Abstract
Dental procedures produce a large amount of spatter and aerosols that create concern for the transmission of airborne diseases, such as Covid-19. This study established a methodology with the objective of evaluating new associated strategies to reduce the risk of cross-transmission in a health environment by simulating spread of potentially contaminated dispersion particles (PCDP) in the environment. This crossover study, was conducted in a school clinic environment (4 clinics containing 12 dental chairs each). As a positive control group (without barriers), 12 professionals activated at the same time the turbine of dental drill, for one minute, with a bacterial solution (Lactobacillus casei Shirota, 1.5x108 CFU/mL), which had been added in the cooling reservoir of the dental equipment. In the experimental groups, the professionals made use of; a) an individual biosafety barrier in dentistry (IBBD) which consists of a metal support covered by a disposable PVC film barrier; b) a Mobile Unit of Disinfection by Ultraviolet-C, consisting of 8 UV lamps-C of 95W, of 304μW/cm2 of irradiance each, connected for 15 minutes (UV-C) and; c) the association between the two methods (IBBD + UV-C). In each clinic, 56 Petri dishes containing MRS agar were positioned on the lamps, benches and on the floor. In addition, plates were placed prior to each test (negative control group) and plates were also placed in the corridor that connects the four clinics. In the groups without barrier and IBBD + UV-C the passive air microorganisms in Petri dishes was also evaluated at times of 30, 60, 90 and 120 minutes after the end of the dental's drill activation. The mean (standard deviation) of CFU of L. casei Shirota for the positive control group was 3905 (1521), while in the experimental groups the mean using the IBBD was 940 (466) CFU, establishing a reduction on average, of 75% (p<0.0001). For the UV-C group, the mean was 260 (309) CFU and the association of the use of IBBD + UV-C promoted an overall average count of 152 (257) CFU, establishing a reduction on average of 93% and 96%, respectively (p<0.0001). Considering these results and the study model used, the individual biosafety barrier associated with UV-C technology showed to be efficient strategies to reduce the dispersion of bioaerosols generated in an environment with high rate of PCDP generation and may be an alternative for the improvement of biosafety in different healthy environment.
Highlights
Most dental treatments are aerosol-generating procedures (AGPs) that produce a mixture of spatter, drops and aerosols containing saliva, blood, irrigating water, and viable microorganisms [1]
From the Petri dishes arranged in dental clinics before the beginning of the tests, the control group had low Lactobacillus casei Shirota Colony Forming Units (CFU) counts
The group without barriers had mean of 1.3 (1.0) CFU; the IBBD group 11.3 (6.1); the ultraviolet light technology band C (UV-C) group 1.0 (0.8) and in the IBBD + UV-C group 2.3 (2.1), with no statistically significant difference (p>0.05) between the dental clinics used for the experiments
Summary
Most dental treatments are aerosol-generating procedures (AGPs) that produce a mixture of spatter, drops and aerosols containing saliva, blood, irrigating water, and viable microorganisms (including bacteria, fungi, and viruses) [1]. Used dental instruments, including dental handpieces and ultrasonic equipment, generate a large potentially contaminated dispersion particles (PCDP), which pose a risk to professionals and patients [2, 3]. These microparticles are invisible, mapping their spatial distribution within the clinical environment is neglected, developing better ways to mitigate the risk of disease transmission is of great importance. The PCDP generated during the appointments can remain in the air for less time (droplets, 5–100μm) or longer (aerosols, 5μm) and these fall on the surfaces of the environment under the influence of gravity, following a ballistic trajectory from the point of origin. Much more attention was focused on dental aerosol generating procedures (AGPs) because of Covid-19 [6]. Especially when people are close to each other, it has been proven that Covid-19 spreads by aerial transmission [7]
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