Periodontics · patient case question
The surgically exposed interproximal defect — bone lost between two adjacent roots with the facial and lingual plates intact — is best described as:
Patient case: Periodontal bone loss assessed on radiograph and at surgery
Patient: Female, 52 years old
Chief Complaint: “My gums have pulled back and my back teeth feel loose.”
Background: Irregular dental attendance. Former smoker. No relevant medical history.
Vital Signs: BP 126/78 mmHg · HR 74 bpm
Findings: Radiographs show angular loss of the crestal bone on the mesial of #30, the crest sloping apically away from the CEJ rather than running parallel to it. At #19, a periodontal probe calibrated in millimetres reads 4 mm in the sulcus, and the gingival margin sits 1 mm CORONAL to the CEJ. A surgical photograph after flap reflection shows an interproximal defect in which the bone is lost between two adjacent roots while the facial and lingual plates remain.
Show answer and explanation
Correct answer: C. An interdental crater
- A. A one-walled or hemiseptal defect has lost the interproximal septum together with one of the facial or lingual plates, leaving a single bony wall. It is the least favourable defect for regeneration.
- B. A three-walled intrabony defect is bounded by the root plus three bony walls, most often on the mesial or distal of a single tooth. It has the best regenerative prognosis, but it is not the pattern described.
- C. CORRECT. An INTERDENTAL CRATER is a two-walled defect in which the interproximal bone is resorbed while the FACIAL and LINGUAL walls remain standing, producing a bowl or trough between them. Craters are the commonest osseous defect, accounting for roughly a third of all defects and about two-thirds of those in the mandible, because the interdental septum has the thinnest cortex and the richest vascular supply.
- D. A circumferential defect surrounds the root on all sides in a moat pattern; it involves a single tooth rather than the septum between two.
Note: Count the remaining WALLS, not the missing bone. Regenerative predictability rises with wall count and with narrowness: three-walled and narrow does best, one-walled and wide does worst, and craters are usually managed by osseous recontouring rather than regeneration.