Absence of carious lesions at margins of glass-ionomer cement and amalgam restorations: An update of systematic review evidence.

CORRESPONDENCE Open Access
Absence of carious lesions at margins of
glass-ionomer cement and amalgam restorations:
An update of systematic review evidence
Steffen Mickenautsch*, Veerasamy Yengopal
Abstract
Background: This article aims to update the existing systematic review evidence elicited by Mickenautsch et al. up
to 18 January 2008 (published in the European Journal of Paediatric Dentistry in 2009) and addressing the review
question of whether, in the same dentition and same cavity class, glass-ionomer cement (GIC) restored cavities
show less recurrent carious lesions on cavity margins than cavities restored with amalgam.
Methods: The systematic literature search was extended beyond the original search date and a further hand-
search and reference check was done. The quality of accepted trials was assessed, using updated quality criteria,
and the risk of bias was investigated in more depth than previously reported. In addition, the focus of quantitative
synthesis was shifted to single datasets extracted from the accepted trials.
Results: The database search (up to 10 August 2010) identified 1 new trial, in addition to the 9 included in the
original systematic review, and 11 further trials were included after a hand-search and reference check. Of these 21
trials, 11 were excluded and 10 were accepted for data extraction and quality assessment. Thirteen dichotomous
datasets of primary outcomes and 4 datasets with secondary outcomes were extracted. Meta-analysis and
cumulative meta-analysis were used in combining clinically homogenous datasets. The overall results of the
computed datasets suggest that GIC has a higher caries-preventive effect than amalgam for restorations in
permanent teeth. No difference was found for restorations in the primary dentition.
Conclusion: This outcome is in agreement with the conclusions of the original systematic review. Although the
findings of the trials identified in this update may be considered to be less affected by attrition- and publication
bias, their risk of selection- and detection/performance bias is high. Thus, verification of the currently available
results requires further high-quality randomised control trials.
Introduction
Carious lesions associated with the margins of tooth
restorations have been defined as recurrent or secondary
caries [1]. In recent years it has been suggested that pla-
cing a filling does not cure caries and that the “recurrence”
of lesions on restoration margins results from neglecting
to treat caries as a disease before placing a restoration [2].
Part of the treatment of caries is encouraging remineralisa-
tion in the cavity walls [3]. Ten Cate and van Duinen [4]
have shown, in-situ, a hyper-remineralisation effect in
demineralised tooth tissues bordering glass ionomer
cement (GIC) type restorations. The significant reminera-
lisation potential of GIC has been ascribed to the release
of fluoride ions, facilitated by a hydrophilic environment
[5]. In addition, the release of strontium by GIC and its
diffusion into demineralised tooth tissue, thus further aid-
ing remineralisation, has been observed [6]. Moreover, it
has been suggested that carious lesions are rarely the
cause of GIC restoration failures [1].
Mickenautsch et al. [7], in a previous systematic review
with meta-analysis, first reported on the combined results
of trials comparing the absence of carious lesions at mar-
gins of GIC and amalgam restorations. This meta-analysis
was limited, owing to a low number of identified rando-
mised control trials. It concluded that after 6 years the
absence of carious lesions at margins of single-surface GIC
* Correspondence: neem@global.co.za
Division of Public Oral Health, Faculty of Health Sciences, University of the
Witwatersrand - 7 York Rd., Parktown/Johannesburg 2193, South Africa
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© 2011 Mickenautsch et al; licensee BioMed Central Ltd. This is an open access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly cited.

restorations was higher than their absence on amalgam
fillings of permanent teeth. Results for both multiple- and
single-surface restorations in primary teeth showed no dif-
ference between the two materials.
The results of this meta-analysis were based on a sys-
tematic search of literature until 5 January 2008 [7]. It has
been suggested that once the search date of a systematic
review is older than even 1 year, users should check for
more recent trials on the same topic to see whether new
evidence has altered the findings of a given systematic
review [8]. In addition, the original quality assessment cri-
teria [7] may be questioned on grounds of being ineffective
in judging the true internal validity of trials on basis of risk
of bias [9,10]. Therefore, the aim of this update is to pro-
vide a more in-depth assessment of bias-risk in trials.
Thus, this quantitative systematic review aims to
update the existing evidence provided by the original
article [7] regarding the review question of whether, in
the same dentition and same cavity class, glass-ionomer
cement (GIC) restored cavities show less recurrent car-
ious lesions on cavity margins than cavities restored
with amalgam.
Materials and methods
In order to update the existing evidence, the systematic
literature search was extended from the original search
date and a further hand-search and reference check
were done. Updated quality criteria were used in asses-
sing the quality of accepted trials (Table 1) [9-12] and
the risk of bias was investigated in more depth than in
the previous report. In addition, the focus of quantita-
tive synthesis was shifted to single datasets (DS)
extracted from the accepted trials.
Literature search, review and quality assessment of trials
The search strategy used in the previous review [7] was
replicated for this review update, using the search terms:
Dental Caries OR Dental Caries Susceptibility OR Root
Caries OR Tooth Demineralization AND Glass Ionomer
Cements OR Cermet Cements AND Cariostatic Agents
OR Dental Caries OR Cariostatic Agents AND Dental
Amalgam OR silver mercury amalgam and Ionomer$
and amalg$ and cariosta$. Only the start and cut-off
dates were changed. The databases Biomed Central,
Cochrane Oral Health Reviews, Cochrane Library,
Directory Of Open Access Journals, Expanded Academic
ASAP PLUS, Meta Register Of Controlled Trials,
PubMed and Science-Direct, were searched for relevant
papers published between 8 January 2008 (the search
cut-off date of the original systematic review) and 10
August 2010. Criteria for trial inclusion were:
- 2-arm clinical prospective study design;
- Comparison of GIC versus Amalgam;
- Year of publication of trials, identified through
hand-search/reference check, from 1990.
Included trials were excluded after further review if:
- No outcome measure related to caries was reported;
- No computable data, consisting of number of teeth
included at baseline (BSL), number of observed
effects (n) and total number of evaluations (N), per
treatment group was reported.
Included trials that passed the exclusion criteria were
accepted for further quality assessment and data extrac-
tion. Review, data extraction and quality assessment of
the accepted trials was undertaken independently by
two reviewers (SM and VY). Differences were resolved
through discussion and consensus.
