Research Methodology in Dentistry seminar

It will be my great honour to lecture again along side my supervisor, Dr Ario Santini, at a seminar on Research Methodology in Dentistry. The seminar will take place at Belgrade University School of Dentistry on Thursday, June 10 (9am-1pm). The seminar is accredited by the Serbian Health Council and each attendee gets 4 CE points.



Programme:

9-9.15 Opening remarks
9.15-9.45 Dr Vesna Miletic: Literature search (MEDLINE and KoBSON)
9.45-10.45 Dr Ario Santini: Designing a study protocol
10.45-11 Break
11-12 Dr Ario Santini: Writing a scientific article
12-12.30 Dr Vesna Miletic: Managing references with EndNote
12.30-1 pm Discussion and practical work

The seminar is free for professors and clinical lecturers of Belgrade School of Dentistry. Contact me at vesna.miletic@gmail.com  to reserve a seat.

************************************************************************************

Scientific journals focusing on dental materials

Two journals in the Science Citation Index (SCI) database focus exclusively on dental materials: (1) Dental Materials and (2) Dental Materials Journal.

Dental Materials is published monthly by the Academy of Dental Materials and is currently ranked 4/55 in the Dentistry, Oral Surgery & Medicine discipline and 5/19 in the Materials Science, Biomaterials discipline. Its impact factor for 2008 is 2.941. It is available through ScienceDirect but requires personal or institutional subscription for full text access. Abstracts can be accessed for free. January 2010 issue of Dental Materials is a free sample and full texts can be downloaded as PDF files. This issue is available HERE.


Dental Materials Journal is published bi-monthly by the Japanese Society for Dental Materials and Devices and is currently ranked 51/55 in the Dentistry, Oral Surgery & Medicine discipline and 15/19 in the Materials Science & Biomaterials discipline. Its impact factor for 2008 is 0.713. Dental Materials Journal is available through FreeMedical journals or at publisher's website HERE. All issues are free and full texts can be downloaded as PDF files.

Though I access full texts in most dental journals through my University online library, occasionally there are articles which cannot be obtained this way. Another way of obtaining an article in its entirety is to send a reprint request to the corresponding author. Fortunately, there is an email address attached to most abstracts on PubMed/MEDLINE. I have been able to obtain almost all articles from the authors whom I sent reprint requests. The only problem may arise when the provided email address becomes inactive. This often happens when an author changes institutions and institutional email addresses. This is why I, for example, always provide my gmail address for correspondence when submitting an article for publication.

Biocompatiblity of resin-based materials: Bisphenol-A

Bisphenol-A is an organic compound with two phenol functional groups, commonly used in the production of many plastic products. Studies have shown that bisphenol-A may have adverse health effects such as hormonal, developmental, neurological as well as carcinogenic.

In spite of this, bisphenol-A may be part of dental resin-based materials as a direct ingredient, as a by-product of bio-degradation of other ingredients or as a trace material left-over from the manufacture of other ingredients. Though bisphenol-A is rarely used as a direct ingredient in dental composites, adhesives or sealants, it is a starting ingredient in the manufacture of the most commonly used resin - BisGMA. Also, some other, less frequently used resins, such as Bis-DMA, are also produced using bisphenol-A.

Concerns about bisphenol-A have been raised since studies have shown that various components of dental composites, adhesives and sealants may leach out and have potential local or systemic adverse effects. An in vivo study using an ELISA system showed that up to 100 ng/ml of bisphenol-A may be released into saliva from resin-based composites immediately after placement (Sasaki et al. 2005). Also, a more recent study showed that BisGMA, but also BisGA and BisDMA, all bisphenol-A - based monomers, may leach out from in vivo placed composite restorations (Uzunova et al. 2008). On the other hand, no traces of bisphenol-A were found from chemically and light-cured orthodontic adhesives after in vitro accelerated aging and elution (Eliades et al. 2007).

Over the past few years, both the FDA and ADA have supported research on biocompatibility and safety of resin-based materials containing bisphenol-A. Both organizations issued statements in 2007 (FDA) and 2008 (ADA) that the low-level of BPA exposure that may result from dental materials poses no known health threat. However, further research on this subject is encouraged by the ADA.

References:

• Sasaki N, Okuda K, Kato T. Salivary bisphenol-A levels detected by ELISA after restoration with composite resin. J Mater Sci: Mater in Med 2005;16:297-300.
• Uzunova Y, Lukanov L, Filipov I, Vladimirov S. High-performance liquid chromatographic determination of unreacted monomers and other residues contained in dental composites. J Biochem Biophys Methods 2008;70:883-888.
• Eliades T, Hiskia A, Eliades G, Athanasiou AE. Assessment of bisphenol-A release from orthodontic adhesives. Am J Orthod Dentofacial Orthol 2007;131:72-75.
  

