<\/p>\n
1. Randomized controlled clinical studies<\/span> represent the gold standard. Randomization (random assignment to the test group or to the control group) and double blinding (neither the researcher nor the patient know if the patient belongs to the test group or the control group) allow the researcher to lower the risk of introducing bias.<\/p>\n 2. Non-randomized controlled clinical studies<\/span> are performed as above reported but they are not randomized.<\/p>\n OBSERVATIONAL STUDIES<\/strong> (characterized by a less important level of evidence):<\/p>\n <\/p>\n 1. Group or cohort studies<\/span> (or prospective). Two groups are compared: one group is made up of individuals exposed to the causal treatment\/agent while the other is the control group. Both are observed over time (prospective study) in order to deduce the incidence of a given pathology\/condition.<\/p>\n 2. Case\/control studies<\/span> (or retrospective). Two groups are monitored; only one is made up of individuals affected by a given pathology\/condition. The two groups are assessed on the basis of data collected in the past (retrospective or historical study) to discover the causal agent.<\/p>\n 3. Transversal studies<\/span> (or prevalence). The observation is limited to a given period of time.<\/p>\n Currently, the most important source for keeping abreast of the updates in medicine is the scientific literature. Nevertheless, when attempting to consult it, numerous problems are encountered, due to the great number of scientific articles which have accumulated over the decades.<\/p>\n By means of the internet it is now very practical to search for scientific articles using the MEDLINE<\/b> database (Medical Literature Analysis and Retrieval System Online), run by the American NLM<\/b> (National Library of Medicine). It is freely available for consultation through Entrez and the dedicated search engine Pubmed. MEDLINE contains more than 16 million index-linked articles, enabling specific searches.<\/p>\n The Cochrane Collaboration<\/b> offers a similar method for analyzing the available medical databases. The synthetic results obtained are summarized in the so-called Systematic Reviews, published on the Internet in an electronic database named the Cochrane Library<\/a><\/b>.<\/p>\n The expression \u201csystematic review\u201d refers to the results of an analysis of the scientific literature available on a whole particular topic conducted according to the EB rules (Evidence-Based). In particular, the systematic review can be distinguished from other types of analyses by the fact that the entire procedure is conducted applying the following criteria:<\/p>\n 1)<\/strong> The questions must be formulated according to the so-called PICO <\/b>rule (P<\/i><\/b>opulation, I<\/b>ntervention, C<\/b>omparison and O<\/b>utcome)<\/i>. This methodology involves choosing one group of individuals (Population) to be subjected to a specific type of intervention (Intervention). The latter must be compared to other types of intervention or to a placebo (Comparison) in order to study and interpret the obtained results (Outcome).<\/p>\n 2)<\/strong> The data collected (by consulting internet databases, printed journals or experts in the sector) is critically assessed so as to assign it a level of scientific validity. In this context, the studies can be listed on the basis of decreasing validity as follows:<\/p>\n <\/p>\n a) Randomized controlled studies (RCTs);<\/p>\n b) Non-randomized controlled studies (CTs);<\/p>\n c) Cohort Studies;<\/p>\n d) Case\/Control Studies;<\/p>\n e) Crossover Studies;<\/p>\n f) Case Studies;<\/p>\n g) Expert Opinions.<\/p>\n <\/p>\n The level of scientific evidence has in turn been classified into 5 levels by the U.S. Preventive Services Task Force<\/i>:<\/p>\n Level I:<\/strong> at least one well-planned randomized controlled study;<\/p>\n Level II-1:<\/strong> non-randomized controlled studies;<\/p>\n Level II-2:<\/strong> group studies or case\/control studies, preferably conducted by more than one centre or research group;<\/p>\n Level II-3:<\/strong> case reports and series with or without the intervention. Even a dramatic result in an uncontrolled study belongs to this type of evidence;<\/p>\n Level III:<\/strong> opinions of experts based on clinical experience, from descriptive studies or from committees’ reports.<\/p>\n <\/p>\n 3)<\/strong> Analysis of the data must allow for the validity of the study to be determined, which must be of two types:<\/p>\n a. Internal<\/i>, concerning the method used to devise the study and thus its rationality;<\/p>\n b. External<\/i>, concerning the possibility of applying the results obtained to the general population.<\/p>\n Different systematic reviews can be subjected to a meta-analysis. This is a statistical analysis performed by assigning values of scientificity and reliability by means of the characteristics used to design and realize the study. Meta-analyses allow for the comparison of different studies and enable general and validated clinical information to be extracted.