In contrast to the original published systematic review
[7], quality assessment of accepted trials was undertaken
on the basis of availability of evidence indicating successful
prevention of selection- and detection/performance bias
from start to end of each trial. The new criteria (Table 1)
differ from those used in the first review [7]. It has been
argued that the inclusion of bias-preventing measures (e.g.
randomisation, blinding/masking) into the trial methodol-
ogy only demonstrates an attempt to reduce bias risk but
does not carry proof in itself that such attempt was indeed
successful and that it is far more important to judge trial
quality according to evidence that indicates to what extent
such attempt has succeeded [9]. Against this background
the quality criteria were adjusted accordingly. Thus, where
trials only reported that randomisation was conducted or
included a detailed description of the randomisation pro-
cess, this was not considered adequate if they failed to pro-
vide any evidence that randomisation was indeed effective
throughout the trial.
Potential attrition- and publication bias was not investi-
gated in the original systematic review [7]. This update
used RevMan Version 4.2 statistical software by The Nor-
dic Cochrane Centre, The Cochrane Collaboration (Copen-
hagen; 2003) in conducting sensitivity analysis in order to
investigate potential risk of attrition bias in trials. To inves-
tigate publication bias, a funnel plot was generated, using
the datasets from the included clinical trials. The standard
error (SE) of the Mean differences was plotted on the
Y-axis, and the log of the Relative Risk (RR) on the X-axis,
using MIX Version 1.7 meta-analysis software [13]. In
addition, the Egger’s linear regression method [14] was
used to calculate an intercept with 95% Confidence Interval
(CI) with statistical significance set at a = 0.05.
Data extraction and analysis
All data concerning primary and secondary outcomes of
accepted trials were extracted as single dichotomous
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Table 1 Quality assessment criteria of trials
Selection bias
Score Criteria Impact on bias risk
Randomisation and concealment
A (i) Randomisation: Details of any adequate type of allocation method
that generates random sequences with the patient as unit of
randomisation are reported.1
(ii) Concealment: Trial provides evidence2 that concealment was
indeed effective and that the random sequence could not have been
observed or predicted throughout the duration of the trial.
Doubts may still exist whether the trial results are influenced by
selection bias but no indication can be found from the trial report to
support such doubt.
B (i) Randomisation: Details of any adequate type of allocation method
that generates random sequences with the patient as unit of
randomisation are reported.1
(ii) Concealment: Trial reports on any adequate method to prevent
direct observation3 and prediction4 of the allocation sequence and
sequence generation rules.
Despite the implementation of method considered to be able to
prevent unmasking of the concealed allocation sequence through
direct observation and prediction, there are reasons to expect that
the concealed allocation sequence may have been unmasked during
the cause of the trial.
C (i) Randomisation: Details of any adequate type of allocation method
that generates random sequences with the patient as unit of
randomisation are reported.1
(ii) Concealment: Trial reports on any adequate method to prevent
direct operator observation of allocation sequence and sequence
generation rules3. However, the allocation sequence and sequence
generation may have been sufficiently predicted.
Despite the implementation of method considered to be able to
prevent unmasking of the concealed allocation sequence through
direct observation, there are reasons to expect that operators could
have predicted the concealed allocation sequence.
D (i) Randomisation: Details of any adequate type of allocation method
that generates random sequences with the patient as unit of
randomisation are reported.1
(ii) Concealment: The trial report does not include information on
how the allocation of random sequence was concealed. The
allocation could have been directly observed and/or predicted.
Despite the theoretical chance for each patient to be allocated to
either treatment group, operator knowledge of the allocation
sequence may have lead to patient allocation that favoured the
outcome of one type of treatment above the other.
0 Trial does not comply with criteria A - D. No guaranty of equal chance for patients to be allocated to either
treatment group, thus allocation may have favoured the outcome of
one type of treatment above the other.
Baseline data for randomised trials
A Baseline data collected before randomisation and reported for both
treatment groups. Data shows no significant differences between
both groups.
Evidence is given that randomisation has lead to equal groups
suggesting little risk of selection bias.
B Baseline data collected before randomisation and reported for both
treatment groups. Data shows significant differences between both
groups but has been statistically adjusted appropriately.
Differences have been adjusted, thus the influence of possible
selection bias appears to be reduced.
C Baseline data collected before randomisation and reported for both
treatment groups. Data shows significant differences between both
groups without being statistically adjusted.
Reported differences may be due to ineffective randomisation, thus
indicate risk of selection bias.
0 Trial does not comply with criteria A - C. No evidence is given whether randomisation has indeed lead to
equal groups with differences beyond chance, thus differences may
exists indicating selection bias.
Detection/Performance bias
Blinding/Masking
Score Criteria Impact on bias risk
A (i) Trial reports on any type of method that is known to prevent
patient AND operator AND evaluator to discern whether patients are
allocated to the test- or the control group (Blinding/Masking).
(ii) Trial reports a process with which the effect of Blinding/Masking
was evaluated, as well as the results of such evaluation.
Evidence is given that the trial results may not have been influenced
by detection/performance bias that may have favored the outcome
of one type of treatment above the other.
B (i) Trial reports on any type of method that is known to prevent
patient AND operator AND evaluator to discern whether patients are
allocated to the test- or the control group (Blinding/Masking).
(ii) Trial report does not give reason for doubt that the patient
allocation to either the test- or the control group has been
unmasked throughout the duration of the trial.
Doubts may still exist whether the trial results are influenced by
detection/performance bias but no indication can be found from the
trial report to support such doubt. However, no evaluation of the
Blinding/Masking effect has been included in the trial, thus no
evidence for lack of bias is given.
C (i) Trial reports on any type of method that is known to prevent
patient AND operator AND evaluator to discern whether patients are
allocated to the test- or the control group (Blinding/Masking).
(ii) Trial report gives reason for doubt that the patient allocation to
either the test- or the control group has been unmasked throughout
the duration of the trial.
Despite the implementation of method considered to be able to
prevent unmasking, there are reasons to expect that operators/
patients could have discovered the allocation.
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datasets, containing the number of observed effects (n)
and the total number of evaluations (N) for both the
control and the test groups. The Cochrane RevMan,
Version 4.2 software package was used in computing
the Relative Risk (RR, 95% CI). Statistical significance
was set at a = 0.05.