Essential toolkit for a dental materials scientist: Search engine (Part II)

ISI Web of Knowledge (Web of Science)

ISI Web of Knowledge (also known as Web of Science) is a research platform by Thomson Reuters that comprises seven databases containing information gathered from thousands of scholarly journals, books, book series, reports and conferences. It contains three multidisciplinary indexes to the journal literature of the sciences, social sciences and art and humanities; two conference proceedings citation indexes for sciences, social sciences and humanities and two chemistry databases (Index Chemicus and Current Chemical Reactions).

Search panel is very intuitive and user-friendly and allows search by various categories, similar to Medline, such as topic, title, author, title, journal, year of publication, address, conference, language, document type, funding agency and grant number.



A search can be saved under Marked List and forwarded to an email address as plain text or html.

ISI web of Knowledge offers an option to create citation reports which include the total and average number of times certain items (e.g. journal articles) have been cited and also the number of citations per year. Furthermore, ISI Web of Knowledge displays a list of articles in which an article of interest has been cited.


Cited Reference Search is an option to search for articles that cite a certain person’s work. A search can be done using a person’s name, the journal where an article is published and/or the year of publication.


Another useful tool is that EndNote Web version is integrated with ISI Web of Knowledge. This allows a search to be saved as an Endnote bibliography and directly cited while typing. A search can also be exported to other types of Reference software if you have it installed on your computer (EndNote, Reference Manager or ProCite). I will address EndNote as part of the essential toolkit of a dental materials scientist in a separate blog post.

Essential toolkit for a dental materials scientist: Search engine (Part I)

MEDLINE

For many clinical researchers, MEDLINE is probably the starting point for any article search. MEDLINE comprises over 5000 journals published worldwide and is the largest part of the PubMed database, a service of the U.S. National Library of Medicine. PubMed also contains other life science journals.

As a result of U.S. National Institutes of Health Public Access policy aimed at increasing free access to articles, Pubmed Central (PMC) has been created as a free digital archive of biomedical and life sciences journal literature. It contains journals which submit articles regularly but also articles published by NIH-funded researchers in journals currently not on the PMC list. Full text is available in either HTML or PDF format.

A particularly useful tool available at PubMed is “MyNCBI” which allows searches to be saved and filtering options and automatic searches set up. It is located in the top right corner of the PubMed homepage and requires registration (free). MyNCBI offers various features but among the most useful are automatic searches and collections.

Automatic search: Once you enter keywords and search results are generated, you should save the search by clicking the “Save Search” option next to the search box. The search is saved to MyNCBI. Then, you can enable automated search in MyNCBI and the results will be emailed to you daily or once a week or month, according to the settings. The same keywords from the initial search will be used every time in the automated search.

Collection: Once you enter keywords and search results are generated, you should save the search by clicking the “Send to” option and selecting “Collections” from a drop down menu. A collection can be made public by selecting the appropriate option in MyNCBI, in which case a direct URL or HTML for web pages and blogs are generated.

You can access MyNCBI through PubMed homepage, but if no PubMed search is intended, then you can use a direct link to MyNCBI

Dental Research in the UK: Funding

In 2006, the British Society for Dental Research (BSDR) commissioned a position paper on oral and dental research within the United Kingdom which would serve as a foundation and a framework for a national plan for oral and dental research. This paper was written by Iain Chapple, Paula Farthing, David Williams and Michael Curtis in 2006 and updated in December 2007.

According to this strategic review, the UK dental school research income in the period 2000-2004 was less than 2% of medical schools research income. Knowing that the NHS spend on dental care was about 5% of the total NHS healthcare spend, this indicates that dental research was under funded compared to medical research.

The majority of dental research funding was provided by UK government, industry and charities over this five-year period. Funding from research councils, EU and other sources constituted up to one third of the overall funding per year. It is interesting that most of the charitable funding came from the Wellcome Trust since there is no national charitable source dedicated to oral research.

The best financed research in UK dental schools has been basic with more than two thirds of awarded grants. Less than one third of grants was awarded for clinical research in dental schools. These data are based on grants awarded between 2000 and 2005 by the Medical Research Council (cca. £6m), Wellcome Trust (£8.68m), Biotechnology and Biological Sciences Research Council (£cca. 1.2 m) and Engineering and Physical Sciences Research Council (£520k). The percentage of dental materials research funding has not been reported in this position paper.

