EVIDENCE-BASED DENTISTRY: INTERPRETATION AND CRITICAL REVIEW OF THE SCIENTIFIC LITERATURE
Dr. Fernando Ricci
Dr. Fabio Cozzolino
The studies reported in the literature used to perform systematic reviews can be briefly classified as follows.
Scientific studies can be carried out as either experiments or observations. In the former, the researcher sets all the evaluable parameters of the study while, in the latter, he merely observes the clinical events. The temporal lasting of the study can be considered as a precise moment in time (transversal studies) or as a running line over time (longitudinal studies). The latter can in turn be conducted on pre-existing data (retrospective studies) or on data which is collected over time (prospective studies).
EXPERIMENTAL STUDIES (the most significant in terms of evidence):
1. Randomized controlled clinical studies 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.
2. Non-randomized controlled clinical studies are performed as above reported but they are not randomized.
OBSERVATIONAL STUDIES (characterized by a less important level of evidence):
1. Group or cohort studies (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.
2. Case/control studies (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.
3. Transversal studies (or prevalence). The observation is limited to a given period of time.
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.
By means of the internet it is now very practical to search for scientific articles using the MEDLINE database (Medical Literature Analysis and Retrieval System Online), run by the American NLM (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.
The Cochrane Collaboration 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.
The expression “systematic review” 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:
1) The questions must be formulated according to the so-called PICO rule (Population, Intervention, Comparison and Outcome). 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).
2) 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:
a) Randomized controlled studies (RCTs);
b) Non-randomized controlled studies (CTs);
c) Cohort Studies;
d) Case/Control Studies;
e) Crossover Studies;
f) Case Studies;
g) Expert Opinions.
The level of scientific evidence has in turn been classified into 5 levels by the U.S. Preventive Services Task Force:
Level I: at least one well-planned randomized controlled study;
Level II-1: non-randomized controlled studies;
Level II-2: group studies or case/control studies, preferably conducted by more than one centre or research group;
Level II-3: case reports and series with or without the intervention. Even a dramatic result in an uncontrolled study belongs to this type of evidence;
Level III: opinions of experts based on clinical experience, from descriptive studies or from committees' reports.
3) Analysis of the data must allow for the validity of the study to be determined, which must be of two types:
a. Internal, concerning the method used to devise the study and thus its rationality;
b. External, concerning the possibility of applying the results obtained to the general population.
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.
4) The final results of a systematic reviews are critically examined in order to provide practical indications and to identify the basis for further investigations.
5) A Consensus Report 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:
a. Do you believe that the systematic review is complete and accurate?
b. Does new information exist which came to light after the preparation work ended?
c. Can the reviewers’ interpretations and conclusions be shared?
d. What research is still necessary in the field examined?
e. Are the results of the systematic review useful for the treatment of patients?
In particular, the answer to point “e” classifies the practical usefulness of the results.
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:
a. Strong: level I coherent studies;
b. Moderate: level II-1 or II-2 coherent studies or extrapolations from level II-1 studies;
c. Limited: level II-3 studies or extrapolations from level II-1 or II-2 studies;
d. Incomplete or insufficient: non-coherent or non conclusive studies of any level, anecdotal evidence or level III.
BIBLIOMETRIC INDICATORS AND CONSULTATION OF THE SCIENTIFIC LITERATURE
By defining a scientific journal as “impacted” or “index-linked”, different characteristics are implicitly assigned: the two terms, which are often misused, are not synonyms.
The “Institute for Scientific Information (ISI)” publishes two scientific repertories every year:
- Science Citation Index (SCI) (index-linked journals)
- Journal of Citation Reports (JCR) (journals with an ISSN code and Impact Factor)
The SCI 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 “index-linked” journals. However, not all of them have an Impact Factor.
On the other hand, the JCR 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.
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.
The Impact Factor (IF) allows the importance of a journal to be determined in comparison to other journals in the same applicative area.
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 two year period preceding the reference year. The denominator is represented by the number of articles published by the journal in the two year period preceding the reference year.
Put more simply, the IF indicates the frequency of citations of the “average article” of the journal.
The Immediacy Index (II) 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.
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.
Put more simply, the II refers to the IF of the journal in the current year.
The Cited Half Life (CHL) measures the validity of the cited articles over time.
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.
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 “importance”.
