Gel phase formation at resin-modified glass-ionomer/tooth interfaces.

Area of Science:

• Dental Materials Science
• Biomaterials Chemistry
• Adhesion Science

Background:

• Glass-ionomers exhibit excellent bonding retention, potentially due to ionic interactions between polyalkenoic acid and hydroxyapatite.
• Resin-modified glass-ionomers (RMGIs) combine glass-ionomer and resin composite properties, but their adhesive mechanisms require further elucidation.

Purpose of the Study:

• To investigate the extent to which the self-adhesiveness of RMGIs is attributable to chemical bonding with tooth substrates.
• To characterize the interaction of three RMGIs with dentin using advanced microscopy and spectroscopy techniques.

Main Methods:

• Utilized electron microscopy and atomic force microscopy for interfacial ultrastructural analysis.
• Employed X-ray photoelectron spectroscopy (XPS) to determine chemical interactions at the interface.
• Correlated microscopy findings with XPS data to understand bonding mechanisms.

Main Results:

• Two RMGIs showed shallow hybridization of hydroxyapatite-coated collagen with a deposited gel phase from polyalkenoic acid interaction with calcium.
• One RMGI bonded to dentin without forming a hybrid layer or gel phase.
• XPS confirmed electrostatic interaction between RMGI polycarboxylic acids and hydroxyapatite.

Conclusions:

• RMGI self-adhesiveness is primarily due to ionic bonding with hydroxyapatite surrounding collagen.
• Micro-mechanical interlocking contributes to adhesion in RMGIs that also hybridize dentin.