A radiograph shows distal caries with an adjacent vertical (J-shaped) periodontal bony defect on the distal of the same tooth. What is the most likely cause of the defect?

Correct answer: A. The carious lesion / local plaque retention

• A. Correct. A localized vertical/angular defect adjacent to caries reflects a local plaque-retentive factor (the carious lesion/overhang) driving site-specific bone loss.
• B. Smoking causes generalized periodontal destruction, not an isolated single-surface defect tied to caries.
• C. Pure occlusal trauma widens the PDL but does not by itself create this caries-associated angular defect.
• D. A clear local etiology (caries) is present, so 'idiopathic' is incorrect.