What may occur if a patient closes their lips and spits into the saliva ejector?

When a patient closes their lips and spits into the saliva ejector, retraction towards the patient's mouth may occur due to the negative pressure that can develop in the system. This situation arises because saliva ejectors operate by creating a vacuum that pulls fluid away from the mouth. If the patient's lips are sealed around the ejector while generating this negative pressure, it can lead to a backflow of fluids toward the oral cavity instead of effectively evacuating them.

This phenomenon is important to understand in infection control practices, as it can potentially expose healthcare workers and the patient to contaminants present in saliva or other fluids. Proper use and positioning of the saliva ejector, along with instructing the patient on the correct way to use it, can help prevent such occurrences and maintain a safe and hygienic environment during dental procedures.