Meta-analysis, using RevMan Version 4.2 statistical
software by The Nordic Cochrane Centre, The Cochrane
Collaboration (Copenhagen; 2003), was considered for
datasets only if they complied with the previously pub-
lished criteria for clinical homogeneity [7]. The percen-
tage of total variations across datasets (I2) was used in
assessing statistical heterogeneity [15]. Statistical signifi-
cance for assessing statistical heterogeneity was set at a =
0.10. A fixed-effects model was used for meta-analysis
under condition of statistical homogeneity of datasets.
Pooled datasets were assigned Mantel-Haenszel weights
directly proportionate to their sample sizes.
Cumulative meta-analysis, using MIX Version 1.7
meta-analysis software [13], was performed for datasets
of consecutive follow-up periods, which also showed clin-
ical and statistical homogeneity, in order to investigate
whether a chronological trend of the available evidence
might be observed.
Results
Literature search
In addition to the 9 trials included in the original meta-
analysis [16-24], one trial [25] was identified during the
new database search and a further 11 [26-36] from the
hand-search and reference check were included (Figure 1).
Of these 21 trials, 11 were excluded [16-19,30-36], for
reasons shown in Table 2. Ten trials passed the exclusion
criteria and were accepted for data extraction and quality
assessment [20-29]. Of the accepted trials two were of
parallel group design [22,24] and five were split-mouth
studies [20,23,27-29]. Three trials used the tooth and
not the patient as unit of randomisation [21,25,26] and
can be regarded as of partial split-mouth design: in one
trial 20 out of 50 patients received more than one type of
restoration [21]; during one trial 45 patients were treated
with 38 amalgam and 35 GIC restorations [25] and in one
further trial 92 out of 666 patients received both types of
materials [26].
Table 1 Quality assessment criteria of trials (Continued)
0 No process reported or implemented able to blind/mask patients
AND operators whether patients where allocated to either the test-
or the control group (It is insufficient to report that blinding/masking
was done without reporting the details of the process).
Knowledge about the patient allocation may have caused patients/
operator to act in a way that may have favoured the outcome of
one type of treatment above the other,
Attrition bias
Loss - to follow up
Score Criteria Impact on bias risk
A Available case analysis, loss-to-follow up reported per treatment
group. Subsequent sensitivity analysis does not indicate a possible
risk of bias.
The trial allows extracting evidence that attrition may not have
favoured the outcome of one type of treatment above the other.
B Available case analysis, loss-to-follow up reported per treatment
group. Subsequent sensitivity analysis indicates a possible risk of bias.
The trial allows assessing the risk that attrition may have favoured
the outcome of one type of treatment above the other.
0 Trial does not report number of included participants per treatment
group at baseline or gives any indication that would allow
ascertaining the loss-to-follow up rate per treatment group.
The trial carries an unknown risk that attrition may have favoured the
outcome of one type of treatment above the other.
Run-in phase
A No run-in phase reported or discernable during which patients were
given the active treatment or the placebo/control.
The trial may not carry the risk of bias due to exclusion of patients
who would not respond well to e.g. the active treatment.
0 Run-in phase reported or discernable during which patients were
given the active treatment or the placebo/control.
During a run-in phase only patients were selected for randomisation
that have responded/not responded to the active treatment of the
placebo/control. This may favour the outcome of one type of
treatment above the other as patients who did not respond well to
either are excluded.
Trial endpoints
0 The trial reports on secondary or surrogate outcomes as endpoints. Even if the surrogate results would highly correlate with primary (i.e.
clinical) outcomes, they cannot serve as valid replacements and need
to be regarded for hypothesis development, only.
A The trial reports on primary outcomes as endpoints. Primary outcomes may provide evidence for hypothesis testing.
1Excluded are types of allocation methods that are considered as inadequate: cluster randomisation, fixed block randomisation with block size 2, minimisation,
alternation, randomisation of teeth, use of date of birth or patient record number, “quasi"-randomisation, split-mouth.
2E.g. by reporting results of the Berger-Exner Test or any other statistical tests that show that covariates of compared groups were similar at baseline.
3E.g. by opening of opaque envelope, obtaining allocation from tables, computer generated or from other sources.
4E.g. central randomisation, sequence allocation by other than operator; excluding varied block randomisation.
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Data extraction and analysis results
Thirteen individual computable datasets (DS 01-12,14) of
primary outcomes and 4 datasets with secondary out-
comes (DS 13,15-17) were extracted from the 10 accepted
trials. Characteristics of these trials and their datasets are
shown in Table 3. It has to be noted that the two trials by
Mandari et al., 2001 and 2003 [23,27], as well by Taifour
et al., 2002 and Frencken et al., 2007 [22,24] report each of
different datasets from the same trials.
Of the primary datasets, 9 reflected results for restora-
tions in primary teeth, with 3 datasets for single-surface
restorations (DS 03,10,11); 2 datasets for multiple-
surface restorations (DS 02,04) and 4 datasets (DS
01,07,08,14) for primary teeth in which single- and mul-
tiple-surface restorations were combined. Four datasets
showed results in permanent teeth: 3 datasets for single
surface restorations (DS 05,06,09) and one dataset for
multiple surface restorations (DS 12).
Figure 1 Flow diagram of trial selection. N = Number of trials; DS = Dataset number.
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The four datasets that showed secondary outcome
results were related to caries progression (DS 13,15,16)
and regression (DS 17) in approximal tooth surfaces
adjacent to restoration surfaces of neighbouring teeth
[26,29].
The computed results of each dataset are shown in
Table 4.
Computed results for restorations in permanent teeth
Of the four datasets, two (DS 05, 06) were considered as
fulfilling the criteria for clinical homogeneity [23,24].
Additional analysis established a low statistical heteroge-
neity (I2 = 56.7%, p = 0.13). For that reason the decision
was made to pool both datasets, using a fixed-effects
model. The meta-analysis results shown in Figure 2 sug-
gest that margins of single-surface GIC restorations in
permanent teeth had a 65% lower chance of developing
carious lesions on restoration margins after 6 years than
did similar teeth restored with amalgam (RR 0.35; 95%
CI 0.19 - 0.65; p = 0.001). No difference was found
between single-surface restorations after 1 year (DS 09:
RR 0.56; 95% CI 0.25 - 1.24, p = 0.15) [27].
