What is removed to increase bonding?

• A. Smear layer (1-2 mm)
• B. Dentin surface irregularities
• C. Enamel layer
• D. Saliva

Answer: (A)

Bonding to dentin works best when the adhesive can penetrate the surface and form a strong hybrid layer. The smear layer is a film of debris left on the dentin after tooth preparation; it can block resin infiltration into the dentin and seal tubules, preventing effective bonding. Removing this layer—typically with an acid etch or appropriate primers—exposes the underlying collagen and dentinal tubules, allowing the adhesive resin to infiltrate, create a robust hybrid layer, and form resin tags that enhance adhesion.

Other options don’t fit because they describe surface features or barriers rather than the actual block to bonding. Creating or relying on dentin surface irregularities helps mechanical interlock after bonding, not removing a barrier. Removing the enamel layer isn’t the goal; rather, etching enamel increases micromechanical retention. Saliva contamination affects bonding but isn’t the substance whose removal directly increases bonding in the same way the smear layer does.