Impact Factor Listing for journals on Dentistry, Oral Surgery & Medicine
2009 JCR Science Edition
List by impact factor
| List by impact factor Journal Title | 2009 Total Cites | ImpactFactor | 2009 Articles | Cited Half-life |
| Journal of clinical periodontology | 7155 | 3.549 | 140 | 7.9 |
| Journal of dental research | 12340 | 3.458 | 172 | 9.9 |
| Oral oncology | 3905 | 3.123 | 207 | 5.2 |
| Periodontology 2000 | 1760 | 3.027 | 38 | 7.4 |
| Journal of endodontics | 7898 | 2.953 | 277 | 6.8 |
| Clinical oral implants research | 5416 | 2.920 | 188 | 6.7 |
| Dental materials | 5661 | 2.882 | 208 | 5.5 |
| Caries research | 2904 | 2.462 | 62 | 8.9 |
| Clinical implant dentistry and related research | 1111 | 2.452 | 38 | 6.0 |
| Community dentistry and oral epidemiology | 2567 | 2.418 | 62 | 9.4 |
| Oral microbiology and immunology | 1973 | 2.336 | 83 | 6.9 |
| Clinical oral investigations | 956 | 2.233 | 55 | 4.6 |
| International endodontic journal | 3642 | 2.223 | 128 | 6.6 |
| Journal of periodontology | 10313 | 2.192 | 237 | 8.9 |
| Journal of oral pathology & medicine | 3198 | 2.144 | 117 | 8.8 |
| Journal of dentistry | 3271 | 2.000 | 136 | 6.8 |
| The International journal of oral & maxillofacial implants | 5440 | 1.978 | 143 | 9.1 |
| Journal of periodontal research | 2549 | 1.966 | 100 | 8.4 |
| European journal of oral sciences | 2340 | 1.956 | 107 | 6.1 |
| Oral diseases | 1681 | 1.922 | 83 | 5.3 |
| The Journal of the American Dental Association | 4800 | 1.726 | 108 | >10.0 |
| The International journal of periodontics & restorative dentistry | 1932 | 1.702 | 58 | 9.1 |
| Operative dentistry | 2188 | 1.683 | 100 | 6.5 |
| Archives of oral biology | 4452 | 1.649 | 171 | >10.0 |
| The Journal of adhesive dentistry | 938 | 1.638 | 56 | 5.5 |
| Orthodontics and craniofacial research | 446 | 1.607 | 38 | 4.6 |
| Journal of oral and maxillofacial surgery | 8986 | 1.580 | 424 | 8.9 |
| Implant dentistry | 900 | 1.505 | 60 | 6.0 |
| Oral surgery oral medicine oral pathology oral radiology and endodontology | 10077 | 1.499 | 447 | >10.0 |
| Journal of oral rehabilitation | 3546 | 1.483 | 113 | 7.9 |
| International journal of oral and maxillofacial surgery | 4103 | 1.444 | 200 | 8.0 |
| Acta odontologica scandinavica | 2134 | 1.412 | 57 | >10.0 |
| American journal of orthodontics and dentofacial orthopedics | 7929 | 1.327 | 253 | >10.0 |
| British journal of oral & maxillofacial surgery | 2475 | 1.327 | 162 | 8.7 |
| Dental traumatology | 1325 | 1.316 | 121 | 5.0 |
| American journal of dentistry | 1783 | 1.314 | 71 | 8.0 |
| Journal of orofacial pain | 963 | 1.263 | 29 | 7.6 |
| Journal of cranio-maxillo-facial surgery | 1699 | 1.252 | 74 | 8.0 |
| Dento maxillo facial radiology | 1429 | 1.229 | 73 | 6.1 |
| The International journal of prosthodontics | 2318 | 1.227 | 99 | 7.5 |
| Australian dental journal | 1022 | 1.220 | 68 | 9.8 |
| The Journal of prosthetic dentistry | 6680 | 1.215 | 101 | >10.0 |
| International journal of paediatric dentistry | 846 | 1.141 | 61 | 6.4 |
| British dental journal | 2950 | 1.089 | 136 | >10.0 |
| Journal of dental education | 1747 | 1.087 | 127 | 5.7 |
| European journal of dental education | 356 | 1.024 | 44 | 4.8 |
| Gerodontology | 465 | 1.014 | 44 | 5.9 |
| European journal of orthodontics | 2340 | 0.975 | 98 | >10.0 |
| Community dental health | 678 | 0.969 | 20 | 9.0 |
| Journal of public health dentistry | 738 | 0.961 | 41 | 9.2 |
| Journal of the Canadian Dental Association | 929 | 0.959 | 44 | 7.1 |
| Angle orthodontist | 3178 | 0.937 | 170 | 9.4 |
| Dental materials journal | 857 | 0.929 | 95 | 4.7 |
| Swedish dental journal | 639 | 0.927 | 22 | >10.0 |
| Journal of orofacial orthopedics | 388 | 0.890 | 35 | 6.3 |
| Cleft palate-craniofacial journal | 2301 | 0.884 | 97 | >10.0 |
| Journal of esthetic and restorative dentistry | 395 | 0.797 | 36 | 5.6 |
| Odontology | 103 | 0.650 | 17 | 5.4 |
| Quintessence international | 1790 | 0.635 | 113 | 9.5 |
| International dental journal | 1223 | 0.632 | 51 | >10.0 |
| Journal of cranio-mandibular practice | 430 | 0.412 | 8 | 9.9 |
| Journal of applied oral science | 201 | 0.386 | 109 | 4.0 |
| Revue de stomatologie et de chirurgie maxillo-faciale | 250 | 0.349 | 64 | 9.6 |
| Journal of dental sciences | 16 | 0.107 | 28 |
Nevertheless, other analogous repertories and scientific search engines also exist, like for example, Embase.
