This picture illustrates a bad day for the restorative dentist. A ceramic crown crack – BUMMER. Having lived through the birth and growth of bonding, and having settled into the comfort zone that was created by the total etch three step systems (the 4th generation), I was under the impression that total etch of a preparation prior to use of a bonding system would always provide the maximum bond strengths.
True, those strengths might be matched without etching the dentin, but I never thought I was reducing the bond by etching the dentin. Turns out I was wrong. There are a number of products, Clearfil SE and Unicem 2 among them, that have lowered bond strengths to dentin if you etch the dentin with phosphoric acid. Others do best WITH a total etch, All Bond Universal, Scotchbond Universal, and Elect are the three discussed by John Burgess when I became aware of this difference.
The blessing and the curse of being in dentistry at this point in history is the rapid rate of change. A short time after I started using the self-etching materials I switched to selective etch – BUT that was a move to reduce chances of sensitivity since it seemed that the bond strengths were just as good as not total etching the dentin. It seemed a prudent move in spite of the fact that I was experiencing virtually zero sensitivity as it was. I was always careful to keep things wet. Thankfully, that rationale might have saved me some additional bad days since I haven't etched a lot of dentin in the past few months.
What this reinforces for me is the importance of reading and understanding the manufacturers' recommendations when using a new product clinically. I am NOT a directions kind of guy, it's a weakness - and it might have weakened my bond strength.