2. • Periodontics is a rapidly changing field with
advances in the ability to diagnose, prevent
disease and slow its progression, and
regenerate lost periodontium. The recent focus
is on clinical decision-making and it is our
duty to offer the best possible care for patients in
an evidence-based manner.
• Evidence-based approach (EBA) offers a bridge
from science to clinical practice.
3. ADVANTAGES OF EVIDENCE-BASED APPROACH
compared with other assessment methods (Newman
et al, 2003)
• Objective
• Scientifically sound
• Patient-focused
• Incorporates clinical experience
• Stresses good judgment
• Is thorough and comprehensive
• Uses transparent methodology
5. • EVIDENCE BASED MEDICINE (EBM):
– Terminology introduced by EBM working group in
1992.
– Evidence based health care was defined as an
approach to decision-making in which the
clinician uses the best evidence available, in
consultation with the patient, to decide upon the
option which suits the patient best. (Gray M,
1997)
– Defined as the integration of the best research
evidence with clinical expertise & patient values.
(Sackett et al, 2000)
6. • Using evidence from the medical literature to
answer questions, direct clinical action & guide
practice was pioneered and the term EBM was
coined by the clinical epidemiology group at
McMaster University, Ontario, Canada, in 1980s.
• However, the following aspects of EBM are new:
– Methods of generating high quality evidence
– Statistical tools for synthesizing & analyzing the
evidence
– Ways for assessing & applying the evidence
7. • EVIDENCE BASED DECISION MAKING (EBDM):
– Defined as formalized process & structure for
learning the skills for searching relevant evidence &
critical appraisal so that the best scientific evidence
is considered when making patient care decisions.
– Fundamental principles (EBM working group,
2002):
• Evidence alone is never sufficient to make a
clinical decision
• Hierarchies of quality & applicability of evidence
exist to guide clinical decision making.
8. Evidence based decision making
Scientific
evidence
Patient
preferences/
values
Clinical patient
circumstances
Experience
&
judgment
9. Need for evidence based decision making
Emerged in response to the need to
1. Improve the quality of health care: driven by
following forces:
a. Variations in practice pattern: due to time gap
between availability & application of current
research knowledge
b. Difficulty that clinicians confront in
assimilating scientific evidence into their
practices.
2. Demonstrate the best use of limited resources
10.
11. Barriers to implementing evidence-based
methods in dental practice (Sutherland 2000)
• A lack of appropriate skills on the part of dentists in
– formulating clear questions
– executing efficient electronic searches
– evaluating the literature
• A lack of good clinical research in the form of well-
designed randomized trials
• Fear and mistrust by dentists regarding the use of
the evidence, especially by third-party funders and
regulatory authorities.
13. • EVIDENCE BASED DENTISTRY: an approach to oral
health care that requires the judicious integration of
systematic assessments of clinically relevant scientific
evidence, relating to patient’s oral & medical condition
& history, with the dentist’s clinical expertise &
patient’s treatment needs & preferences. (ADA, 2002)
• EVIDENCE BASED PERIODONTOLOGY: an
approach to patient care
– Evidence-based periodontology is the application of
evidence-based health care to periodontology.
– It is a tool to support decision making and
integrating the best evidence available with clinical
practice. (Needleman et al, 2005)
15. Development of evidence based
periodontology
• Evidence-based periodontology is built upon
developments in clinical research design
throughout the 18th, 19th and 20th centuries.
• EBM: pioneered by clinical epidemiology group
at McMaster University, Canada.
• One of the earliest to take up the challenge in
periodontology (in fact in oral health research
overall) was Alexia Antczak Bouckoms in
Boston, USA.
16. • They challenged the methods and quality of
periodontal clinical research in the mid 1980s
and set up an Oral Health Group as part of the
Cochrane Collaboration in 1994.
• The editorial base of the Oral Health group
subsequently moved to Manchester University in
1997.
• The first Cochrane systematic review in
periodontology was published in 2001 and
researched the effect of GTR for infrabony
defects.
