This week in the office the theme has been around placing cord. Yes, I admit it, I am still a two cord dentist most of the time. I have yet to find an alternative technique that predictably creates appropriate impression flash. Getting fabulous impressions is not a given with any technique; the magic is in how you use it. Over the years I have learned a few tips that make using cord highly predictable. My initial prep margin is placed equigingival, which creates a reference to tissue position for placing the primary cord. With a perio probe, measure sulcus depth and decide where in relation to the base of the sulcus you plan to place the prep margin. With this information I begin with a size zero cord. I gently place it into the sulcus. Using my original (equigingival) margin as a reference I make certain the top of this first cord is precisely positioned using a probe.
The next step is to refine the prep, dropping the margin to the top of the primary cord and polishing. I use a size one for the top cord, and my favorite is UniBraid by Dux Dental due to its rigidity. The stiffness of the cord is essential to hold the space at the top of the tissue that will become impression flash. The critical step in placing the top cord is being able to see it around the entire circumference of the prep. Any place you can not see the top cord, it has been placed too deep, and you will miss the impression. Once the cord is in place and has been allowed a few moments to work it is time for the impression.
If cord is pulled dry it will take away a layer of tissue and bleeding will result. Prior to pulling the top cord moisten it with water. After the cord has been removed, dry the teeth and tissue prior to injecting light body material. This technique has helped me create predictable impressions for many years.