What are the four key steps to achieve resin-dentin bonding with contemporary adhesive systems?

• A. Rinse only, then air-dry completely, apply primer
• B. Etch with hydrofluoric acid, rinse, air-dry, apply cement
• C. Etch with phosphoric acid, rinse and gently dry to maintain a moist dentin surface, apply primer/adhesive, and light-cure to form the hybrid layer.
• D. Apply primer, air-dry, then rinse, and apply composite

Answer: (C)

Resin-dentin bonding relies on forming a resin-infused hybrid layer by properly preparing the dentin surface. Start with phosphoric acid etching to remove the smear layer and create a porous, demineralized collagen network. Rinse away the acid and gently dry to leave a moist dentin surface—too much drying collapses collagen and hinders resin infiltration. Then apply the primer/adhesive so the resin can infiltrate the exposed collagen and establish a robust bond at the dentin, forming the interface. Finally, light-cure to polymerize the adhesive, solidifying the hybrid layer that provides micromechanical retention for the resin composite.

Using an acid for ceramics or omitting steps—like skipping etching, drying appropriately, or bypassing the adhesive application—won’t produce the proper hybrid layer and would weaken bonding.