Coherence of evidence from systematic reviews as a basis for evidence strength - a case study in support of an epistemological proposition.

CORRESPONDENCE Open Access
Coherence of evidence from systematic reviews
as a basis for evidence strength - a case study in
support of an epistemological proposition
Steffen Mickenautsch
Abstract
Background: This article aims to offer, on the basis of Coherence theory, the epistemological proposition that
mutually supportive evidence from multiple systematic reviews may successfully refute radical, philosophical
scepticism.
Methods: A case study including seven systematic reviews is presented with the objective of refuting radical
philosophical scepticism towards the belief that glass-ionomer cements (GIC) are beneficial in tooth caries therapy.
The case study illustrates how principles of logical and empirical coherence may be applied as evidence in support
of specific beliefs in healthcare.
Results: The results show that radical scepticism may epistemologically be refuted on the basis of logical and
empirical coherence. For success, several systematic reviews covering interconnected beliefs are needed. In praxis,
these systematic reviews would also need to be of high quality and its conclusions based on reviewed high quality
trials.
Conclusions: A refutation of radical philosophical scepticism to clinical evidence may be achieved, if and only if
such evidence is based on the logical and empirical coherence of multiple systematic review results. Practical
application also requires focus on the quality of the systematic reviews and reviewed trials.
Introduction
Epistemology is described as the branch of philosophy
that concerns itself with questions regarding human
knowledge [1]. One particular epistemological question
relates to the Object - Subject distinction and asks
whether the objective world is subjectively knowable at
all. It has been proposed that the real (objective) world
and our (subjective) perception of the real world are not
the same. Descartes (1641) argued that all that we can
know of the real world is tainted by our senses and abil-
ities of understanding [2]. Kant (1998 [1781]) distin-
guished between the unknowable Ding an sich (German:
The thing in itself) and the knowable Erscheinung (Ger-
man: Phenomenon) [3]. Postmodernism contends that
the notion of reality is an illusion [4]. Quine (1964)
described physical objects as mere cultural posits [5],
and cognitive psychology and neuroscience have pre-
sented evidence that sense experience, the ‘bedrock of
empirical knowledge’, is actively edited by human per-
ception [4]. Such ‘editing’ renders sense experience sub-
jective to the particular observer [6].
All these examples [2-6] share the common concept
that some form of bias determines subjective perception
concerning real world events. Bias, also called systematic
error, manifests in various forms and number, and con-
stitutes any factor in the knowledge acquisition process
that systematically diverts its outcomes from true values
[7]. The concept of knowledge has been defined as true
and justified belief [1]. Systematic error, therefore, limits
the trueness and thus justifiability of such belief (thus
its value to be considered as knowledge) and so widens
the gap between the real (objective) world and our (sub-
jective) perception of it. In order to limit the influence
of some forms of systematic errors in the field of health-
care, methodological interventions for clinical trials,
such as randomisation, blinding and intention-to-treat
Correspondence: neem@global.co.za
SYSTEM Initiative/Department of Community Dentistry, Faculty of Health
Sciences, University of the Witwatersrand, 7 York Rd., Parktown/
Johannesburg 2193, South Africa
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© 2012 Mickenautsch; 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.

analysis, are proposed [8] and have been shown to be
effective [9,10]. Clinical trials that employ such metho-
dological interventions are identified and synthesized
through systematic reviews. Systematic reviews present:
(i) a synthesis of the acquired knowledge regarding one
particular clinical question derived from all relevant stu-
dies that are identifiable at one point in time, (ii) iden-
tify the level of validity and the subsequent potential
systematic error risk associated with the acquired
knowledge and (iii) provide recommendations for
improving any identified shortcoming related to internal
validity, for further research. Owing to continued further
research, systematic reviews also provide continued
updates of their synthesis [10]. For this reason, in most
cases systematic reviews provide the most objective
knowledge possible about real world events; such as
answers to clinical questions concerning causalities, with
the least possible systematic error.
However, the described distinction between the real
(objective) world and (subjective) perception of the real
world [2-6] has also given ground to radical, philosophi-
cal scepticism about whether it is possible to gain
knowledge of real (objective) world events, at all [1].
