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Experience of Clinical Trials in General Dental Practice

J. Clarkson

Dental Health Services Research Unit, Dundee Dental Hospital & School, University of Dundee, Dundee, Scotland, UK; j.e.clarkson{at}chs.dundee.ac.uk

KEY WORDS: Clinical trial • general dental practice

There is considerable debate about the feasibility and appropriateness of research in dental primary care, particularly the conduct of clinical trials compared with other research designs. While an evidence-based approach to clinical practice is advocated to improve patient care, research relevant to primary care is sparse, with a gap between research findings and clinical practice. Conducting research in a primary care setting is important, while recruitment and retention methods are crucial for generalizability of the results. Systematic reviews show that high-quality trials provide more reliable outcomes, due to methods such as concealment of allocation to groups, blinding, and particularly outcome assessment and loss to follow-up. Our experience of clinical trials in general dental practice has given insight into the design and conduct that ensure feasibility and generalizability. However, only with adequate funding, good infrastructure, and networks can research be conducted in dental primary care.

	Introduction

TOP Introduction Examples of Clinical Trials... The Scottish Dental Practice... References

 
The feasibility and appropriateness of research in dental primary care, particularly the conduct of clinical trials compared with other research designs, have been the subject of much debate. This paper will discuss the feasibility of conducting clinical trials and issues relating to the generalizability of results. It will also describe the function and structure of the Scottish Dental Practice Based Research Network (Scottish Dental PBRN).

An evidence-based approach to clinical practice is advocated to improve the quality of patient care. While there is a shortage of research relevant to primary care, there is also a gap between research findings and clinical practice. The importance of conducting research in a primary care setting is acknowledged and linked to initiatives in research and development at policy level in the UK and other countries. There have been attempts to estimate the differential between where dental care is provided and the research conducted. Approximately 90% of dental care is delivered in a primary care setting, compared with 2% of published research. The proportion of research grant monies allocated to research in primary care is small and has been estimated to be 7% from the Department of Health UK, 4.6% Medical Research Council, and 0.1% The Wellcome Trust. For the situation to be redressed, the challenge is how best to develop structures and systems that will assist with capability and capacity-building. If an evaluative culture and knowledge-based dental health service are to be achieved, it will be important to have sustainability for investments in research activity and links with education.

Why clinical trials compared with other research designs? Randomized controlled trials are considered the principal research design for clinical interventions in healthcare. A frequent misapprehension is that observational studies in primary care are easier to conduct, requiring less effort and resource compared with clinical trials. It is the research question that should determine the appropriate study design, and while etiological hypotheses cannot generally be tested in randomized experiments, there are few situations in which dental interventions could not be randomized. With the advent of systematic reviews and the considerable amount of methodological developments in this area, it is now possible to appreciate more fully the benefit of minimizing confounding and bias, as achieved in a randomized trial. Comparison of meta-analyses evaluating the effectiveness of beta-carotene for cardiovascular mortality in six observational studies with that of four randomized trials clearly demonstrates this issue. Meta-analysis of the cohort studies shows a significantly lower risk of cardiovascular death for adults taking beta-carotene. However, the randomized trials indicate a moderate adverse effect of beta-carotene (Egger et al., 2001).

This discrepancy between observational and trial results is not unique. While there are also examples where results of these two types of studies are similar, it is important to consider the implications. This is particularly true for dental research, where many of the interventions are preventive, and the risk of bias and confounding in observational studies is most likely to occur, because preventive agents are most likely to be used by motivated healthier individuals.

In addition to the design of research, its quality also has implications for the reliability of the outcome. Again, it is the science of systematic reviews that has provided insight into the importance of this. On average, high-quality trials provide more reliable estimates of treatment effect than do low-quality trials, where it is estimated that the intervention effect can be exaggerated by 20–40% (Juni et al., 2001). The features of quality that are most correlated with this relate to the generation of allocation to group, concealment of allocation, blinding (in particular outcome assessment), and loss to follow-up.

