F13.
Discuss the importance of sealant penetration into the etched enamel and three
conditions which can impair or influence sealant penetration.
The
key mechanism behind sealant bonding is micro-mechanical retention. In other
words, the bonding resin must infiltrate the enamel surface and form tags. Such
a tag formation is most efficient if there is a preferential etch pattern either
in the periphery or in the center of the rods. However, the orientation of
enamel rods may differ considerable at different locations. For example, it is
known that enamel on primary teeth is more irregularly oriented than on
permanent teeth, making it more difficult to form a reliable etch pattern on
primary teeth. Another factor is that the surface energy of the enamel must be
high when the sealant is placed. Unfortunately, small oil drops are often spread
over the tooth surface when the surface is air-dried. Such oil drops decrease
the surface energy and makes it more difficult for the bonding resin to wet the
etched enamel surface. The same is also true if water or saliva contaminates the
etched enamel surface.
In
addition to the above considerations, the viscosity of the sealant should be
low. Low viscosity facilitates the infiltration of the resin into narrow
fissures and/or pits. It also makes it easier for entrapped air bubbles to float
up and escape.
Three
conditions which can impair or influence sealant penetration:
Enamel
rod structure
Contaminations