Surgical mask
While there are clear guidelines for hand disinfection and use of gloves to comply with the hygiene protocol [
40], little attention has been paid to contamination potential of other components of the personal protective equipment itself. In 2021, a German research group was able to show for the first time that a surgical mask worn during aerosol-producing dental treatment can itself be a source of bacterial contamination after treatment. Previously unused surgical masks served as controls. It was recommended to change the surgical mask after each patient and not to touch the used mask after treatment with hands or new gloves [
33]. The contamination rate of surgical masks, on the other hand, has more been studied and compared in different ways in literature. The study group just mentioned also compared contamination of surgical masks with the forehead after aerosol-producing dental treatments finding out that forehead contamination with bacteria was significantly lower in comparison to the surgical mask used. This was attributed to natural protection mechanisms of the skin. In both studies, the detected bacteria belonged to the oral and cutaneous flora, also potentially pathogens like
S. aureus could be found. The forehead before treatment and unused surgical masks served as controls [
34]. Several studies with limited study quality and significance due to lack of controls have also addressed contamination rate of masks. They could all detect massive contamination on masks after aerosol-producing treatments in dentistry [
41‐
43]. The spectrum of microorganisms in these studies was very similar. In addition to staphylococci and streptococci,
Pseudomonas and
E. coli, often detected in nosocomial bloodstream infections [
44], were dominant. Furthermore, one of these studies was able to show that the outside of surgical masks was significantly more contaminated with bacteria and fungi than the inside [
41].
Comparison of contamination of outside and inside of masks was also subject of several in vitro studies showing that the inner side of the mask is regularly contaminated during treatments [
45‐
48]. In one of these studies, contamination on the outer surface and even on the inner surface of single-layered surgical masks could be detected by both the operator and assistant on the dummy head where cavity preparation was performed using filter papers to assess the spread of the spray [
45]. Moreover, aerosol distribution could even be found on the inside of a KN95 mask for all users and all devices (air polishing with an airflow device or ultrasonic scaling) during simulated periodontal treatment on a mannequin with fluorescein salivation, even though an additional face shield was worn [
47].
In addition to bacterial contamination by aerosols, contamination of masks with blood was also investigated. Aguilar-Duran et al. examined face masks and caps of oral surgeons and assistants for blood contamination during 101 aerosol-producing various surgical procedures. Almost half of the 202 samples from assistants and oral surgeons were contaminated though a face shield was worn. 18.8% were macroscopically contaminated with blood. Interestingly, in 40% of the cases, clinicians were unaware of blood contamination. Dentists were more contaminated than assistants. No controls were included. In this context, it was strongly recommended protecting the face during oral surgery procedures, especially when using rotating equipment [
49].
Many dental procedures generate droplets and aerosols contaminated with blood and bacteria, possibly leading to disease transmission [
50]. In context of the COVID-19 pandemic, a systematic review was published summarizing the effectiveness of respiratory protective equipment (RPE) including mask, face shield, respirator, and goggles as a barrier against aerosolized microbes finding out that they can curb the spread of infection among healthcare workers. However, effectiveness of filtration is limited by mask-fit factor, period of wear, wetness of masks, fabrication quality, airflow dynamics, and inhalant particle size [
50].
Protective eyewear
Goggles have been rarely studied so far. The few existing studies show that they regularly become contaminated during aerosol-producing dental treatments [
47,
51]. One study in particular has dealt with this issue in detail investigating the quantitative saliva and blood contamination of protective eyewear during aerosol-producing dental treatments. Goggles were disinfected before treatment. Contamination with blood was detected in all samples, with the highest amount found after professional tooth cleaning. Macroscopically detectable contamination was detected on 60.4% of protective eyewear. Macroscopically clean protective eyewear contained up to 12% contamination with blood. It was recommended to wear protective goggles without fail and to disinfect them after each patient since disinfection was effective against blood and saliva contamination [
51].
Especially since Corona pandemic, eye protection has become increasingly important during treatment. Unprotected eyes and unprotected mucous membranes increase the risk of contracting COVID-19, so eyes should be protected with goggles. In addition, proper handling of protective eyewear is important, as they are rarely changed and disinfected during routine wear. Regular disinfection of goggles to avoid cross-contamination is, therefore, advisable [
28,
52].