17. • The 1996 World Workshop in Periodontology held
by the AAP included elements of evidence-based
healthcare.
• The 2002 European Workshop on Periodontology
became the first international workshop to use
rigorous systematic reviews to inform the
consensus.
• A similar approach was used subsequently by the
AAP for the Contemporary Science Workshop in
2003.
18. • Many other groups are now using similar methods
in healthcare and research.
• The International Center for Evidence-Based Oral
Health was launched in 2003 to produce high
quality evidence-based research with an emphasis
on, but not limited to, periodontology and implants
and to provide generic training in systematic
reviews and research methods.
20. EBDM process & skills (Sackett et al, 2000)
1. Converting information needs/problems into
clinical questions so they can be answered
2. Conducting a computerized search with maximum
efficiency for finding the best external evidence
with which to answer the question
3. Critically appraising the evidence for its validity and
usefulness (clinical applicability)
4. Applying the results of the appraisal, or evidence,
in clinical practice
5. Evaluating the process and your performance
21. The steps of evidence-based
Periodontology (Clarkson et al, 2003)
External validity:
generalizing findings
Internal validity:
Research methodology
22. 1. Asking good questions: the PICO process
(Sackett et al, 2000)
• A well-built question should include 4 parts that
identify the
– patient Problem/ Population
– Intervention
– Comparison
– Outcomes
• The format to structure the question:
“ for a patient with ___ (P), will ___ (I) as compared
to ___ (C) increase/ decrease/ provide better/ in
doing ___ (O)?”
23. • Purpose of using PICO to frame the question:
– Forces the clinician to focus on what he/ she &
the patient believe to be the most important single
issue & outcome.
– Facilitates next step in process, computerized
search, by identifying key terms to be used in the
search.
– Allows identification of the type of evidence &
information required to solve the problem, as well
as considerations for measuring effectiveness of
intervention & application of EBDM process.
24. 2. Searching for & acquiring the evidence
• Evidence is considered the synthesis of all valid
research that answers a specific question,
which distinguishes it from a single research
study. (Greenhalgh, 1996)
• Evidence can help inform decisions about
whether a method of diagnosis/ treatment is
effective relative to other methods of
diagnoses/ to other treatments, & under what
circumstances.
25. Types of Evidence based sources
Primary sources:
Original research
publications that have
not been filtered/
synthesized
Secondary sources:
Synthesized publications of
primary literature:
• SRs
• Meta-analyses
• EB article reviews
• Clinical practice guidelines
& protocols
26. • Searching the evidence
– Use biomedical database:
• MEDLINE (Pubmed, strong on English-
language studies)
• EMBASE (strong on other European
languages),
• HealthSTAR
• CINALH (cumulative index to nursing & allied
health )
• CENTRAL (the Cochrane Collaboration register
of trials records)/ Cochrane collaboration library
(Database of SRs)
27. – Electronic journals
– Evidence based journals: provide concise &
easy to read summaries of original research
articles & SRs selected from biomedical
literature:
1.Journal of evidence based dental practice
2.Evidence based dentistry
• PICO question provides the foundation for
search terms.
28. Hierarchy & Levels of clinical evidence
Meta-analysis,
systematic reviews
RCTs
Cohort studies
Case control studies
Case reports
Ideas, editorials, opinions
Animal research
In vitro (test tube) research
Relevance
to
answering
clinical
questions
Amount
of
available
literature
29.
30.
31.
32. • This hierarchy of evidence is based on the
concept of causation & need to control bias.
• Systematic Reviews & meta-analyses using 2/>
RCTs of human subjects are considered the gold
standard for evidence because of their strict
protocols to reduce bias.
• A systematic review (SR) can be defined as a
review of a clearly formulated question that
attempts to minimize bias using systematic and
explicit methods to identify, select, critically
appraise & summarize relevant research.
33.
34.
35. Purposes of systematic review
• Reduces a large amount of information to a
manageable size.
