Previous research indicated that microorganisms can remain viable on radiographic equipment for up to 48 h and as long as 2 weeks in X-ray developer/fixer [21]. If proper disinfection techniques is not applied when taking any dental radiograph, the potential for cross-contamination of radiographic equipment with blood and/or saliva would be significantly high [17, 18, 21].
Most reusable items used in dental radiology are considered semi-critical (contact with mucous membrane) or non-critical (contact with intact skin). Reusable semi-critic items such as bite guides, film positioning devices must be sterilized with high-level disinfectants after each use or covered with plastic sheets, wraps or pieces with adhesive edges, if sterilization or barrier-protection is not possible, then disposable items should be used [17, 18, 21]. Non-critical items such as chin rest, hand grasps can be barrier-protected and the covers must be changed after each patient. Surface barriers provide adequate protection while eliminating the need for clean and disinfect surfaces between patients [17]. Lead-apron and thyroid collars should be disinfected with a low-level disinfectant (e.g. quaternary ammonium compounds) and should be suspended on a coat hanger after each use. Attention should be paid to minimize the positioning and exposure errors during radiographic examination in order to eliminate the need for repeated exposures which may additionally increase the risk of contamination. The working station (computers, screens, scanners etc.) should be kept remote from the patient examination rooms and the operator in charge of exposures should have limited access to the working station or to the dark room. The radiologists should have a separate room to interpret images and prepare the reports. On the basis of experience with SARS, the use of a remote satellite radiography center or utilization of mobile radiographic equipment are also recommended for patients with known COVID-19 disease [28].
Oral rinse with 1% hydrogen peroxide or 0.2% povidone solution prior to any dental procedure has been shown to reduce viral load [29]. Considering the close contact of mucous membranes during panoramic, CBCT and intraoral examination, we recommend oral rinsing for the patients before using these techniques.
Panoramic radiography
The panoramic radiography room must be prepared, the machine should be turned on and the rotating component should be returned to the start point before the patient is accepted. If conventional films or storage phosphor sensors are used, the cassette should be placed before accepting the patient [17, 18].
Non-critical surfaces and items during panoramic radiography includes chin rest, handgrips, head-positioning devices/head stabilizers, remote switch, control panel (chairs if patients need to be seated). All non-critical items should be barrier-protected with plastic sheets or wraps, and should be changed after each patient. Non-critical items can be disinfected with intermediate level disinfectants (70% ethyl alcohol, 70% isopropyl alcohol) daily and when contaminated. The bite-guide (semi-critical item) must either be covered with a disposable sheath or sterilized following patient use. If both options are not possible, then disposable bite-guides must be employed [17, 18, 21].
In order to minimize the spent time in the examination room, registration of the patients should take place outside and the patient must remove all metal accessories and dentures before entering the room [17, 18, 21].
In case of physical contact with the patient during positioning, the gloves must be changed before taking the cassette out after exposure (for conventional films and storage phosphor plates).
The cassettes should be held with clean gloves during transfer to the work station or dark room.
CBCT imaging
Same infection control measures also apply for CBCT. The only difference is the type of non-critical items on the device.
Non-critical items on CBCT devices include remote switch, control panel, chin rest, handgrips, head stabilizers, patient table (supine positioning) and patient chair (seated positioning). All non-critical items should be barrier-protected as described above and disposable bite guides must be used if barrier-protection or sterilization is not possible.
USG imaging
Swellings and pain in masticatory muscles may also require ultrasound (US) imaging during COVID-19 pandemic. Transducers may carry pathogens, including viruses such as human papillomavirus (HPV), unless properly disinfected between examination sessions. The infection prevention and control recommendations of Ultrasound Working Group of the European Society of Radiology should also be followed for COVID-19 [30]. High level of disinfection should be applied for ultrasound transducers. The transducers must be used with protective covers such as medical gloves, or condoms during contact with mucous membranes or any body fluids (including interventional procedures, injections, tissue sampling, use in the theater, etc.). Sterile gel should be used inside and outside covers. The following specific measures are recommended by American Institute of Ultrasound in Medicine (AIUM) for COVID-19 [31].
