Aerosol Generation
Please find the latest guidelines on what's is deemed a AGE
Aerosols are generated in routine dental procedures and though patient behaviours (coughing and sneezing). Measures should be taken to reduce minimise the risks of transmission of Coronavirus associated with aerosols from all dental procedures.
- Public Health England’s COVID-19 guidance for infection prevention and control in healthcare settings states that ‘human coronaviruses can survive on inanimate objects and can remain viable for up to 5 days at temperatures of 22-25°C and relative humidity of 40-50% (which is typical of air-conditioned indoor environments)’, and highlights the risk of ‘extensive environmental contamination’ from the use of ‘potentially infectious Aerosol Generating Procedures’ including ‘some dental procedures’.
Risk factors:
● Exposure to aerosols and droplets, which can arise from natural sources (coughing, sneezing, talking and respiratory function)
● Type of procedure
● Level of aerosol created
● Length of time of procedure
● Utilisation of mitigating factors – such as high- volume aspiration or using rubber dam
Management Principles:
- Avoid all high risk aerosol generating procedures during high level COVID-19 alert periods
- Where aerosol generating procedures(AGPs) cannot be avoided take it is essential to take measures/ employ techniques to reduce amount, duration and contamination of aerosol [SEE REDUCING AEROSOL & INFECTION RISK]
- It is essential to use recommended personal protective equipment PPE and ensure face protection (e.g. FFP2 or FFP3 mask and visor or PAPR hood and appropriate outer garments) when generating aerosols
- Employ measures to remove aerosols which are generated, in particular four-handed dentistry and high-volume suction where available.
- Decontamination of the environment which must be carried out following recommended decontamination procedures and timings (allowing time for air clearance).
High Risk Aerosol Generating Procedures
Please see image at the bottom for risk assessing for Aerosol Generating Exposures
- Use of high speed (turbine) drills/hanpieces
- Use of ultrasonic / mechanised scalers
- Use of air-driven surgical handpieces
- Air abrasion
- Air polishing
- Slow speed polishing
- Use of high pressure 3:1 air syringe (“NB Risk of aerosols could be reduced when using a 3:1 if only the irrigation function is used, followed by low pressure air flow from the 3:1 and all performed with directed high volume suction. Dry guards, cotton wool or gauze can also help with drying and moisture control”)
- Opening teeth for drainage
Procedures that are at low risk of generating aerosol
- Examinations;
- Taking intra-oral radiographs;
- Handscaling with suction;
- Simple / non-surgical extractions (“NB If this became a surgical extraction, a slow speed reducing handpiece could be used for bone removal, with cooling provided using saline dispensed via a syringe along with high speed suction. If this is not a suitable option, temporisation or referral would need to be considered”)
- Removal of caries using hand excavation;
- Using slow-speed handpiece;
- Local Anaesthesia.
- Use of SLOW handpiece with or without irrigation
- Placement of temporary fillings
- Suction
- Soft tissue surgery (e.g. biopsy)
- Incision and drainage [we assume of a soft tissue]
- Irrigation with saline
Some non-aerosol generating procedures may increase the risk of aerosol exposure (e.g. stimulate gag reflexes, saliva, sneezing and coughing) and should be either undertaken with additional care with patients who may be prone to this. Alternatives can be considered e.g. using extraoral instead of intraoral radiographs.
