Why are patients instructed to lift and extrude their tongue during a mandibular impression?

Patients are instructed to lift and extrude their tongue during a mandibular impression to ensure that the lingual aspect of the alveolar process is captured accurately. This action exposes the area more effectively, allowing for a detailed impression that includes the contours of the tongue and the surrounding soft tissues. An accurate representation of the lingual aspect is essential, as it contributes to the overall fit and function of any dental prosthetic or restorative work that will be created from the impression.

The other options do play roles in the comfort and usability of the impression process but do not address the specific anatomical accuracy needed for capturing the lingual aspect of the alveolar process as effectively as this technique does. For instance, while lifting the tongue might make the process more comfortable and can help with easier tray removal, those factors do not directly contribute to the primary goal of ensuring a precise impression of the anatomical structures needed for future dental work.