An all-in-one adhesive does not etch beyond hybrid layers.

Area of Science:

• Dental Materials Science
• Biomaterials Engineering
• Adhesive Dentistry

Background:

• All-in-one self-etching adhesives are widely used in restorative dentistry.
• Concerns exist regarding the continuous etching of dentin tubules by residual acidic monomers post-polymerization.
• The long-term stability of the hybrid layer, crucial for adhesion, is not fully understood under various oral conditions.

Purpose of the Study:

• To investigate if unpolymerized acidic monomers in aggressive all-in-one adhesives etch beyond dentin hybrid layers.
• To evaluate the effect of different storage environments (water vs. alkaline buffer) on hybrid layer integrity.
• To assess the influence of these conditions on biomimetic remineralization.

Main Methods:

• Dentin surfaces bonded with Adper Prompt L-Pop were prepared.
• Samples were stored in water (pH 6.8) or glycine buffer (pH 11.1) for six weeks.
• Further samples were immersed in a biomimetic remineralizing medium for up to 4 months.
• Analysis included Confocal Laser Scanning Microscopy (CLSM), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM).

Main Results:

• No significant difference in demineralization thickness was observed between water and glycine buffer groups after 6 weeks.
• However, the glycine buffer group exhibited increased permeability and compromised hybrid layer integrity at its base.
• Biomimetic remineralization results corroborated the morphological findings, showing degradation at the hybrid layer base in the alkaline condition.

Conclusions:

• Unpolymerized acidic monomers do not appear to etch significantly beyond the hybrid layer in the tested conditions.
• Alkaline environments (simulating certain oral conditions) can degrade the hybrid layer's integrity and increase permeability.
• The findings highlight the importance of the oral environment's pH in maintaining the longevity of dental adhesive restorations.