Tooth Bonding
Please find Part 1 by clicking here and learn more about the basics
of bonding as used in cosmetic dentistry and explained
in the 'Procedures' section.
The visible part of your tooth consists of two different
principal hard tissue components. The outer one is called
enamel, which covers the tooth like a protective shell.
The central one is called dentin, which forms the bulk
portion of your tooth. It surrounds the dental pulp,
which contains the nerve, blood vessels, and connective
tissue. I am not going too much into dental biology,
because this may be too boring for you.
However, compared to enamel, the dentin has a
very high water content and lots of organic matrix
(collagen etc.). The old dental resins used for
white fillings were only good on enamel, because
they were hydrophobic (like oil on water). Enamel
has a very low water content and is densely packed
with calcium crystals of different orientations.
These calcium crystals dissolve differently once
exposed to the acid of the etchant. This creates
a surface pattern that provides a mechanical micro-retention
for the resin (even though hydrophobic).
The trick of the new bonding agents is to overcome
the high water content and the high amount of
hydrophilic matrix of the dentin. The bonding
agents form a so-called 'hybrid layer' within
the upper layers of the dentin. This layer seals
the exposed dentin and creates very high bonding
strengths for anything that is linked via a regular
resin to it.
Hybridized dentin is a molecular-level mixture
of adhesive polymers and dental hard tissues.
It is created by diffusion of resin monomers
into the acid-etched surface.
The mineral phase of the dentin is purposely dissolved
to expose the collagen matrix. This creates a layer
of a loose collagen fibril network. This layer is very
vulnerable to dehydration and has to be carefully managed
by an experienced hand to prevent its collapse (see picture below). The
placement of rubberdam around the treated tooth is mandatory
during this procedure (see the blue rubberdam on the
animated version below). The collagen network is now
diffused with hydrophilic resins forming a hybrid layer
of resin-embedded collagen fibers. The hybrid layer
is chemically and physically very different from the
original tooth structure. It even resists acid attacks.
|
Do you want a "bonding" experience?
|
Click
here to see the entire bonding experience in sequence.
(This
file is 560k and will take about 1min 30sec to download
with a 56k modem.)
top^
|
