Lecture 2: Evidence Level and Types of Research

Do you recommend flossing to your patients? Of course YES! Because: I have been taught to. I read textbooks about benefits of flossing. ADA’s recommendation! I have read research articles.

Levels of evidence (Meta analysis) Systematic Reviews Randomized Controlled Trials Cohort Case Control Case Series, Case reports Editorial, Expert Opinion The levels of evidence was developed by the Oxford Centre for Evidence-Based Medicine

Editorials & Expert Opinion Experts (give you many hints) Textbook (Take a look at its references) Guideline (Take a look at its references)

Case Series, Case Reports Descriptive reports No control group is involved No experimental manipulation is involved Case reports simply describe each case. Usually it reports small number (1-3,4..) of patients. Case series studies are also descriptive reports by using collecting similar multiple cases. Usually reports larger number of patients.

How to Manage the Supernumerary Teeth in Cleidocranial Dysplasia

PubMed PubMed: "cleidocranial dysplasia"[MeSH Terms] AND "tooth, supernumerary"[MeSH Terms] AND ("therapy"[Subheading] OR "therapeutics"[MeSH Terms])

What can I do?

First Molars have Big Decays! Indirect pulp capping + composite filling Glassionomer filling RCT + Crown EXT

Pubmed "child"[MeSH Terms] AND "tooth extraction"[MeSH Terms] AND "Tooth Migration"[Mesh Terms] AND ("space"[All Fields] AND closure[All Fields])

Case control study, cohort, RCT and systematic literature review

Levels of evidence (Meta analysis) Systematic Reviews Randomized Controlled Trials Cohort Case Control Case Series, Case reports Editorial, Expert Opinion The levels of evidence was developed by the Oxford Centre for Evidence-Based Medicine

Case Control Observational, retrospective study Outcome is measured before exposure Patients Non-patients

Case Control Case control studies are conducted to identify cause and/or risk factor that may contribute to the outcome (condition/disease).

Case Control Method for rare disorders or those with long lag between exposure and outcome (It is had to collect subjects!) Relatively fewer subjects needed than cross- sectional studies (still depend of hypothesis) Reliance on recall or records to determine exposure status Potential bias: recall, selection when individuals or groups being compared are different. - e.g. study of children’s dental caries in Cleveland is not representative of the USA.

Why these people have incisal trauma? 1.Grouping: incisal trauma people vs. non- incisal trauma people (control) 2.Take a look at their general, oral health history, etc. 3.Abstract possible factors (variables: X 1, X 2,,,X n ) WhenHowWhereBreakfastDentition Previous traumaBMIDevelopmental problemsSeizure

Why these kids have ECC? 4.Compare the variables between trauma people vs. non-trauma people 5.(Logistic) Regression model analysis Y= a 1 X 1 +a 2 X 2 +…….a n X n +α X i : explanatory variables (independent variables) a i : regression coefficient So that we can estimate Y from the independent variables (X i ) for the individual and estimate the effect of an independent variable on the dependent variable

Cohort -Prospective vs. Retrospective Cohort Studies- Prospective Retrospective

Lecture 2: Evidence Level and Types of Research

Do you recommend flossing to your patients? Of course YES! Because: I have been taught to. I read textbooks about benefits of flossing. ADA’s recommendation! I have read research articles.

Levels of evidence (Meta analysis) Systematic Reviews Randomized Controlled Trials Cohort Case Control Case Series, Case reports Editorial, Expert Opinion The levels of evidence was developed by the Oxford Centre for Evidence-Based Medicine

Editorials & Expert Opinion Experts (give you many hints) Textbook (Take a look at its references) Guideline (Take a look at its references)

Case Series, Case Reports Descriptive reports No control group is involved No experimental manipulation is involved Case reports simply describe each case. Usually it reports small number (1-3,4..) of patients. Case series studies are also descriptive reports by using collecting similar multiple cases. Usually reports larger number of patients.

How to Manage the Supernumerary Teeth in Cleidocranial Dysplasia

PubMed PubMed: "cleidocranial dysplasia"[MeSH Terms] AND "tooth, supernumerary"[MeSH Terms] AND ("therapy"[Subheading] OR "therapeutics"[MeSH Terms])

What can I do?

First Molars have Big Decays! Indirect pulp capping + composite filling Glassionomer filling RCT + Crown EXT

Pubmed "child"[MeSH Terms] AND "tooth extraction"[MeSH Terms] AND "Tooth Migration"[Mesh Terms] AND ("space"[All Fields] AND closure[All Fields])

Case control study, cohort, RCT and systematic literature review

Case Control Observational, retrospective study Outcome is measured before exposure Patients Non-patients

Case Control Case control studies are conducted to identify cause and/or risk factor that may contribute to the outcome (condition/disease).

