Bacterial contamination of forehead skin and surgical mask in aerosol-producing dental treatment

Bacterial contamination potential of personal protective equipment itself in dental aerosol-producing treatments

Personal protective equipment (PPE) has long been a high priority in dental aerosol-producing treatments. Since COVID-19 pandemic, its importance has increased yet again. While importance of PPE in preventing transmission and thus possible infection of pathogens is well known, contamination potential of PPE after treatment itself is less investigated. This review aims to give an overview of the current literature and contamination potential (viral, blood, bacterial) of components of protective equipment itself. The literature search was performed using the Medline database; furthermore, a hand search was conducted. Last search took place on 23 November 2022. Two categories of hygiene-related keywords were formed (category A: mask, face shield, goggles, eyewear, personal protective equipment; category B: contamination, aerosol). Each keyword from one category was combined with all keywords from the other one. In addition, the keyword "dental" was always added. First, a title and abstract screening was performed. Afterward, a full-text analysis was followed for the included studies. A total of 648 search hits were found in the Medline database. 47 were included after title and abstract screening. 22 studies were excluded after full-text analysis, 25 studies were included. The hand search resulted in 4 studies that were included. Bacterial contamination of PPE after treatment has been adequately studied, contamination with blood less. Microorganisms mainly originate from the oral and cutaneous flora; however, a transmission of potential pathogens like Staphylococcus aureus or Escherichia coli was also described. Studies showing transmission pathways starting from PPE and its various components are lacking. No measures have yet been described that fully protect the protective equipment from contamination. There is growing awareness that PPE itself can be a source of pathogen transmission, and thus possible infection. Therefore, not only wearing of protective clothing, but also conscious handling of it is crucial for transmission and possible infection prevention. However, studies showing transmission pathways starting from PPE and its various components are lacking. Several studies have investigated what measures can be taken to protect the protective equipment itself. So far, none of the methods evaluated can prevent contamination of PPE.

Dental aerosol-producing treatments: Comparison of contamination patterns of face shields and surgical masks

During the COVID-19 pandemic, dental face shields were recommended to protect the eyes. This study aimed to examine to what extent face shield and mask contamination differ when a pre-procedural mouth rinsing with Chlorhexidine (CHX) is conducted before treatment. In this prospective, randomized study, three groups of subjects were formed (rinsing with 0.1% CHX, water, or no rinsing (control) before aerosol-producing treatments). After each of the 301 treatments, the practitioner's face shield was swabbed with eSwab and the mask was brought into contact with agar plates. Sampling was done from the exterior surface only. Samples were cultured for 48 h at 35 °C under aerobic and anaerobic conditions. Bacteria were classified by phenotypic characteristics, biochemical test methods, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Colony-forming units were counted and mean values were compared (WSR, H-test, U-test, p < 0.05). Within each subject group, face shields showed significantly more contamination than surgical masks (control group: 350 CFU, 50 CFU; intervention water: 270 CFU, 40 CFU; intervention CHX: 250 CFU, 30 CFU). Comparison of face shields of the different subject groups did not reveal any statistically significant differences. However, CHX resulted in a statistically significant bacterial reduction on surgical masks compared to the water and control group (control: 50 CFU, intervention water: 40 CFU, intervention CHX: 30 CFU). Contamination of face shields and surgical masks was highest in the control group, followed by the water group, and lowest in the intervention group with CHX. Streptococcus spp. and Staphylococcus spp. dominated, representing the oral and cutaneous flora. Contamination of masks worn with or without face shields did not differ. Presumably, face shields intercept first splashes and droplets, while the masks were mainly exposed to bioaerosol mist. Consequently, face shields protect the facial region and surroundings from splashes and droplets, but not the mask itself. A pre-procedural mouth rinse with CHX had no statistically significant reducing effect on contamination of the face shield, but a statistically significant reducing effect was observed on contamination of the mask.

Detection of viable oral bacteria of the patient on the surgical mask of dentists

INTRODUCTION AND AIM

Bioaerosols contaminate the personal protective equipment (PPE), especially masks. The PPE harbors microorganisms from various sources. However, no previous studies have investigated the specific sources of bacteria found on used masks and their correlation with those from the treated patient.

