Dentin interaction with universal adhesive containing isopropanol solvent studied by solid-state NMR spectroscopy

Area of Science:

• Biomaterials Science
• Dental Materials
• Adhesion Science

Background:

• Understanding dentin-adhesive interactions is crucial for durable dental restorations.
• Hydrolytic degradation of the dentin matrix is a significant concern for restoration longevity.
• The role of water molecules and solvents in adhesive bonding requires further elucidation.

Purpose of the Study:

• To investigate the chemical and structural changes in dentin's mineral and collagen phases upon application of a mild universal adhesive.
• To elucidate the specific roles of isopropanol and water molecule dynamics in this process.
• To compare the effects of self-etch and etch-and-rinse modes on dentin-adhesive interactions.

Main Methods:

• In vitro application of a mild universal adhesive on dentin using self-etch and etch-and-rinse modes.
• Solid-state nuclear magnetic resonance (NMR) spectroscopy was employed to analyze chemical and structural changes.
• Assessment of mineral phase composition, collagen integrity, and water molecule dynamics.

Main Results:

• The etch-and-rinse mode reduced inorganic apatite and reorganized the mineral phase more than the self-etch mode.
• Isopropanol significantly decreased free water molecules in both modes, preserving collagen structure.
• Adhesive monomers infiltrated the collagen, with no significant changes to the collagen's initial structure observed.

Conclusions:

• Mild universal adhesives, particularly with isopropanol, can mitigate hydrolytic degradation by reducing unstable water molecules.
• Preserving collagen integrity is key to forming a stable dentin resin hybrid layer.
• The findings offer insights for designing more effective and durable dental adhesives.