Re-opening of dental services: A rapid review of international sources. Part II.

Separating the signal from the noise regarding masks.

Link to the Dental Elf

File:Face Masks used to prevent the spread of Coronavirus in ...

Bottom Line

As the number of clinical guidelines and standard operating procedures increases, we are seeing a reduction in consensus regarding a clear way forward in patient management. If we are going to take an evidence-based approach in a land devoid of direct evidence the policy makers are going to have to defer to the clinical expertise, and local knowledge of the profession in regards to the choice of PPE regarding Covid-19 negative patients requiring aerosol generating procedures.


The recent ‘Cochrane Recommendations for the re-opening of dental services: a rapid review of international sources’ has been updated  on the 16th May to include a further 5 international guidelines. The document now reviews 17 guidance documents from 16 countries (France, Spain, Portugal, Austria, Switzerland, Belgium, Netherlands, Norway, Denmark, Malta, America CDC, America ADA, Canada, Australia, New Zealand, India). The common themes and the relevant recommendations were divided into 5 domains:

  1. Practice preparation and patient considerations.
  2. Personal protective equipment (PPE) for dental practice personnel.
  3. Management of the clinical room.
  4. Dental procedures.
  5. Post-operative cleaning/disinfection/waste management.


The data was extracted in a similar way to the previous review. The five domains have mostly remained the same with little change in domains 1, 3, 4, and 5. The exception being domain 2 (PPE for dental practice personnel). The domain almost doubled in size to 29 subgroups from the original 15, but at the same time there was a reduction in the consensus with the mean dropping from 58% to 30% (See Figure 1.).


As with the previous review I selected the subgroups that achieved to filter out the large number of subgroups with a low degree of consensus. In the original paper there were 10 subgroups that scored ≥ 50%, in the update this reduced to 7 which constitutes a 42% reduction in agreement considering the expansion of the domain. (See Figure 2).

Figure 2. Subgroups with greater than 50% consensus.



Looking at these subgroup headings there is a lot of duplication especially regarding the use of FFP2 and FFP3 masks and the infective status of the patient. To try and clarify this matter a subgroup analysis was undertaken (See Figure 3,).

Figure 3. Mask selection


From this chart it was obvious that for Covid negative patients the consensus was for the use of surgical masks, and with Covid infective patients requiring an aerosol generating procedure (AGP) an FFP3 mask should be used. There was however a grey area around the use of a surgical mask combined with a face shield/visor, and an FFP2 mask for Covid negative patients requiring an AGP, the prevalence of asymptomatic patients being very low in the community (ONS, 2020). There was 41% (95% CI: 18% to 65%) agreement regarding the surgical masks, against 59% (95% CI: 35% to 82%) agreement for the use of an FFP2 mask, however as the sample size was small (n=17) the result was not statistically significant (p= 0.29).


What can we conclude from the update? Due to the lack of hard evidence regarding the effectiveness of PPE in the real-world clinical environment the guidelines would appear to be based on opinion that ranges from the precautionary principle that all patients should be considered infective, to a more pragmatic approach based on the professions current cross infection strategies. In a perfect world we would like to see well  design randomised controlled studies to answer these questions, but this does not address the here-and-now of real-world dentistry. If we are going to follow the principles of evidence-based dentistry (Sackett et al., 1996) the clinicians are going have to make the decision of using surgical masks, or FFP2 masks  for AGPs based on individual clinical expertise, best available evidence, and their patients values and preferences rather than rigid guidelines that can’t adapt to local circumstances.


ONS. 2020. Coronavirus (COVID-19) Infection Survey pilot: England, 14 May 2020 [Online]. Available: [Accessed].

SACKETT, D. L., ROSENBERG, W. M., GRAY, J. M., HAYNES, R. B. & RICHARDSON, W. S. 1996. Evidence based medicine: what it is and what it isn’t. British Medical Journal Publishing Group.

Please may I take your temperature. Screening for Covid-19?


Bottom line

Even though handheld infrared thermometers are convenient to use to check if a patient has an elevated body temperature, they aren’t sufficiently accurate for screening purposes. Using recent Office of National Statistics data on the prevalence of Covid-19 in the population the false positive rate is too high (>95%). The major confounders regarding accuracy are environmental temperature, humidity, gender, exercise, and age.