<\/p>\n 4)<\/strong> The final results of a systematic reviews are critically examined in order to provide practical indications and to identify the basis for further investigations.<\/p>\n 5)<\/strong> A Consensus Report<\/i> is supplied by groups of researchers and clinicians with experience, stature and International credibility, who are requested to create the report on a specific topic. This is done by answering the following questions:<\/p>\n a.<\/strong> Do you believe that the systematic review is complete and accurate?<\/p>\n b.<\/strong> Does new information exist which came to light after the preparation work ended?<\/p>\n c.<\/strong> Can the reviewers\u2019 interpretations and conclusions be shared?<\/p>\n d.<\/strong> What research is still necessary in the field examined?<\/p>\n e.<\/strong> Are the results of the systematic review useful for the treatment of patients?<\/p><\/blockquote>\n In particular, the answer to point \u201ce\u201d classifies the practical usefulness of the results.<\/p>\n This usefulness is categorized on the basis of the level of evidence of the studies which produce the results. The evidence is defined as follows:<\/p>\n a.<\/strong> Strong: level I coherent studies;<\/p>\n b.<\/strong> Moderate: level II-1 or II-2 coherent studies or extrapolations from level II-1 studies;<\/p>\n c.<\/strong> Limited: level II-3 studies or extrapolations from level II-1 or II-2 studies;<\/p>\n d.<\/strong> Incomplete or insufficient: non-coherent or non conclusive studies of any level, anecdotal evidence or level III.<\/p>\n <\/p><\/blockquote>\n <\/p>\n BIBLIOMETRIC INDICATORS AND CONSULTATION OF THE SCIENTIFIC LITERATURE<\/b><\/p>\n By defining a scientific journal as \u201cimpacted\u201d or \u201cindex-linked\u201d, different characteristics are implicitly assigned: the two terms, which are often misused, are not synonyms.<\/p>\n The \u201cInstitute for Scientific Information (ISI)\u201d publishes two scientific repertories every year:<\/p>\n – Science Citation Index (SCI) (index-linked journals)<\/p>\n – Journal of Citation Reports (JCR) (journals with an ISSN code and Impact Factor)<\/p>\n <\/p>\n The SCI<\/strong> is a list of the scientific journals entered in the Index Medicus, the former being a collection of journals whose scientific validity is judged relevant by a committee of International experts. This list therefore includes the so-called \u201cindex-linked\u201d journals. However, not all of them have an Impact Factor.<\/p>\n On the other hand, the JCR<\/strong> annually reports the list of journals to which this parameter is assigned. By referring to the ISSN numeric code, a scientific journal or text can easily be found.<\/p>\n At present, there are three main bibliometrical indicators used to express the importance of a journal: Impact Factor, Immediacy Index and Cited Half Life. Each of these is calculated yearly based on the scientific production and editorial activity of each journal.<\/p>\n <\/p>\n The Impact Factor (IF)<\/b> allows the importance of a journal to be determined in comparison to other journals in the same applicative area.<\/p>\n It is expressed by means of a number which is calculated using a simple fraction: the numerator is represented by the number of citations<\/b> of the articles of the journal in the two year period preceding the reference year. The denominator is represented by the number of articles published<\/b> by the journal in the two year period preceding the reference year.<\/p>\n Put more simply, the IF indicates the frequency of citations of the \u201caverage article\u201d of the journal.<\/p>\n <\/p>\n The Immediacy Index (II)<\/b> measures how fast an article of a journal is cited on average and how often the articles of the journal are cited in the same year.<\/p>\n It is expressed by means of a number which is calculated using a simple fraction: the numerator is represented by the number of citations of the articles of the journal in the reference year. The denominator is represented by the number of articles published by the journal in the reference year.<\/p>\n Put more simply, the II refers to the IF of the journal in the current year.<\/p>\n <\/p>\n The Cited Half Life (CHL)<\/b> measures the validity of the cited articles over time.<\/p>\n It is expressed by means of a number which is calculated on the basis of the number of years, going back from the current year, that account for half the total citations received by the journal in the current year.<\/p>\n Put in more simple terms, the CHL can be considered an indicator of persistence, of measure, that is to say, the duration of the usefulness of a publication over time. It also provides indications on its current usefulness and \u201cimportance\u201d.<\/p>\n <\/p>\n Impact Factor Listing for journals on Dentistry, Oral Surgery <\/b>& Medicine <\/b><\/p>\n 2009 JCR Science Edition <\/b><\/p>\n List by impact factor <\/b><\/p>\n
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