- 1.
Cleaning—Cleaning involves all ancillary equipment involved in the procedure at hand. A cover sheet may be used as a physical barrier between the keyboard/console and the operator, in addition to low level disinfectant cleaning. If possible, a dedicated system (scanner and transducers) for COVID-19 positive or suspected patients should be used. Transducers should be cleaned after each examination with soap/water and low level disinfectant (quaternary ammonium) sprays or wipes.
- 2.
Disinfection—As stated above, all internal transducers (e.g., intraoral, transesophageal) as well as intraoperative transducers require high level disinfection before they can be used on another patient. For disinfection, an antiseptic agent-impregnated towel (such as glutaraldehyde, peracetic acid, ortho-phthalaldehyde, hypochlorite/hypochlorous acid, phenol/phenolate) as well as a type C ultraviolet light can be used [30, 31].
Intraoral radiography
During intraoral radiography transmission of the disease is possible through either direct contact with saliva or cross-contamination. Cross-contamination may also occur when the clinician handles the digital sensors or opens film packets [17,18,19,20,21].
Use of autoclavable or disposable film/receptor holders is recommended to decrease clinician’s contact with saliva while placing the film/receptor [17].
The high-touch and non-critical items such as tube head, X-ray cone, control panel, exposure button, head rest and adjustment control, chair and adjustment control and countertop/working area should be barrier-protected (plastic sheets, wraps) and the barriers should be changed after each patient. Intermediate level disinfectants (70% ethyl alcohol, 70% isopropyl alcohol) can be used for disinfection of these items on a daily basis or when contaminated [17, 18, 21].
Paper towels should be kept ready over the counter in order to remove excess saliva after exposure.
Film/receptor holders (packed and sterilized) and film/storage phosphor plates should be dispensed aseptically in a disposable container.
Plastic sheaths must be used for all kind of intraoral films/receptors and the integrity of sealed barrier must be verified before placement. The use of double barriers for films and plates and latex finger cots in conjunction with a plastic sheath for direct digital sensors will more effectively prevent cross-contamination [32, 33].
If charged-coupled-device (CCD) sensors are used the cord must be wrapped with a plastic cover before placement and the cover must be changed after each patient [17].
Following exposure, the plastic sheaths should be immersed in disinfectant solution and left to air dry. The sheaths must be opened carefully, hand contact with the film/receptor and contact with saliva must be avoided. While opening the protective cover, the films and phosphor plates should be allowed to drop out in a clean disposable cup and the cup must be held with clean gloves. Then, the film/plate can then be transferred to work station or dark room [17, 32, 33].
Since digital receptors cannot be sterilized by conventional means. Manufacturers’ recommendations should be followed. For digital sensors (CCD and plates) wiping with intermediate level disinfectants after each use (70% ethyl alcohol, 70% isopropyl alcohol) is recommended. Phosphor plates may also be gas sterilized with ethylene oxide [17, 32, 33].
For conventional films, the operator in dark room must remove the film from the vinyl package without touching the film. The lead foil, black paper and the package should be discarded and film should be allowed to drop out on a clean disposable cup before manual/automated processing [17].
Second hard copies of radiographic images should be avoided and teleradiology systems should be preferred to prevent contamination [14].
A majority of these infection control procedures have been already known as inseparable parts of everyday dental radiology practice, however, the new COVID-19 disease has dramatically altered our habits and the way we live our lives due to high transmission rate. More serious implementation and control of current infection control regulations is absolutely required to manage the disease and prevent the global spread of the virus. It is obvious that this pandemic will inevitably trigger a new era in dental profession both during normalization period and afterwards. Therefore, the present guide has been awarded for infection control when practicing dental radiography during this pandemic. These recommendations which are based on the previous reports and current data on the disease can be also be applied during possible future outbreaks.