Radical, philosophical scepticism does not just question
current standards of evidence: it completely denies that
any causality existing independently from our perception
in the real world is knowable at all; regardless of the
availability and strength of evidence, e.g. as presented in
systematic reviews that supports knowledge of such
causality. By disregarding such evidence, radical, philo-
sophical scepticism denies any justification for or against
any perception of objective knowledge. Among the main
modes of argument utilized in radical, philosophical
scepticism are the five modes of Agrippa [1,11]. These
modes of argument state: (i) for each thesis there is a
possible antithesis but without the option of Fichte’s
synthesis through thesis and antithesis [12] - because:
(ii) each point of view is relative to each particular clai-
mant and thus cannot hold general truth; because: (iii)
proof of any point of view or thesis is not possible, as
every proof, evidence or justification requires for its own
proof, evidence or justification, thus entering into an
infinite regress of proof that is incapable of proving any-
thing; (iv) to end such infinite regress of proof by refus-
ing further proof shows lack of proof; and (v) to reason
in circles by referring back to already stated proof also
shows lack of proof [11].
In accordance with the Agrippean argument, evidence
elicited from single systematic reviews as proof in clini-
cal practice is vulnerable to radical scepticism. An
example is the argument that population-based research
(research conducted, e.g. through randomised control
trials (RCT) and subsequently appraised through sys-
tematic reviews) cannot be applicable to the treatment
of individual patients [13]. The validity of population-
based results, so it is argued, may only be applied to the
population as such but remains irrelevant to the single
patient, as individual patient data and a population
average are never the same [13]. Such criticism denies
the ability of systematic review evidence to describe
objective causality. It employs the Agrippean argument
that: (i) like any other thesis, the thesis of objective evi-
dence by systematic reviews is contradictable; (ii) the
thesis of objective evidence by systematic reviews (the
population average) is relative and thus cannot be valid
for the individual patient because the general validity of
such thesis cannot be proven (see Agrippean modes of
argument iii - v).
The aim of this article is to offer the epistemological
proposition that, with reference to the Coherence theory
and illustrated by one case study, evidence from multi-
ple systematic reviews, if mutually supportive (= logi-
cally and empirically coherent) may be able in principle
and on philosophical ground to terminate the infinite
regress of proof and thus refute the Agrippean argument
against it. This article further aims to highlight some
aspects concerning the translation of such proposition
from philosophical grounds into health care praxis.
Coherence theory
The key to refuting the Agrippean argument is to termi-
nate the infinite regression of proof. The radical sceptic
rejects refusal of further proof and circular reference to
proof, preventing formation of a successful refutation. A
possible epistemological solution to this problem is to
assert that not just one single belief but many, are
expressed in a thesis. Such beliefs do not exist indepen-
dently from each other but form a system or web of
mutually supporting beliefs that justify each other. This
line of argument against radical scepticism has been
called the Coherence theory [14-16]. The Coherence
theory states that beliefs are justified if they are systema-
tically interconnected and provide mutual proof for each
other [1]. Such mutual proofs do not constitute mere
circularity but logical coherence, thus terminating the
need for infinite regression of proof. According to
Coherence theory in epistemology, justification of proof
of a belief depends on how well it fits into the web of
beliefs, thus stating that individual beliefs are justified by
virtue of belonging to a coherent view. This argument
has been criticized on the grounds that it allows any
form of belief, no matter how unlikely or likely; to be
considered as justified as long as it is surrounded by sui-
table supporting beliefs [1]. Even if such supporting
beliefs are as unlikely as the main belief, it may still
form a coherent system. Against such background, the
Coherence theory is unable to make a clear distinction
between aspects of the real world (causality) and
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delusions. However, it has been argued that the Coher-
ence theory is not a theory of truth but a theory of justi-
fication [1]. The distinction between a coherent real
world system and a coherent system of delusion can be
made only on the basis of its relation to evidence. Such
evidence has to be empirical: facts about the real world
ascertained from observation and experiment. For a
coherent system to be proof of truth, it not only needs
to be: (i) logically coherent in terms of its interconnect-
ing beliefs, but also (ii) coherent in terms of the empiri-
cal evidence on which all interconnecting beliefs are
based (empirical coherence).
