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
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