Dental professionals providing face-to-face urgent care may also wish to be aware that guidance from the British Association of Oral Surgeons and British Association of Oral and Maxillofacial Surgeons advises that all urgent dental procedures, including oral examination, are treated as potential aerosol-generating exposures
REDUCING AEROSOL & INFECTION RISK
- Avoidance of AGP as far as possible via AAA/ non AGP during high Covid-19 alert phase
- There is insufficient evidence to show patient pre-rinsing with 1% Hydrogen peroxide or 0.2% povidone-iodine has notable benefit due to rapid recolonisation also need care regarding allergens being introduced and risk of anaphylaxis this is no longer a recommendation
- Use of high speed suction significantly reduces aerosol
- Use of rubber dam reported can reduce quantity of bio-aerosol by 90 – 98%
- Irrigation with Saline in a syringe as an alternate to 3 in 1
- Keeping contact and treatment as short and as minimal as possible
- Decontamination of the whole operative field, to include rubber dam and tooth, with sodium hypochlorite
- Access the pulp chamber only without instrumentation of the root canal system where appropriate
- Removal of caries with hand excavator or slow handpiece
- Four handed dentistry
- Use of a system to generate a negative pressure environment
- Offering a patient to take a tissue to sneeze and cough into during their visit
ENVIRONMENTAL CONSIDERATIONS
- Negative pressure rooms/ utilisation of extraction mechanical ventilation
- A/C units and fans should be turned off
- Air purifiers/filtration units- [limited evidence base at present]
- Waiting appropriate fallow down period according to risk factors See Risk Assessment page
- Keep surgery door closed and windows open
- Disinfection with 1000ppm Chlorine plus disinfection after AGE or other disinfective solution effective against enveloped viruses
HIGH RISK AEROSOL GENERATING PROCEDURES
Are procedures that are at high risk of causing aerosol generation. High speed drills water from triple air syringes 3-in-1 syringes, Ultrasonic scalers, Surgical extractions access of cavity such as for extirpation
They should treatment should be avoided and delayed to when national COVID-19 alert level is reduced were possible
- Runner nurse opens surgery door from outside to allow patient entry
- Surgery space is kept bare
- Escort should not enter the treatment room
- PPE should be worn and donned according PHE guidance, please see PPE page
- All extra items that may be needed kept on a trolley outside the surgery
- No paper notes or other paper left out
- Digital clinical records may be completed in the surgery while wearing PPE, or in a clean area following doffing of PPE and hand hygiene. If not washable, the keyboard and mouse should be covered with single-use cling film.
- Surgery door kept shut throughout procedure and if there is a window, it is kept open
- Runner / "clean" nurse passes items to operating staff when required
- A rubber dam should be placed over the tooth and sealed well
- High power suction aspirator [where available] should be used as far as possible this can reduce aerosol produced
- Decontamination of the whole operative field, to include rubber dam and tooth, with sodium hypochlorite
- Robust infection control should be adhered throughout procedures in line with Standard infection control procedures and COVID-19 transmission based infection control procedures
- Patient asked to leave and where ever possible asked to leave out a separate exit from surgery and to sanitise /wash hands on exit
- Treatment should be completed in one visit where possible
- Respirators and final close eye protection should not be touched or removed in the room at any point during the procedure or after the procedures
- Doffing of PPE at appropriate station
- Room vacated for 1hr following end of aerosol exposure if the room is needed sooner please follow latest PHE guideline
- Terminal clean as outlined infection control page should include mopping of the floor
THE FALLOW PERIOD by FGDP (uk)
Clearance of infectious particles after an AGE in dentistry is usually considered to be dependent on the ventilation and air change within the room. However, other factors such as the type of procedure carried out, the use of HVA, the use of rubber dam, the duration of aerosol generation and the size and shape of the room also have to be taken into account when deciding how long it would take for clearance of infectious viral particles after a particular procedure. A Risk Stratification Matrix has been developed to assist practitioners in assessing the risks posed by AGEs. (See Section 3 of FGDP guidance)
- Standard decontamination procedures should be followed
- Routine cleaning for low risk AGEs
- High risk AGEs require appropriate doffing of gown, with mask retained and removed outside the surgery
- A fallow time of 60 minutes is currently recommended, timed from cessation of the dental AGE
- Mitigating measures may be implanted to reduce this figure
- Floor cleaning should be undertaken at the end of each high-risk AGE or the end of each session.
