All-in-one self-etch model adhesives: HEMA-free and without phase separation

Area of Science:

• Dental Materials Science
• Adhesive Dentistry
• Polymer Chemistry

Background:

• Hydrophilic monomers like HEMA can cause phase separation in dental adhesives.
• Developing HEMA-free formulations is crucial for stable, long-lasting dental restorations.
• All-in-one self-etch adhesives simplify clinical application but often face stability challenges.

Purpose of the Study:

• To design and synthesize HEMA-free, all-in-one, self-etch dental adhesives.
• To ensure these novel adhesives exhibit no phase separation.
• To evaluate the bonding efficiency and marginal adaptation of these adhesives on extracted human teeth.

Main Methods:

• Adhesives were formulated using UDMA, 4-META (or 4-MET), varying water content (0-45%), and acetone or ethanol as solvents.
• Phase separation was assessed visually under ambient conditions.
• Shear bond strengths (SBS) to enamel and dentin were measured.
• Marginal gap width (MGW) was evaluated in dentin cavities.

Main Results:

• Formulations with ≤5% water (solvent: acetone/ethanol) or ≤8% water (solvent: acetone) showed no phase separation.
• Acetone-based adhesives demonstrated superior dentin bond strengths and marginal adaptation compared to ethanol-based ones.
• Water content significantly influenced enamel bond strength in one adhesive system (2), with no difference between 4-META and 4-MET.

Conclusions:

• HEMA-free, all-in-one self-etch adhesives can be successfully designed without phase separation.
• These simplified adhesives maintain high bonding efficiency to both enamel and dentin.
• Optimized water content and solvent choice are key factors for adhesive stability and performance.