A periapical radiograph shows a radiolucency at the apex of tooth #10. The tooth responds normally to vitality testing and is asymptomatic. Most likely explanation?

Correct answer: B. The lateral fossa of the maxilla superimposed over the apex

• A. Tube-to-patient distance affects magnification and sharpness, not the appearance of a localized radiolucency.
• B. CORRECT. The lateral fossa (incisive fossa) is a normal depression in the maxilla just lateral to the anterior nasal spine, overlying the lateral incisor root. The thinner bone there projects as a diffuse radiolucency over the apex. The decisive finding is that the tooth is VITAL and asymptomatic — anatomy, not pathology.
• C. A lateral periodontal cyst appears along the LATERAL root surface between vital teeth, most often in the mandibular premolar-canine region, and is well-corticated.
• D. Periapical pathology of endodontic origin requires a necrotic pulp. A tooth responding normally to cold and EPT rules this out.

Note: Anatomical radiolucencies that mimic periapical lesions on the maxillary anteriors: lateral fossa, incisive foramen, and the nasal fossa. Vitality testing is what separates all of them from pathology.