Case study
In order to show how the above principles of Coherence
theory may be applied in support of specific beliefs in
healthcare, a case study including seven systematic reviews
[17-23], all co-written and published by the author, was
conducted. These systematic reviews related to various
aspects of the clinical use of glass-ionomer cements (GIC)
and dental caries. The format of a case study was chosen
in order to explore without high methodological restric-
tions the potential usefulness of Coherence theory in this
context and to contribute new insights for discussion and
further study. As Coherence theory is rooted in philoso-
phical/epistemological thinking, this article limits its line
of argument mainly on philosophical/epistemological
grounds. However, some practical implications, relevant to
the field of health care are also discussed.
The specific objective of this case study was to illus-
trate, as example, the refutation of radical scepticism
towards the belief that GICs are beneficial in tooth car-
ies therapy on the basis of logical and empirical coher-
ence, and included the following steps:
(i) Conducting and publication of systematic review
articles addressing different review questions con-
cerning the main belief regarding clinical benefits of
GICs in tooth caries therapy;
(ii) Extraction of ‘web’components, separated by
common categories, that are contained in the sys-
tematic reviews;
(iii) Construction of a ‘web-of-beliefs’ frame from the
extracted components;
(iv) Setting of conditions that need to be in place in
the constructed ‘web-of-beliefs’ in order for it to be
considered coherent;
(v) Discussion about whether the specific information
provided by the systematic reviews fulfils the conditions
for (a) logical coherence and (b) empirical coherence.
Systematic review sample
The format of systematic reviews of trials was chosen
above other forms of scientific investigation (i.e.
randomised control trials, observational studies, clinical
case reports or narrative reviews/expert opinion), as
these are considered to provide the most comprehensive
answers to clinical questions, with the least possible sys-
tematic error [10]. All systematic reviews were of quan-
titative (as opposed to qualitative) nature. Some
included meta-analyses for precision of results. The sys-
tematic reviews were undertaken in order to answer
separate clinical review questions, but all with relevance
to the main belief that GIC is beneficial in caries ther-
apy. All systematic reviews were published in MED-
LINE- listed peer-reviewed dental journals between
September 2009 and February 2011. The language of
publication was English.
Of the seven systematic reviews, three included con-
ventional GIC (C-GIC) [17,18,22] and three, resin-modi-
fied GIC (RM-GIC) [19,20,23] as the test material. One
systematic review investigated both versions of GIC, in
comparison [21]. Two systematic reviews investigated
the fissure sealant performance of GIC [17,19]. The
other five investigated its performance as a material for
tooth restorations [18,20-23]. The investigated outcome
measures of the seven systematic reviews were tooth
remineralisation [20], absence of tooth caries
[17-19,21,23] and long-time survival of tooth restora-
tions [22].
The strength of systematic review evidence relies on
(i) the quality of trials reviewed and (ii) the quality of
the systematic review itself. The AMSTAR (Assessment
of Multiple SysTemAtic Reviews) tool [24-26] was used
for critical self-assessment of the quality of the systema-
tic review articles. The results are shown in Table 1. On
the basis of this assessment, the AMSTAR score for
three systematic reviews was 9 [19,21,23], three systema-
tic reviews scored 8 [18,20,22] and one scored 7 [17].
An AMSTAR score between 8 and 11 has been sug-
gested to indicate a high level of systematic review qual-
ity and a score between 4 and 7, a medium one [27].
According to such interpretation, six of the seven sys-
tematic reviews were of high quality and one of medium
quality. However, the quality of systematic review results
can only be as good as the quality of its reviewed trials.
The use of the AMSTAR tool does not establish
whether systematic reviews judged the quality of trials
according to whether or not bias was successfully pre-
vented. Selection bias, besides e.g. detection/perfor-
mance-, attrition- or publication bias, is one of the most
important types of bias in clinical trials and effectively
diverts trial results away from the truth, even in absence
of any other types of bias risk [8]. Therefore, selection
bias due to lack of adequate concealment of the random
sequence allocation was assessed in all reviewed trials.
