Detection of the hybrid layer biodegradation initiation factor with a scanning electron microscope

Area of Science:

• Biomaterials science
• Dental materials science
• Adhesive dentistry

Background:

• The hybrid layer is crucial for dental restoration bonding.
• Understanding hybrid layer biodegradation is essential for long-term restoration success.
• The origin and mechanisms of hybrid layer degradation require further elucidation.

Purpose of the Study:

• To determine the origin of hybrid layer biodegradation.
• To investigate biodegradation mechanisms on enamel and dentin surfaces.
• To compare the influence of different luting systems on bond strength and degradation.

Main Methods:

• Micro shear bond strength tests were performed on human third molars.
• Samples were subjected to thermocycling and silver nitrate immersion.
• Scanning electron microscopy (SEM) in back-scattered mode was used for analysis.

Main Results:

• Etch-and-rinse systems exhibited higher bond strength compared to self-etch systems.
• Bond strength was significantly higher in self-adhesive and etch-and-rinse groups on dentin and NaOCl-treated dentin.
• SEM revealed collagen biodegradation within the hybrid layer on dentin due to acid etching.
• Resin degradation on enamel surfaces was associated with resin monomers in adhesive systems.

Conclusions:

• Acid etching initiates collagen biodegradation in the hybrid layer on dentin.
• Resin monomers in adhesives contribute to resin degradation on enamel surfaces.
• Different luting systems and surface treatments influence bond strength and degradation pathways.