Bonding on dentin surface has been the subject of extensive research in the past years. Composite fillings, porcelain veneers, dentin bonded crowns etc, all rely on the bond strength between the dentin substrate and the restoration.
The strength of different bonding systems has been examined on various studies but without taking into account the role of the etching agent. .
The research has shown that phosphoric acid of a concentration around 37% is ideal to etch enamel and dentin. There are 2 problems with phosphoric acid. First, is that it is fluid and the second is that it is colourless. By being fluid it makes it impossible to selectively etch enamel and then the dentin. Being colourless makes it hard to see where the dentist is etching. To overcome these problems, the manufacturers have added various ingredients to create gels that are easy to see and don't flow so easily. Very common ingredients are submicron silica and oxalate.
This study examined the effect of 3 different types of acid etchants on the bond strengths of 3 different bonding systems. The study showed that gels containing oxalate resulted in significantly lower bnd strengths for all 3 systems, followed by the gel containing silica. Best results were given by a phosphoric acid liquid not containing any silica or oxalate.
So, next time you order your favourite acid etchant have a look and see what's in it.
http://rapidshare.com/files/286238288/etch.pdf
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