• Determines the consistency & generalization of
results. Also offers the opportunity to explain any
inconsistencies.
• Usually cheaper and quicker to conduct than to
embark on a new study.
• May reduce the delay between research
discoveries and the implementation of new
effective treatment strategies.
36. • Combines information from individual studies so
results in an increase in the power of the
investigation & the precision in obtaining estimates
of the effects of interest. Thus, the SR has a
greater chance of eliciting significant treatment
effects, which is particularly helpful if the
prevalence of the condition is low or if the effect of
interest is small.
• Limits bias and improves the reliability and
accuracy of recommendations because of its
formalized and thorough method of investigation.
37.
38. • Meta-analysis:
– A special form of systematic review (sometimes
called an overview)
– A statistical approach to combining the results from
separate but similar studies to provide an overall
quantitative summary of the effect of interest. Thus,
increasing the sample size, power & the precision of
estimates of treatment effects & exposure risks.
– In practice, the meta-analysis is open to criticism,
essentially on four grounds (Glass et al., 1981):
1.Publication bias: Because journals rarely publish
a negative trial in which a clinically significant
effect is essentially ruled out.
39. 2. Clinical heterogeneity in features of studies
(design, outcome measure, measuring technique,
definition of variables & subjects, duration of
follow-up).
3. Quality of studies (mostly only high quality
studies) included. Instead both ‘good’ and ‘bad’
studies should be included & handled empirically
by conducting separate analyses for groups of
studies of similar quality & examining whether the
results differ for poorly and well designed studies.
4. The results included in the meta-analysis may not
be independent.
40. • This “ladder of evidence” was developed to a
large extent for questions related to
interventions or therapy. For questions related
to diagnosis, prognosis or causation, other
study designs such as cohort studies or case
control studies will often be more appropriate.
For these types of studies, it is useful to think
of the various study designs not as a
hierarchy, but as categories of evidence,
where the strongest design which is possible,
practical & ethical should be used.
41.
42. • Clinical practice guidelines & protocols:
– Guidelines are systematically developed statements to
assist practitioner & patient decisions about appropriate
health care for specific clinical circumstances. (National
Academy of sciences, 2000)
– Should incorporate the best available scientific evidence.
– Includes:
• ADA guidelines
• AHA guidelines
– AAP position papers, statements & parameters of care,
although not identified as guidelines, have been
developed & updated on multiple aspects of periodontal
practice.
43. 3. Appraising the evidence
• Critical Appraisal: The process of assessing &
interpreting evidence by systematically
considering its validity, results & relevance to your
own work.
• Critical analysis guides:
– CASP (critical appraisal skills program): to
review RCTs, SRs & several other types of
studies.
– CONSORT (Consolidated Standards of
Reporting Trials) for RCTs
44. – STARD (Standards for Reporting of Diagnostic
Accuracy) for reporting studies on diagnostic
tests.
– Guidelines for reporting SRs:
• QUOROM (Quality of Reporting of Meta-
analyses)
• MOOSE (Meta-analysis Of Observational
Studies in Epidemiology)
• QUADAS (Quality Assessment of studies of
Diagnostic Accuracy included in SRs)
45. • Common ways used to report results (Sackett &
colleagues, 2000): measures to be reported in
determining the magnitude of therapy results:
1. Event Rate: The proportion of patients in a
group in whom the event is observed. Control
Event Rate (CER) & Experimental Event
Rate (EER) are used to refer to this in control
and experimental groups of patients
respectively.
2. Absolute Risk Reduction (ARR): The
difference in event rate between the control
group (CER) & the experimental group (EER).
46. Relative Risk Reduction (RRR): The percent
reduction in events in the treated group event
rate (EER) compared to the control group event
rate (CER
3. Numbers needed to treat (NNT): the number of
patients (surfaces, periodontal pockets) that
would need to be treated with the experimental
treatment or intervention to achieve one
additional patient (surfaces, periodontal pockets)
who has a favorable response.