SETTING, DESIGN, MATERIAL AND METHODS

Intraoral samples from the patient were collected prior to dental aerosol-producing treatments using a nylon flock fiber swab. After treatment, the practitioner's mask was imprinted onto agar plates.

MAIN OUTCOME METHODS

Following cultivation, colony forming units were counted and identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). After the samples were analyzed, the intraoral samples as well as the mask samples were assessed for the presence of identical species, which were subsequently quantified.

RESULTS

126 treatments were included. One species match occurred most frequently (26.2%), followed by two (11.9%%) and three or more (3.97%). In the intraoral samples, Neisseria subflava occurred most often, within mask samples Staphylococcus epidermidis were detected most. Staphylococcus aureus could be cultivated three times more often in intraoral samples than on the mask.

DISCUSSION AND CONCLUSION

Oral microorganisms originating from the patient's oral cavity can be found on the outside of masks. When using PPE during treatments, it should therefore always be in mind that potentially pathogenic microorganisms may land on the mask becoming a source of for itself.

High-volume evacuation mitigates viral aerosol spread in dental procedures

Dental healthcare personnel (DHCP) are subjected to microbe-containing aerosols and splatters in their everyday work. Safer work conditions must be developed to ensure the functioning of the healthcare system. By simulating dental procedures, we aimed to compare the virus-containing aerosol generation of four common dental instruments, and high-volume evacuation (HVE) in their mitigation. Moreover, we combined the detection of infectious viruses with RT-qPCR to form a fuller view of virus-containing aerosol spread in dental procedures. The air-water syringe produced the highest number of aerosols. HVE greatly reduced aerosol concentrations during procedures. The air-water syringe spread infectious virus-containing aerosols throughout the room, while other instruments only did so to close proximity. Additionally, infectious viruses were detected on the face shields of DHCP. Virus genomes were detected throughout the room with all instruments, indicating that more resilient viruses might remain infectious and pose a health hazard. HVE reduced the spread of both infectious viruses and viral genomes, however, it did not fully prevent them. We recommend meticulous use of HVE, a well-fitting mask and face shields in dental procedures. We advise particular caution when operating with the air-water syringe. Due to limited repetitions, this study should be considered a proof-of-concept report.

Particle generation and dispersion from high-speed dental drilling

OBJECTIVE

To investigate the characteristics of particle generation and dispersion during dental procedure using digital inline holography (DIH) METHODS: Particles at two locations, near-field and far-field, which represent the field closer to the procedure location and within 0.5 m from the procedure location respectively, are studied using two different DIH systems. The effect of three parameters namely rotational speed, coolant flow rate, and bur angle on particle generation and dispersion are evaluated by using 10 different operating conditions. The particle characteristics at different operating conditions are estimated from the holograms using machine learning-based analysis.

RESULTS

The particle concentration decreased by at least two orders of magnitude between the near-field and far-field locations across the 10 different operating conditions, indicating significant dispersion of the particles. High rotational speed is found to produce a larger number of smaller particles, while lower rotational speeds generate larger particles. Coolant flow rate is found to have a greater impact on particle transport to the far-field location. Irregular shape dental particles account for 29% of total particles at far-field location, with the majority of these irregular shape particles having diameters ranging from 12 to 18 μm.

CONCLUSIONS

All three parameters have significant effects on particle generation and dispersion, with rotational speed having a more significant influence on particle generation at near-field and coolant flow rate playing a more important role on particle transport to the far-field.

CLINICAL RELEVANCE

This study provides valuable insights on particle characteristics during high-speed drilling. It can help dental professionals minimize exposure risks for themselves and patients by optimizing clinical operating conditions.

Medical Face Masks Do Not Affect Acid-Base Balance Yet Might Facilitate the Transmission of Staphylococcus aureus in Hospital Settings during the COVID-19 Pandemic

INTRODUCTION

Due to the SARS-CoV-2 coronavirus pandemic, the wearing of masks has become a common phenomenon. Most of the undesirable effects of using a protective face covering are usually related to the prolonged time of its wearing, and the adverse consequences of face coverings should be considered two-fold. The aim of the study was to evaluate the rate of contamination of the three types of face coverings (surgical, N95, and FFP2 masks) with the microorganism-aerobic bacteria, yeasts, and molds-after the 3 h exposure time. The study aimed to investigate the effects of wearing FFP2 masks (KN95) on respiratory function and the acid-base balance of the human body.

