The Research Process in Dental Hygiene and Oral Epidemiology

Learning Objectives for the Research Process

• Define all key terms associated with the research process.
• Describe and compare the various research approaches utilized in dental hygiene.
• Describe the various research designs used specifically in oral epidemiology.
• Describe the methods used to conduct research studies.
• List the individual parts of a research design.

Basic Components of the Research Process

• The Question: Every research study begins with a specific question to be posed.
• Significance: Identifying why the research question is significant to the field.
• Existing Knowledge: Determining what is already known about the question or the broader topic through prior research.
• Proposed Methodology: Outlining how the researcher proposes to answer the question.

The Research Question and Hypothesis Development

• The Starting Point: Research always begins with a question. The first step in the actual planning process is the development of a hypothesis.
• Example Question: "Which means of instrumentation is superior in periodontal debridement?"
• Research (Positive) Hypothesis: This predicts a positive outcome or significant difference.
  • Example: "Ultrasonic instrumentation is significantly more effective than hand scaling during periodontal debridement."
• Null Hypothesis: This predicts a negative outcome or no significant difference. Most hypotheses are stated in this form.
  • Example: "Ultrasonic instrumentation is not significantly more effective than hand scaling during periodontal debridement."
  • Scientific Utility: The null hypothesis is rejected if the research finds a statistically significant difference.
• Hypothesis Classification Examples:
  • Research Hypothesis: "Brand X significantly whitens teeth."
  • Research Question: "Does Brand X toothpaste really whiten teeth?"
  • Null Hypothesis: "There is no statistically significant difference between Brand X and a placebo when comparing the whitening of teeth."
• Hypothesis Characteristics: Refer to Box 16-1 for specific characteristics required when formulating a hypothesis.

The Research Proposal and Literature Review

• Research Proposal: Once a valid hypothesis is stated, a detailed plan for the study—the research proposal—must be written. Its purposes include:
  • Validating the significance of the research.
  • Securing funding for the study.
• Literature Review (Step 2): A review of all pertinent reports and studies to determine what is currently known about the issue. This step is crucial for finding current literature and contextualizing the new study.
• Research Project Design (Step 3): Designing the project depends heavily on the research approach chosen. Researchers should review Box 16-2 ("Questions to Ask When Writing a Research Proposal," P. 197).
• Components of a Research Proposal:
  • The Research Question.
  • The Review of the Literature.
  • The Research Study Design.

Research Approaches and Preliminary Studies

• Shared Actions: All dental hygiene research approaches involve observing, describing, measuring, analyzing, and interpreting occurring phenomena.
• Key Terminology:
  • Data: The information collected during the study, ranging from questionnaires to clinical testing results.
  • Variable: A treatment, drug, or educational component whose value may change over the course of a research study.
• Pilot Study:
  • A small-scale version of a study conducted before the main research process begins.
  • Serves as a "trial run" for the long-term study.
  • Used to work out unforeseen errors in the overall plan for conducting a study.

Descriptive vs. Analytic Research

• Descriptive Research: Attempts to identify and describe the topic being researched. For example, identifying the magnitude or distribution of a disease.
• Analytic Research: Attempts to establish why and how a condition exists or came to be. This approach may test a hypothesis regarding the relationship between an exposure and a disease.

Historical Research Approach

• Purpose: To determine the meaning of past events by reviewing records and literature and conducting interviews.
• Methods:
  • Records review.
  • Interviews.
  • Literature reviews.
• Focus: It looks at the incidence and prevalence of disease in a population over time to provide new insights and recommendations for the future.
• Limitations:
  • Difficulty locating accurate data.
  • Existing gaps in knowledge.
  • Inability to replicate the events.
  • Biased reports or distortion of events over time.
• Examples:
  • The development of the ADHA community water fluoridation program from 1945 to 2005.
  • The evolution of dental hygiene degree programs in the United States.

Descriptive Research Designs

• Purpose: Describe the presence and distribution of a disease or health condition at one point in time.
• Primary Method: Often utilizes the survey method.
• Subtypes of Descriptive Research:
  • Survey: Gathers broad information about the status quo, usually involving a large sample size. Techniques include interviews, indices, and questionnaires (e.g., Use of pit and fissure sealants by dental hygienists).
  • Case Study: An in-depth report on a single person, group, event, or situation. Methods include observation, testing, and records reviews (e.g., Periodontium assessment of children grades 1-10).
  • Cross-sectional: Studies a cross-section of a population in a limited period of time.
  • Cohort or Longitudinal: A group is observed over a long period of time. This is time-consuming, requires an extended financial commitment, and often results in a loss of subjects (e.g., Changes in children’s periodontium over time).
  • Document or Content Analysis: Conducted specifically to analyze documents themselves.
  • Trend Study: Combines descriptive and historical research to establish patterns from the past and present to predict future occurrences (e.g., ADHA actions regarding expanding the scope of practice for dental hygienists).
  • Correlational Research: Measures the relationship between variables by comparing two sets of data.

