A common technique used when taking fixed prosthetic impressions is packing a cord. Packing a cord will help stop the bleeding and assist in achieving good retraction in the sulcus before inserting impression material. Dentists often pack a single cord as part of their impression taking technique. However, using a double cord technique can produce better tissue displacement, resulting in better impressions and better results for the laboratory, dentist and patient.
Why pack two cords instead of one?
Packing two cords has two main advantages over packing a single cord:
Margins are better defined with two cords. Single cords often leave extremely thin margin areas resulting in deformed impressions. In a deep sulcus, using two cords can help prevent tissue from collapsing over the top of the cord. Tissue collapse restricts access of the impression material and can cause the material to tear.
Steps for packing two cords:
Prepare the tooth.
Choose one small cord (#00) and one large cord (#02). Because the sulcus is V-shaped, the first cord should be smaller. It will help control seepage and hemorrhage. (Consult your dental supply company for the best cord options.)
Pack the small cord (#00) below the margin of the tooth.
Pack the large cord (#02) directly on top of the small cord.
Remove the large cord after a minimum of 5 minutes.
Optional Step: Remove the small cord. Some dentists prefer to leave the small cord in while taking the impression. However, this cord can sometimes stick to the impression material causing a small irregularity in the margin.
Proceed with the impression.
How does a double cord technique help us produce a better prosthetic at the lab?
As your laboratory, our goal is to provide you with the best fit for every prosthetic. The double cord technique often results in a more accurate impression, which eliminates any guess work at the lab when trimming the die. Well defined margins on an impression help us prevent margins from coming up short or open on the prosthetic which results in less seepage and provides a more accurate fit when placed in the patient's mouth.