Adhesion to dental tissues is one of the main lines of research
today, mainly the chemical evolution of adhesives, which allowed
the restorative procedures to be performed with greater speed
and predictability. Bonding to dentin is a unique form of tissue
engineering in which a matrix of demineralized collagen with
residual crystals of hydroxyapatite is used as the basis for the
infiltration of resinous monomers, forming the hybrid layer. Most
adhesive systems currently available on the market produce good
initial bond strength values, allowing the clinician to stick to the
dental structure without the need for retentive preparation .
Despite technological advances in adhesive materials, clinical and
laboratory studies [2,3] confirm the inexorable degradation of the
bonding of the composite resin to dental tissues in the long term .
The simplification of adhesive procedures was done at the expense
of the use of more hydrophilic resinous monomers, responsible
for the formation of hybrid layers with lower hydrolytic stability4.
Ideally, the network of collagen fibrils exposed after conditioning
with phosphoric acid should be completely infiltrated. However, it
is known that there is a decrease in the diffusion gradient of the
resinous monomers, creating defects at the base of the hybrid layer
which manifest morphologically as an unprotected collagen zone.
The collagen fibrils of this non-infiltrated zone show structural
instability, since they are not enveloped by the resinous monomers