Case Control Method for rare disorders or those with long lag between exposure and outcome (It is had to collect subjects!) Relatively fewer subjects needed than cross- sectional studies (still depend of hypothesis) Reliance on recall or records to determine exposure status Potential bias: recall, selection when individuals or groups being compared are different. - e.g. study of children’s dental caries in Cleveland is not representative of the USA.

Why these people have incisal trauma? 1.Grouping: incisal trauma people vs. non- incisal trauma people (control) 2.Take a look at their general, oral health history, etc. 3.Abstract possible factors (variables: X 1, X 2,,,X n ) WhenHowWhereBreakfastDentition Previous traumaBMIDevelopmental problemsSeizure

Cohort -Prospective vs. Retrospective Cohort Studies- Prospective Retrospective

Cohort Observational, prospective or retrospective study Exposure is measured before outcome A cohort study involves identification of two groups (cohorts) of subjects – one that received the exposure of interest – one that did not – following these cohorts forward for the outcome of interest. The researchers do not assign the exposure or randomize the groups (RCTs are experimental, while cohort studies are observational.)

Large sample sizes or long follow-up necessary Non-randomization Subjects can be matched (same characters) Exposure may be linked to a hidden confounder Blinding is difficult Difficult to conduct study for rare disease Cohort

Observational, prospective or retrospective study Exposure is measured before outcome A cohort study involves identification of two groups (cohorts) of subjects – one that received the exposure of interest – one that did not – following these cohorts forward for the outcome of interest. The researchers do not assign the exposure or randomize the groups (RCTs are experimental, while cohort studies are observational.)

Large sample sizes or long follow-up necessary Non-randomization Subjects can be matched (same characters) Exposure may be linked to a hidden confounder Blinding is difficult Difficult to conduct study for rare disease Cohort

Current condition Smoking habit Do you smoke? Yes Child smokes No child smokes No Child smokes No child smokes Follow-up

Randomized Controlled Trials Experimental, prospective study Participants are randomly allocated into an experimental group or a control group and followed over time for the variables/outcomes of interest. Each participant has an equal chance of being assigned to an experimental or control group, thereby reducing potential bias.

Randomized Controlled Trials

Unbiased distribution of confounders Able to conduct under blinding condition Comparatively expensive: time and money Volunteer bias A bias comes from the fact that a particular sample can contain only those participants who are actually willing to participate in the study. Volunteers tend to have a higher social status and intelligence. Also, those who participate and find the topic particularly interesting are more likely to volunteer for that study, same to those who are expected to be evaluated on a positive level (Heiman, 2002).

Systematic Reviews A summary of the literature that uses explicit methods to perform a comprehensive literature search and critical appraisal of individual studies, and that uses statistical techniques to combine these valid studies. Floss?

Systematic Reviews -Meta analysis- A particular type of systematic review Meta-analyses are not comprehensive Meta-analysis combine (synthesize) and summarize quantitative data from multiple studies using statistical methodology. A strategy to strengthen evidence (giving the results more statistical power), therefore, more credibility than the individual RCT studies. Only compatible data is combined into a larger data set.

to increase the numbers of observations and their statistical power to improve estimates of the effect size of an intervention or association to assess the generalizability of the conclusions to a more varied range of patients or treatment protocols to resolve uncertainty when reports disagree to identify the need and planning for larger trials or studies to answer questions not posed at the start of individual trials to obtain the most unbiased results A retrospective Publication bias Need at least two trained researchers

PICO(PECO) To ask the right question in order to perform the evidence-based decision-making process, begin with a patient question or problem. A "well-built" question should include four parts, referred to as PICO(PECO) that identify the patient problem or population (P), intervention (I) or exposure (E), comparison (C) and outcome(s) (O). (Sackett DL, Richardson WS, Rosenberg W, Haynes RB (1997). Evidence-based medicine: How to practice and teach EBM. New York: Churchill Livingston.)

AMSTARAMSTAR (A Measurement Tool to Assess Systematic Reviews) 1. To develop and evaluate reviews 2. As a guide to conduct of reviews 3. As an aid to teaching about systematic reviews. Example 1.Was an 'a priori' design provided? 2.Was there duplicate study selection and data extraction? 3.Was a comprehensive literature search performed?

Questions?