Which one of the following is the first action that must be carried out to an alginate impression that has just been removed from the patient's mouth in an effort to render it safe to be handled by the laboratory staff?

When an alginate impression is removed from the patient’s mouth, the first action should be to rinse under running water to remove gross debris. This step is critical because it helps to eliminate saliva, blood, and food particles that may be present on the impression. Removing these contaminants is essential for ensuring that the impression is clean before any further disinfection processes are conducted.

Proper handling of the impression not only prevents the risk of cross-contamination and infection but also prepares it for subsequent storage or disinfection measures. Rinsing establishes a clean base, allowing any chemicals or other disinfecting agents applied later to work more effectively.

While covering with damp gauze can help prevent the impression from drying out and disinfecting it is important for safety, those actions should occur after the initial rinsing process to ensure the best results in terms of hygiene and impression integrity. Rinsing first prioritizes immediate cleanliness and prepares the impression for safe handling by laboratory staff.