Twenty years of handling evaluations and practice-based research by the PREP panel

Handling of dental materials

Readers will remember materials which they have purchased, used once and confined to the back of the practice storage cupboard. Reasons for discarding a material may include the following handling, or other, problems:

It may therefore be considered that the assessment of the handling of a material is of importance. Additionally, it has been considered that ease of use of a material enhances clinical effectiveness,2 so it is the responsibility of manufacturers to strive to develop materials which are straightforward and easy to use, with these aspects of the material having been thoroughly tested, along with physical properties, before the product launch.

The performance or handling of a restorative material by one operator is necessarily subjective, but when practitioners band together to form a group in order to assess the handling of new materials in dental practice, the results are likely to be more objective and general. All of this is possible when practitioner-based research groups are teamed with the expertise available in academic institutions. A UK-based group of practice-based researchers is the PREP (Product Research and Evaluation by Practitioners) Panel. This group, which is co-ordinated by the authors, was established in 1993 with six general dental practitioners, and has grown to contain 35 dental practitioners located across the UK, with one in mainland Europe. The group has completed over 70 projects, ‘handling’ evaluations of materials and techniques. By carrying out the work in general dental practice, it is possible to place large numbers of restorations (for example, 875 in a recent evaluation of Scotchbond Universal (3M ESPE, Seefeld, Germany)) during the evaluations, ensuring a comprehensive assessment of the material under scrutiny. In the majority of the evaluations, the views of the participating dentists are collated and presented in the form of Visual Analogue Scales (generally 0–5, where 5 = ideal), with satisfaction with the material under evaluation being compared with the practitioner's previous material (Figure 1). Over the years, only two materials have achieved a maximum score of 5 for ease of use, these being G-Bond (GC, Leuven, Belgium) in 2006 and Beautibond (Shofu, Tonbridge, UK) in 2012. One of the authors (FJTB) also helps co-ordinate, with Dr Dominic Stewardson, a practice-based research group local to the West Midlands known as BRIDGE (Birmingham Research in Dental General PracticE). Readers may have noted their recent work on Class V restorations with the results indicating optimum performance when resin-modified glass ionomer was used.3

The PREP Panel has carried out over 70 handling evaluations in its 20-year history, and it may be of interest to examine the generic types of product for which handling assessments have been commissioned. These are presented in Table 1, with details of the manufacturers who have commissioned these evaluations being presented in Table 2.

It is clear that resin-based materials predominate, perhaps not a surprise since these are the materials which have seen much development in recent decades, especially dentine-bonding agents which have demonstrated steady improvement. While the report of the handling evaluation is for the commissioning company's eyes only, the majority of the reports go on to be published (in journals such as The Dentist). This enables practising dentists to read the views of a group of general dentists on a particular material.

Table 2 also provides information on the companies who value this type of research, and who presumably place importance upon the view of practising dentists on how easily (or otherwise) a product handles. In this regard, over the years, the feedback from the PREP Panel has led to changes in product packaging (for example, a bottle which can be stood upside down without leaking) and handling, the latter including a suggested change in the setting time of an impression material which was considered to set too slowly. The manufacturers then produced, for the UK market, a version of their impression material which set faster!

Practice-based research

The logical development of a group which carries out handling evaluations, such as the PREP Panel, is to evaluate the performance of the restorations which were placed during the handling evaluation over a period of time. As a result, the PREP Panel today also carries out clinical trials, as well as handling evaluations, with ten such trials having been completed to date, with its first clinical evaluation being a one-year evaluation of a compomer, published in 1998.4 While one-year evaluations are not sufficient to predict the longer-term performance of a restoration in a patient's mouth, these may be useful to assess the potential for short-term catastrophic failure of a material, with this being of particular value if the material is a newly-developed one, such as compomers were at the time of the PREP Panel study. Longer-term evaluations provide added value for the clinician, patient and/or third party funder, but the number of cohort clinical studies (especially from a general practice base) which extend beyond five years is small. However, among the recent evaluations carried out by the PREP Panel is the five-year evaluation of 42 Lava (3M ESPE, Seefeld, Germany) three-unit, zirconia-based, all-ceramic bridges, with the results indicating excellent performance of the zirconia core.5 Another five-year study, that of the low shrinkage-stress composite Filtek Silorane (3M ESPE, Seefeld, Germany) will be completed when the restorations are assessed in the summer of 2013, with the results of the three–year evaluation indicating good performance, with very low incidence of post-operative sensitivity in comparison to publications on conventional composites placed in posterior teeth.6 This may be considered to be a particular advantage for the use of this material. Studies are ongoing which will examine the effect, at three years, of selective enamel etching on marginal integrity of resin-based composite restorations.