	Examples of Clinical Trials in General Dental Practice

TOP Introduction Examples of Clinical Trials... The Scottish Dental Practice... References

 
The feasibility of conducting high-quality research in primary care is related to the recruitment and retention of participants. Successful recruitment of dentists appears to be more likely if the topic is relevant to their practice, and there is minimum disruption to clinical care systems, good communication, administrative support, and feedback from the research team. Active participation in the generation of the research idea, and absolute remuneration for time involved do not appear to be the most important factors. This does not mean that time should not be appropriately remunerated to reflect participation in what is increasingly considered a valuable post-graduate activity linked to continuing professional development. The success of recruitment and retention of dentists is demonstrated in a five-year randomized controlled trial of toothpaste. This trial was conducted in the Northwest of England, where 24 GDPs agreed to participate and recruited 4211 of their adult patients. After five years, 23 dentists remained involved, along with 2799 (66%) of their patients (Worthington et al., 1999). The importance of generalizability of recruiting a representative sample of dentists in either a cluster or patient-randomized trial remains debatable. Often, it is a selected group which participates in general practice research or research in primary care. The impact of this on patient-based clinical results has yet to be determined.

A trial evaluating the effectiveness of different dissemination and implementation strategies for evidence-based guidelines, using the Scottish Intercollegiate Guidelines Network (SIGN) for the appropriate removal of third molar teeth (SIGN 43, 2000), raised some important questions. During the recruitment phase, 565 dentists were approached, and a self-selected group of 51 practices across Scotland volunteered. Practices were randomly allocated to one of four groups to evaluate the effects of computer-aided learning and audit and feedback on adherence to the guideline. The number of recruited practices was considered sufficient, based on a sample size calculation based on previous estimates of clinical practice and experience of cluster trials in medicine. It had been estimated that as much as 80% of clinical decision-making for patients with third molar problems would be inappropriate. This was based on data published prior to the development of the guideline. Surprisingly, the baseline pre-intervention data revealed a 74% agreement with the clinical guideline at the start of the trial (Bahrami et al., 2004). This difference between the expected and actual adherence to the guideline at baseline may reflect the bias of self-selection. Access to national treatment data, however, revealed a clear decline in the rate of third molar teeth extracted in Scotland NHS practices two years prior to the publication of the guideline and the start of the trial. This raises the question of whether the high compliance rate at the start of the trial was truly the result of self-selection. Alternatively, it mirrored dental practice across the country, and therefore the study dentists were representative and provided generalizable results. It will be increasingly important to be flexible in primary care research, to account for changes that might take place between having a research idea and securing funding.

In Scotland, efforts are being made to increase participation in research, to develop the evidence base in dental primary care. For two years, the vocational dental practitioners in Northeast Scotland have participated in randomized controlled trials. The aim has been to answer relevant clinical questions while increasing awareness and knowledge of research methods and the validity of evidence. The first trial investigated patient attitudes toward a routine scale-and-polish and compared the experiences of hand vs. ultrasonic instrumentation (Clarkson et al., 2001; Bonner et al., 2005). The second trial evaluated personalized oral health advice supported by professional literature, compared with routine advice on oral health outcomes and patient-reported behavior (Young et al., 2003). A third trial has now been conducted, involving all vocational dental practitioners in Scotland, to evaluate the effect of evidence-based oral hygiene instruction, including the use of a powered toothbrush (http://www.dundee.ac.uk/dhsru/research/vdptrial.htm).

There are methodological challenges that need to be overcome to deliver trials in dental primary care and ensure high quality. In the above examples, randomization was computer-generated, and allocation to groups was concealed in opaque envelopes; however, neither patients nor outcome assessors were blind. Double-blinding is often difficult to achieve, particularly for clinical interventions, where a placebo is not possible. The importance of blind assessment in dental primary care research has been observed in a caries trial where children were examined by two assessors, one blind and the other not blind to treatment group. The blind assessor did not find a significant benefit of the preventive intervention, while the clinician involved found a statistically significant difference in dmft.

