Potential smear layer interference with bonding of self-etching adhesives to dentin

Area of Science:

• Dental Materials Science
• Adhesive Dentistry
• Biomaterials

Background:

• Self-etching adhesives simplify dental procedures by combining etching and priming.
• The smear layer, a byproduct of cavity preparation, can affect adhesive-dentin interaction.
• Understanding the influence of the smear layer on different self-etching adhesive types is crucial for predictable clinical outcomes.

Purpose of the Study:

• To investigate how the smear layer impacts the bonding effectiveness of self-etching dental adhesives.
• To compare the performance of self-etching adhesives with varying etching potentials when applied to smear-layered versus smear-free dentin.

Main Methods:

• Human molars were prepared to create both bur-cut (smear-layered) and smear-free dentin surfaces.
• Five adhesive systems were tested: a strong one-step, two ultra-mild one-step, a mild two-step self-etching adhesive, and a three-step etch-and-rinse control.
• Microtensile bond strength (µTBS) was measured after 24-hour water storage, and failure modes were analyzed using stereomicroscopy and SEM.

Main Results:

• Mild and ultra-mild self-etching adhesives exhibited significantly lower bond strength on smear-layered dentin compared to smear-free dentin.
• A strong one-step self-etching adhesive showed less sensitivity to the smear layer.
• The etch-and-rinse control adhesive demonstrated the highest bond strength, unaffected by the smear layer.
• SEM analysis confirmed smear debris incorporation into the adhesive layer with ultra-mild adhesives on bur-cut dentin.

Conclusions:

• Smear debris negatively interferes with the bonding efficacy of mild and ultra-mild self-etching adhesives.
• The etching potential of self-etching adhesives influences their susceptibility to smear layer contamination.
• Etch-and-rinse adhesives may offer more reliable bonding in the presence of a smear layer.