47. Tools for assessing evidence
1. Be skeptical:
a. Large number of effective periodontal
treatments may be telltale sign of a
challenging chronic disease.
b. Complex nature of periodontal disease with
both genetic & environmental causes,
makes the diagnosis, treatment &
investigation challenging.
c. Scientific quality of periodontal studies have
been rated as low. (Antczak)
48. 2. Don’t trust biologic plausibility
a. Decisions based on “causal chain thinking,
sometimes referred to as deductive
inference/ deductive reasoning/ logical
system” are not universal, thus classified as
level 5 in EB medicine.
causes
causes
A B C
49. b. Much of our knowledge on prevention &
management of chronic periodontitis depends
largely on deductive reasoning:
i. Short term changes in PD/ AL have been
assumed to translate into tangible, long term
patient benefits.
ii. Evidence that plaque control affects the
most forms of periodontal diseases is still
weak.
iii. Use of antibiotics for painful periodontal
abscess is rationalized on deductive
inference.
50. 3. What level of controlled evidence is
available?
• Inductive reasoning: rational thoughts
based on systematic experiments
• Systematic experiments routine in clinical
research:
i. RCT: gold standard design in clinical
research
ii. Cohort study
iii. Case-control study
51. • An important challenge in assessment of
controlled evidence is determining whether
the association between exposure & endpoint
is causal using following factors:
i. Temporality
ii. Presence of pretrial hypothesis
iii. Size/ strength of reported association
• Conclusions based on controlled study
designs are always surrounded with a degree
of uncertainty.
52. 4. Did the cause precede the effect?
• Unequivocal establishment of temporality is an
essential element of causality, i.e, cause needs to
precede the effect & can be difficult to establish
for chronic diseases, including epidemiology of
periodontal diseases.
• Many studies in periodontal research suffer from
unclear temporality:
a. Studies relating to plaque/ specific infections to
periodontal disease.
b. Observed microbial profiles: result/ cause of
periodontitis?
c. Potential association between chronic
periodontitis & systemic diseases.
53. 5. Prediction
Essential characteristic of scientific enterprise:
prediction: hypothesis/ ideas predict observations,
they can not be fitted into observed data.
a. A common post trial modification of hypothesis is to
evaluate proper/ improper subgroups of original study
sample.
– Improper subgroups are based on patient
characteristics that may have been influenced by the
exposure. Results of such analyses are almost always
meaningless when establishing causality.
– Proper subgroups are based on patient characteristics
that cannot be influenced by the exposure. E.g.., age,
gender, race. Even these results may turn out to be
misleading in majority of cases.
54. b. After/ during the conduct of study, the exposure definition
can be changed/ the no. of exposures under the study
can be modified. The results of such studies can not be
duplicated.
c. In periodontal research the absence of a specific pre-trial
defined primary endpoint permits effortless changing of
the endpoint definition.
• Data torturing: deviating from pretrial hypothesis
(Mills, 1993)
– Opportunistic data torturing: exploring data without the
goal of proving a particular point of view. It is an
essential aspect of scientific activity & hypothesis
generation.
– Procrustean data torturing: exploring data without the
goal of proving a particular point of view.
55. 6. What is clinically relevant pretrial hypothesis?
Characteristics of pretrial hypothesis:
a. Clinically relevant endpoint (outcome in PICO)
– Endpoint: measurement related to a disease
process/ condition & used to assess the exposure
effect.
• True endpoint: tangible outcomes that directly
measure how a pt. feels, functions/ survives.
Pretrial specification of true endpoint is the first
requirement for a clinically relevant study.
• Surrogate endpoint: intangible outcomes used
as a substitute for true endpoint. Treatment
effects on surrogates do not necessarily
translate into real clinical benefit.
56. a. Relevant exposure comparisons (intervention & control
in PICO): providing the control subjects with less than
standard dose of treatment is example of clinically
irrelevant research.
b. Study sample representative of real world clinical
patients (patient in PICO)
c. Small error rates:to minimize false positive & negative
conclusions.