Retrospective Research (Ex Post Facto)

• Purpose: Investigates possible causes of disease by using medical records after the fact.
• Case-Control Study: Compares two groups: the "case group" (those with the condition/disease) and a second group that does not have the condition. Also known as case history or ex post facto.
• Ecologic Study: Attempts to relate an outcome with exposure to a suspected risk factor to establish a functional relationship.
  • Advantage: Low cost and quick to conduct using existing data.
  • Disadvantage: Uses existing data which may be incomplete.
  • Warning: Health recommendations should not be made from ecologic studies alone.

Experimental Research Approach (Clinical Trials)

• Purpose: Investigates cause-and-effect relationships through the manipulation of variables.
• Control Group: The group that stays constant; often receives a placebo (no treatment).
• Independent Variable: The variable that is being manipulated by the researcher.
• Dependent Variable: The outcome that is being measured or studied.
• Double-Blind Study: A study where neither the subject nor the researcher knows who is in the control group (placebo) and who is in the treatment group (receiving independent variables).

Specific Experimental Designs

• Pretest-Posttest Design: Measurements are taken before the independent variable is introduced and again after. A risk is "pretest sensitization," where learning occurs from the pretest, affecting the study variables.
• Posttest Only: Introduces the independent variable first and then measures the dependent variable. This is conducted when a pretest is impractical.
• Time Series Design: The dependent variable is measured several times over a specific period. This is highly valuable in experimental studies (e.g., Measuring the reduction in hypersensitivity repeatedly over months to ensure results are lasting).
• Factorial Design: Used to study two or more independent variables in combination. (e.g., Comparing the effectiveness of power vs. manual toothbrushes while simultaneously comparing tufted vs. traditional floss).

Examiner Reliability and Calibration

• Interexaminer Reliability: Consistency of performance by different investigators when using the same data collection instrument (e.g., Multiple examiners recording the same probing depths for one patient).
• Intraexaminer Reliability: Consistency of performance by the same investigator when using a data collection instrument over time (e.g., Your own probing depths remaining consistent each time you collect data).

Experimental Controls and Methods

• Crossover Design: Participants are randomly assigned to a study or control group. After a set time, participants are switched (crossed over) to the opposite group.
• Washout Period: A period in a crossover study where participants in both groups receive no treatment to ensure the effects of the first treatment have cleared.
• Split Mouth Design: One side of the mouth serves as the test treatment area, while the other side functions as the control.

Quasi-Experimental Approach

• Definition: An experimental study that lacks inherent control (no control group).
• Usage: Used when a control group is not practical or necessary. Results are often used when planning further studies.
• Example: Studying the use of a mandibular advancing oral appliance to treat obstructive sleep apnea.

Population Sampling Strategies

• Goal: To generalize research results, the sample must be a representative subset of the population.
• Sample Size: Large samples provide the most accurate representation. Plans must include "attrition" (selecting a larger initial size to accommodate the expected loss of participants).
• Sampling Types:
  • Random: Every subject is selected independently and randomly; reduces the chance of bias.
  • Stratified: Choosing subjects based on specific subgroups like age, gender, or income.
  • Systemic: Selecting every $n^{th}$ subject to participate.
  • Judgmental: Subjects are selected based on the personal judgment of the researcher regarding who is a "typical" participant; creates bias.
  • Convenience: Selecting a group that is already together and convenient for the evaluator; creates bias.

Data Analysis, Interpretation, and Publication

• Analysis Timing: Data are collected for statistical analysis after completion or at specific intervals. The analysis method must be selected prior to starting the study.
• Resources: Biostatisticians and various computer programs are utilized for analysis.
• Limitations of Research:
  • No single research study can prove a hypothesis.
  • Most articles conclude with a caveat that more research is warranted.
  • No single study can be applied beyond the specific population that was studied.
• Evidence-Based Practice: Research must be published to be considered part of evidence-based practice.