Objectives Surgical masks are usually contaminated during dental treatment. So far it has not been investigated whether a surgical mask itself can be a source of microbial transmission. The aim of this study was therefore to investigate the microbiological contamination of surgical masks during dental treatment and the transfer of microorganisms from the mask to the hands. Materials and methods Five dental treatment modalities were studied: carious cavity preparation (P-caries, n = 10), tooth substance preparation (P-tooth, n = 10), trepanation and root canal treatment (P-endo, n = 10), supragingival ultrasonic application (US-supra, n = 10), and subgingival periodontal ultrasonic instrumentation (US-sub, n = 10). Bacterial contamination of mask and gloves worn during treatment was tested by imprinting on agar plates. Additionally, before masks were tested, their outer surface was touched with a new sterile glove. This glove was also imprinted on agar. Bacteria were identified by MALDI TOF mass spectrometry. Colony-forming units (CFU) were scored: score 0: 0 CFU, score 1: < 102 CFU, score 2: > 102 CFU, score 3: dense microbial growth. Results All masks and all gloves used during treatment displayed bacterial contamination (sample scores 0/1/2/3: masks 0/46/3/1 and gloves 0/31/10/9). After touching the masks with new sterile gloves, microorganisms were recovered with the following contamination scores: P-caries: 4/6/0/0, P-tooth: 2/8/0/0: P-endo: 7/3/0/0, US-supra: 0/9/1/0, US-sub: 2/8/0/0. No statistically significant differences were detected between the treatment modalities. Streptococci spp. and Staphylococci spp. representing the oral and cutaneous flora dominated. Conclusions Surgical masks are contaminated after aerosol-producing dental treatment procedures. Used masks have a potential to be a source of bacterial contamination of the hands. Clinical relevance Dental staff should avoid touching the outer surface of masks with their hands to prevent transmission of pathogens. It is recommendable to change the mask after each treated patient followed by hand disinfection.

Background: Bacterial contamination of dental professionals' facial skin and protective equipment from treatment-related aerosols and droplets are poorly studied. Methods: This prospective study analyzed samples from 67 consecutive aerosol-producing dental treatments. Sterile nylon swabs served to collect samples from dental professionals' foreheads before and after exposure. Contact samples were obtained from used surgical masks. Samples were incubated on agar under aerobic and anaerobic conditions. Bacteria were classified by MALDI-TOF mass spectrometry. We determined the frequencies of obligate and facultative oral bacteria and scored bacterial growth (0: none; 1: < 100 colonies; 2: >100 colonies; 3: dense). Results: Bacteria were detected in 95% of skin-swab and 76% of mask samples. Median bacterial scores were 2 for forehead samples before and after treatment, and 1 for masks. Obligate and facultative oral bacteria were more frequent (6% and 30%) in samples from exposed forehead skin, which also showed increased bacterial scores (28%). 5% of samples contained methicillin-sensitive Staphylococcus aureus; 3% contained obligate anaerobes. Conclusion: Exposed forehead skin was significantly less contaminated with obligate oral bacteria than expected based on surgical mask findings. Exposed forehead skin showed increased contamination attributable to aerosol-producing procedures. The forehead's physiological skin microbiota may offer some protection against bacterial contamination.

BackgroundBacterial 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).MethodsIn 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 &lt; 0.05).ResultsChlorhexidine 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.ConclusionA 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.

Background Microbial contamination of dental professionals’ facial protective equipment and skin from aerosols and droplets generated during dental treatment has not been studied in all aspects so far. Our aim was therefore to investigate and compare treatment-related bacterial contamination of the forehead skin and surgical mask of dental practitioners. Methods We analyzed samples from 67 consecutive aerosol-producing conservative-preventive dental treatments. Sterile nylon swabs were used to collect samples from the forehead skin before and after performing treatment. Contact samples were obtained from the used surgical face masks. Samples were cultivated on agar under aerobic and anaerobic conditions. Bacteria were classified by MALDI-TOF mass spectrometry. The frequency of detection of obligate and facultative oral bacteria, as well as an increase in bacterial abundance, were examined (bacterial scoring: 0: no growth on agar; 1: <102 colonies; 2: >102 colonies; 3: dense bacterial growth). Results Bacteria were detected in 95% of the skin swabs and 76% of mask samples. Median bacterial scores were 2 for the forehead skin samples before and after treatment, and 1 for samples obtained from masks. Obligate and facultative oral bacteria were more frequent (6% and 30%) in samples from forehead skin after treatment. Samples taken from the forehead skin after treatment showed increased scores for these bacteria (28%). Five percent of samples were positive for methicillin-sensitive Staphylococcus aureus (MSSA). Obligate anaerobes were present in 3% of samples. Conclusions Although exposed during treatment, the forehead skin was significantly less contaminated with obligate oral bacteria than expected based on the surgical face mask findings. Forehead skin samples showed an increase in bacteria in the after treatment, which can be attributed to aerosol-producing procedures. We hypothesize that the forehead’s physiological skin flora may offer some protection against contamination with other microorganisms.