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Dr. Michael Buonocore, by identifying
phosphoric acid solution as an effective surface treatment for enamel, had made
a milestone contribution to dentistry. Adhesive dentistry was launched when he
discovered that enamel etching created microscopic surface irregularities into
which resin material could flow and interlock with, to allow a strong mechanical
bond. Enamel bonding systems of earlier years consisted of phosphoric acid for
etching and a resin-bonding agent.
The area of the tooth receiving a restoration
consists of dentin as well as enamel. The fact that a strong bond to dentin is
also mandatory for the long-term prognosis of a restoration was identified and
researches followed. Dentin consisting of collagen fibers and dentinal tubules
filled with fluid was a challenge to obtain adhesion. The primer was introduced
to ensure optimal wetting and bonding to the hydrated dentin surface.
Attempts continued to achieve chemical
adhesion to tooth structure, apart from the mechanical interlocking, In 1978,
Kuraray launched Clearfil bond system F, the first dental bonding system that
offered mechanical and chemical adhesion to both enamel and dentin. Kuraray also
introduced the Total etching (simultaneous etching of both enamel and
dentin with phosphoric acid) developed by Dr. Takao Fusayama.
In 1981, Kuraray developed a new phosphate
monomer (MDP-10 Methacryloyloxydecyl Dihydrogen Phosphate), which improved
adhesion to dentin. Since MDP not only improved enamel and dentin adhesion, but
also produced excellent adhesion to dental metals, it led to the development of
Panavia dental adhesive cement. Those of us who have used Panavia for cementing
crowns and bridges know what an excellent and reliable adhesion it provides.
The ‘total etch’ concept was
accepted in America only in 1990, when Bisco introduced All Bond and total etch
instruction. John Kanca played a key role in the Bisco project. The All Bond
procedure, derived from Kanca’s concept was,
E + nxP + B i.e.,
Etch, Prime (n coats) and finally, Bond.
Subsequently there was the simplification,
E + nxPB These ‘one
bottle’ systems were to facilitate clinical use. They combined the primer and
adhesive into one solution to be applied after total etch. ‘Prime and Bond’
from Dentsply incorporated this concept.
The shortcomings of ‘one bottle’ bonds
include the potential for excessive dentin decalcification and their reliance on
very careful moisture control to achieve good bonding and sealing results.
Soon there was a paradigm shift
EP + B This one was
from Kuraray in the ‘Liner Bond 2’, a self-etching primer. The advantages
include gentler etching, elimination of water rinsing, and dentin sealing that
virtually eliminates postoperative sensitivity. Also, there is no need to worry
about preventing collagen collapse.
The next simplification has also arrived in
the market,
nxEPB , which is
Espe’s Prompt L- Pop, which is a water based self etching adhesive that once
activated in the "blister pack", has a pH value of approximately 1.0.
It produces the known surface porosity used for micromechanical retention in
enamel, with the dentin surface also being conditioned in a similar manner.
Prompt L- Pop is
a unit dose system, with etchant, primer, adhesive and microbrush sealed in a
triple lollipop- shaped aluminium foil package. It is used for direct
application with all standard composites (eg. Pertac II, Tetric Ceram, Z 100, Z
250, Spectrum TPH, Herculite XRV), compomers (eg. Dyract AP, Compoglass, F 2000
and Hytac) and Ormocers (these are organically modified ceramics eg. Definite
from Degussa).
Meanwhile, Tokuyama has launched ‘One-Up
Bond’ that will be the first EPB to contain color change polymerization
indicators. When light cured completely, it shifts from pink to tooth color.
Ref:
1. J Clinical Orthodontics. Oct 200
2. J of Dentistry for children May-June 2000
3. Internet source
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