Lecture 2: Evidence Level and Types of Research

1. Lecture 2: Evidence Level and Types of Research

2. 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.

3. Levels of evidence The levels of evidence was developed by the Oxford Centre for Evidence-Based Medicine

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

5. 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.

6. How to Manage the Supernumerary Teeth in Cleidocranial Dysplasia

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

10. What can I do?

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

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

14. Case control study, cohort, RCT and systematic literature review

15. Levels of evidence The levels of evidence was developed by the Oxford Centre for Evidence-Based Medicine

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

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

18. 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.

19. Why these people have incisal trauma? • Grouping: incisal trauma people vs. non- incisal trauma people (control) • Take a look at their general, oral health history, etc. • Abstract possible factors (variables: X1, X2,,,Xn) When Where How Breakfast Dentition Previous trauma BMI Seizure Developmental problems

20. Why these kids have ECC? • Compare the variables between trauma people vs. non-trauma people • (Logistic) Regression model analysis Y= a1X1+a2X2+…….anXn+α So that we can estimate Y from the independent variables (Xi) for the individual and estimate the effect of an independent variable on the dependent variable Xi: explanatory variables (independent variables) ai: regression coefficient

21. Cohort-Prospective vs. Retrospective Cohort Studies- Retrospective Prospective

22. Lecture 2: Evidence Level and Types of Research

23. 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.

24. Levels of evidence The levels of evidence was developed by the Oxford Centre for Evidence-Based Medicine

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

26. 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.

27. How to Manage the Supernumerary Teeth in Cleidocranial Dysplasia

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

31. What can I do?

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

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

35. Case control study, cohort, RCT and systematic literature review

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

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

38. 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.

39. Why these people have incisal trauma? • Grouping: incisal trauma people vs. non- incisal trauma people (control) • Take a look at their general, oral health history, etc. • Abstract possible factors (variables: X1, X2,,,Xn) When Where How Breakfast Dentition Previous trauma BMI Seizure Developmental problems

40. Cohort-Prospective vs. Retrospective Cohort Studies- Retrospective Prospective

41. 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.)

42. Cohort • 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

43. 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.)

44. Cohort • 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

45. Smoking habit Current condition Follow-up

46. 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.

47. Randomized Controlled Trials

48. 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).

49. 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?

50. 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.