- No paper records should be retained in the surgery during high risk AGEs or during the fallow period
- Scrubs should be changed daily and washed at the highest possible temperature
At the time of writing, there is a lack of evidence to give an accurate time required for clearance of infectious aerosols after a particular procedure (Fallow Period), before decontamination of the surgery can begin. This is partly because of the variables stated above, but also because our knowledge of the infectivity of aerosols generated through carrying out dental treatment on COVID-19 individuals is still evolving.
Current guidance from PHE based on advice from the New and Emerging Respiratory Virus Threats Advisory Group (NERVTAG), recommends a fallow period of 60 minutes in a single room with 6 air changes per hour (ACH) following AGPs (high risk AGEs).
Given that our knowledge of dental aerosols is still evolving, and the potential risk of transmission of COVID-19 through aerosols, we currently accept that 60 minutes should be the recommended Fallow Period needed after a high-risk AGE. This should be timed from the cessation of aerosol generation. This recommendation would be applicable for a surgery in which 6 ACH can be assured, whether by means of an open window and/or additional mechanical methods. A practitioner can choose to adjust this time if, after carrying out a thorough risk assessment, it is considered that the risk from an AGE can be modified. It would be expected that any such risk assessment which leads to an adjustment in the Fallow Period from 60 minutes is clearly documented and can be evidenced if requested later.
Examples of justifiable mitigation would be:
- Type of procedure carried out – whether a high or low risk AGE
- Use of rubber dam
- Use of HVA
- Duration of the aerosol generation
- Dimensions of the room
- Methods of ventilation
Opening windows or the use of a single room air conditioning unit, or air conditioning system that has recirculation turned off (extraction only mode) will improve ventilation. Air purifiers / air cleaners containing a HEPA filter and/or other adjuncts have been suggested as supplementary measures. There is currently not enough evidence to say whether the use of these measures will result in reducing the clearance time of potentially infective aerosols, but this view may change as further evidence emerges.Treatments involving AGEs should be avoided in windowless rooms and those with windows that cannot be opened, unless they have additional mechanical extraction ventilation. As our knowledge of COVID-19 and its transmission through dental AGEs increases, the duration of the Fallow Period is likely to be reviewed. In practical terms, consideration should be given to undertaking high risk AGEs at the end of a session, particularly during the early stages of the return to work, when National alert levels may still be high.
It is widely considered that many dental procedures create a negligible level of aerosol, and should be considered a low risk AGE. In these circumstances, the operating area can be decontaminated without implementation of a fallow period.
It is recommended that team members wear fluid-resistant surgical masks, eye protection and plastic aprons during decontamination of the surgery. Surfaces should be cleaned using a detergent and then disinfected using a virucidal agent. The floor should be cleaned thoroughly with a mop after every treatment involving a high-risk AGE. We recommend the use reusable or washable mop heads where possible, to reduce both the financial and environmental costs. Risk of contamination can be mitigated by using a suitable virucidal solution to clean the mop or consider a detachable mop head or cleaner which can be washed and reused.
If no high-risk procedures have been undertaken, floor cleaning should be done at the end of each session. Team members should be trained in appropriate environmental cleaning methods, and this is facilitated by decluttering all work surfaces and removing wall art. Reusable instruments should be decontaminated in accordance with national guidelines.
In view of financial and environmental cost of using single use disposable mops, we recommend a more pragmatic risk-based approach.
Digital clinical records may be completed in the surgery while wearing PPE, or in a clean area following doffing of PPE and hand hygiene. If not washable, the keyboard and mouse should be covered with single-use cling film. SARS-CoV-2 remains viable for 24 hours on cardboard. Copies of radiographs should be placed in a clear plastic sleeve that can be disinfected or disposed of as infectious waste. Paper records should be completed in a clean area following doffing of PPE and hand hygiene.
Scrubs should not be worn outside the practice. They should be taken home for washing after a day’s wear in a sealed plastic bag, pillowcase or dissolvable single- use bag. They should be washed separately from other clothing at the highest possible temperature in a half-full load and then tumble dried or ironed.