Allocation, using for example central randomisation,
was considered to be adequate concealment. The result
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Table 1 Result of critical self-assessment of systematic review quality (AMSTAR)
AMSTAR components Yengopal
et al.,
2009 [17]
Yengopal and
Mickenautsch,
2010 [19]
Mickenautsch
et al., 2010
[21]
Mickenautsch
et al., 2010
[22]
Mickenautsch
et al., 2009
[18]
Mickenautsch
and
Yengopal,
2010 [20]
Yengopal and
Mickenautsch,
2011 [23]
(1) Was an ‘a priori’ design
provided? The research
question and inclusion criteria
should be established before
the conduct of the review.
X X X X X X X
(2) Was there duplicate study
selection and data
extraction? There should be at
least two independent data
extractors and a consensus
procedure for disagreements
should be in place.
X X X X X X X
(3) Was a comprehensive
literature search performed?
At least two electronic sources
should be searched. The report
must include years and
databases used (e.g. Central,
EMBASE, and MEDLINE). Key
words and/or MeSH terms
must be stated and where
feasible the search strategy
should be provided. All
searches should be
supplemented by consulting
current contents, textbooks,
specialized registers, or experts
in the particular field of study,
and by reviewing the
references in the studies found.
X X X X X X X
(4) Was the status of
publication (i.e. grey
literature) used as an
inclusion criterion? The
authors should state that they
searched for reports regardless
of their publication type. The
authors should state whether
or not they excluded any
reports (from the systematic
review), based on their
publication status, language
etc.
X X X X
(5) Was a list of studies
(included and excluded)
provided? A list of included
and excluded studies should
be provided.
X X X X X X X
(6) Were the characteristics
of the included studies
provided? In an aggregated
form such as table, data from
the original studies should be
provided on the participants,
interventions and outcomes.
The ranges of characteristics in
all studies analysed e.g. age,
race, sex, relevant socio-
economic data, disease status,
severity, or other diseases
should be reported.
X X X X X X X
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showed that none of the 47 trials accepted for review
included adequate allocation concealment in their
methodology.
Web-of-beliefs and components
All beliefs investigated by the seven systematic reviews:
belief related to GICs remineralising effect (Belief 1), car-
ies-preventive effect (Belief 2), restoration survival (Belief
3), are mutual to the main belief regarding GIC’s benefit
in caries therapy. All systematic reviews contained the
component categories: Test material (Tn); Control mate-
rial (Cn); Treatment type (TNn) and Outcome measure
(OMn). Details about the specific components per category
are shown in Table 2. These various component categories
interconnect by virtue of the methodology employed in
the systematic reviews, thus forming strings, such as:
{
Test material − control material − investigated treatment type − outcome measure
}
or
{Tn − Cn − TNn − OMn}
Table 1 Result of critical self-assessment of systematic review quality (AMSTAR) (Continued)
(7) Was the scientific quality
of the included studies
assessed and documented?
’A priori’ methods of
assessment should be provided
(e.g. for effectiveness studies if
the author(s) chose to include
only randomised, double-blind,
placebo controlled studies or
allocation concealment as
inclusion criteria); or other
types of studies alternative
items will be relevant.
X X X X X X X
(8) Was the scientific quality
of the included studies used
appropriately in formulating
conclusions? The result of the
methodological rigor and
scientific quality should be
considered in the analysis and
the conclusions of the review
and explicitly stated in
formulating recommendations.
X X X X X
(9) Were the methods used
to combine the findings of
the studies appropriate? For
the pooled results, a test
should be done to ensure the
studies were combinable, to
assess their homogeneity (i.e.
Chi-squared test for
homogeneity, I2). If
heterogeneity exists a random
effects model should be used
and/or the clinical
appropriateness of combining
should be taken into
consideration (i.e. is it sensible
to combine?).
X X X X X X
(10) Was the likelihood of
publication bias assessed?
