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DENT 514: Research Methods

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  1. DENT 514: Research Methods Masahiro Heima, DDS, PhD

  2. Lecture 1: Generate Scientific Questions and Systematic Search for Scientific Articles

  3. Generate questions Process of generating a question: • Find what you want to know/what you don’t know. • Replace your question with objective variables. • If you want to know subjective items, use a validated measure to replace subjective questions. Numbers or categories

  4. Generate questions Is my OHI good? • Think what does “good” mean? • What is your definition of “good”? • Objective vs. Subjective? • What are objective variables for “good”? • Are there any validated variables? Subjective Plaque score? Understanding? Frequency of brushing? Cost-efficiency? Patients’ Quality Of Life? DMFT?

  5. What population is your target? • Human being? • The US population? • population such as Caucasians in the US? • Your patients? • Animals? • Materials?

  6. Search for Answer • Ask somebody • Read textbooks • Use internet search engines such as Google • Use better engines such as Google Scholar • Use scientific article database such as PubMed • Manual search

  7. Systematic Searching for the Answer • Searching engine such as PubMed • Thesaurus search (MeSH) • Boolean operators (using AND, OR and NOT) • Limits and specialized filters • The level of evidence/publication type/research design • Record queries with searching results in order to reproduce the search • "Dental Caries Susceptibility"[Mesh] AND "Dental Caries/psychology"[Mesh]

  8. Example

  9. An Example Children from low-income families have many caries. Why? If I give them lots of money, will the number of carious teeth be decreased? Objective outcome: The number of dental caries Target population: children from low-income families Topic: preventive strategies Searching articles systematically: "dental caries"[MeSH Terms] AND "prevention and control"[Subheading] AND "dmf index"[MeSH Terms] AND "child"[MeSH Terms] AND "poverty"[MeSH Terms] They have many benefits from the government in order to compensate for their low income to prevent caries. It sounds like giving money and/or financial support is not effective enough.

  10. Why do they still have many caries? Searching articles systematically for strategies for prevention and etiology of dental caries for low-income children. Socioeconomic factors (income, education, and parent occupation) affects children’s number of caries. Especially, caregiver education level influence is greater than income level.

  11. Systematically searching for the influence of parental education level on children’s oral health care behavior, which in turn reduces the number of children’s carious teeth. I have found: Parental education level influence on: their oral health care behavior their children’s oral health care behavior the number of their children’s carious teeth. Children’s oral health care behavior is influenced by parental behavior.

  12. Is influence of parental education level on the child's number of carious teeth mediated by both parent's and child’s oral health behavior? There is no research about it. Brainstorming to generate a research

  13. Hypothetical Model Parental education level Parental oral health care Children’s oral health care Children’s caries

  14. Generating questions for research • I don’t know about A. (Your question) • What is A? (dig down into what you have to know) • Brainstorming to generate potential research questions (from ideas of other people) • You will have many questions in the brainstorming session. • Select specific questions (Find what you have to know for your question and generate a hypothesis) • Is the hypothesis possible to prove? (make sure the hypothesis is statistically provable)

  15. Hypothesis for Statistics • Null hypothesis (H0): A = B, there is no difference. • Alternative hypothesis (H1): A ≠ B, there is difference. • Statistics tell you the probability of A=B occurring. • Usual statistics are used to say A and B are “different.” • Equivalence tests are used to say A and B are “equivalent.” Equivalence does not mean that A and B are the same, but that they are similar.

  16. How to Use the Null Hypothesis Researchers calculate the probability of occurring A=B (there is no difference). If the probability is LESS than 5% (there is little probability of A=B occurring), and we REJECT the null hypothesis. If the probability is MORE than 5% (there is enough probability of A=B occurring), we CANNOT REJECT the null hypothesis. We say there is a “significant difference” between A and B. We have to say “no significant difference” between A and B. If A = B then there is “Type I error” If A≠ B, then there is “Type II error”

  17. Hypothetical Model Parental education level P>0.05 P<0.05 P>0.05 Parental oral health care Children’s oral health care P<0.05 P<0.05 Children’s caries

  18. Background/Introduction The place to state: • Rationale for your research • Facts • Previous research • who were the subjects • what were the results/conclusions • what were the limitations • Justification- addresses gaps or shortcomings of previously conducted research. • Objectives/hypotheses

  19. Tips of how to report your project • The CONSORT Statement for the randomized clinical trial studies ( • The STROBE Statement for the observational studies (

  20. Questions?