Final answer:
Soft tissue structures are not helpful for mounting radiographs compared to identifiable landmarks such as the apices of the teeth, occlusal surfaces, and contacts between adjacent teeth.
Step-by-step explanation:
The question is asking which of the listed landmarks does not help with the mounting of radiographs. The correct answer here is soft tissue structures. When mounting radiographs, especially dental X-rays, landmarks such as the apices of the teeth, occlusal surfaces of the teeth, and contacts between adjacent teeth are crucial for accurate positioning and orientation.
These landmarks are bony or hard tissues that are easily identifiable on X-rays.
In contrast, soft tissue structures are less distinct and less reliable for mounting radiographs.