Which muscle primarily acts on the disto-lingual contour of a lower denture?

The mylohyoid muscle is the primary muscle that acts on the disto-lingual contour of a lower denture. This muscle forms the floor of the mouth and plays a crucial role in supporting the lower denture by providing a stable base. Its contraction helps in elevating the tongue and creating a good seal between the denture and the soft tissue, which is essential for the stability and retention of the lower denture during activities such as speaking and chewing.

The mentalis muscle, involved in actions related to the lower lip and chin, primarily affects facial expressions rather than denture stability. While the masseter muscle is a powerful jaw muscle responsible for chewing, it primarily acts on the mandible itself and does not directly influence the contours of a lower denture. The buccinator muscle, which helps in controlling the movement of food within the mouth and assists in chewing, also does not significantly affect the disto-lingual contour of a lower denture.

In summary, the mylohyoid muscle is vital for the support and stabilization of the lower denture, especially in the region of the disto-lingual contour, making it the correct choice.