A radiograph shows bone loss around tooth #29 with caries extending to and below the CEJ. What is the cause of the bone loss?

Correct answer: C. The subgingival carious lesion acting as a persistent plaque-retentive irritant

• A. Vertical root fracture typically produces an isolated narrow deep pocket and a J-shaped radiolucency, not this pattern.
• B. An endo-perio lesion would require pulpal necrosis, which is not indicated here.
• C. Correct. A subgingival carious lesion creates an irretrievable plaque trap. Bacteria are shielded from cleaning, driving chronic localized inflammation and vertical bone loss — control requires caries removal and margin relocation.
• D. Occlusal trauma alone widens the PDL space but does not cause attachment loss without a bacterial component.