolar primer + adhesive separator pliers force, area Curing with argon laser‑ 10.43±2.71 bond strength found for argon laser
teeth precoated metallic attached with a between Curing with visible light‑8.96±2.80 curing (10 s) and conventional light
brackets strain gauge bracket base Mandible curing (40 s) in orthodontic brackets
and wings Curing with argon laser‑ 9.81±3.00
Curing with visible light‑ 9.60±3.16
bracket base
bracket base
application
Sheer/peel
Sheer/peel
force, area
force, area
and wings
Type and
between
between
1h
separator pliers
digital force
debonding
a modified
Modified
gauge
Digital
phosphoric acid
XT composite +
metal brackets
brackets, 37%
Transbond XT
Self‑etching
Materials
10 premolar
premolar on
both sides
218 teeth
maxillary
teeth
et al., 2008
Hasan,
Penido
layer, in the brackets, and enamel during debonding the bracket‑adhesive interface without any damage
is inhomogeneous.[15] Moreover, the approximation of to the enamel.[17] One study found to measure the
the actual contact area of the bracket base, variation bond strength of orthodontic brackets using regular
of the bracket surface morphology, and adhesive debonding plier.[3] They applied the load on two
thickness are the impediments for converting the different locations on the bracket‑wedging force on
units of debonding force to stress. Therefore, the peak the area between the bracket base and enamel (base
debonding force developed at the site of failure should method) and shear/peel force on the area between
be the measure of the bonding efficiency. the wings and base of the bracket (wings method).
The later area and the mode of force application were
In vivo bond strength was first successfully, measured also preferred by most of the in vivo bond strength
using digital force gauge attached to a stainless‑steel studies.[2,4‑7] The greater debonding force was required
crossmember and a modified‑elastic spacer in the base method than in the wings method because
instrument.[2] The instrument was designed to apply further the point of force application is away from the
shear/peel load on the area between the base and bracket/adhesive/enamel interface, the lesser force
the bracket base. The short arm of the crossmember will be required to dislodge the brackets. Despite that,
was made similar, to the debonding plier at the tip in both methods, the majority of bracket debonding
for engaging the bracket in the space between the occurred at the adhesive/enamel interface suggesting
base and the wings in the mesiodistal direction. The the imminent enamel damage. Besides, structural
elastic spacer instrument was soldered to metal pads damage to the bracket is more common in wings
at the tip with a groove allowing free movement of method. No study found to evaluate the effect of
the crossmember during force application. Before tensile loading modes on the bond strength in vivo.
debonding, the occlusal splints were given to patients Although the tensile debonding test may not simulate
for protection as one pad of the plier tip was rested on the bracket debonding in clinical situations, it can
the occlusal surface of the teeth and the other pad on provide valuable information on the relative bond
the force gauge with the crossmember engaged to the strengths for the comparison of debonding techniques,
bracket. While the plier handles were compressed, the clinically. However, in comparison to the sheer/peel
plier pads move away from each other and applied loading, the force required for debonding brackets
force on the occlusal surface of the tooth on one side lesser when a tensile load is applied on the bracket
and the force gauge on the other side. This allowed found in a finite element analysis.[16]
shearing of the bracket by the crossmember engaged to
it, while, the force gauge recorded the peak force at the Several studies used a strain gauge to measure the
time of bond failure. Later, this idea of measuring bond bracket debonding force in vivo.[3,7] Strain gauges are
strength was followed by three more studies, but with the electrical transducers that sense the mechanical
little modification.[4‑6] Instead of inserting the acrylic deformation and converts it into a range of electrical
splint into the mouth during debonding, rubber pad resistance.[2] Strain gauges are accurate and lightweight
was applied on the tip of the modified elastic spacer but very much responsive to the temperature change
instrument.[5] As the digital force gauge is capable which can influence to alter the measurements. In
of measuring both tension and compression, in two both of the studies, no measures were mentioned for
studies, they encased the force gauge in an aluminum compensating the temperature alteration which may
box snugly to measure the true shear force without any have an influence on the bond strength results.
external disturbances.[4,6] But according to the finite
element analysis, brackets are exposed to combinations Validation and interexaminer calibration is very
of tension, shear peel, and torsional loading modes in important to assess the accuracy of any experimental
all directions clinically during debonding.[16] instrument. Although the two studies validated their
debonding device by comparing the results with
Debonding force and the resulting iatrogenic enamel the gold standard universal testing machine,[2,4] no
damage during debonding orthodontic brackets may study calibrates their experimental instrument for
vary with the type of force, the area of force application, interexaminer reliability.
and the type of debonding instrument used.[16‑18] The
bracket failure at the interface between the adhesive In the majority of the studies, the in vivo bond strength of
and the enamel removes a layer of enamel.[19] Only, orthodontic brackets on premolar teeth was considered
the manufacturer‑made bracket debonding pliers only.[2,4,5,7] Two studies measured the bond strength of
are capable of performing consistent separation at orthodontic brackets on different teeth in vivo under