An assessment of publication
bias should include a
combination of graphical aids
(e.g. funnel plot, other available
test) and/or statistical tests (e.g.
Egger regression test).
X
(11) Was the conflict of
interest stated? Potential
source of support should be
clearly acknowledged in both
the systematic review and the
included studies.
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Through the various components present in each sys-
tematic review per category, various different strings
may thus be generated (Table 3). The various beliefs are
expressed and tested along these constructed methodo-
logical strings. As each string makes use of at least one
of the various components, these strings can be graphi-
cally merged and thus illustrate the outline structure of
a ‘web-of-beliefs’ frame, relevant to the overall topic as
to whether GIC is beneficial in caries therapy (Figure 1).
The illustration of such frame in the form of a graph
gives an overview of how the various beliefs are con-
nected and form into a ‘web’. Figure 1 also serves as a
map to graphically discern the interconnections between
the various requirements of coherence.
Requirements for coherence
Whether this web-of-beliefs is indeed ‘coherent’ depends
on how well its underlying concepts are logically coher-
ent, as well as on the empirical coherence of its underly-
ing clinical evidence.
Within the framework of this case study, logical
coherence was based on the tautologies that:
(i) Tooth remineralisation (OM1) is conceptually
closer related to absence of carious tooth lesions
(OM2) than to lesion presence;
(ii) Absence of carious tooth lesions (OM2) on
restoration margins is conceptually closer related to
tooth restoration survival (OM3) than to failure.
In biological/clinical terms, these tautologies are over-
simplified, as the process of the caries disease is rather
complex. However, within the philosophical context of
this case study, these tautologies mean that the higher
the tooth remineralisation effect, the less the occurrence
of carious tooth lesions is expected to be and the less the
occurrence of lesions on restoration margins, the higher
the survival of tooth restorations is expected to be.
Coherence of clinical evidence (Empirical coherence)
will mean that the following conditions are fulfilled,
within the framework of this case study:
(i) The remineralisation effect (OM1) associated with
test materials (Tn) is at least not lower than with
control materials (Cn), regardless of the type of
treatment (TNn);
(ii) Absence of carious tooth lesions (OM2) asso-
ciated with test materials (Tn) is at least not lower
than with control materials (Cn), regardless of the
type of treatment (TNn);
(iii) Tooth restoration survival (OM3) associated with
test materials (Tn) is at least not lower than with
control materials (Cn), for tooth restoration as treat-
ment type (TN1);
(iv) There are no differences in the clinical outcomes
between the different versions of the test materials
(T1 and 2) regardless of type of treatment (TNn) and
outcome measure (OMn);
(v) There is no difference between the clinical out-
comes of the same version of the test material (T1 or
2) in comparison to different control materials (Cn),
(under condition of same type of treatment (TNn)
and outcome measure (OMn);
(vi) There is no difference between the clinical out-
comes of the different version of test material (Tn)
in comparison to the same control material (C1,2,3 or
4) (under condition of same type of treatment (TNn)
and outcome measure (OMn).
Table 3 Case study: constructed methodological strings per systematic review
Beliefs related to: Systematic review Methodological string
Belief 1: Remineralising effect of GIC Mickenautsch and Yengopal, 2010 [20] {T1 - C4 - TN1 - OM1}
Belief 2: Caries-preventive effect of GIC Yengopal et al., 2009 [17] {T2 - C1 - TN2 - OM2}
Yengopal and Mickenautsch, 2010 [19] {T1 - C1 - TN2 - OM2}
Mickenautsch et al., 2010 [21] {T1 - T2 - TN1 - OM2}
Mickenautsch et al., 2009 [18] {T2 - C3 - TN1 - OM2}
Yengopal and Mickenautsch, 2011 [23] {T1 - C2 - TN1 - OM2}
Belief 3: GIC restoration survival Mickenautsch et al., 2010 [22] {T2 - C3 - TN1 - OM3}
Table 2 Case study: web of beliefs components
Category Component Symbol
Test material Resin-modified GIC T1
Conventional GIC T2
Control material Resin C1
Composite resin C2
Amalgam C3
Other C4
Treatment type Tooth restoration TN1
Tooth pits and fissure sealant TN2
Outcome measure Tooth remineralisation OM1
Absence of carious tooth lesions OM2
Tooth restoration survival OM3
GIC glass-ionomer cement
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The information provided by the systematic reviews
were discussed in relation to these conditions, to estab-
lish whether it complied with the requirements for
coherence:
Logical coherence
In order to fulfil the condition of logical coherence the
tautologies that: (i) the higher the tooth remineralisa-
tion effect, the less the occurrence of carious tooth
lesions and (ii) the less the occurrence of carious tooth
lesions on restoration margins, the higher will be the
occurrence of the survival of tooth restorations, were
adopted. Tautology is a philosophical term that
describes a statement that is true in every circum-
stance, thus forming a necessary truth [28]. This
necessary truth is circumscribed in the commonly
accepted definition of carious tooth lesions [29] and its
occurrence on restorative margins as a common cause
of tooth restoration failure [30].