Other components of the personal protective equipment
Some clinical and in vitro studies have looked at contamination of PPE as a whole or little regarded parts.
Bacterial contamination on sleeves of scrub jackets is higher than on the chest, as is the case when using ultrasonic or air polishers. Aerosol contamination is produced even when examining the patient or during hand scaling [
56]. Again, bacteria of the dermal and oral flora were detected (Staphylococcus, Micrococcus, Bacillus, Actinomyces, Corynebacterium).
Al-Eid et al. investigated 30 oral surgical procedures for removal of one or both impacted mandibular third molars for visually indiscernible blood contamination using luminol. Luminol is mainly used in forensics for detection of invisible traces of blood. The PPE was worn by the oral surgeon, the patient, and assistant. Disposable protective equipment was used. Blood contamination could be found in all PPE (face masks, eyewear, surgical gown, sterile gloves) used by clinicians except head caps and shoe covers. Furthermore, eyewear and chest drapes used by patients were contaminated. Gloves and face masks of the surgeon were contaminated in all treatment cases, protective eyewear in 26 cases, and surgical gown in 22 cases. For the assistant, gloves were contaminated in all treatments, mask and glasses in 24 cases, and surgical gown in 20 cases. They recommended disinfection of all clinical surfaces and mandatory PPE for doctors and patients during every procedure, as imperceptible blood contamination occurs even during minor surgical ones [
57].
In addition to the clinical studies already described, in vitro studies have also been conducted to investigate the PPE. Watanabe et al. investigated contamination patterns by adenosine triphosphate (ATP) bioluminescence analysis before and after dental treatment (ultrasonic scaling, professional mechanical tooth cleaning) on masks fitted with a surgical face shield, chest, goggles, and doctor’s gowned right arm, as well as on patient’s goggles. ATP is a useful marker in living microorganisms such as bacteria, fungi, and protozoa. The ATP bioluminescence method has long been used in monitoring surface contamination in hospitals and the food industry. The research group indicated that the contamination on every surface tested increased significantly after dental treatment. They summarized that aerosols and splashes generated during dental treatment have the potential transmitting infections to dentist and patient [
58].
Nóbrega et al. described, in their review, that microorganisms could be found on many parts of the PPE after aerosol-producing dental treatments such as scrub jacket, sleeves, masks, and face shields. Different types of microorganisms like bacteria (Staphylococcus auricularis and epidermidis), viruses, and fungi were found.
They recommend, therefore, usage of PPE and regular disinfection procedures [
59]. Also, Chanpong et al. recommended to wear a full PPE during aerosol-producing treatments and to switch between patients. They examined the extent of splashing during aerosol-generating procedures (up to 120 s) with a melamine resin visible under UV light in dental staff using a dental mannequin. In addition, a patient cough was simulated. After treatments, splashes were detected on body, arms, face, and legs of the dentist and assistant. As expected, the cough produced more splashes than the short aerosol-producing treatments; furthermore, contamination was found on the crown of the head, shoes, and back of the dental personnel [
60]. Kaufmann et al. demonstrated that practitioners clothing (gloves, shoe, shirt, cap) is always contaminated. Ultrasonic scaling resulted in less contamination than air polishing. Moreover, probe contamination decreased with increasing distance from patient's mouth for both devices. [
47]. Chen et al. demonstrated that when teeth were cleaned with water containing red pigments, every single waterproof protective gown was contaminated [
54].
Reske et al. examined all PPE (gloves, face mask, eye protection, disposable gown) during donning, with a fluorescent marker applied to palms and abdomen finding out that self-contamination regularly occurs when donning and doffing PPE. The highest frequency of protocol deviations was in hand hygiene and use of disposable gowns. Protocol deviations were significantly associated with fluorescence. Participants were scanned for baseline fluorescence. Areas with fluorescence were cleaned, if possible, otherwise it was not taken into account [
61]. The study shows again that the PPE itself can be a source of contamination, therefore handling it needs to be trained.