In the recent Cochrane ‘Recommendations for the re-opening of dental services: a rapid review of international sources’(Cochrane, 2020) some of the guidelines recommended temperature screening of the patients at reception for elevated body temperature. The rational being that if a patient is infected with Covid -19 the body’s response to the virus often results in core body temperature increase. Traditionally body temperature was taken with a glass/mercury or electronic thermometer that required intimate contact with the patient but now there are handheld infrared thermometers (HIRT) that are quick and require only skin contact via the ear canal, or contactless by measuring the forehead skin temperature. In this opinion paper we aim to find out how effective temperature screening is in detecting Covid infected patients.


To reduced unnecessary searching through the literature to answer this question the diagnostic accuracy data was extracted from two rapid reviews, the most recent from the Emergency Care Research Institute (ECRI, 2020), and the second from the Canadian Agency for Drugs and Technologies in Health (CADTH, 2014). It was possible to extract the sensitivity and specificity data for 10 studies measuring the effectiveness of HIRT for forehead temperature (FT), and 7 studies measuring ear (tympanic) temperature (TT). The data was extracted and back transformed into a classic 2×2 table giving us the true positive (TP), false negative (FN), false positive (FP) and true negative (TN) data and meta-analysis was carried out using the ‘mada’ package in R. The summary estimate for sensitivity and specificity for TT and FT are tabulated below (See Table 1).

Table 1. Summary estimates for IR thermometer

Measurement location Sensitivity Specificity
Tympanic temperature 78.7 (95% CI: 69.4 to 85.8) 91.8 (95% CI: 75.7 to 97.6)
Forehead temperature 51.1 (95% CI: 19.3 to 82.0) 97.1 (95% CI: 92.2 to 99.0)

The results for the TT and TF results were plotted together on to a Summary Receiver Operating Characteristic (sROC) curve for comparison. The y-axis represents the sensitivity (1.0 =100%), and the x-axis represents 1- specificity (0.1 = 10%), the solid triangle and circle are the summary estimates, and the ellipses are the 95% confidence areas. ( Figure 1.)

Figure 1. Comparison of diagnostic accuracy tests


A perfect diagnostic test would be in the extreme top left corner representing 100% true positives and 0% false positives and from the chart we can see that point is outside the 95% confidence area meaning that both tests are poor for screening. To clarify this point I transformed the sensitivity/specificity results into a frequency tree (Figure 2) using a diagnostic test calculator (

 Figure 2. Frequency trees for diagnostic tests for screening Covid-19 (Prevalence 1:400)

Frequency tree

If these thermometers are used for screening patient for Covid infection then out of every  838 patients who test positive with elevated TT only 20 will be infected which corresponds to a probability of 2.4% and for the FT that rises to 4.2%.

What happens if we use these thermometers to confirm a diagnosis of fever where we set a prevalence of 95% instead of 0.0025% (Figure 3.).

Figure 3. Frequency trees for diagnostic tests to confirm fever

Frequency tree_v1

Conclusions  The authors of the  recent ECRI report concluded:-

Temperature screening programs using IR alone or with a questionnaire for mass screening are ineffective for detecting infected persons, based on our review of evidence from 2 large systematic reviews (SRs), 3 simulation studies, and 6 diagnostic cohort studies (not included in the SRs). Under best-case scenarios, simulation studies suggest such screening will miss more than half of infected individuals. They are ineffective for mass screening because of the low number of infected individuals who have fever at the time of screening and inconsistent technique by operators.


Both pieces of diagnostic equipment produce highly variable results whether used for screening or confirming a diagnosis of febrile illness. The limitations are well described in the CADTH report (CADTH, 2014):

The retrieved studies have mentioned potential confounders for measure of temperature such as sweat, gender, age, the range of temperature, the rater, physical activity, the use of antipyretic drugs and emotional state. These factors are even more susceptible to vary in a real world conditions than in a clinical study setting. Moreover, the different brand/model/mode of devices used make it difficult to draw general conclusions on a class of thermometers. Also, a fair number of pediatric studies were included in the present review, limiting the extrapolation of their results to a general population.

In conclusion if a patients temperature needs to be taken then tympanic temperature is more reliable than forehead temperature, however its use for screening in the practice creates another layer of complexity in the cross infect/record keeping process with little diagnostic value.

Disclaimer:  The article has not been peer-reviewed; it should not replace individual clinical judgement, and the sources cited should be checked. The views expressed in this commentary represent the views of the author and not necessarily those of the host institution. The views are not a substitute for professional advice.