Empirical coherence
The evidence provided by the seven systematic reviews
complies with all set conditions for coherence of evi-
dence (Table 4). No non-compliance that would be in
contradiction of coherence within the established web-
of-beliefs has been identified: Remineralisation in asso-
ciation with GIC has not been found lower than with
the control [20]. Such remineralising effect supports the
belief that GIC is not associated with a higher caries
risk (= logical coherence tautology) and that belief has
Figure 1 Case study: graphical illustration of web of beliefs frame. See Table 2 for explanation of symbols.
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been confirmed [17-19,23]. Such caries resistance in
turn supports the belief that the survival rate of GIC-
based (ART) tooth restorations is at least not lower
than that of the control (= logical coherence tautology).
That belief was shown to be correct [22]. In addition,
the different versions of GIC do not give different clini-
cal results, because they both contain the same active
ingredient [17,19,21] and the anti-cariogenic efficacy of
GIC was shown, even when compared against those of
different control materials [17-19,23]. Against this back-
ground and within the set web-of-beliefs, empirical
coherence appears to be confirmed.
Further aspects of evidence
In line with the Coherence theory, the logical and
empirical coherence presented in this case study may be
regarded as sufficient to terminate the infinite regression
of proof imposed by radical scepticism. This means that
radical philosophical scepticism towards the clinical
benefit of GIC regarding caries may be successfully
refuted in epistemological terms. However, it is impor-
tant to note that such epistemological proposition can
only be translated successfully into practice if and only
if no general scepticism concerning the validity of the
underlying empirical evidence arises. In the presented
case study, empirical evidence is provided by seven sys-
tematic reviews. Systematic reviews are regarded as pro-
viding the highest form of evidence to healthcare
questions [10]. Nonetheless, systematic reviews do not
by virtue of their nature provide high empirical evi-
dence. Rather, such evidence can be regarded as valid
only when the systematic reviews and the trials reviewed
are of high quality. The AMSTAR tool has been pro-
posed as one method for measuring the quality of sys-
tematic reviews. Critical self-assessment by use of the
AMSTAR tool showed a general high quality in the sys-
tematic reviews included in the case study (Table 1).
However, even if empirical evidence is provided by
high-quality systematic reviews, this evidence can only
be as valid as the evidence provided by the clinical trials
reviewed. Assessment of all 47 trials found reason for
doubt (= lack of reporting adequate random allocation
concealment) of evidence validity, owing to the high risk
of selection bias. It has been emphasized that selection
bias can be successfully prevented only if the allocation
sequence remains truly random and free from potential
Table 4 Case study: compliance of systematic review evidence with conditions for coherence of evidence
Systematic review Review conclusion Evidence in regard to
conditions for
coherence of evidence
(i) (ii) (iii) (iv) (v) (vi)
Yengopal et al., 2009
[17]
... indicating no difference in the caries-preventive effect of GIC and resin-based fissure sealant
material
2 5a 6
Yengopal and
Mickenautsch, 2010 [19]
... found no conclusive evidence that either material was superior to the other in preventing
dental caries
2 5b 6
Mickenautsch et al.,
2010 [21]
... indicating no difference in the caries preventive effect between both types of materials 4
Mickenautsch et al.,
2010 [22]
In the permanent dentition the longevity of ART is equal to or greater than that of equivalent
amalgam restorations for up to 6.3 years and is site-dependent. No difference was observed
in primary teeth.
