Topographic aspects of airborne contamination caused by the use of dental handpieces in the operative environment

Abstract

Background: The use of dental handpieces produces aerosols containing microbial agents, bacteria, and viruses representing a high-risk situation for airborne cross infections. The aim of this study was to map and quantify the biological contamination of a dental operatory environment using a biological tracer.

Methods: Streptococcus mutans suspension was infused into the mouth of a manikin, and an operator performed standardized dental procedures using an air turbine, a contra-angle handpiece, or an ultrasonic scaler. The presence of the tracer was measured at 90 sites on the dental unit and the surrounding surfaces of the operatory environment.

Results: All tested instruments spread the tracer over the entire dental unit and the surrounding environment, including the walls and ceiling. The pattern and degree of contamination were related to the distance from the infection source. The maximum distance of tracer detection was 360 centimeters for air turbine, 300 cm for contra-angle handpiece, and 240 cm for ultrasonic scaler. No surface of the operative environment was free from the tracer after the use of the air turbine.

Conclusions: Attention should be paid to minimize or avoid the use of rotary and ultrasonic instruments when concerns for the airborne spreading of pandemic disease agents are present.

Practical implications: This study supports the recommendations of dental associations to avoid treatments generating aerosols, especially during pandemic periods. Guidelines for the management of dental procedures involving aerosols, as well as methods for the modification of aerosols aimed to inactivate the infective agent, are urgently needed.

Keywords: Aerosols; Streptococcus; air microbiology; bacteria; communicable disease control; cross infection; decontamination; dental equipment; disease transmission; patient-to-professional.

Figure 1

The dental unit inside the operative environment. A. Opened agar plates that were used to evaluate the blank can be seen. The manikin head was mounted in a working position, and the bacterial suspension was attached with a drip. B. Arrows show the locations of 2 of the 6 plates that mapped tracer presence on the ceiling. C. The location of the detection sites on the floor, 60 centimeters apart from each other.

Figure 2

Schemes representing the topographic distribution and the tracer levels after the dental procedures using the following: air turbine (A), contra-angle (B), and ultrasonic scaler (C) handpieces. Each red dot represents a measurement site on the dental unit. The 3 sites on the dental light source were averaged. The dimension of the dot represents the tracer level. The spreading pattern of spatter and aerosols close to the tip of each handpiece is displayed under each corresponding scheme. Air turbine produced the finest and farthest-spreading microparticles. CFU: Colony-forming units. cm²: Square centimeter. X: Contamination value of each site.

Figure 3

Schemes representing the topographic distribution and the tracer levels after the dental procedures using the following: air turbine (A), contra-angle (B), and ultrasonic scaler (C) handpieces. Each red dot represents a measurement site of the operatory, including the ceilings, depicted below the main schemes. Values greater than 0.20 colony-forming units per square centimeter (CFU/cm²) are considered as high contamination levels, and the corresponding surfaces are displayed in red. Lower values indicate moderate contamination, and the corresponding surfaces are displayed in orange. White dots and surfaces represent no detection of the tracer.

Figure 4

Tracer presence on the different locations of the dental unit and in the operating environment expressed as colony-forming units per square centimeter (CFU/cm²). Mean (standard deviation) values are indicated, and different superscript letters indicate significant differences between groups (Tukey test, P < .05).