Presentation on theme: "Reading the Dental Literature"— Presentation transcript:
1 Reading the Dental Literature A Brief Guide to Critical Literature ReviewCathy Hollister, RDH, MSPH, PhDNashville Area Dental Support Center
2 Session GoalTo review key concepts in interpreting current, relevant dental research so that clinicians can use appropriate publications for clinical decision making.
3 Learning ObjectivesAt the end of this session, participants will be able to:Name a strength and weakness of review articles and original research reportsExplain the benefits of a quasi-experimental study designExplain the importance of internal and external validityInterpret a p value
4 Key Points to Consider: Peer Reviewed Publications Is the material primary or secondary?What was the study design?Internal Validity: does the study measure want was intendedExternal Validity: can the results be generalizedStatisticsAre the results statistically significant?Are the results clinically significant?
5 What is the Publication Type? Research(Primary)ExperimentsQuasi-Experimental(quantitative)DescriptiveQualitativeReviews(Secondary)Standard ReviewSystematic ReviewCommentaryEditorialOpinion/Position
6 Primary Research Strengths Weaknesses Includes a full description of researchFocusedControls for confounding variables (the ability to control for other variables differs by study design)WeaknessesScope is limitedMay not be generalizable to other populations or times
7 Review Articles Strengths Weaknesses Includes relevant material from many types of studiesPresents studies conducted over a period of timeWeaknessesThe reader may be unable to evaluate appropriateness of the articles included in the reviewMay present only one point of view
8 Review ArticleConsider the review article: Mercury Toxicity and Treatment: A review of the literatureNotice the lack of strict criteria that opens the possibility of author bias to stress a particular point of viewNotice also that for the reader, it can be very difficult to evaluate the quality of the reviewed articlesOverall conclusion: Mercury is toxic
9 Systematic ReviewsA specific type of review article that has strict inclusion criteria resulting in:Only high quality research is includedSelection bias is reduced
10 Insufficient evidence, need more study Systematic ReviewThe Cochrane Collaboration conducts systematic reviews on a variety of topics.WeaknessFew studies meet inclusion criteria, therefore it can bedifficult to draw strong conclusionsExample: Dental Amalgam and Multiple Sclerosis: A Systematic Review and Meta-AnalysisOverall Conclusion:Insufficient evidence, need more study
11 Original ResearchNow consider Neurobehavioral Effects of Dental Amalgam in ChildrenThis Randomized Clinical Trial measured the impact of mercury exposure in dental amalgam on neurobehavioral assessments.Notice the narrow focus of the research and the specific means of measuring the impact of mercury exposure.Overall conclusion: Dental amalgam poses no significant neurobehavioral risk in children over the age of 7 in Portugal
12 3 Articles: Different Conclusions These articles had a common topic: dental amalgam and the possible consequences to exposure to mercuryThese were all published in peer reviewed journalsConsider the similarities and differences in the conclusions.What would you consider to be a strength and weakness of each article?What overall conclusions could you draw after reading these 3 publications?
13 Primary Research Key Points to Consider Study Design Validity InternalExternalStatistics
14 What is the Study Design? ExperimentsRandomized Clinical TrialsPretest-Intervention-PosttestQuasi-ExperimentalCohortCase ControlTime or Case SeriesDescriptiveEpidemiological SurveysSurveillanceCross SectionalQualitativeEthnography or PhenomenologyGrounded TheorySingle or multiple case studies
15 Experiments:RCT Strengths Weaknesses Determines Causality Risk of other factors is minimizedDetermines dose responseWeaknessesExpensiveMay be unethicalMay have small sample sizesMay not replicate real life situations
16 Quasi-Experimental Design CohortA group with similar characteristics followed through timeCase ControlIdentify people with a condition (cases) and very similar people without the condition (controls)Compare previous exposuresTime SeriesMultiple cross sectional surveys
17 Quasi-Experimental Design StrengthsLess expensiveAvoids ethical concernsMore likely to replicate real situationsWeaknessesUsually includes biasesMany variables not under strict controlConfounding variables may not be eliminated
18 Confounders: Crime & Ice Cream Crime increases in the summerIce cream consumption increases in the summerTherefore:Eating ice cream causes crimeORCriminals like ice cream
20 Article Review: Maternal Amalgam Study design, Validity, Statistical significance, clinical significanceAre the conclusions are supported by the data?Potential sources of bias?Are there confounders?What can you learn from this study?What questions ARE NOT answered in this study?
21 Study Design Strengths Descriptive, observational Retrospective (to determine previous exposures)StrengthsReflects real life situationInexpensive and no ethical concernsWeaknessesCannot determine causalityBias and confounders
22 Validity: Internal and External Is the study free from bias?Did the study measure what was intended?ExternalCan you generalize the results to other groups?
23 Internal Validity Did the study measure what was intended? Even with the best study design, sources of bias may be unavoidable and may affect study’s impactBiasCausal RelationshipsConfounders
24 Common Threats to Internal Validity Selection Bias: some participants were systematically excluded from the studyMeasurement error: study does not measure what was intended to be measuredRecall Bias: people do not remember past events accuratelyAmbiguity about the direction of the causal relationship: Which came first, chicken or egg?
25 External Validity How generalizable are the results of the study? Even with excellent internal validity, the results may not be applicable to your population of interest due to systematic differences.Example:Race, gender, and socioeconomic status are common risk factors for many diseases. Results of a periodontal study on healthy adults may not apply to adults with diabetes.
26 Probability Statistics are based on probability. Some natural variation will always occur within groups.Statistics are used to test the likelihood that findings are the result of the intervention and not a result of this natural variation.Statistics are used to project if similar findings would occur in any other sample or in the overall population.
27 P ValueA p value is a measure of the likelihood that the results of the study happened BECAUSE of the intervention, and not because of normal variations in the study group.The smaller the p value, the more significant the finding. A report of p<.05 means that ,“There is less than a 5% probability that the study findings happened by chance and chance alone.”p<.01 means, “There is less that 1% probability that the findings are due to chance and chance alone.”
28 Clinical vs Statistical Significance If the results of the study reach statistical significance, consider if the finding is really important clinically Example:A periodontal intervention reduced pocket depth by 0.03mm (p<.01) (Statistically significant, or the result was due to the intervention and not a result of normal variation among the study participants)Is a gain of 0.03mm important to periodontal health? (Clinically significant)
29 SummaryEvery scientific publication has weaknesses, no clinical question can be answered by a single study or articleRepeated results lend strength to conclusionsConsider the differences between the study population and YOUR populationStatistical significance may not mean clinical significance