Endodontics · patient case question
The premolar bitewing from the full mouth series shows several dark bands running across the image. What is the most likely explanation?
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: B. Artifact produced by bending the film or sensor
- A. Incorrect. The mandibular canal is a single well-defined radiolucent band with corticated superior and inferior borders, running in a consistent anatomic path, not scattered irregular lines.
- B. Correct. Bending the receptor distorts the geometry between the emulsion and the beam, producing characteristic dark bands or streaks in the resulting image. This is a common finding in a full mouth series where receptors are forced into the palatal vault or the floor of the mouth.
- C. Incorrect. A foreign body would appear radiopaque — white — as a discrete object with definable borders, not as diffuse dark bands.
- D. Incorrect. Cervical burnout is a radiolucent band at the cervical region between the enamel edge and the alveolar crest, caused by differential absorption. It occupies a specific anatomic location rather than crossing the whole image.
Note: Common receptor artifacts to recognize: bending produces dark bands, fingernail pressure produces a crescent-shaped dark mark, static electricity produces branching lines, and double exposure produces two superimposed images.