Tissue management for an exquisite impression depends on two factors. The first goal is to move the gingival tissues away from the margins and create a space for the impression material. The ideal space allows the technician the opportunity to create emergence profile and properly contour the restoration. The next goal of tissue management is to control moisture, as almost all of our impression materials are hydrophobic. As part of this process we often have to manage the tissue bleeding.
There are many ways to gain retraction today for final impressions. With all those options I still find that a two cord technique creates the most predictability in my hands. One of the challenges with a double cord technique is the removal of the top cord when there are multiple preps to impress at once. A technique I learned many years ago of using a continuous top cord makes this step much simpler. This technique is designed to be used with veneer preps, and can not be used if the preparations include the lingual surface of the tooth.
One of the things we work on often int he practice is improving the quality of our alginate impressions. They are one of the critical factors in our success, and yet something we often take for granted that we do well. Small inaccuracies in an alginate can introduce errors that then get magnified downstream in the restorative process. The accuracy begins with selection of the proper tray size and customizing it with rope wax. Once we have the tray picked out and customized we are ready for the alginate. There are a variety of alginates on the market. Deciding which one to use is about the properties you prefer, like color change or double pour and the handling properties. Working with alginate is the same no matter which brand you use. Measuring the powder and the liquid is one of the critical steps and is often not done.
Earlier this year in a post on tissue management I mentioned using cord as part of a restorative protocol to protect the gingival tissues. Since then I have gotten multiple questions about “how” I do this and decided I’d answer in a post instead of one by one via e-mail. One of the things I like the least is tissue that is cut or bleeding when I am trying to get an impression. Many years ago I learned a technique that eliminated most of the tissue damage I had been causing during the preparation of the tooth.
Alginate impressions are one of the main stays in a general dental practice. Think about all of the clinical procedures that we do whose success depends on an accurate alginate impression, from diagnostic planning on models to the fit of removable prostheses and more. In the face of the important role that alginate plays it is also one of the most overlooked and under trained technique we do. This week in my office we have had the opportunity to take a large number of alginate impressions and the conversation about how to take them and what the expectations are for success.
Last week I experimented with a new impression technique for diagnostic models. I’ll admit that I was reticent to try it at first, as I feel pretty comfortable with my old technique. I am a believer in taking diagnostic impressions with VPS material. This grants us the ability to pour extra models as needed for a number of months after we take the impressions, streamlining making occlusal appliances or performing a diagnostic equilibration.
Capturing an accurate impression is a key step in restoration success. It dictates the ability of the lab to fabricate a well fitting restoration and create adequate marginal seal. When we think about accuracy at the margins we need to strive to take impressions with adequate flash beyond the edge of the prep. Onlay preparations have the unique characteristic of having both horizontal and vertical margins we need to capture.
I have heard it estimated that in the next five years 31% of all dental impressions will be captured digitally. So why are so many dentists making the investment? I have had the opportunity to take digital impressions with the Cerec System by Sirona for the last few years. Both as a practitioner and as an educator I love the technology and I have experienced many advantages. The foundation of the advantages is that you get to see your own preparations and the final impression and model in real-time while the patient is still present. One of the most frustrating things in private practice is getting a call from the lab that an impression I took has flaws. Often there is no question, and we will have to call the patient and have them come back in, get them numb, take off the provisional and take a new impression. This is an in inconvenience for the patient, diminishes the productivity of the procedure and can potentially impact how the patient feels about our office. Other times the lab is calling so that
Accurate impressions are a critical ingredient in our ability to deliver quality restorations to our patients. They are also the one thing that laboratory technicians agree dentists need to do better. An accurate well taken impression has many qualities, but a key ingredient is obtaining adequate margin flash. Flash is the amount of the impression material that captures the tooth beyond the preparation margin. This “extra” material that has gone past the margin is vital to the technician as they fabricate the final restoration. The first question is how much flash do we need to deem an impression accurate.
Impression materials come in all shapes and sizes, or more accurately different viscosity and set times. For years I was in search of the perfect material that would do everything I need in my office. With this approach I was often frustrated when using fast set by the feeling I had to rush, or the feeling of wasted time using slow set as I watched the clock tick down until I could check the impression. Recently I decided to match the impression material to the clinical procedure and minimize some of these frustrations.