CADTH. 2014. Non-Contact Thermometers for Detecting Fever: A Review of Clinical Effectiveness [Online]. Available: [Accessed].

COCHRANE. 2020. Recommendations for the re-opening of dental services: a rapid review of international sources [Online]. Available: [Accessed].

ECRI. 2020. Infrared Temperature Screening to Identify Potentially Infected Staff or Visitors Presenting to Healthcare Facilities during Infectious Disease Outbreaks [Online]. Available: [Accessed].


Recommendations for the re-opening of dental services: a rapid review of international sources


Link to Dental Elf

The coronavirus 2 (SARS-CoV-2 (Covid-19)) pandemic has shut, or severely restricted the provision of only but the most essential dental care globally. From the data now currently available we have past the initial peak of infection within the population but it may still take a considerable time to develop a treatment or vaccine for the virus, in the meantime we will have to learn to function with the virus in the community. The purpose of this rapid review was to scope through the current international guidelines on re-opening dental services to help policy and decision makers establish robust practical evidence-based guidelines (Cochrane, 2020).


 Between the 2nd and 6th May a rapid review was conducted of the international guidance  for reopening dental services utilising the WHO and the Alliance for Health Policy and Systems Research approach. A grey literature search was undertaken with the assistance of the information scientists at Cochrane Oral Health. Single data extraction was performed and quality was not assessed or validated.


  • The review identified 12 guidance documents from 11 countries between the 18th March to the 5th
  • Below are listed the recommendations by domain that scored >50%:
    • Practice preparation and patient considerations
      • Patient triage by telephone (92%)
      • Social distancing in the waiting area reception (75%)
    • PPE for dental practice personnel
      • Always wear face mask (67%)
      • Unsuspected COVID-19 patients
        • Eye protection (100%)
        • FFP2 mask (50%)
      • Unsuspected COVID-19 patients undergoing AGPs
        • Disposable surgical gown (75%)
        • FFP2 mask (67%)
        • Surgical hat (50%)
      • Confirmed COVID19 patients
        • Eye protection, single use of gloves and disposable surgical gown (100%)
        • FFP2 mask (75%)
        • Surgical hat (67%)
      • Confirmed COVID19 patients undergoing AGPs
        • FFP2 mask (83%)
      • Management of the clinical room
        • Clinical room should be kept clear (50%)
      • Dental procedures.
        • Reduce or avoid AGPs (100%)
        • Reduce the risk of transmission (92%)
        • Rubber dam and high-volume suction (83%)
        • High volume suction (92%)
        • Minimally invasive procedures (50%)
      • Post-operative cleaning/disinfection/waste management
        • Cleaning and disinfection of all surfaces following every patient contact (75%)


The authors concluded:

‘This rapid review has provided a summary of the international guidance documents published to date. It summarises the main elements of the included documents and highlights several key messages intended to assist policy and decision makers to produce comprehensive national guidance for their own settings. In the majority of the sources addressing specific COVID-19 concerns, there was no referenced, underpinning evidence’.


This rapid review generated a substantial volume of data that can be challenging to interpret. To help develop some context of the balance of information I extracted data both at the domain and subgroup level to produce a summary weight of consensus per domain (See Figure 1.).


What the chart shows us is that there is a high degree of agreement about the clinical aspects of managing individual dental patients, as seen from the PPE and procedures domains, even though there is weak evidence supporting these recommendations. Guidance on how we are going to solve the re-opening problem is significantly weaker (p=0.01) in the domains of practice preparation and patient considerations, management of the clinical room, and post-operative procedures. There is nothing new here in terms of guideline construction as they are generally formulated with very little stakeholder involvement, evidence-base, or applicability (Domains 2,3 and 5 of the AGREE II criteria) (Howe, 2017). The purpose of the review was to identify these weaknesses and address them in the future guideline  development.

Disclaimer:  The article has not been peer-reviewed; it should not replace individual clinical judgement, and the sources cited should be checked. The views expressed in this commentary represent the views of the author and not necessarily those of the host institution. The views are not a substitute for professional advice.


COCHRANE. 2020. Recommendations for the re-opening of dental services: a rapid review of international sources [Online]. Available: [Accessed].

HOWE, M. S. 2017. What is the methodological quality of published dental implant guidelines? Evid Based Dent, 18, 35-36.