One dataset for multiple-surface restoration (DS 12)
was identified. The results of this dataset indicate no
difference between the two types of restoration after 2
years (RR 0.14; 95% CI 0.01 - 2.53; p = 0.18) [29].
Computed results for restorations in primary teeth
Of the nine datasets, two (DS 02,04) were found to fulfil
the criteria for clinical homogeneity [21,22]. Additional
analysis established a low statistical heterogeneity (I2 =
0%, p = 0.67). For that reason the decision was made to
pool both datasets, using a fixed effect model. The meta-
analysis results shown in Figure 3 indicate no difference
between the types of multiple-surface restorations, with
regard to the chance of developing carious lesions on
margins after 3 years (RR 0.38; 95% CI 0.13 - 1.12; p =
0.08). All the other datasets also showed no difference
between GIC and amalgam in this regard (Table 4).
In order to investigate whether a possible trend may be
assumed in the comparisons of GIC and amalgam, the
chronological results from 4 datasets concerning restora-
tions (single- and multiple surface combined) after 1 year
(DS 07), 2 years (DS 08), 3 years (DS 14) and 5 years (DS
01) were included in a cumulative meta-analysis
[20,25,26]. The datasets were considered homogenous in
all aspects except in their follow-up periods. In addition,
a lack of statistical heterogeneity was established (I2 =
5.94%; p = 0.36). The cumulative Relative Risk indicates
no statistical significant difference between the two mate-
rials after 5 years (RR 0.75; 95% CI 0.45 - 1.23; p = 0.26).
However, a shift was observed in the cumulative Relative
Risk over time, with a continued reduction of the 95%
confidence intervals in favour of GIC (Figure 4).
Computed results of secondary outcomes for restorations
Three datasets (DS 13,15,16) reported on caries progres-
sion, and one dataset (DS 17) reported on caries regres-
sion on approximal surfaces of primary or permanent
teeth adjacent to each filling material. The results indi-
cate a statistically significant lower caries progression in
surfaces adjacent to GIC and showed no difference
between the two materials in caries regression after 3
years (Table 4).
Quality assessment of trial results
Selection-, Detection-/Performance bias risk
The results of the quality assessment regarding selec-
tion- and detection/performance bias are shown in
Table 5. None of the accepted trials reported sufficient
details of any randomisation process that had indeed
given each patient the same chance to be allocated to
either the GIC or the amalgam group and to ensure
that direct observation and prediction of the allocation
sequences was successfully prevented. Only two trials
[22,24] had reported baseline data collected before ran-
domisation and reported for both treatment groups, sta-
tistically compared this data between groups and found
the difference statistically not significant (p > 0.05). No
accepted trial reported on successful blinding/masking
of patients, operators and trial evaluators.
Attrition bias risk
All datasets were computed under the assumption that
either (i) all restored teeth lost to follow-up developed
caries on margins or (ii) no restored teeth lost to
Table 2 Excluded trials with reasons for exclusion
Article Reason for exclusion
Hickel and Voss, 1990 [31] Does not report on caries as trial outcome
Frencken et al., 2006 [33] Does not report on caries as trial outcome
Smith et al., 1990 [34] Does not report on caries as trial outcome
Smales et al., 1990 [35] Does not report on caries as trial outcome
Yip et al., 2002 [36] Does not report on caries as trial outcome
Phantumvanit et al., 1996
[16]
No computable data reported: Does not
report on number of same type of units for
caries (tooth surfaces) as total number of
evaluated units (restored teeth), baseline
number of units
Rahimtoola and van
Amerongen, 2002 [17]
No computable data reported: Does not
report on number of evaluated GIC/
Amalgam restorations
Taifour et al., 2003 [18] No computable data reported: Does not
report on number of baseline, restorations,
number of evaluated restorations, number
of restorations with caries (GIC/Amalgam)
Qvist et al., 2004 [19] No computable data reported: Does not
report on number loss-to-follow up
restorations per GIC/Amalgam
Rahimtoola and van
Amerongen, 1997 [30]
Published study protocol-no results
reported
Mjör and Jokstad, 1993
[32]
No computable data reported: Number of
carious teeth not reported as quantitative
units per GIC/Amalgam
GIC = Glass-ionomer cement.
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Table 3 Details of accepted trials
Article DS Patient
character-istics/
potential
confounders*
GIC treatment group Amalgam treatment group Outcome
measure
Evaluation Dentition/Teeth/
Restoration
Study
period
Type of
material
BSL N n LTF Type of
material
BSL N n LTF Criteria Method
Welbury et al., 1991 [20] 01 [1] Ketac Fil 119 51 7 68 Amalcap 119 51 11 68 Recurrent
caries
USPHS Clinical
examination
Primary/Molars/Class I & II 5 years
Östlund et al., 1992 [21] 02 [2] Chem Fil 25 10 0 15 ANA
2000
25 23 1 2 Recurrent
caries
USPHS Clinical
examination
Primary/Molars/Class II 3 years
Taifour et al., 2002 [22] 03 [3] Fuji IX/
Ketac Molar
610 475 9 135 Avalloy 425 331 11 94 Caries on
margin
ART Clinical
examination
Primary/Molars/Single
surface
3 years
04 478 106 4 372 380 84 9 296 Primary/Molars/Multiple
surface
Mandari et al., 2003 [23] 05 [4] Fuji II 223 173 3 50 ANA
2000
207 162 16 45 Recurrent
caries
Modified
USPHS
Clinical
examination
Permanent/Molars/Single
surface
6 years
Frencken et al., 2007
[24]
06 [5] Fuji IX/
Ketac Molar
487 153 11 334 Avalloy 403 108 15 295 Caries on
margin
ART Clinical
examination
Permanent/Molars/Single
surface
6.3
years
Daou et al., 2009 [25] 07 [6] Fuji IX 35 33 4 2 Permite
C
38 36 1 2 Recurrent
caries
USPHS Clinical
examination
Primary/Molars/Class I & II 1 year
08 35 23 3 12 38 21 3 17 2 years
Mandari et al., 2001 [27] 09 [7] Fuji II 223 211 9 12 ANA
2000
207 196 15 11 Recurrent
caries
Modified
USPHS
Clinical
examination
Permanent/Molars/Single
surface
2 years
Yu et al., 2004 [28] 10 [8] Fuji IX/
Ketac Molar-
aplicap
45 37 0 8 GK
amalgam
32 23 0 9 Recurrent
caries
ART Clinical
examination
Primary/Molars/Single
surface
1 year
11 45 29 0 16 32 18 0 14 2 years
Svanberg, 1992 [29] 12 [9] Ketac Silver 18 14 0 4 Disper-
salloy
18 14 3 4 Recurrent
caries
SNBHW Clinical
examination
Permanent/Molars &
Premolars/GIC = Tunnel/
Amalgam = Class II
3 years
13 11 11 3 0 11 11 9 0 Caries
progression
Probing &
Bitewing
Permanent/approximal
adjacent surfaces
Qvist et al., 1997 [26] 14 [10] Ketac Fil 515 334 11 181 Disper-
salloy
543 306 17 237 Recurrent
caries
DPDHS Clinical
examination
Primary/Class I, II and III/V 3 years
15 127 105 25 22 127 94 47 33 Caries
progression
Primary & permanent/
approximal adjacent
surfaces (sound or arrested
caries)
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Table 3 Details of accepted trials (Continued)
16 156 120 25 36 183 129 47 54 Caries
progression
Primary/approximal adjacent
surfaces (carious or active
lesion)
17 156 120 66 36 183 129 78 54 No caries
regression
Primary/approximal adjacent
surfaces (carious or active
lesion)
DS = Dataset number; BSL = Number of teeth at baseline; N = Number of teeth evaluated; n = Number of teeth with caries, LTF = Loss-to-follow-up; USPHS = United States Public Health Service criteria; ART =
Criteria for atraumatic restorative treatment; SNBHW = Criteria according to the Swedish National Board for Health and Welfare; DPHS = Danish Public Dental Health Service criteria.
