***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Previous papers in this series on evidence -based dentistry have discussed the first 2 steps in seeking answers to clinical problems formulating a clear question and strategically search ing for evidence . The next step , critical appraisal of the evidence , is made easier if one underst and s the basic concepts of clinical research design . The strongest design , especially for questions related to therapeutic or preventive interventions , is the r and omized , controlled trial . Questions relating to diagnosis , prognosis and causation are often studied with observational , rather than experimental , research design s. The strongest study design should be used whenever possible . Rules have been established to grade research evidence . This paper , the fourth in the series , presents an overview of research methodology most commonly used in the dental literature OBJECTIVES To compare learning outcomes and perceptions of facilitator behaviours and small-group process in  problem-based learning ( PBL ) groups led by students and those led by faculty . DESIGN A prospect i ve , Latin-square cross-over design was employed . Second-year medical students participated in 11 PBL cases over the course of the academic year . For each case , half the student groups were led by faculty and the other half by a student group member selected r and omly to serve in the facilitator role .  Learning outcomes were assessed by performance on objective examinations covering factual material s pertinent to the case . Perceptions of facilitator behaviours and of group functioning were assessed with a question naire completed at the end of each individual case . Focus-group discussion s were held to gain more in-depth information about student perceptions and experience . Student-led sessions were observed at r and om by the investigators . SETTING A state-supported , US medical school with a hybrid lecture-based and problem-based curriculum . SUBJECTS One hundred and twenty-seven second-year medical students and 30 basic science and clinical faculty . RESULTS No differences were detected in student performance on the objective evaluation based on whether the facilitator was a faculty member or peer group member , nor were there any differences in the perceptions of group process . Students gave peer facilitators slightly higher ratings in the second semester of the experiment . In the focus-group discussion s , students voiced a general preference for student-led groups because they felt they were more efficient . Observation and focus-group reports suggest that groups led by students sometimes took short cuts in the PBL process . CONCLUSION In a hybrid lecture- and PBL-based curriculum , student performance on objective examinations covering PBL material s is unaffected by the status of the facilitator ( student vs. faculty ) . However , in peer-facilitated groups , students sometimes took short cuts in the PBL process that may undermine some of the intended goals of PBL Since the publication of Physicians for the Twenty-First Century —‘‘the GPEP Report ’ ’ of 1984 , medical educators have identified the need for physicians to become lifelong learners . Part of the impetus for this conclusion arises from several studies that have demonstrated that knowledge and /or competence of physicians  decline as a function of time since graduation ; the evidence indicates the cause to be failure to acquire new knowledge rather than a tendency to forget previously learned material . Thus , physicians need to be trained to identify the relevant medical literature ( i.e. , information-seeking skills ) and to apply ‘ ‘ critical appraisal ’’ techniques to analyze potentially useful articles culled from the literature search . There is little published evidence that educational interventions around critical appraisal teaching in undergraduate or postgraduate medical curricula impact in a sustained way the knowledge of epidemiologic principles or the critical application of current research information for clinical decision making . In considering the impact on conceptual knowledge , one could argue that there is a lack of vali date d tools available for evaluating critical appraisal skills ; alternatively , the format of instruction , timing in the curriculum , and duration of instruction may be at fault . More important , studies have not addressed the issue of whether the demonstration of mastery of particular critical appraisal skills can be related to clinical decision making . Ultimately , such mastery becomes largely irrelevant if it does not translate into better judgment . The authors of this study were concerned that , despite the inclusion in the first-year undergraduate curriculum of several focused objectives surrounding critical appraisal in the domain of clinical epidemiology , feedback from clinical faculty suggested that students had only rudimentary knowledge of the application of these principles at the end of the first year . In contrast to this feedback , problem-based learning ( PBL ) is believed to hold the potential to equip graduates with the skills to learn after graduation . In fact , several studies have shown significant differences between students of PBL  and students of conventional curricula in the use of recently published medical literature . With this inconsistency in mind , two experimental questions were asked 
    Output:
    
Problem-based learning and evidence -based health care interventions increased student knowledge of medical topics and their ability to search , evaluate , and appraise medical literature .
Dental students in a problem-based learning curriculum  , emphasizing evidence -based practice s , scored higher on the NDB I ( National Dentistry Boards , Part I ) than students in traditional curricula .
Considering the strength of evidence in the review ed literature , we concluded that an evidence -based approach to clinical care is effective