Friday, October 16, 2009
Retraction cords :For Better Impressions
Good impressions start with good retraction, but often the process is rushed and the impression is resultantly compromised. Most trained prosthodontists agree that two to three minutes is insufficient to achieve good tissue deflection. Consequently, most prosthodontists pack retraction cord for at least five minutes to achieve good tissue memory. This is one of the main secrets in achieving a good impression.
Gingival retracting cords including propylhexedrine (e.g., propylhexedrine HCI) for providing hemostasis and retraction or displacement of gingival tissue. The retraction cords include a hemostatic and tissue stiffening and retraction effective amount of propylhexedrine which avoids the negative side effects associated with the use of epinephrine, commonly used in conventional retraction cords. Retraction cords incorporating propylhexedrine do not cause increased blood pressure or accelerated heart rate. In addition, such retraction cords may include astringents, such as iron (III) salts without causing discoloration of the retraction cord, the patient's teeth or gums, or the fingers of the dental practitioner.
Retraction: Two alternative methods.
Single Cord Technique:
This technique is most common, but often insufficient. The single cord retraction technique is best used when preparing margins at, or above tissue. If gingival tissues are healthy and no bleeding occurs when the cord is packed, this is usually an accepted method.
Double Cord Technique:
The double cord retraction technique is best used when sub-gingival margins are required, and/or if the tissue health is less than ideal. Double cord technique is not simply inserting two cords. The technique sequence listed below will give the best result.
Enough coronal structure is removed to gain easy access to the interproximal areas. Try to avoid preparing areas close to the gingival tissue. Gently an extra thin cord such as Deknatel suture or # I retraction cord (impregnated with an astringent of your choice) is inserted into the sulcus. The Deknatel or # I cord will provide a slight tissue deflection allowing more access will serve as a depth gauge .Then a braided cord impregnated with astringent is packed to achieve adequate tissue displacement. Cord placed below tissue will simply train the upper tissue to curl, defeating the process of tissue deflection. Furthermore, try to use the largest braided cord possible to achieve the greatest tissue deflection. After a minimum of five minutes, the upper braided cord is removed , (leaving the suture cord in place) and the impression is made.