Sir, the drive towards evidence-based dentistry would appear to be creating increasing difficulties owing to the absence of relevant high quality research to support even routine investigations and treatment modalities.

However, there would appear to be a useful parallel approach which could be referred to as indirect evidence-based care and I believe that the taking of pre-treatment radiographs for teeth to be restored with crowns provides an interesting example.

An evidence-based guide to dental radiography providing prescribing advice for minor oral surgery, periodontal and restorative care, has been produced by the Faculty of General Dental Practitioners (UK)1 with statutory IR(ME)R 2000 regulations at its core. However, despite attempts by the authors to produce a robust evidence-based reference, their efforts were thwarted by a paucity of relevant high quality research evidence. The result is that the evidence for individual radiographic examination treatment modalities ranges from weak to virtually absent.

So, for pre-treatment radiography for crowns, the FGDP advice is that a periapical radiograph should be taken but the 'evidence' for the advice is a recommendation from a specialist dental association which was merely providing an opinion and for which there were no supporting papers or arguments.

Clearly for teeth which give no pulpal response and where the cause is undiagnosed and/or not yet appropriately addressed, then radiographic examination with informed consent remains an appropriate investigation. However, if the tooth is firm, vital and has a good periodontal status based upon non-radiographic periodontal indices, then the clinician faces an NNT (number need to treat) dilemma which arises from research suggesting that for periapical dental radiography there is one death for every 3 million exposures.

Furthermore, the FGDP guidance on taking periapical radiographs did not extend to the same teeth in the event that a plastic restoration was to be placed. Therefore, was the guidance driven by financial concerns, in turn prompted by the need for evidence in the event of a patient complaint to a professional registration body or professional negligence litigation?

I submitted the above arguments in respect of vital teeth requiring laboratory fabricated restorations. The only counter argument put was that radiographs could identify partial necrosis (with apical involvement) in multi-rooted teeth. A search for the incidence of such occurrences found no relevant evidence but there are in turn a number of indirect counter arguments:

  • Imaging of the periapical tissues using the LCPA technique could fail to identify a lesion

  • The incidence of relevant post treatment pulpal necrosis would appear to be low (PMID: 12473995) where a low trauma technique is used

  • The radiographic NNT would appear to be potentially very high to identify each lesion. Therefore both the radiological risk and financial costs are likely to be very high for each identified case

  • Where necessary, RCT through the restoration is likely to be successful

  • A retrospective study to determine the incidence of such lesions in vital teeth is feasible and potentially less fraught than undertaking an appropriate double blind study to resolve the issue given the potential difficulties from both clinical and ethical perspectives.

Therefore, rather than focusing directly upon comparing outcomes with and without radiographs, I believe that the evidence base dilemma could be substantially addressed by an indirect evidence-based approach. This involves calculating the overall probability of adverse findings additional to those which can be ascertained without using ionising radiation and then assessing the potential value of the additional clinical evidence which the most potentially appropriate radiograph can provide and its associated risks. While this is currently applied implicitly, formal scientific assessments would appear to be indicated.

I understand that these arguments may contribute to a revision of FGDP(UK) guidelines but my PCT and the DPD have accepted them for not taking radiographs for vital teeth which are to be restored with laboratory fabricated restorations.