Infection Prevention Basics

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.

Figure 1.
Image: Breaking the "chain of infection".
Breaking the “chain of infection”