In dentistry, microorganisms and diseases may be transmitted in four ways:
- Direct contact with microorganisms from an infected person .
- Indirect contact with contaminated objects, such as instruments, equipment handles, or surfaces.
- Droplet infection from sprays or spatter containing microorganisms, which travel a short distance before settling.
- Airborne routes involve aerosols (droplets), which are very small and can remain suspended in the air and travel further before settling.
For a disease to be transmitted, a number of conditions must be present. This “chain of infection” includes:2
- a pathogen in sufficient numbers and of sufficient virulence to cause disease
- a place for the pathogen to reside and multiply (a “reservoir”)
- a way for the pathogen to leave its reservoir and reach a new host (the mode of transmission), such as through dental treatment
- a portal of entry through which the microorganisms can enter a new host, (e.g., needlestick/sharps injury or contact with mucosa or nonintact skin).3
- a susceptible host
Infection control strategies interrupt this cycle, thus preventing disease transmission.