California Registered Dental Assistant (RDA) Written Practice Exam

What primarily makes up dental unit waterline biofilm?

1. Water bacteria

2. Saliva

3. Bloodborne pathogens

4. Chemical residues

The correct answer is: Water bacteria

Dental unit waterline biofilm is primarily made up of microorganisms found in water known as water bacteria. This biofilm is formed by bacteria attaching themselves to the internal surfaces of the waterline tubes, leading to a buildup of microbes. Saliva, bloodborne pathogens, and chemical residues can also contribute to the formation of biofilm, but they are not the primary components. Saliva may contain bacteria that can contribute to biofilm growth, but it is not the main component. Bloodborne pathogens can enter the waterlines from contaminated hands or instruments, but they do not primarily make up the biofilm. Chemical residues may accumulate in the waterlines, but they are not the primary source of biofilm formation. Therefore, the best answer is A Water bacteria.