A gingival retraction cord is a small string temporarily placed beneath the gum line around a tooth prepared for a crown, veneer, or other restoration. This procedure is a common step in restorative dentistry, designed to ensure the final restoration fits with precision. The primary goal of using this cord is to create a clear, dry space in the gingival sulcus—the shallow groove between the tooth and the gum—to capture a precise impression of the prepared tooth. This temporary displacement allows the impression material to flow accurately past the preparation margin, which is the edge where the restoration will meet the natural tooth structure.
The Necessity of Tissue Displacement
The need for the retraction cord arises from the location of the preparation margin on the tooth. This margin is often placed slightly below the free gingival margin to hide the edge of the restoration and ensure a natural appearance. When the margin is subgingival (below the gum line), the surrounding soft tissue obscures it, preventing the impression material from accurately recording the area. The cord works mechanically by pushing the delicate gum tissue laterally and slightly away from the prepared tooth surface.
This temporary separation creates a space necessary for the impression material to flow into and set without being compressed by the surrounding tissue. The cord is often impregnated with a hemostatic agent, such as aluminum chloride, which helps control minor bleeding and the flow of sulcular fluid. A dry, clean field is necessary for the impression material to set properly and capture the minute details of the tooth margin.
Synchronization with Impression Material Setting
The precise moment of gingival retraction cord removal is dictated by the manufacturer’s instructions for the impression material and the technique chosen by the dentist. The cord must remain in place long enough to achieve adequate tissue displacement, typically three to five minutes, but not so long as to cause permanent tissue damage. For impression materials using a two-viscosity technique, the cord is generally removed just before the material is seated.
In a common approach, the cord is removed immediately before the light-body material is injected around the prepared tooth and the heavy-body material is seated in the tray. This timing is important because the gum tissue begins to collapse back toward the tooth almost immediately after the cord is pulled out, often within 20 seconds. The impression material must be placed into the open sulcus quickly to capture the margin before the tissue rebounds. If a double-cord technique is used, the thinner, deeper cord may remain to maintain hemostasis while only the thicker cord is removed right before the impression is taken.
The Technique for Safe Cord Removal
The process of removing the retraction cord must be performed with care to avoid causing trauma to the newly retracted gum tissue. It is recommended to wet the cord thoroughly before removal, especially if it is dry or if a hemostatic agent has caused it to stick. Wetting the cord helps loosen it and prevents the cord from tearing the sulcular lining, which could immediately cause bleeding and compromise the impression.
The cord is typically grasped at one end using cotton pliers and slowly withdrawn from the gingival sulcus. If the cord was packed sequentially, the removal must also be sequential, ensuring no pieces are left behind. Gentle, continuous traction is applied, following the path in which the cord was placed, to minimize the risk of tissue rebound.
Immediate Post-Procedure Assessment
Immediately after the retraction cord is removed and the impression is taken, a careful assessment of the site is performed. The primary check is for hemostasis, ensuring that all bleeding has stopped and the gingival tissues are not actively hemorrhaging. Any residual bleeding or tissue tags can indicate excessive trauma during placement or removal, which may lead to temporary inflammation.
The patient may experience a mild, temporary sensation of pressure or slight tenderness where the cord was placed. The dentist also inspects the impression to confirm that the preparation margin is clearly and completely captured, without any voids, tears, or contamination. A successful impression shows a distinct, continuous line of the prepared tooth margin, confirming the retraction process achieved its goal of precise tissue displacement.