Practice-based research – advantages and disadvantages

The types of research appropriate to general dental practice have been considered to be:7

The advantages and disadvantages have previously been discussed,7 but are summarized in Table 3.

From Table 3, it should be noted that the uncontrolled nature of practice-based research may be considered as both a disadvantage and an advantage, depending on how the research is viewed. However, the advantage is that the work includes practitioners from different backgrounds (undergraduate and postgraduate), and a variety of patients, all of which contribute to the potentially uncontrolled variations that are seen in general dental practice. In this regard, practice-based research is real world.

It is apparent that increasing numbers of dentists are becoming interested in practice-based research, particularly in the USA, where a $70million grant was awarded by the National Institute of Dental and Craniofacial Research in 2003. This has facilitated the establishment of a number of practice-based research networks that have completed a variety of projects.8^,9 In this regard, Mjör and colleagues wrote:8 ‘Hopefully this announcement will harbinger a fundamental shift towards recognising the major role that practice-based dental research can have in advancing oral health science worldwide’. While this level of funding makes UK-based counterparts green with envy, practice-based research continues to prosper in the UK and Europe and has led to the establishment of a Network for Practice-Based Research within the auspices of the International Association of Dental Research (IADR).

Along with the authors of the present paper, Ivar Mjör and Nairn Wilson have been staunch supporters of practice-based research, making a number of well made statements, for example:10‘Real world, practice-based data from general dental practice are needed to qualify and supplement the findings of experimental investigations’. They have also suggested that work from the field of general dental practice can be used to illustrate the discrepancies between research data and clinical practice. In this respect, it is the view of the authors of the present paper that, since the majority of dental treatment, worldwide, is carried out in the general practice setting, it is appropriate that this is also the setting for the majority of research into, for example, restoration longevity to be carried out.

It has been suggested that clinicians join a research network to have the opportunity to answer questions relating to the routing of dental care.9 For those who are interested in becoming involved, the first decision relates to time available. If this is not an issue, then the next stage could be to form, or join, a practice-based research group with like-minded colleagues. If one or more of them have a background in research, then that is helpful and, if not, then achieving contact with an academic with knowledge of research is essential. On an individual practice basis, however, if practitioners record the details of the placement of restorations and their subsequent evaluations in sufficient detail, they are then creating a database by which large numbers of restorations may be assessed. Not only is such information of value to the research community, but also to the patients of the practice, who are likely to be interested in the potential outcome for their treatment. In this regard, it may be considered appropriate that research into restoration longevity in dental practice is used as part of the consent process11 before a patient embarks upon a particular type of treatment, since it may be the failure of a restoration to provide what the patient considers to be adequate service which leads that patient to seek the services of a lawyer.

Finally, the importance of evaluating new materials has been discussed by Merte and colleagues1 who, while writing about the failure of a material which was designed as an amalgam substitute, stated: ‘As long as laboratory methods cannot substitute clinical evaluations, the introduction of new materials should be supported by short term clinical studies’. This underlines the value of (practice-based) clinical evaluations, whether short or long term, especially of newly developed materials.

Conclusion

Practice-based research has come of age. Starting with product handling evaluations, it has grown to make an increasingly important contribution to dental research, especially in the field of restorative dentistry and assessment of restoration longevity.