Some of the identified reasons for under funding dental research in UK dental schools include the lack of representation on review panels of research councils and major charities, the absence of a national charitable source for funding oral research and underscoring grant proposals by internal panels in spite of high scores by external expert reviewers.

Four priority areas have been proposed in this position paper:

• Establishing a dedicated Oral and Dental Research Charity
• Better representation for oral and dental research on review panels
• Developing critical mass through nationally-coordinated research consortia and
• Encouraging inter-school collaboration.

Light curing of resin-based composites and adhesive systems

Light cured resin-based materials are predominantly used in current dental practice. Light curing protocols have changed over time following changes particularly in light-curing units (LCUs) since the photoinitiator system in these materials has remained virtually unchanged. Though there are attempts to modify the photoinitiator system, the most frequently used one is based on camphorquinone and a tertiary amine.

On the other hand, the LCU technology has been developing in several directions. LCUs comprise four different types of light sources: halogen, light-emitting diode (LED), plasma arc and laser. Halogen and LED LCUs are most often used in dental practice and studied in the dental literature. Light intensity and curing time have been identified as important parameters in monomer conversion which affect mechanical characteristics of the resultant polymer and subsequently its clinical performance. As light intensity has increased from about 500 mW/cm2 which is characteristic of the so-called ‘conventional’ LCUs to more than 700 mW/cm2 in the so-called ‘high-power’ LCUs, most manufacturers recommend shorter curing time. Consensus opinion in the current dental literature is that light energy density (light intensity multiplied by curing time) is a more important determinant of the degree of conversion of resin-based composites (RBCs) and adhesives than light intensity. It is currently recommended to cure adhesive systems for 20 s with LCUs operating at intensities of about 500 mW/cm2 and 10 s with LCUs operating at intensities of more than 700 mW/cm2. For RBCs, the recommended curing time is 40 s with the former LCUs and 20 s with the latter ones. The recommended thickness for each layer of RBCs in the incremental technique is still 2 mm.
Though many LCUs possess additional curing modes, such as soft-start or pulse in order to reduce polymerisation shrinkage of RBCs, there is no scientific evidence that these modes affect the long-term clinical performance of resin-based restorations.

It has been shown that maximum absorption range of camphorquinone is about 468 nm and therefore most LCUs, especially LED and plasma arc, have a very narrow emission range. However, the absorption range of co-initiators may be outside the emission range of such LCUs, thus, leading to insufficient conversion. Most recently, the so-called ‘poly-wave’ LCUs have been introduced on the market in an attempt to cover the absorption range of the entire photoinitiator system and produce maximum conversion for a given material. Future studies will show whether this new approach ensures such monomer to polymer conversion which would lead to better mechanical properties of RBCs and adhesives.

Studies have shown that increased curing distances lead to lower degree of conversion and it has recently been suggested that 6 mm may be a cut-off distance. However, it should be noted that various LCUs and materials may exhibit differences in curing efficiency at various distances. Therefore, as a general rule, the LCU tip should be placed as close as possible to the surface of RBCs and adhesives.

The superficial layer of RBCs and adhesives is insufficiently cured due to oxygen inhibition. It is removed by polishing RBCs but in adhesives, this layer serves as an intermediate zone enabling the formation of the RBC-adhesive bond. It is, therefore, important to use RBCs and adhesives with compatible chemical composition in order to achieve optimal RBC-adhesive bond by interaction of compatible monomers from both materials.

Research methodology: The effect of "material A" on treatment outcome

I've recently discussed with a colleague the possibility to prove or disprove the efficacy of a certain clinical procedure on treatment outcome. Since this is the dental materials blog, I'm going to make the parallel between clinical procedures and dental materials and discuss this matter as if it was about dental materials. From the research methodology point of view, it makes no difference whether it is a dental material or a clinical procedure.

