Darin O'Bryan, D.D.S. There is a lot of talk out there about not needing retraction with the Omnicam. With the color of our models we can determine where our margin is based on the difference of the tooth structure and the gingiva. While there are a lot of cases you don’t need to use retraction, there are some situations that you are still going to want to have some form of tissue separation.
The automatic margin finder likes a very clean margin and without retraction it is much harder to have a definitive line. Supra gingival margins when possible are a no brainer - but what about the other situation we run into clinically?
Here are times you are going to want retraction.
1. Any time there is excess tissue that is covering the margin. This is when I use my laser to get the tissue out of the way and not have to worry about it any more. Retraction cord works as well. I prefer a two-cord technique when I use retraction cord. This way I can leave one cord in for better retraction, easier imaging and easier clean up. The cord helps keep the cement out of the margin. Retraction gels won’t work as well unless you have something to physically displace the tissue.
2. Deep preparations. The deeper the preparation the harder it is to determine exactly where the color separation occurs. Having a gap between the tissue and the tooth will aid in this.
3. Bleeding tissue. Here it is not so much retraction that is needed but hemostasis. Blood interferes with the imaging and also can hide the margin.
4. When there is translucent enamel. This makes it very hard to determine where the tooth stops and the tissue starts.
5. Subgingival preps that get into the slightly white looking tissue. This tissue blends in very closely with the color of the band of enamel at the margin, again making it very hard to determine exactly where the tissue ends and tooth starts.
The better your separation the faster and easier your design time will be. The auto margin finder has more accurate information to read and so gives a better line that only needs minimal refinement.
