- The double-cord technique is considered the most suitable method for managing deep subgingival tooth preparations due to its ability to provide effective and controlled gingival retraction.
- This technique involves placing two retraction cords sequentially: the first cord is placed deeply into the sulcus to gently displace the gingiva away from the tooth, while the second, smaller cord is placed above the first to further retract the gingiva and control bleeding.

Key points include:
- Effective sulcular displacement: The double-cord technique allows for better access and visibility of the preparation margin, which is critical when the margin is located deep within the sulcus.
- Hemostasis control: The use of two cords, with medicated options available, helps to control gingival bleeding, improving impression quality.
- Improved impression material flow: By creating a clear and dry field, this method facilitates the accurate capture of fine details of the subgingival margin.

In comparison:
- Single-cord technique may be insufficient for deep subgingival margins as it provides less gingival displacement and poor hemorrhage control.
- Expasyl paste retraction is minimally invasive but generally less effective for deep sulcus management and may not control bleeding adequately.
- Electrosurgical gingival retraction offers rapid tissue removal and retraction but carries risks of tissue damage and delayed healing, making it less ideal for subgingival margin management.

Therefore, the double-cord technique remains the gold standard when precise and controlled gingival retraction is required for deep subgingival preparations.

Reference: Sturdevant's Art and Science of Operative Dentistry, 7th Edition, Chapter 17 / Page 430-435