What is a hydrophilic resin used in bonding agents?

• A. Hydroxyethyl methacrylate (HEMA)
• B. Bis-GMA
• C. TEGDMA
• D. UDMA

Answer: (A)

Hydrophilic resins in bonding agents are used to improve wetting and penetration of the moist dentin surface. Hydroxyethyl methacrylate (HEMA) is the classic hydrophilic monomer chosen for this purpose because its hydroxyl groups attract water, allowing it to flow into and infiltrate the exposed collagen network and form resin tags even when dentin isn’t perfectly dry. This enhances immediate bond strength to dentin by promoting better adaptation at the bonding interface. A trade-off is that HEMA can absorb water over time, which may lead to hydrolytic degradation and affect durability. The other monomers are less hydrophilic: Bis-GMA is highly viscous and relatively hydrophobic; TEGDMA is used mainly to reduce viscosity and is not as hydrophilic as HEMA; UDMA is also less hydrophilic and contributes more to the resin matrix’s strength and stability rather than wetting capability.