The importance of contamination in trials is not well-understood. There has been an increase in the number of cluster-randomized controlled trials conducted in primary care, and they are considered the gold standard when the outcome is related to the health care practitioner rather than to the patient. A factor that influences the sample size of a cluster trial is the intra-cluster correlation coefficient (ICC). In medical practice research, this has rarely been higher than 0.1. The ICC reflects the variation in care that is delivered by either individual clinicians or a group of clinicians in a medical practice. It cannot be assumed that the same ICC would apply to dental practice. In a recent analysis of data concerned with the provision of tissue sealants, ICCs as high as 0.5 have been calculated (ERUPT Final Report, 2005). The implication of this difference for a cluster trial powered for a main-effect change of 22–33% is an increase in the number of practices from 84 to 200 and the number of patients from 1400 to 3400. It is because of the implications for the cost and conduct of trials that studies to answer some of these important methodological issues are being planned.

	The Scottish Dental Practice Based Research Network (Scottish Dental PBRN)

TOP Introduction Examples of Clinical Trials... The Scottish Dental Practice... References

 
The Scottish Dental PBRN has been developed to promote the implementation of evidence-based practice through the conduct of high-quality research and dissemination of research evidence. This is one of the activities supported by the Scottish Consortium for Development and Education in Dental Primary Care. The Scottish Consortium is a unique partnership among the three dental institutions in Scotland: the universities of Dundee, Edinburgh, and Glasgow, with Chief Scientist-funded Dental Health Services Research Unit and NHS Education for Scotland (Clarkson et al., 2000). Other activities include providing support to dentists in primary care by making available higher training fellowships so that they can undertake post-graduate degrees. The Scottish Dental PBRN currently has 300 members from the General Dental Service, Community Dental Service, and Professionals Complementary to Dentistry. Support is provided for the transfer of research ideas to project development from individuals or groups. Collaboration and partnership with academic colleagues are facilitated, because the mutual need for expertise is recognized. The priority is to support clinically relevant and policy-related questions. High-quality research is promoted, particularly randomized controlled trials that are designed with minimal bias. The Scottish Dental PBRN is promoting the idea of recognizing verifiable research activity with remuneration and possible links to an accreditation scheme, to ensure quality.

The Scottish Dental PBRN has a steering group that reflects the groups interested and involved in research in Scotland. Activity has focused on supporting research by developing projects and recruiting dentists for ongoing studies. ERUPT (Evidence from Research Used in Preventive Treatment) is a trial designed to evaluate the effects of remuneration and training in evidence-based practice on the implementation of evidence. The Scottish Dental PBRN facilitated the design of this trial and secured funding from a call for research to investigate the effect of the organization of primary care on inequalities in health. Local co-ordinators were recruited from the network to assist with trial recruitment. One hundred and fifty general dental practitioners were required, and work was carried out with the Practitioner Services Division, to identify a random sample of dentists and use routinely collected data (Turner, 2003; Turner et al., 2005; http://www.dundee.ac.uk/dhsru/research/eviderupt.htm). This is the first time that there has been research collaboration between all three dental institutions in Scotland and the Information Services Division of the Scottish Executive.

An example of how the Scottish Dental PBRN has recruited dentists for a study is an investigation into the feasibility of general dental practitioners’ collecting epidemiological data on adults. In this study, ten general dental practitioners and five epidemiologists examined the same ten patients. There were no differences in the mean DMFT scores, and the GDPs exhibited greater reliability among themselves, though assessments for decay were more variable than those of the epidemiologists (Nuttall and Clarkson, 2005).

The effectiveness of the support culture for research in primary care is exemplified in the following. In a routine audit, a general dental practitioner was found to be placing stainless steel crowns in children without caries removal, tooth preparation, or local anesthetic. The feasibility and acceptability of this technique were assessed by a group of dentists funded to participate in a regional primary care research network, TayRen (Evans et al., 2000). One of these dentists was later successful in being awarded a Chief Scientist Office research fellowship to co-ordinate a randomized controlled trial comparing this new treatment, the ’Hall Technique’, with current practice. This has enabled the practitioner to work part time for a PhD with government and industry sponsorship.

