Which cement is MOST appropriate for the definitive cementation of a ceramic onlay?

Correct answer: A. Resin cement

• A. CORRECT. RESIN CEMENT is required for bonded ceramic restorations. Ceramic onlays depend on adhesive bonding for their strength: the resin cement reinforces the ceramic, supports thin unsupported cusps, and links the restoration to etched enamel and dentin. Resin cement also offers the highest bond strength, lowest solubility and best esthetics. Combined with hydrofluoric acid etching and a silane coupling agent on the intaglio surface, it produces a durable ceramic-to-tooth union.
• B. Conventional glass ionomer releases fluoride and bonds chemically to tooth structure, but it lacks the strength and bond to ceramic needed to support an onlay, and it is more soluble.
• C. Zinc oxide–eugenol is a PROVISIONAL cement. Eugenol also INHIBITS the polymerization of resin, so it must be avoided entirely when a resin-bonded restoration is planned.
• D. Zinc phosphate is a historical luting agent with no adhesion — it retains restorations purely mechanically and cannot reinforce ceramic.

Note: Ceramic bonding sequence: etch the intaglio with hydrofluoric acid (etch time varies by ceramic), rinse, apply SILANE, then the adhesive resin cement. For zirconia the protocol differs — HF does not etch it; use air abrasion and an MDP-containing primer instead.