This is the fifth part in Dr. Jeff Bonk's “Dental Cloacopapyrology” series.
For restorative doctors preparing teeth for fixed prosthetics, obtaining an accurate impression for the final prosthetic is paramount for restoration success. Whether the impression technique is analog or digital, preparation margins must be visible.
To achieve efficient and effective margins, having materials, and using techniques that give adequate tissue retraction with minimal cost and high predictability is the ideal. Here's a technique I use have used for almost 30 years with complete predictability.
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Following the tooth preparation and refinement of margins (a critical step that is well explained and demonstrated in the "Restorative Design" workshop), a single, triple-zero braided retraction cord is gently tucked into the sulcus. This cord remains in place until the provisional restoration is fabricated, contoured, and cemented, at which time it is removed from the sulcus.
The key to exposing and capturing precise preparation margins is using a wisp of cotton dipped in Hemodent, a buffered aluminum chloride solution from Premier Dental, and dabbed almost dry. The cotton wisp is pulled from a cotton roll and may be varied in thickness. One end of the wisp may be only a few fibers of cotton, whereas the other end has gradual thickness.
Next, the Hemodent impregnated cotton wisp is gently placed over the pre-existing retraction cord. The varied cotton thickness allows for minimal tissue manipulation during wisp placement. Leave the wisp of cotton in place for about two minutes. If using an analog technique, this is approximately the time it takes to prepare a syringe and fill the impression tray.
Finally, the wisp is removed, and the light-bodied impression material is injected into the sulcus and the full tray is seated. Upon removal, a definitive and accurate replica of the prepared margin is observed.
Jeffrey Bonk, D.D.S., is a member of Spear Resident Faculty.