The more we learn about adhesive dentistry, the more critical it has become to have control over the placement of phosphoric acid etchant. I utilize a variety of techniques clinically for creating a strong durable bond. When I have chosen to use a total etch approach to a restoration, then it is critical that I control the timing of the etching process. If the phosphoric acid gel is in contact with the enamel less than twenty-five seconds, I will have inadequately prepared the tooth surface. More than fifteen seconds on dentin, and now I have over-etched and run the risk of decreased bond strengths and post operative sensitivity. I also very often choose to utilize a self etching dentin adhesive in a hybrid technique, where I want to selectively etch the enamel margins first, without getting the phosphoric acid on the dentin at all. This same technique is being employed more and more when using self etching self priming resin cements to seat indirect restorations.
There are several challenges to selectively placing etching gel. One of the first challenges I run into is the diameter of the tip as I dispense the phosphoric acid. I am looking for a bead of the gel in the range of 1-1.5mm wide when I try and rim just the enamel margins. Many of the different products I have tried make this difficult to impossible as the dispensing tip is too large and I get a very wide band of gel. Another issue is the viscosity of the etchant, products that are too thin are difficult to control precisely when placing on the tooth, and then they tend to run or spread onto other tooth surfaces that I was not intending to etch, like the dentin. So the goal is to have a phosphoric acid between 30-40% that is viscous enough to hold it’s shape and stay where we put it, and can be dispensed through a very narrow tip and create a 1-1.5mm wide band.
At the recent ADA meeting I found such an etching gel, Select HV Etch from Bisco. I was skeptical to say the least when at the booth I watched as the rep drew a smiley face on a mixing pad with the gel to show me how precisely you can control the material being dispensed. I have been using it routinely for the last few weeks and the ability to control the material and where you apply it is excellent, and it has allowed me to utilize a selective etching technique with the desired precision. It’s nice to have one less piece of my bonding process that is challenging.