* Potential confounders = Reported fluoride exposure; high-sugary diet; poor oral hygiene; high past caries experience.
Patient characteristics:
[1] Split-mouth trial. 76 patients, age 5 - 11 years; patients attending the Department of Child Dental Health at Newcastle Dental Hospital (UK) for routine restorative care; subjects were admitted to the trials if they
required at least 1 pair of restorations in their deciduous molar dentition; paired cavities either Class I or II, if possible in the same tooth type; restoration always in different quadrants per pair; any cavity was
suitable for inclusion; a cavity was excluded if it could only be satisfactory restored using a stainless steel crown; restorations placed between October 1982 and March 1987;caries removal by drill.
Potential confounders reported: none.
[2] Partial split-mouth trial. 56 patients, age 4-6 years regularly treated at one Public Dental Service clinic in Jönköping, Sweden who showed manifest caries lesion on the mesial surface of a 2nd primary molar;
lesion not atypical or extended into buccal or lingual tooth surfaces; lesion completely surrounded by healthy enamel and should not reach the pulp; caries removal by drill;
Potential confounders reported: none.
[3] Parallel group trial. 835 patients, age 6-7 years from Damascus, Syria; with dentinal lesions with an opening wide enough for the smallest excavator to enter (diameter = 0.9 mm, without pulp involvement; size of
restorations varied from small to large; dental caries prevalence 85%; mean dmfts and dmft scores of molars plus canines 9.0 and 4.4, respectively; GIC restorations placed after caries removal by hand excavation
(ART).
Potential confounders reported: High past caries experience.
[4] Split-mouth trial. 152 patients from a cohort of grade 3-5 pupils, mean age 11 years in need of 2 or more restorations; from urban and rural schools near Dar es Salaam, Tanzania; selection criteria concerned
dentine lesions in the occlusal surface that showed no evidence of pulpal involvement; pupils needed to have a dentine lesion present in contralateral permanent molars; infected dentine was removed with slow-
speed drill and excavators or by hand excavation with use of Caridex.
Potential confounders reported: none.
[5] Parallel group trial. A total of 108 children of the ART group (GIC) and 84 children of the amalgam group were examined at evaluation year 6.3 - from Damascus, Syria; mean age 13.8 years; high risk for dentine
lesion development (mean DMFT score 5.5); the mean DMFT and DMFS scores of the children in the ART group were 5.5 (SD 3.0) and 8.2 (SD 5.4) respectively; the mean DMFT and DMFS scores of the children in
the amalgam group were 6.0 (SD 1/4 3.3) and 9.4 (SD 6.4); there was no statistically significant difference in caries scores between the children of the two groups (P > 0.05); the mean plaque score for the children in
the ART and amalgam group were 1.3 (SD 0.58) and 1.2 (SD 0.52), respectively (see also [3]).
Potential confounders reported: Poor oral hygiene; high past caries experience.
[6] Partial split-mouth trial. 45 girls 6-8 years old from a private school (boarding and regular school) in Beirut, Lebanon; from a low socio-economic background with their first and second primary molars requiring
new Class I or Class II restorations; specific criteria included vital teeth with normal appearance and morphology, and teeth with or without adjacent teeth; the children routinely (before and during study) received
information and instructions to improve their oral hygiene, and had two dental examinations per year; criteria for exclusion from the study: patients having behavioural problems, patients with general health
problems, patients with poor oral hygiene, molars requiring pulpotomy or pulpectomy; caries removal with drill;
Potential confounders reported: none.
[7] Split-mouth trial. see [4]
[8] Split-mouth trial. 60 Chinese children with mean age 7.4 (SD 1.24) years; 27 boys, 33 girls in Bejing; caries removal for GIC (ART) restorations by hand excavation or drill.
Potential confounders reported: none.
[9] Split-mouth trial. 18 caries-active patients, aged 13-16 years; from the regular clientele visiting one of the dental clinics of the Public Dental Health Service in Kronoberg, Sweden; with proximal primary, early
carious lesions on contralateral posterior teeth needed restorative treatment; lesion extending into dentin; have progressed into deeper zone since preceding information; caries removal by drill.
Potential confounders reported: none.
[10] Partial split-mouth trial. 666 children, from 3 to 13 years of age within the Danish Public Dental Health Service in the municipalities of Vaerløse and Hillerød, Denmark. The caries experience among children and
adolescents in the two municipalities is below the national average; caries removal by drill.
Potential confounders reported: Low past caries experience.
