Which of the following describes the radiographic finding of a maxillary left first bicuspid defect described as 2-wall infrabony defect?

• A. 2-wall infrabony defect
• B. 1-wall defect
• C. 3-wall infrabony defect
• D. Horizontal bone loss

Answer: (A)

Infrabony defects are described by how many osseous walls remain around the tooth. A two-wall infrabony defect means two walls of bone still bound the defect, creating a vertical trough along the root. On a radiograph this shows up as a localized vertical radiolucency beneath the alveolar crest that is bounded on two sides by remaining bone walls. This is a vertical bone loss pattern, not horizontal.

Horizontal bone loss would look like a generalized reduction in bone height around the tooth without a distinct vertical trough. A one-wall defect would have only a single bounding wall, resulting in a narrower, less contained radiolucency. A three-wall infrabony defect would be bounded by three walls and appear more crater-like or well-contained. Therefore, the radiographic finding described aligns with a two-wall infrabony defect.