– Type I error rate: likelihood of concluding there is an
effect, when in truth there is no effect. It is set by the
investigator at 1% or 5%.
– Type II error rate: likelihood of concluding there is no
effect, when in truth there is an effect. It is set by the
investigator at 10% or 20%. Complement of type II
error rate (1- type II error rate) is referred to as power
of the study.
57. 7. Size of association
• The larger the association, the less likely it is caused
by bias, & the more likely it is causal.
• A simple way to calculate the size of association is to
calculate the odds ratio.
• The Odds for an event is the probability that an
event happens divided by the probability that an
event does not happen.
• Odds Ratio: ratio of odds. Ranges between zero &
infinity:
– OR=1: absence of association
– OR>1: harmful effect
– OR<1: protective effect
58. • Confidence interval: range of numbers between
the upper & lower confidence limits.
– Contains true OR with a certain predetermined
probability (e.g. 95%)
8. Methodological errors
• Confounding is a term that describes the
situation where an estimate of the association
between an exposure and the disease is mixed
up with the real effect of another exposure on the
same disease, the two exposures being
correlated.
59. Criteria for a variable to induce association
Confounding Variable
Endpoint
Exposure
Causal
association
Association
present?
(not
necessarily
causal)
Investigated Causal association
60. • Confounding can be dealt with at the design stage of an
investigation by:
a. Randomization: usually the most effective way of
minimizing the problem of confounding.
b. Restriction: participation of specific groups which are
similar to each other with respect to the confounder
c. Matching: comparison groups with similar backgrounds
• Confounding can also be controlled for in the analysis by:
a. Stratification: strength of the association is measured
separately in each well-defined subgroup & the results
are pooled together using basic statistical techniques
to obtain an overall summary measure of the
association adjusted or controlled for the effects of the
confounder.
61. b. Statistical modeling – mathematical techniques that
can simultaneously take into consideration the effects
of several possible confounders recorded by the
investigators.
• In epidemiologic studies with no randomization, following
points need to be considered in the assessment of
causality:
a. Identification of all confounders:
• Crude association: association unadjusted for any
potential confounders
• Adjusted association: crude association adjusted for
potential confounders
62. b. Accuracy of measurement of confounders:
• A discrepancy between measured & true value
of confounder will result in incomplete removal
of bias, leading to spurious associations.
• The remaining bias is referred to as residual
confounding, one of the reasons on less
effectiveness of case-control & cohort studies
compared to randomized trials in identifying
small effects.
c. Appropriateness of statistical model: any
misspecification of functional relationship cause
bias.
63. Bias
• A systematic error that leads to results which are
consistently wrong in one or another direction.
• The main types of bias:
1. Selection bias: how subjects were selected for
inclusion in a study. It is a major concern in the
design of case-control studies. It is essential to
ensure that controls are representative of the
population from which the cases originated and
randomization is properly achieved.
2. Performance bias: provision of care. Blinding is
essential to rule out this bias.
64. 3. Detection/measurement bias: assessment of
outcomes, may be introduced by
a. the observer (observer bias),
b. by the study individual (responder bias)
c. by the instruments (instrument bias) used to
make the measurements
4. Attrition bias: occurrence and handling of patient
attrition (withdrawal from the study before its
completion)
65. 5. Publication bias: the greater likelihood of publication of
studies with positive results than those with neutral or
negative results. As a result, interventions appear to
perform better than they will in clinical practice. Graphic &
formal statistical tests are available to investigate
publication bias but need approximately 10 or more
studies to have adequate power.
• Chance: sampling error: plays a role in most studies of
humans since it is rarely if ever possible to include an
entire population in an investigation, therefore, studies
attempt to infer information about the population on the
basis of that obtained from representative samples drawn
from that population & the extent of inference is assessed
by statistical significance tests & confidence intervals.
