Radiographic interpretation, discoloration and denture assessment

Correct answer: A. About 8 years

• A. Correct. Permanent mandibular canines erupt at roughly 9 to 10 years. An unerupted canine places the child before that — around 8 years, consistent with a mixed dentition in which first molars and incisors have already arrived.
• B. At 15 the permanent dentition is complete apart from the third molars.
• C. At 4 the dentition would be entirely primary, with no permanent teeth showing at all.
• D. By 12 the canines and premolars are normally in place and the second molars are erupting.

Note: Useful anchors: first permanent molars and mandibular central incisors at 6-7, mandibular canines at 9-10, second molars at 11-13.

Correct answer: B. Periapical (radicular) cyst

• A. Condensing osteitis is radiopaque, not radiolucent — a sclerotic bone response to low-grade pulpal inflammation.
• B. Correct. A radiolucency at the apex of a pulpally necrotic tooth is inflammatory in origin. A well-defined, larger lesion favours a radicular cyst, which arises from proliferation of the epithelial rests of Malassez.
• C. Periapical cemento-osseous dysplasia occurs at vital teeth, most often the mandibular anteriors in middle-aged Black women, and passes through radiolucent, mixed and radiopaque stages.
• D. Idiopathic osteosclerosis is also radiopaque, and by definition occurs at a tooth with a normal, vital pulp.

Note: Radiographs alone cannot separate a granuloma from a cyst — that requires histology. Vitality testing is what distinguishes an inflammatory lesion from a fibro-osseous one.

Correct answer: C. Veneers

• A. Microabrasion removes only the outermost enamel and is effective for superficial fluorosis-type defects, not for deep dentinal staining.
• B. Root canal treatment addresses discoloration caused by pulpal necrosis in a single tooth, which is a different problem entirely.
• C. Correct. Tetracycline staining is intrinsic and distributed throughout the dentine, so it cannot be removed. Veneers mask it — and for severe banded discoloration, full-coverage crowns may be needed.
• D. Bleaching can lighten mild cases, but severe banded tetracycline staining responds poorly and often unevenly.

Note: The staining arises when tetracycline is taken during odontogenesis — it chelates calcium and is incorporated into the mineralising tissue, which is why the drug is avoided in pregnancy and in children under 8.

Correct answer: D. The inferior alveolar nerve

• A. The lingual nerve carries general sensation from the anterior two-thirds of the tongue, the floor of the mouth and the lingual gingiva — not pulpal sensation.
• B. The buccal nerve supplies the buccal soft tissue of the mandibular molars only, which is why a separate injection is needed for soft tissue there.
• C. The mylohyoid nerve is chiefly motor to mylohyoid and the anterior belly of digastric, though accessory innervation from it is one explanation for failed inferior alveolar blocks.
• D. Correct. The inferior alveolar nerve, a branch of V3, runs in the mandibular canal and supplies the pulps of all mandibular teeth through its dental branches.

Correct answer: D. Stability

• A. Retention is resistance to vertical dislodgement away from the tissue — the denture dropping when the mouth opens.
• B. Aesthetics concerns appearance and has nothing to do with the mechanics of displacement.
• C. Support is resistance to vertical seating forces, provided by the ridge and the palate; loss of support causes soreness and settling.
• D. Correct. Stability is resistance to horizontal and rotational displacement. Lateral rocking is the definition of instability, usually from a poorly adapted base, an unbalanced occlusion, or a resorbed ridge.