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follow-up developed caries on margins. The results did
not change the conclusions for the majority of datasets.
However, a possible risk of attrition bias was identified
in the results of three datasets (DS 02, 05, 14) extracted
from three trials [21,23,26]. The results of sensitivity
analysis showed:
(i) For dataset 02 [21]: If it were assumed that all
restored teeth lost to follow-up had developed caries
on restoration margins, the result would be signifi-
cantly in favour of amalgam (RR 5.00; 95% CI 1.65 -
15.15; p = 0.004);
(ii) For dataset 05 [23]: If it were assumed that all
restored teeth lost to follow-up had developed caries
on restoration margins, the result would show no
significant difference between the two treatment
groups (RR 0.81; 95% 0.59 - 1.11; p = 0.18);
(iii) For dataset 14 [26]: If it were assumed that all
restored teeth lost to follow-up had no caries pro-
gression on tooth surfaces adjacent to either mate-
rial, the result would not show a significant
difference between the two treatment groups (RR
0.68; 95% CI 0.32 - 1.44; p = 0.32).
In line with the potential influence of attrition bias on
datasets 02 and 05, the meta-analysis results (Figure 2
and 3) would change for single-surface restorations in
permanent, and multi-surface restorations in primary
teeth to RR 0.90; 95% CI 0.83 - 0.98; p = 0.01 and RR
1.02; 95% CI 0.95 - 1.09; p = 0.67 respectively, if it were
assumed that all restored teeth lost to follow-up had
developed caries on margins
In addition to the risk of bias due to loss-to-follow-up,
no trial indicated that a run-in phase was implemented
before randomisation (Table 5).
Publication bias risk
Publication bias was investigated, using one funnel plot
(Figure 5). The funnel plot covering data for caries pro-
gression showed an even distribution that did not sug-
gest publication bias. Egger’s linear regression method
for the same datasets showed an intercept of 0.96 (95%
CI -2.03 - 0.11; p = 0.07). The regression result was not
statistically significant.
Discussion
The aim of this quantitative systematic review was to
update the existing evidence related to the review ques-
tion about whether, on margins of restored tooth cav-
ities in the same dentition and of same cavity class,
GIC-restored cavities show less recurrent carious lesions
than cavities restored with amalgam.
The new systematic literature search found 12 more
trials [25-36] that could be included for review. This
was possible because of the publication of one new trial
Table 4 Results of individual datasets
Article DS RR 95% CI p-value
Welbury et al., 1991 [20] 01 0.64 0.27 - 1.51 0.31
Östlund et al., 1992 [21] 02 0.73 0.03 - 16.47 0.84
Taifour et al., 2002 [22] 03 0.57 0.24 - 1.36 0.21
04 0.35 0.11 - 1.10 0.07
Mandari et al., 2003 [23] 05 0.18 0.05 - 0.59 0.005*
Frencken et al., 2007 [24] 06 0.52 0.25 - 1.08 0.08
Daou et al., 2009 [25] 07 4.36 0.51 - 37.09 0.18
08 0.91 0.21 - 4.04 0.90
Mandari et al., 2001 [27] 09 0.56 0.25 - 1.24 0.15
Yu et al., 2004 [28] 10 Not estimable
11 Not estimable
Svanberg, 1992 [29] 12 0.14 0.01 - 2.53 0.18
13 0.33 0.12 - 0.91 0.03*
Qvist et al., 1997 [26] 14 0.59 0.28 - 1.25 0.17
15 0.48 0.32 - 0.71 0.0003*
16 0.57 0.38 - 0.87 0.0009*
17 0.91 0.73 - 1.13 0.38
DS = Dataset number; RR = Relative risk; CI = Confidence interval; Not estimable
= data from both treatment groups are essentially the same: p = 1.00.
*Statistically significant difference, in favour of GIC.
Figure 2 Forrest plot of meta-analysis results concerning caries on margins of single-surface restorations in permanent teeth after 6
years. Study or sub-category = Dataset number; GIC = Glass-ionomer cement; RR = Relative Risk; CI = Confidence Interval; n = number of teeth
with caries on restoration margins; N = Total number of evaluated teeth.
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Figure 3 Forrest plot of meta-analysis results concerning caries on margins of multiple-surface restorations in primary teeth after
3 years. Study or sub-category = Dataset number; GIC = Glass-ionomer cement; RR = Relative Risk; CI = Confidence Interval; n = number of
teeth with caries on restoration margins; N = Total number of evaluated teeth.
Figure 4 Forrest plot of cumulative meta-analysis results concerning caries on restoration margins in primary teeth (single- and
multiple surface restorations combined). RR = Relative Risk; MH = Mantel-Haenszel weight.
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since the original search cut-off date; a more thorough
hand-search and reference check of the literature, and
broader inclusion criteria. Of the 12 new included trials,
7 were excluded [30-36], as they did not comply with
the stated exclusion criteria. One trial [19] that was
accepted in the originally published systematic review
[7] was now excluded, as it did not report on loss-to-fol-
low-up restorations per treatment group, which that
made it impossible to discern the total number of eva-
luations (N) at the end of the follow-up period. There-
fore, it was also not possible to use sensitivity analysis
to assess the potential risk of attrition bias for this trial.
In comparison to the original published systematic
review [7], this update presents an improvement in the
output of its systematic literature search. However,
other aspects in the methodology of this review update
might still have contributed to limitations in its results:
(i) not all relevant publications were listed in the
selected databases; (ii) The chosen search terms may
not have been broad enough; (iii) not all relevant publi-
cations could be found through hand-search and refer-
ence check. Furthermore, we decided to limit inclusion
of trials found through hand-search and reference check
to trials published from 1990, only. Thus, some relevant
studies published before 1990 would not have been
identified. However, a plausible basis for the hypothesis
that GIC may contain caries preventive characteristics
was only developed in the mid-Nineties [4]. Trials that
investigated the characteristics of GIC before that period
may therefore not contain observations concerning car-
ies on restoration margins as primary outcomes. Such
assumption is confirmed by the fact that the majority of
trials excluded from this review due to lack of reported
outcome measure related to caries were published
before 1995 [31,34,35].