3
Mickenautsch et al.,
2009 [18]
Carious lesions at margins of single-surface GIC restorations are less common than with
amalgam fillings after 6 years in permanent teeth. No difference was observed in primary
teeth.
2 5a
Mickenautsch and
Yengopal, 2010 [20]
The evidence suggests that RM-GIC is associated with a higher reduction of demineralization
in adjacent hard tooth tissue than that of composite resin without fluoride. No difference was
found when RM-GIC was compared with fluoride-containing composite.
1
Yengopal and
Mickenautsch, 2011 [23]
The overall results showed no difference between the materials or indicated that RM-GIC has
a superior caries-preventive effect.
2 5b
Evidence Compliance/non-compliance with conditions for coherence of evidence
1 Compliance. No lower remineralisation than that of control was observed, as per condition (i).
2 Compliance. No lower absence of caries than that of control was observed, as per condition (ii).
3 Compliance. No lower survival rate was observed, as per condition (iii).
4 Compliance. No difference was observed, as per condition (iv).
5a Compliance. No difference was observed for RM-GIC, as per condition (v).
5b Compliance. No difference was observed for GIC, as per condition (v).
6 Compliance. No difference was observed, as per condition (vi).
GIC glass-ionomer cement; ART tooth restoration with GIC; RM-GIC resin-modified GIC.
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interference throughout the trial [31,32]. Thus, it is
important that trials should include an effective process
for concealing the random allocation sequence and that
by the end of each trial this process has indeed pre-
vented direct observation and prediction of the random
sequence allocation [31,32]. Egger et al., 2003 reported a
treatment effect overestimation of between 21% and
54% due to selection bias, solely caused by lack of allo-
cation concealment during the randomisation process
[9]. The seriousness of such overestimation becomes
clear under consideration that in a condition of a 50%
overestimation, the actual result for a test treatment
would be a 20% higher relative risk (RR 1.20) than for
the control, while the trial report would claim a 20%
lower relative risk (RR 0.80). Thus, in this example, the
true result of the trial would constitute the complete
opposite of the reported trial result. Such high percen-
tages of over-estimation due to bias may therefore lead
to situations where ineffective treatment procedures are
presented as effective. For this reason, all trial results
identified in the seven systematic reviews need to be
interpreted with caution.
Conclusion
Radical, philosophical scepticism towards the benefit of
clinical procedures in healthcare may epistemologically
be refuted on the basis of logical and empirical coher-
ence. Such coherence indicates causality in the real
(objective) world - in this example GIC related to car-
ies-therapeutic benefit - that exists independently of
(subjective) perceptions or scepticism. Empirical coher-
ence is provided from clinical evidence. Such evidence is
acquired through clinical trials and subsequently synthe-
sised by (quantitative) systematic reviews. A single sys-
tematic review covering one topic may be insufficient
for refuting the Agrippean argument. For this, several
systematic reviews covering interconnected beliefs may
be needed. It is stressed that a successful application of
such epistemological proposition into practice regarding
refutation of radical, philosophical scepticism towards
the benefit of a particular clinical procedure is possible
only if these systematic reviews are of high quality and
the quality of reviewed clinical trials is high enough to
withstand general scepticism concerning trial validity.
Authors’ contributions
SM developed the concept and outline and wrote this paper.
Competing interests
The author contributes to the conduct and publication of systematic reviews
concerned with topics related to Minimum Intervention (MI) in dentistry.
Received: 3 October 2011 Accepted: 12 January 2012
Published: 12 January 2012
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doi:10.1186/1756-0500-5-26
Cite this article as: Mickenautsch: Coherence of evidence from
systematic reviews as a basis for evidence strength - a case study in
support of an epistemological proposition. BMC Research Notes 2012
5:26.
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