Challenges for dissemination are recognized, and Tuith (now www.ScottishDental.org/pbrn) is an online resource that has been designed to support the Scottish Dental PBRN. It provides information about research activity, supports research projects, and provides access to best evidence. It receives over 5000 hits per month, and the most frequently accessed pages are the links to guidelines and practice guidance.

Our experience of clinical trials in general dental practice has given us insight into aspects of design and conduct that guide decision-making for feasibility and generalizability. It is only with adequate funding, good infrastructure, and networks such as the Scottish Dental PBRN that research can be conducted in dental primary care. Also, it is only high-quality research that will provide the profession with reliable evidence for interventions for oral health.

	References

TOP Introduction Examples of Clinical Trials... The Scottish Dental Practice... References

 
Bahrami M, Deery C, Clarkson JE, Pitts NB, Johnston M, Ricketts I, et al. (2004). Effectiveness of strategies to disseminate and implement clinical guidelines for the management of impacted and unerupted third molars in primary dental care, a cluster randomised controlled trial. Br Dent J 197:691–696.[Medline]

Bonner BC, Young L, Smith PA, McCombes W, Clarkson JE (2005). A randomised controlled trial to explore attitudes to routine scale and polish and compare manual versus ultrasonic scaling in the general dental service in Scotland [ISRCTN99609795]. BMC Oral Health 5:3.[Medline]

Clarkson JE, Murray M, Pitts NB, MacFarlane TW, Newton JP, Burke FJ, et al. (2000). Scottish consortium for development and education in dental primary care. Br Dent J 189:222–223.[Medline]

Clarkson JE, Young L, Smith P, Bonner BC (2001). A randomised controlled trial to explore attitudes to routine scale and polish and compare manual versus ultrasonic scaling (ISRCTN99609795). http://www.dundee.ac.uk/tuith/Articles/rt06.htm

Egger M, Smith GD, Schneider M (2001). Systematic reviews of observational studies. In: Systematic reviews in health care: meta-analysis in context. Egger M, Smith GD, Altman DG, editors. London: BMJ Books, pp. 211–227.

The ERUPT study (The effect of remuneration and education on the implementation of research evidence to reduce inequalities in oral health) Final Report submitted to funding bodies, Chief Scientist Office of the Scottish Executive and Scottish Higher Education Funding Council, December 2005.

Evans DJP, Southwick CAP, Foley JI, Innes NP, Pavitt SH, Hall N (2000). The Hall technique: a pilot trial of a novel use of preformed metal crowns for managing carious primary teeth. http://www.dundee.ac.uk/tuith/Articles/rt03.htm

Juni P, Altman DG, Egger M (2001). Assessing the quality of randomised controlled trials. In: Systematic reviews in health care: meta-analysis in context. Egger M, Smith GD, Altman DG, editors. London: BMJ Books, pp. 87–108.

Nuttall NM, Clarkson JE (2005). Can dental epidemiological information be gathered during routine dental examinations by general dental practitioners? Community Dent Health 22:101–105.[Medline]

SIGN 43 (2000). Scottish Intercollegiate Guidelines Network. Management of unerupted and impacted third molar teeth. http://www.sign.ac.uk/guidelines/fulltext/43/index.html

Turner S (2003). Study of primary care dentistry ERUPTs into life. SSPC Link Newsletter. http://www.nes.scot.nhs.uk/docs/publications/sspc_link2.pdf

Turner S, Pitts N, Cardno L, Southwick C, Clarkson J (2005). Recruitment and retention of dentists in primary care research (abstract). J Dent Res 84(Spec Iss A):3185. http://iadr.confex.com/iadr/2005Balt/techprogram/abstract_61246.htm

Worthington HV, Clarkson JE, Davies RM (1999). Extraction of teeth over 5 years in regularly attending adults. Community Dent Oral Epidemiol 27:187–194.[Medline]

Young L, Bonner BC, Smith P, Clarkson JE (2003). A randomised controlled trial to investigate the effects of enhanced oral health advice upon self-reported patient behaviour, oral cleanliness, and gingival health (ISRCTN55563468). http://www.dundee.ac.uk/tuith/Articles/rt07.htm

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