Selection-, Detection-/Performance bias risk
All of the accepted trials appear to be limited by risk of
selection- and detection/performance bias. Bias or sys-
tematic error may affect studies, causing either an over-
or an under-estimation of the treatment effect of an
investigated clinical procedure. Overestimation has been
observed to be the most common [37]. Kjaergard et al.
reported a treatment effect overestimation of 48%
caused by lack of random sequence allocation [38] and
Egger et al. reported a treatment effect overestimation
of 54% and 53% due respectively to lack of allocation
concealment and lack of evaluator blinding [39].
It has been emphasized that selection bias can be suc-
cessfully prevented only if the allocation sequence
remains truly random and free from potential interfer-
ence throughout the trial [9,10]. For this reason it is
important that trials include an effective process for
concealing the random allocation sequence and that
such process has indeed prevented direct observation
and prediction of the random sequence allocation
throughout each trial [9,10]. Quality assessment in
terms of the internal validity of trials should, therefore,
be a measure of the result of random sequence alloca-
tion and allocation concealment, and not only of its
reported attempt. All trials accepted in this systematic
review failed to report not only on evidence of success-
ful sequence allocation and allocation concealment
results but also on necessary details about how sequence
allocation and allocation concealment was attempted
(Table 5). None of the trials therefore provide any guar-
antee that each patient had an equal chance to be allo-
cated to either treatment group and thus their allocation
may have favoured the outcome of one type of treat-
ment above the other. One measure for testing whether
random sequence allocation has been successful is test-
ing whether covariates differ between treatment groups
at baseline [9]. Only two articles, reporting different
datasets from the same trial, had included such a test
and reported on its outcome [22,24]. The statistically
non-significant results (p > 0.05) suggest a successful
random allocation. However, doubt remains regarding
potential bias risk, as other non- balanced covariates
may exist that were not tested for and/or not reported.
From the onset, successful blinding or masking
appeared not to have been possible in all trials, owing to
the obvious differences between GIC and amalgam in
their clinical appearance. For that reason the allocation
to either treatment group was visible to patients, opera-
tors and evaluators. However, the difficulties of success-
ful blinding still carry the danger of detection-/
performance bias, which thus may have affected the
results of the trials. Potential knowledge of superiority
claims prior to the trial may have led patients to change
their oral hygiene habits, operators to place restorations
more carefully or evaluators to apply evaluation criteria
more subjectively. This in turn may have favoured the
outcome of one type of treatment above the other.
Attrition bias risk
Sensitivity analysis may be used to establish whether
missing data could have affected the trial outcomes, by
assuming that the numbers of restoration lost to evalua-
tion were either failures or successes [40]. Comparison
of the resulting analysis results with reported trial out-
comes indicates whether different conclusion should be
drawn. Sensitivity analysis was conducted for all data-
sets. The analysis results differed from reported out-
comes of three datasets (DS 02,05,14) extracted from
three trials [21,23,26]. According to the analysis results,
multiple-surface restorations placed with GIC (DS 02)
would have a 5-times higher chance than amalgam of
developing caries on restoration margins after 3 years in
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Table 5 Results of quality assessment of accepted trials
Article DS Selection bias Detection/Performance bias Attrition bias Trial outcome
Randomisation Baseline data Blinding/Masking Loss-to-follow up Run-in phase
Welbury et al., 1991 [20] 01 0 0 0 A A A
Östlund et al., 1992 [21] 02 0 0 0 B A A
Taifour et al., 2002 [22] 03 0 A 0 A A A
04 0 A 0 A A A
Mandari et al., 2003 [23] 05 0 0 0 B A A
Frencken et al., 2007 [24] 06 0 A 0 A A A
Daou et al., 2009 [25] 07 0 0 0 A A A
08 0 0 0 A A A
Mandari et al., 2001 [27] 09 0 0 0 B A A
Yu et al., 2004 [28] 10 0 0 0 A A A
11 0 0 0 A A A
Svanberg, 1992 [29] 12 0 0 0 A A A
13 0 0 0 A A 0
Qvist et al., 1997 [26] 14 0 0 0 B A A
15 0 0 0 A A 0
16 0 0 0 A A 0
17 0 0 0 A A 0
DS = Dataset number.
Figure 5 Funnel plot of dataset results (test for publication bias). RR = Relative Risk.
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primary teeth [21] and single-surface restorations placed
with GIC (DS 05) would have only a 10% (instead of
65%) lesser chance of developing caries on margins than
amalgam after 6 years in permanent teeth [23]. How-
ever, neither would affect the overall conclusions drawn
from the meta-analyses (Figures 2 and 3): that single-
surface GIC restorations have a lesser likelihood of
developing caries on margins in permanent teeth after
6 years and that no difference can be found between the
two materials regarding multiple-surface restorations
after 3 years in primary teeth.
The outcome of dataset 14 would be affected by attri-
tion bias, in that no significant differences between GIC
and amalgam would be found if all patients lost to fol-
low-up were assumed to show no caries progression in
the adjacent teeth [26]. However, a statistically signifi-
cant difference would remain in favour of GIC (p =
0.002) if all lost patients were assumed to show caries
progression. It has been observed that trials with patient
exclusion showed more beneficial test treatment effects
than analyses based on randomisation of all, or most,
patients [41]. This may be due to the possibility that
patients drop out or discontinue treatment if the treat-
ment proves unsuccessful. As no proof is available about
how many patients who were unavailable for evaluation
really did or did not have caries progression, the more
conservative assumption would be that most of them
had progressed caries. Against such a background, a
remaining statistical significant difference between the
treatment groups, in favour of GIC, seems more likely.
A run-in phase is considered to be a stage during a
trial where all patients receive, for example, the test
treatment and only those patients that respond well to
the treatment are later used for random allocation in
either the control or the test group [10]. Such practice
would effectively exclude patients from the randomisa-
tion process and potentially favour, for example, the test
group above the control. No such run-in phase was
indicated in any of the accepted trials (Table 5).
Publication bias risk
Publication bias was investigated by generating a funnel
plot (Figure 5). Publication bias is present when the
results of published research differ from those of all the
research that has been done [42]. Funnel plots are scat-
ter graphs showing the size of studies on the Y-axis
(large studies on top, small studies at the bottom) and
the effect size, observed in these studies, on the X-axis.
