Controlling blood, crevicular fluid, water and saliva while taking impressions is critical. Water and saliva can be controlled by air spray. Blood and crevicular fluid can be controlled by retraction cords, hemostatic agents, electrosurgery or rotary gingival curettage.1
Retraction cords displace gingival tissue mechanically; they also can have a chemical action when impregnated with astringents and vasoconstrictors that cause tissue contraction and hemostasis. Electrosurgery creates a trough around the tooth by removing superficial cell layers from the gingival sulcus’ inner lining through application of an electric current. Rotary gingival curettage removes the sulcular epithelium with a high-speed diamond bur. Azzi and colleagues2 studied the effect of retraction cords, electrosurgery and rotary gingival curettage on gingival recession and loss of attachment in dogs. They found that cords had the smallest effect on the gingiva and rotary curettage had the largest effect.
Astringents impregnated in retraction cords include aluminum chloride, ferric sulfate, alum (potassium aluminum sulfate) and zinc chloride. Alum and ferric sulfate may be irritating and even corrosive at high concentrations, while increased concentrations of zinc chloride may damage bone and tissue permanently.3 The least irritating cords contain buffered aluminum chloride, which may be left in the sulcus for up to 15 minutes without permanent damage.4
Weir and Williams5 reported that soaking retraction cords in aluminum chloride solution enhances hemostasis. This led Runyan and colleagues1 to study whether soaking cords in aluminum chloride solution has any effect on the ability of the cord to absorb moisture. They found that presoaking had no effect on fluid absorption and, therefore, may be a worthwhile adjunct.
Gingival retraction cords containing epinephrine effectively control bleeding; however, from 24 to 92 percent of the epinephrine may be absorbed systemically.6 Epinephrine-impregnated retraction cord contains 8 percent racemic epinephrine. One study estimated the concentration of epinephrine absorbed systemically to be equivalent to approximately 3.9 cartridges of local anesthetic containing 1:100,000 l-epinephrine.7 This estimate is considerably lower than previous estimates because the authors calculated the actual amount of releasable epinephrine in the cord before retraction, which was found to be approximately one-half that of the labeled amount; based their final estimate on the more biologically active l-epinephrine; and found that presoaking in aluminum chloride removed approximately 25 percent of the racemic epinephrine in the cord.
There are conflicting reports on whether epinephrine absorbed from retraction cords has any adverse physiological effects.7–11 The potential epinephrine reactions that can occur following systemic absorption include increased anxiety after cord placement, limb tremor, diaphoresis, headache, florid appearance, tachycardia and elevated blood pressure.6 However, there are many variables that make it difficult to predict the physiological effect. These variables include the concentration of epinephrine absorbed from the cord; the length of time the cord is in the sulcus; the condition of the gingival tissue; the presence of crevicular fluid or saliva; individual patient response; and drug interactions with tricyclic antidepressants, nonselective ß-adrenergic antagonists, certain general anesthetics and cocaine.10,11 Therefore, recommendations have been made to either limit or avoid use of such epinephrine-impregnated retraction cords.7,10,11
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