Sir, we write in relation to Respiratory protection in dentistry,1 a very comprehensive and informative article. However, there are a few points that we would like to draw to your readers' attention, in relation to infection prevention and control measures recommended by Public Health England (PHE) in the North East and Yorkshire:

  1. 1.

    PHE does not advocate placing a surgical mask over a valved respirator ('double-masking') to afford additional protection to the patient from the wearer. HSE2 and NOISH3 instead recommend that a full-face visor is worn in front of all respirators. A full-face visor will protect the respirator from droplet/splatter contamination, and may provide a physical barrier between the patient and exhaled breath/droplets from the wearer. Another concern with 'double masking' is that it could affect its function and may restrict the wearer's ability to breathe

  2. 2.

    PHE would not promote the routine sharing of reusable respirators between staff. Ideally, each member of staff should have their own reusable respirator for optimal infection prevention and control

  3. 3.

    PHE have had confirmed by a 'Fit2Fit' assessor who advises PHE and the Office of the Chief Dental Officer (OCDO) on fit testing best practice that a full-face visor should not be worn during qualitative fit testing. It is only the headband/frame (with the Perspex shield detached) that should be worn, if it could affect the fit of the respirator. The Perspex shield should not be worn as it could act as a barrier between the nebulised fit test solution and the respirator, possibly creating false passes. If the Perspex shield cannot be detached, the whole visor should not be worn. At the outset of fit testing, there was uncertainty about whether the visor should be worn during fit testing. Once we received clarification, some clinicians required a re-test.4We have been in discussion to request that the updated version of the Fit2Fit companion5 clarifies this issue going forward.

Tarik Shembesh, Samy Darwish and Kariem El-Boghdadly respond: We thank Shah et al. for their valuable discourse in response to our paper.1 We wish to highlight some pertinent considerations to further the reader's understanding of respiratory protection.

In relation to double-masking, we agree with the recommendations of HSE2 and NOISH3 of wearing a suitably designed face shield with all respirators, let alone valved ones. Although some professional bodies have made recommendations about double-masking,3,6 we accept that recommendations do often change depending on supply and emergence of evidence. Therefore, it is important to understand the principles behind any recommendations and take a pragmatic approach whenever possible, but also to drive research to answer any gaps in knowledge. There are some disposable respirators with a shrouded valve that are likely to be the ideal product within a healthcare setting. We also welcome developments of disposable filters to be placed over the valves of reusable respirators that are in development by some manufacturers. We urge the profession to help drive such developments so they can become available to the healthcare workforce, including in dentistry, as they will help protect both the patient and wearer whilst maintaining optimum working conditions.

With regard to the sharing of reusable respirators between staff, whilst the manufacturers consider sharing suitably disinfected reusable respirators acceptable practice as has long been the case in industries beyond healthcare, we also agree that it is best practice for each member of the workforce to ideally be in possession of a respirator for their own exclusive use - though we were unable to find guidance explicitly supporting this. Each wearer should be taught responsibility for their own exclusive respirator including how to clean, maintain and inspect it to ensure its fitness for use and to regularly log the inspection, as per manufacturers' instructions.

Finally, as accredited fit-testers, we strongly support the stance, both in theory and practice, that visor shields should not be worn during qualitative fit-testing procedures, though bridge-mounted visor frames or head straps should. Any barrier that could potentially prevent the testing solution reaching the periphery of the mask risks invalidating the test. Wearing the frame ensures as close a replication to the true working conditions as possible. This concern is of course only relevant to the qualitative fit-test as the quantitative fit-test depends on particle counts through a tube attached directly to the respirator via an adaptor, and thus wearing a visor is suitable.