The effect sizes of larger studies have the tendency to
cluster near the mean. Small studies have effect sizes
that are dispersed across a wider range. Results of both
types of studies, plotted on a scatter graph, give the
shape of an inverted, in absence of publication bias sym-
metrical, funnel [43]. Publication bias affects a funnel
plot in the form of a concentration of studies to only
one side (asymmetry). Such asymmetry is created when
particular smaller studies are published only when they
show a larger than average effect. However, if the num-
ber of studies (n) is less than 10, any asymmetry may be
due to chance and not to publication bias [44]. For that
reason the decision was made to plot results of the 17
extracted datasets instead of those of published articles.
Despite this departure from the common use of funnel
plots, the use of datasets (instead of published studies)
will also indicate potential publication bias when only
datasets that show a larger than average effect are pub-
lished and other datasets are not. In this update, the
funnel plot concerning dichotomous RCT data on caries
progression showed a symmetrical spread of dataset
results (Figure 5). As the visual judgement of funnel
plots is subjective, intercepts were calculated (95% CI),
using Eggers regression [14]. The calculated intercept
confirmed a non-significant result. Eggers regression is
used to quantify bias captured by funnel plots [43].
However, its reported power is considered to be low
unless in the presence of severe bias or a high number
(n) of studies/datasets (n >10) [43,44]. Therefore, the
results of the calculated intercept concerning datasets
for caries progression (n = 17) may be ascribed to lack
of severe publication bias.
Data extraction and analysis results
The extended scope of this update did not change the
overall results of the meta-analysis originally published
[7]. However, it has to be noted that these results are
limited by risk of selection- and detection-/performance
bias. As the true extent of such bias impact remains
unknown within the reviewed trials, the results need to
be regarded with caution.
In eight out of the ten accepted trials that used split-
mouth or partial split-mouth design (Table 3) a cross-
over effect caused by fluoride, released from the GIC
restoration, may have reduced the caries susceptibility of
tooth margins surrounding the amalgam restorations
and thus may have confounded the observed results
towards a more equivocal outcome.
It also has to be noted that none of the accepted studies
reported on fluoride exposure of subjects. It can be
assumed that subjects may have been exposed to external
fluoride sources and that this may have increased the car-
ies resistance of teeth restored with amalgam, thus con-
founding the caries-preventive effect of GIC as suggested
by Hara et al. [45]. In this context, it is worth pointing
out that the only trial reporting on a statistically signifi-
cant primary outcome in favour of GIC was conducted in
a developing country in Africa [23], where the opportu-
nities of exposure to external fluoride sources may be
few. The hypothesis that GIC restorations may in general
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be less susceptible to recurrent caries is supported by the
secondary trial outcomes (DS 13,15,16) [26,29].
A significantly lower chance of caries development on
GIC restoration margins was reported in the permanent
dentition only [23]. In the primary dentition, the results
for multiple-surface restorations after 3 years (Figure 3)
suggest that neither of the materials is superior. The
reasons for this remain unclear. It can be assumed that
factors like the larger restoration surface, as well as the
greater difficulties involved in placing restorations in
children than in adults, may outweigh any caries-
preventive properties of GIC in comparison to amalgam.
However, under ideal trial conditions free of bias and
confounder influence, GIC restorations may also have a
lower chance of developing caries on restoration mar-
gins on a long-term basis in primary teeth. This state-
ment should be regarded as a hypothesis requiring
testing through high quality randomised control trials.
Plausibility for this hypothesis is provided by the results
of the included cumulative meta-analysis (Figure 4).
Cumulative meta-analysis is used to provide insights
into how much the efficacy of treatments, often reported
as mean results with 95% confidence intervals, change
over time as evidence accumulates [46]. It is the result
of conducting a new meta-analysis each time a new set
of evidence emerges [47]. A cumulative meta-analysis
not only allows the evaluation of any additional contri-
butions made by individual studies to the cumulatively
combined results of preceding studies [48] but also
allows observation of a trend in evidence direction over
time. The forest plot in Figure 4 shows a steady shift in
cumulative results, starting after 1 to 5 years, in favour
of GIC. The observed shift is caused by a cumulative
change in Relative Risk (from 4.36 to 0.75) and the nar-
rowing of the cumulative 95% confidence interval (from
0.51 - 37.08 to 0.45 - 1.23).
Recommendations for further research
Systematic reviews have been reported as providing the
highest form of clinical evidence [49]. However, the
internal validity of such evidence can only be as good as
the internal validity of the trials reviewed. Although the
trials accepted in this update may be considered not
much affected by attrition- and publication bias, their
risk of selection- and detection/performance bias is
high. Thus, further high quality randomised control
trials (RCT) are needed in order to verify (or disprove)
the currently available results. Such RCTs should adopt
a parallel group design and include randomisation and
allocation concealment methods that can effectively pre-
vent direct observation and prediction of the allocation
sequence. For this purpose the maximum randomisation
method has been suggested [9]. Covariates of both treat-
ment groups should be tested as to whether they differ
at baseline (after randomization). Recently, the inclusion
of the Berger-Exner test has been recommended for
authors of trials needing to investigate whether selection
bias has been introduced into their studies [9,10].
Where bias risk has been found, such risk may be
adjusted statistically [9]. In order to assure that the lack
of blinding may not have led to the favouring of one
treatment above another, trials should use and report on
procedures and tests employed that may have limited, or
at least monitored, potential bias risk. Future trials
should also base their reporting on the CONSORT
statement [50].
Conclusion
The results of this update of previous systematic evi-
dence confirm the findings of the original published
review regarding whether, on margins of restored tooth
cavities in the same dentition and of same cavity class,
GIC-restored cavities show less recurrent carious lesions
than cavities restored with amalgam. Although the find-
ings in this update may be considered less affected by
attrition- and publication bias, their risk of selection-
and detection-/performance bias is high. Therefore,
further high-quality randomised control trials are
needed in order to verify the currently available results.
Authors’ contributions
Both authors contributed equally to the systematic literature search, review,
data extraction and the writing of the manuscript. SM conducted the data
analysis.
Competing interests
The authors declare that they have no competing interests.
Received: 8 October 2010 Accepted: 11 March 2011
Published: 11 March 2011
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doi:10.1186/1756-0500-4-58
Cite this article as: Mickenautsch and Yengopal: Absence of carious
lesions at margins of glass-ionomer cement and amalgam restorations:
An update of systematic review evidence. BMC Research Notes 2011 4:58.
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