Taking the Perfect Impression - Dr. Brandon White, DDS
We recently discussed techniques for obtaining detailed, accurate, and predictable impressions with one of the practices we routinely receive cases from. While there are a variety of techniques which will yield a satisfactory result, we feel it is important that our doctors have several methods available to them to achieve their desired impression outcome on your routine, day-to-day cases. A Rigid frame triple tray (something with metal) is highly recommended if triple tray impressions are chosen.
Setting up for a prep, the assistant soaks both cords in clear hemostatic agent. Unless absolutely necessary, I avoid scrubbing the prep and gingiva with hemostatic. (Image 1)
The primary method used in this practice is a standard two-cord isolation technique. (Image 2) It is necessary to choose a retraction cord sequence which will predictably retract the gingiva.
In this practice, typically a "0" cord is used for the initial cord, the margins finished and refined, then a size 1, 2, or 3 cord is used depending on biotype and gingival appearance. Once the final cord is placed, the margins receive a final finish, and the occlusal reduction clearance is verified. The occlusal relationship of the contralateral dentition is evaluated at this time as well, along with midline if visible. This allows a quick and easy means to confirm proper intercuspation during impression making. By this time, the second cord has been allowed to retract for 4-5 minutes at a minimum, and it is then removed. A Heavy/Wash VPS system for impressing is utilized after rinsing and drying the tooth. Contact of the intra-oral tip with the sulcus is maintained throughout the dispensing of wash material while the assistant loads the impression tray. The material used in this photograph is Kettenbach's Panasil heavy(orange)/wash(blue-green). (Image 3)
The secondary method used in this practice is a two-step heavy/wash technique. It is typically reserved for patients who struggle with moisture control, access issues, or behavior management concerns. A rigid triple tray technique can be utilized, but we recommend including a bite registration. Following the same techniques through allowing the second cord time to retract, the deviation begins by loading the impression tray with a fast set, heavy body impression material (Kulzer Flexitime purple), placement of a thin plastic film over the arch or quadrant to be impressed (cut to the approximate shape of the tray/triple tray), and inserted with the patient occluding as usual. Immediately upon removal, the film is discarded and the assistant loads a wash material (Kulzer Flexitime light body green) (Image 4) while the doctor removes the second cord, rinses and dries the tooth, and the impression is seated - typically by placement on the prepared arch while guiding the patient into occlusion to allow maximum hydraulic pressure while maintaining moisture control.
Brandon White, DDS
The effort and detail made at the impression stage is with the intent to give us in the lab the ability to make an accurate model. When there is no clear separation between the margin and the tissue the margin will always be subject to a higher degree of inaccuracy during model trimming and ultimately the marginal fit.
I want to express my sincere thanks to Dr. Brandon White for sharing his skill and knowledge in an efforts to help the southern Oregon dental community pursue excellence in dentistry.
Mark Hidde - CDT, Owner