In describing an abnormality's effect on surrounding structures, which structure's borders can be displaced or widened?

• A. Teeth
• B. Lamina dura
• C. Periodontal ligament space
• D. Inferior alveolar canal & mental foramen borders

Answer: (D)

When a lesion grows inside bone, it can push against nearby boundaries and cause them to shift or widen. The inferior alveolar canal and the mental foramen are hollow and defined passages within the mandible, so they respond to a growing lesion by being remodeled and their borders can appear displaced or the canal itself may look widened on radiographs.

This is why the borders of the mandibular canal and mental foramen are the structures most likely to show this outward expansion. Other structures, like teeth or the thin lamina dura and surrounding periodontal ligament space, change in different ways (tooth displacement, loss or irregularity of the lamina dura, or widening of the PDL space) but not in the same characteristic border displacement or canal widening that accompanies a lesion expanding within the mandible.