Final answer:
In an axio-lateral mandible X-ray, the best demonstrated side is the one to which the mandible is moved laterally away from the midline, emphasizing important landmarks like the coronoid and condylar processes.
Step-by-step explanation:
When performing an axio-lateral mandible X-ray, the side that is best demonstrated is the side towards which the mandible is moved laterally away from the midline - this is known as the lateral excursion of the mandible. The mandible is the only movable bone of the skull, and during lateral excursion, it moves to either the right or left side, away from the midline. Conversely, medial excursion refers to the movement of the mandible back to the midline. In radiology terms, the axio-lateral projection refers to an X-ray view where the beam enters the axilla (armpit area) and exits laterally, providing a view that demonstrates the side of the mandible to which it has been moved laterally (either the right or left side). Important anatomical structures to consider include the coronoid process and the condylar process, which are important landmarks for this imaging technique.