The effect of displacement time on gingival crevice width.

The authors investigated the length of time medicated displacement cord should remain in the gingival crevice prior to impression making. A silk cord (Deknatel) was placed into the sulcus and was not removed during the study. Medicated cords (Hemodent on Ultrapak #1) were placed into the gingival sulcus for 2, 4, 6, and 8 minutes. Following cord removal, closure of the sulcus was recorded at intervals using a miniature video camera. Crevicular widths were measured at the midbuccal and transitional line angle areas. At both the midbuccal and transitional line angle areas, gingival crevices displaced for 2 minutes were significantly smaller at 20 seconds (P < .05) than crevices following displacement for 4, 6, and 8 minutes. No significant difference in crevicular width was found at any time period after cord removal for crevices displaced for 4, 6, and 8 minutes. At the transitional line angle, crevicular widths were significantly smaller than at the midbuccal at 20 seconds for all times and remained so up to 180 seconds. To achieve a crevicular width of 0.2 mm, cord should remain in the gingival crevice for an optimum time of 4 minutes prior to impression making when using the materials evaluated in this study.