The total etch technique has been utilized in adhesive dentistry for many years. Some clinicians swear by it, and others swear it causes all of their post operative problems. The greatest risk in utilizing a total etch technique is “over-etching” the dentin. Excessive etching of the dentin layer, is associated with increased post op sensitivity for the patient. When dentin is etched for too long, the demineralized zone extends beyond the ability of the primer to penetrate. This layer of demineralized dentin, which is not permeated by primer and resin, allows fluid movement in the dentinal tubules. This movement of fluid pulls on the odontoblastic process and the patient experiences it as pain or sensitivity. Another consequence of dentin that has been etched for too long, is reduced bond strengths. The cause of the alteration in bond strengths is the layer of demineralized dentin beyond the hybrid zone that was developed.
So how do so many total etch enthusiasts use this technique successfully? Total etch is accomplished with phosphoric acid between 30 and 40% in concentration. Dentin should be exposed to the phosphoric acid for no more then 15 seconds and then rinsed thoroughly. Using a small tip on my etching gel, I ring the enamel first, and count to ten seconds. Next I cover all of the dentin and count out the fifteen seconds, “One one thousand, two one thousand…” . I find this to be an accurate way of keeping time, I am not dependent on anyone else for timing, and my patients get a laugh out of it. You can work with your assistant to wear a watch with a sweep second-hand, and count the fifteen seconds for you. I have found it challenging to look at my watch, because often my hands are helping retract and prevent saliva contamination.as soon as I get to fifteen seconds, my assistant places the high volume surgical suction tip ont he tooth, removing the gel. We rinse thoroughly, and dry the dentin.