Cervical lesions in a care-home resident

Correct answer: C. Glass ionomer cement

• A. Composite gives superior aesthetics and wear resistance, but it demands meticulous MOISTURE CONTROL and a multi-step adhesive protocol. A subgingival cervical margin in a xerostomic patient who cannot tolerate rubber dam or a long appointment is precisely the situation in which composite fails.
• B. Indirect ceramic restorations are wholly inappropriate in cost, complexity and the number of appointments required.
• C. CORRECT. GLASS IONOMER is the material of choice here, and every property that matters is in its favour. It bonds CHEMICALLY to dentine and cementum without a separate adhesive step, so placement is quick. It is far more TOLERANT OF MOISTURE than resin, which matters when isolation is impossible. It RELEASES FLUORIDE over time into a mouth at continuing high caries risk. Its weaknesses — lower strength and inferior aesthetics — are of little consequence at a cervical margin in this patient.
• D. Amalgam requires mechanical retention cut into sound tooth structure, which is unnecessarily destructive for a shallow cervical lesion, and it gives no fluoride release in a high-risk mouth.

Note: RESIN-MODIFIED GLASS IONOMER is a sensible compromise, giving improved strength and aesthetics while keeping fluoride release and moisture tolerance. And remember SILVER DIAMINE FLUORIDE for the lesion that cannot be restored, or the patient who cannot tolerate restoration — arrest first, restore later if circumstances allow. The most important long-term intervention in this case is not a material at all: it is training the CAREGIVER in supervised daily brushing with 5000 ppm fluoride toothpaste.

Correct answer: D. The definitive restorative material

• A. The bonding agent is the last step BEFORE the restorative material — applied to conditioned enamel and dentine and light cured. But the restorative material still goes on top of it, which is what the question asks.
• B. Calcium hydroxide goes FIRST, and only over the deepest area closest to the pulp. It is placed as a thin liner and must then be covered, because it is soluble and mechanically weak.
• C. A base sits over the liner and beneath the restorative material, replacing missing dentine bulk and providing thermal insulation where the remaining dentine is thin.
• D. CORRECT. The DEFINITIVE RESTORATIVE MATERIAL is always placed last, over everything beneath it. The sequence runs from the pulp outward: LINER (calcium hydroxide or a calcium silicate, only over the deepest dentine) → BASE if bulk replacement or insulation is needed → ADHESIVE, meaning etch, prime and bond → RESTORATIVE MATERIAL. Each layer protects and is covered by the next.

Note: Liners and bases are used far more sparingly now than in traditional teaching. Current practice restricts calcium hydroxide or a calcium silicate to a genuine or very near pulp exposure; over the rest of the preparation the ADHESIVE itself serves as the liner, and placing unnecessary bulk beneath a restoration simply reduces the bonded tooth surface available.

Correct answer: B. Because of its high configuration (C) factor

• A. Pulpal proximity determines whether a liner is needed and influences post-operative sensitivity, but it has no bearing on the shrinkage geometry of the preparation.
• B. CORRECT. The CONFIGURATION FACTOR is the ratio of BONDED to UNBONDED (free) surfaces in a preparation. The higher that ratio, the less the composite can flow to relieve polymerisation shrinkage, and the more stress is transferred to the adhesive interface — producing marginal gaps, debonding, post-operative sensitivity and white lines at the margin. A Class V is a box bonded on five surfaces with only one free surface, giving a C-factor of about 5, the highest of the cavity classes. Class I is similarly unfavourable. A Class IV, bonded on only one or two surfaces with several free, sits around 0.5 to 1.
• C. A LOW configuration factor is the favourable situation — it means the composite has ample free surface to flow from and can relieve shrinkage stress as it polymerises.
• D. The gingival margin of a Class V often does lie in dentine or cementum rather than enamel, and that genuinely does weaken the bond there — but it is a separate problem from the geometry of shrinkage stress, which is what the question asks about.

Note: Mitigation: place in small INCREMENTS rather than bulk, use a flowable or stress-absorbing liner at the base of the preparation, and consider soft-start curing. Note how this connects to the previous question — it is a further reason GLASS IONOMER suits a Class V, since it sets by an acid-base reaction and does not generate free-radical polymerisation shrinkage in the same way.