The debate between total etching and self etching rages on, but now we have a third choice known as selective etching or a hybrid etching technique. Selective etching combines the best of both the total etch technique and the self etching systems. One of the things that phosphoric acid is good at is effectively etching enamel. In a selective or hybrid etching technique you apply phosphoric acid to the enamel surfaces, avoiding the dentin. After 15 seconds the gel is rinsed off the tooth and the tooth is dried.
If you are using Glutaraldehyde/HEMA or chlorhexidine as part of your adhesive process you would apply this to the tooth next and dry it or rinse it depending on the manufacturer directions. The final step is to utilize a self etching dentin adhesive and now apply it to both the dentin and the enamel surfaces making sure to scrub the dentin and activate the etching component. This technique maximizes enamel bond strengths while eliminating the risk of over-drying the dentin after rinsing off phosphoric acid or over-etching the dentin. Using this technique successfully depends on a phosphoric acid gel that is viscous enough to stay just on the enamel and not run. You will also need a small canula or tip to dispense it against the tooth. This approach can be used with both light activated and dual cure dentin adhesives, under direct and indirect restorations.