Final answer:
The buccal depression in the primary mandibular first molar typically becomes a buccal groove in the adult permanent mandibular first molar. During jaw development, structures like the mental protuberance, coronoid process, and mandibular fossa change to support facial structure and function.
Step-by-step explanation:
The primary mandibular first molar (Man M1) in a child has a buccal depression which, during the transition to the permanent mandibular first molar in adulthood, usually turns into a buccal groove. As the child's jaw develops, several anatomical structures, such as the mental protuberance, the coronoid process of the mandible, and the mandibular fossa, all become more pronounced. The mental protuberance becomes better defined, contributing to the appearance of the chin, the coronoid process becomes more pronounced facilitating muscle attachment, and the mandibular fossa deepens, supporting the temporomandibular joint function.