"Randomized control clinical trial" would probably be the most appropriate study design to evaluate whether a certain material (material A) has any effect whatsoever on the outcome of a particular treatment. In a recently published book "Introduction to randomized control clinical trials" by JNS Matthews, there is a very nice definition:

"A randomized concurrently controlled clinical trial is simply an experiment performed on human subjects to assess the efficacy of a new treatment for some condition. It has two key features:

1. The new treatment is given to a group of patients (treated group) and another treatment, often the most widely used, is given to another group of patients at the same time (control group). This is what makes the trial concurrently controlled.
2. Patients are allocated to one group or another by randomization. "(1)

Also, it is very important to note that:
"Trials are applied to many different modes of treatment... for example, new surgical procedures, screening programs, diagnostic procedures etc."(1)
How does this apply to our material A? A double-blind trial would be impossible in this case, because a clinician would always know the details of the treatment. On the other hand, a single-blind trial would be possible and recommended since the patient wouldn't know the details of the treatment in order to exclude the possible placebo effect.
Patient inclusion criteria should be taken into consideration at the beginning of the trial. These include, but are not restricted to, patient age, general health, the diagnosis of the current dental condition, the history of this condition etc. It would be wise to "standardise" the cohort so that the number of variables is reduced as much as possible. For example, root canal treatment of a pulpitis may have a different outcome than the treatment of periapical disease, because of the nature of the two dental conditions and variations in patients' immunological response to any of them. Therefore, it would be recommended that one of the inclusion criteria is the uniformity of clinical diagnosis.
Randomization would be easy using the table of random numbers. It excludes any potential bias and is always preferred to other ways of patient selection, as long as the number of cases in both the treated and control group is the same or as similarly-sized as possible. Most statistical tests are most powerful when the groups being compared have equal sizes.
Then, once the treatment is performed, the treated group would receive material A and the control group would receive placebo. The outcome of the treatment would be monitored over at least 3 years, using the standard parameters for monitoring the outcome of this particular treatment. After the monitoring period, (an) appropriate statistical test(s) would be used to assess the difference in treatment outcomes between the two groups of patients.
Only then would it be possible to claim that material A has any effect on the outcome of this particular dental treatment.
(1) Matthews JNS. Introduction to randomized control clinical trials. 2nd edition. Chapman&Hall/CRC; Boca Raton, FL, USA; 2006.

Publishing papers: initial observations as an author and a referee

Three basic rules for referees

I've published 9 papers in peer-reviewed dental journals in the last 2 years and have refereed half a dozen papers regarding dental materials, adhesives, resin-based composites, adhesive cements, adhesion, marginal adaptation... Since there's no 'school' or 'course' for referees that I'm aware of, I've started developing my own style. Judging from other people's reviews of my papers, this seems to be the case with most referees out there. I know that the following are very basic rules, but sometimes, even such basic rules are not followed.

Though editors put a lot of effort in finding the right referees for a particular paper, it's possible that a paper ends up in wrong hands, with someone whose field of expertise has almost nothing to do with the subject of the paper. I've noticed very 'interesting' remarks regarding one of my papers indicating that the referee wasn't an expert in the field he/she was referring to. Obviuosly, nowadays a lot of studies are multidisciplinary and this makes it even more difficult for editors to find competent referees. A potential referee may be an expert regarding only a part of a particular study. It's only fair to comment on that part and indicate this to the editor so that a competent person is invited to comment on the other part(s).

So, rule No.1: accept an invitation to review a paper only if you're an expert in the field or at least a part of it and indicate this to the editor. Decline review if the subject of the paper is not your area of expertise.

Another thing I've noticed with people refereeing my papers is that this process sometimes takes ages. Though some journals have taken steps to ensure speedy review within 3-6 weeks, with some journals this may take even more than 6 months. This is simply unacceptable. Being in a referee's position myself, I've realised that even 3 weeks is more than enough to complete a review. Of course, I'm well aware of the fact that referees are very busy and have many, many other things to do. But so are the authors and referees should respect that. It's unfair to keep someone's paper 'under review' for more than a month.

So, rule No.2: accept an invitation to review a paper only if you can complete the review in less than 3 weeks.

Also, I've noticed that there are people who just don't care about the paper they're reviewing. They tend to write and overall impression of the paper without going into specific details. This is not helpful even if the paper is good and especially if it needs to be improved. It's almost like they just skimmed through the paper. On the other hand, there are people who write extensive reviews and I find these extremely helpful.

So, rule No.3: be fully committed to reviewing a paper. Go into minute details when writing a review.

Keywords: dental materials, research, publishing papers, review process.

JCR Science edition 2008

Click here to view the full list of dental journals included in the 2008 Journal Citation Report (JCR). JCR is based on the Web of Science dataset from Thomson Reuters and includes citation data such as:

• number of citations
• impact factor
• 5 year impact factor
• cited half-life

These indicators allow the evaluation and comparison of journals from all areas of science, technology and social sciences. The given list of dental journals in the JCR corresponds to the Current Content for Dentistry, Oral surgery and Medicine.