What should be done to the impression material before pouring it into the stone model?

Before pouring the impression material into the stone model, it is essential to remove excess saliva and disinfect the impression. This step is crucial for several reasons. First, excess saliva can interfere with the setting of the stone, potentially creating bubbles or voids that compromise the final model's accuracy. By drying the impression surface, you ensure a better interface between the impression material and the dental stone, allowing for a more precise reproduction of the oral structures.

Disinfecting the impression is equally important as it maintains a hygienic environment and prevents contamination. This is particularly significant in dental practices as it minimizes the risk of transmitting pathogens to patients and staff. Proper disinfection also ensures that the impression can be handled safely and that any residual biological materials do not affect the quality of the stone model.

The other options do not adequately address the preparation needed for the impression prior to pouring. Heating or cooling the impression could potentially alter its dimensions or properties, and adding more alginate would not be appropriate once the impression is made—it could lead to an inaccurate representation of the oral anatomy. Therefore, removing excess saliva and disinfecting the impression is the most appropriate step to guarantee a successful outcome.