Consultation of Pubmed is very simple: the parameters of the search are entered into the search string, (for example: complete or partial title of the article, surname of one or more of the authors, name of the journal, year of publication, keywords or generic topics). The more parameters used to filter, the more narrowed down will be the search, and the number of articles found will be reduced. Vice versa, a search which is too detailed or too deficient is not likely to successfully identify an article.
The scientific bibliography used in both scientific publications and Pubmed includes information which allows a specific article to be easily identified. Included in this bibliography are, in the following order:
- Surname and first name initial of one or more authors
- Title of the article
- Abbreviation on the basis of the Index Medicus of the journal
- Year of publication
- Number and volume of the journal
- First and last page
Below is an example:
Rossi M et al. The use of Pubmed. J Prosthet Dent, 2008; 43(2):11-13.
Once the article has been identified, it is possible gain access to a summary of the article, which is called abstract, by clicking on the authors. Sometimes additional banners shown on the right of the page show links to the full text articles available online; most often however, the full text articles must be bought from the journal.
Once an article of interest has been identified, simply click on the item “Related articles” shown on the right in order to quicken the search. Pubmed will then perform an automatic search among all the other analogous articles by subject matter.
From the Pubmed homepage it is also possible to access the list of abbreviations of the titles of the journals listed in Index Medicus: simply click on “Journals database” in the menu on the left.
Below is a list of some of the useful links related to Evidence-Based Medicine:
- Centre for Evidence Based Dentistry
http://www.cebd.org/ - Centre for Evidence Based Medicine
www.cebm.net/ - Evidence Based Medicine tool kit
http://www.ebm.med.ualberta.ca/ - Evidence Based thinking about health care
http://www.medicine.ox.ac.uk/bandolier/ - Project Methodology
hebw.uwcm.ac.uk/methodology/index.htm
FOR INFORMATION:
Dr. Fernando Ricci
Born in Rome on 4th March 1952, he graduated with a first class degree with honours in Medicine and Surgery at the Università degli Studi di Roma “La Sapienza”. He then spent four years in the operating theatre where he practiced general surgery, plastic surgery, oral surgery and maxillofacial surgery.
He specialized in parodontal and implant surgery, attending American, Swedish and French universities for approximately ten years. In 1997 he obtained a Masters in Odontostomatology at the A.S.A.S. in Rome, in 2005 a Masters in Oral Surgery at the University of Chieti and in 2007 a Masters in Posturology at the 1° University of Rome
In 2000, the Surgeons and Dentists Association in Rome and the Province invited him to be part of the “Culture Commission” in the ECM refreshers programme. He was entrusted with managing the refreshers course in implantology for 2 years.
He is also passionate about prostheses and occlusion and his teachers include Prof. Gino Passamonti from Tufts University in Boston and Dr. William McHorris, Stuart’s student.
He has been a speaker, chairman and official interpreter at various National and International meetings and congresses. For many years he has held courses in implantology and implant prosthetics on a well-known implant system.
He is self-employed in Rome.
Email: fernando.ricci@studiodottricci.it
Dr. Fabio Cozzolino
Email: fabio.cozzolino@fastwebnet.it
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