Retraction cord is used before crown impressions to expose the subgingival margin. Its effect on the gingival sulcus is:

Correct answer: C. Horizontal (lateral) dilation — moves the gingival wall outward to expose the margin

• A. Retraction cord definitely mechanically dilates — not just drying.
• B. Vertical apical displacement is a secondary, less dominant effect of retraction cord.
• C. Correct. Retraction cord mechanically LATERALLY (horizontally) dilates the gingival sulcus by pushing the free gingival wall outward, exposing the subgingival finish line. It also has a slight apical (vertical) displacement, but HORIZONTAL dilation is the primary and most important action for margin exposure. This allows impression material to flow into the sulcus and accurately capture the margin.
• D. The primary effect is horizontal — vertical is secondary.