Enamel-smear compromises bonding by mild self-etch adhesives

Area of Science:

• Dental Materials Science
• Adhesive Dentistry
• Biomaterials

Background:

• Growing use of ultra-mild self-etch adhesives necessitates improved enamel adhesion.
• Enamel bonding with these adhesives is often compromised.
• Bur debris from cavity preparation may interfere with effective enamel bonding.

Purpose of the Study:

• To investigate the influence of smear layer characteristics on enamel adhesion with ultra-mild self-etch adhesives.
• To compare the effects of different surface preparation methods on smear layer properties and adhesive interaction.

Main Methods:

• High-resolution transmission electron microscopy (TEM) was used to analyze enamel smear layers.
• Enamel surfaces were prepared using both laboratory (SiC paper) and clinical (dental bur) methods.
• Lab-demineralization was employed to visualize resin infiltration patterns.

Main Results:

• Enamel smear layer thickness, crystal density, and size varied based on the preparation method.
• Ultra-mild self-etch adhesive infiltration preferentially followed micro-cracks in bur-prepared enamel.
• A lab-prepared surface resulted in a more uniform and dense smear layer compared to a bur-prepared surface.

Conclusions:

• The surface preparation method critically influences smear layer characteristics and subsequent adhesive interaction.
• Clinically relevant bur preparation creates a smear layer that hinders optimal resin infiltration and enamel bonding.
• Understanding smear layer properties is crucial for enhancing adhesion with ultra-mild self-etch systems.