Bonding to dentin is difficult primarily due to which factor?

• A. Organic and inorganic compositions
• B. Wetness
• C. Pulpal proximity
• D. Surface roughness

Answer: (B)

The main challenge in bonding to dentin is the surface moisture—dentin is naturally wet from dentinal fluid. When dentin is exposed, the smear layer and open tubules leave a hydrated, fluid-filled surface. For a durable bond, adhesive resin must penetrate the demineralized collagen network and form a stable hybrid layer. Water on the surface competes with the resin for space, can dilute and wash away resin monomers, and can cause phase separation of hydrophobic components, all of which hinder proper infiltration and polymerization. While some moisture is needed to keep the collagen scaffold from collapsing, excessive wetness undermines bond integrity, making wetness the primary factor limiting dentin bonding.

Other factors—such as the inherent organic/inorganic composition, pulpal proximity, or surface roughness—play roles in bonding behavior but are not the main barrier. The moisture level at the dentin surface is the critical variable that most strongly determines whether a durable resin-dentin bond can form.