Endodontics · patient case question
What is the most likely cause of the narrow vertical bony defect on the distal of #18?
Patient case: Generalized Caries and a Throbbing Lower Left
Patient: 41-year-old male
Chief Complaint: “The bottom left throbs for twenty minutes every time I drink anything cold.”
Background: No dental care in 6 years. Drinks four sweetened sodas daily. Healthy, no medications, no allergies. Smokes occasionally at social events only.
Medications: None
Vital Signs: BP 122/78 mmHg · HR 74 bpm · RR 16 · T 98.4°F
Findings: Generalized caries. Tooth #19: deep distal caries, exaggerated and lingering response to cold lasting 20 seconds, no percussion tenderness, no periapical radiolucency. Tooth #18: subgingival distal caries with a narrow vertical bony defect on the distal; would require both crown lengthening and root canal treatment to restore. A full mouth radiographic series shows dark bands running across the premolar film.
Show answer and explanation
Correct answer: A. The subgingival distal caries acting as a plaque-retentive factor
- A. Correct. Subgingival caries creates an irregular, undercut surface that plaque colonizes and that cannot be cleaned. Localized chronic inflammation follows, producing an isolated vertical defect on that specific surface. The location of the defect matching the location of the caries is the diagnostic clue.
- B. Incorrect. Vitamin D deficiency has been associated with periodontal disease at a population level, but it would not produce a solitary defect on one surface of one tooth.
- C. Incorrect. Occlusal trauma alone does not cause loss of attachment. It can widen the periodontal ligament space and accelerate destruction where inflammation is already present, but it is a co-factor rather than an initiator.
- D. Incorrect. Smoking is a major periodontal risk factor, but it produces generalized rather than isolated tooth-specific destruction, and occasional social smoking is a weak exposure.
Note: Keep vertical root fracture in mind as a classic cause of an isolated narrow vertical or J-shaped defect, especially in an endodontically treated tooth with a post. Here the untreated tooth with matching distal caries points to the caries.