This SEM photograph shows the composite, adhesive, and dentin bonding interfaces.
Excellent monomerpenetration into dentinal tubules, shown as well defined long resin tags, was achieved. This yields high bond strength, provides a durable bond between the adhesive and dentin substrates, and offers great protection against microleakage and sensitivity. The film thickness of Optibond All-In-One adhesive, shown in this SEM, is about 5 microns.

SEM image shows clearly exposed enamel hydroxyapatite crystals, which present greater rough surface area for micromechanical retention and chemical bonding