A waste of research?

As evidence-based practitioners, readers of Dental Update will be aware of the hierarchy of evidence, but, by way of revision, it is reproduced in Figure 1. It does not mean that in vitro research is worthless. It can be a pointer to, for example, the performance of a given material under loading, but laboratory research cannot accurately predict how that material will perform under the challenging conditions in the mouth. This may raise the question as to nuanced differences between medicine and dentistry when it comes to the hierarchy of evidence: could expert opinion be more important in dentistry than perhaps in medical disciplines? At the upper end of the hierarchy are meta-analyses and systematic reviews, the supposed gold standards. But, how gold are these? A recent letter in the British Dental Journal¹ highlighted the effort going into reviewing primary research, and the idea of an inverted pyramid with a clinical research study being subsequently reviewed and critiqued by numerous individuals who subsequently have their review reviewed and critiqued. There is a real risk this will dissuade busy clinicians from taking part in research, particularly in primary care, where, of course, most dentistry is actually carried out. Much as an in vitro study cannot indicate how a material may behave in the mouth, clinical studies that take place in dental schools and hospitals may not accurately reflect what can be achieved in practice. As alluded to in previous Dental Update Editorials, dentistry needs more research to be carried out in primary care, but if seasoned researchers can't get it right, based on outcomes of systematic reviews, what chance have clinicians in general dental practices? Tips for incorporating research into practice have recently been published,² but taking part in research may be far down the priority list for busy practitioners.

The question ‘End of the road for the randomized controlled trial in restorative dentistry?’ was asked over 5 years ago,³ and in that Dental Update Comment, it was stated that while the evidence-based dentistry (EBD) supplements that are published with the British Dental Journal are essential reading for busy clinicians, the editorial highlighted that ‘one cannot help being struck by the volume of studies which report that there is insufficient randomised controlled clinical trial (RCCT) evidence and a need for further well-designed clinical trials’. In one issue in 2017,⁴ of the 15 studies summarized, five concluded on a similar theme that:

• ‘More clinical trials should be performed’;
• ‘Due to the small number of RCCTs on this topic and their risk of bias’;
• ‘In view of the lack of evidence’;
• ‘No trials met the inclusion criteria − there is a need for well-designed and appropriately conducted clinical trials on this topic’;
• ‘Insufficient evidence’, ‘insufficient evidence to support or refute use of any particular intervention’.

At that time, this seemed to have amounted to a massive waste of effort, as one cannot underestimate the amount of work that has gone into, not only the original studies, but also their reviews, so it seems disappointing that more robust conclusions were not always possible. Has anything changed in 5 years? To answer this, the present authors examined the most recent issue of the journal, Evidence-Based Dentistry.⁵

In this, there were nine systematic reviews (including one review of systematic reviews⁶), in which a total of 25,457 articles were screened, and only 97 of which included, representing another enormous amount of (wasted) effort. In the present authors' opinion, four of the systematic reviews presented a robust conclusion (the review of systematic reviews being among these), while others commented that ‘qualitative results must be considered cautiously’, ‘results quite variable, but significant scientific evidence’, ‘levels of evidence low’, ‘quality of evidence very low’, ‘limited quality of evidence, further RCCTs warranted’. In one systematic review,⁷ again involving much effort, it is our view that the wrong question was asked, given that the authors sought to determine the bond strength of various liners to resin composite restorations, when current thinking is very much against the placement of an intermediate liner under resin composite restorations,⁸ with clinicians instead being encouraged to trust the bonding agent to seal the restoration.

Discussion

RCCTs have been described by Brocklehurst and Hoare,⁹ as ‘the only research design that can demonstrate causality, that is, that an intervention causes a direct change in clinical outcome’. When several of these are linked in a systematic review, one would expect a gold-standard result, given that a systematic review should aim to bring evidence together to answer a predefined research question. This involves, according to Gough,¹⁰ the identification of all primary research relevant to the defined review question, the critical appraisal of this research, and the synthesis of the findings, in other words, combining data from different journal studies in order to produce a new integrated conclusion. For any systematic review to be justified, the research question must address a subject that is important to patients and clinicians alike. It has been considered^11,12 that, if a research question is of low priority to the people affected by the condition, or important outcomes are not considered, or the intervention is considered unacceptable to patients, or too costly to deliver, then that research can be wasteful. Perhaps this is what is happening in dentistry? What can be done about it?

There is a continually growing body of research evidence, and dental practitioners do not have time to keep up to date with it (one of the reasons why Dental Update, continues to publish review articles, and will soon celebrate its fiftieth anniversary). Systematic reviews should be important in this, but should also avoid being part of research waste, by ensuring new research evidence is interpreted in the light of what is already known.¹³ Therefore, in planning a systematic review, Pollock and Berge¹³ suggested that the following questions should be asked: ask a research question, and, check whether a review is needed. A systematic review should be prompted by an interest in a topic, and a wish to answer a specific question, which, as stated above, should be of interest and value to patients and clinicians.

The laudable aim of the uniquely helpful journal, Evidence-Based Dentistry, is to create a dialogue between practitioners and researchers. Its editor recently wrote ‘Ultimately, research methodologies, including economic analysis, systematic reviews and randomised controlled trials, should provide us with a useful way of organising our thoughts…but never a substitute for them’.¹⁴ The question of how to properly organize those thoughts and, at the same time, avoid research waste is important.

Back to the question of research waste, there may be several ways of looking at the suboptimal systematic reviews. One might be that they do impart information, even if it is not of an absolute gold standard. (In that regard, how many things/people actually achieve that, even the most expensive cars occasionally break down!). Another way of looking at it is that, if the systematic review, or indeed any type of research, does not reach a firm conclusion because of reasons previously alluded to, such as, ‘more clinical trials are needed’, then is it not the duty of the reviewer(s) to recommend rejection? That would surely reduce the volume of systematic reviews being published, but that, on the other hand, still equates to a lot of research being wasted.

Rather than spending time finding faults in research methodology in dentistry (valuable as this is), should more effort be spent designing and supporting colleagues in primary care to carry out ‘real world’ research? There is a range of resources to support clinicians,² but often the financial and time pressures in practice prevent uptake.

While availing one's self of best evidence is crucial to developing as a clinician in order to safely optimise outcomes for our patients, encouraging and supporting primary care-based research in dentistry should be prioritized. While systematic reviews often highlight the poor quality of the evidence and, indeed, the paucity of evidence in many areas of dentistry, more needs to be done to encourage high-quality research in practice.

In the meantime, for busy clinicians, Dental Update will continue to provide a mix of best evidence, assimilated by enthusiastic, informed clinicians in order to remain as relevant as ever for the dental team.