RESULTS

The presence of S. aureus was confirmed in both nasal carriers and non-carriers which may demonstrate the cross-contamination and spread of this bacterium via hands. S. aureus was found on external and internal surfaces of face masks of each type, and therefore could also be transmitted via hands from external sources. The 3 h exposure time is not sufficient for Gram-negative rods and mold contamination. Moreover, there were no significant differences in most of the parameters studied between the first and second examinations, both in spirometry and capillary blood gas analysis (p > 0.05).

CHX and a Face Shield Cannot Prevent Contamination of Surgical Masks

Background

Bacterial contamination on surgical masks puts a threat to medical staff and patients. The aim of the study was to investigate its contamination during dental treatments, wearing a face shield and performing a pre-procedural mouth rinsing with chlorhexidine (CHX).

Methods

In this prospective, randomized study, 306 treatments were included, 141 single-tooth (restorations) and 165 total dentition treatments (preventive or periodontal supportive ultrasonic application). A total of three groups (each: n = 102) were formed: participants rinsed for 60 s with 0.1 % CHX or with water before treatment, and, for control, a non-rinsing group was included. In view of the COVID-19 pandemic, a face shield covering the surgical mask enhanced personal protective equipment. After treatment, masks were imprinted on agar plates and incubated at 35°C for 48 h. Bacteria were classified by phenotypic characteristics, biochemical assay methods, and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS). Colonies (CFU) were counted and mean values were compared (Kruskal–Wallis-, U test, p < 0.05).

Results

Chlorhexidine led to a statistically significant reduction of bacterial contamination of the surgical mask (mean: 24 CFU) in comparison with water (mean: 47 CFU) and non-rinsing (mean: 80 CFU). Furthermore, rinsing with water reduced CFU significantly in comparison with the non-rinsing group. There were no significant differences between single or total dentition treatments. Streptococcus spp., Staphylococcus spp., Micrococcus spp., and Bacillus spp. dominated, representing the oral and cutaneous flora.

Conclusion

A pre-procedural mouth rinse is useful to reduce the bacterial load of the surgical mask. However, contamination cannot be prevented completely, even by applying a face shield. In particular, during pandemic, it is important to consider that these additional protective measures are not able to completely avoid the transmission of pathogens bearing aerosols to the facial region. If antiseptic rinsing solutions are not available, rinsing with water is also useful.

Blood and saliva contamination on protective eyewear during dental treatment

Objectives

Dental treatments are inherently associated with the appearance of potentially infective aerosols, blood and saliva splashes. The aim of the present study was to investigate the quantitative contamination of protective eyewear during different dental treatments and the efficacy of the subsequent disinfection.

Materials and methods

Fifty-three standardized protective eyewear shields worn by students, dentists and dental assistants during different aerosol-producing dental treatment modalities (supragingival cleaning, subgingival periodontal instrumentation, trepanation and root canal treatment and carious cavity preparation; within all treatments, dental evacuation systems were used) were analysed, using common forensic techniques. For detection of blood contamination, luminol solution was applied onto the surface of safety shields. A special forensic test paper was used to visualize saliva contamination. Further analysis was conducted after standardized disinfection using the same techniques. Statistical analysis was performed using SPSS.

Results

Macroscopically detectable contamination was found on 60.4% of protective eyewear surfaces. A contamination with blood (median 330 pixels, equivalent to 0.3% of the total surface) was detected on all shields after dental treatment. Between various dental treatments, the contamination with blood tend to be statistically significant (p = 0.054). Highest amount of blood was observed after professional tooth cleaning (median 1,087 pixels). Significant differences of saliva contamination were detected between the different measurements (p < 0.001) with contamination only after dental treatment. Due to the low variance and right-skewed distribution for saliva contamination, no statistical analysis between different treatments could be performed. After disinfection, 0.02% blood contamination and no saliva contamination were detected.

Conclusions

Disinfection is effective against blood and saliva contamination. Macroscopically, clean protective eyewear contains up to 12% surface contamination with blood. Based on the results, it may be concluded that protective eyewear is essential for each dental practitioner.

Clinical relevance

As standard for infection prevention in the dental practice, disinfection of protective eyewear after each patient is necessary.