Evidence-Based Selection of Gingival Retraction Materials
A Clinical Evidence Review

Retraction cords are the clinical standard for predictable gingival displacement. They mechanically push tissue laterally and apically, creating space for impressions, and carry hemostatic agents into the sulcus. Cord types (braided, knitted, twisted) vary: knitted absorb well and resist fraying; braided offer higher tensile strength.

Careful technique prevents iatrogenic damage. Packing force, ideally 20-25 g, avoids epithelial attachment damage and recession. Cord placement for 5-10 minutes ensures adequate displacement without tissue ischemia. Correct diameter selection is critical to prevent overpacking and trauma.

• Knitted Cords: Feature interlocking loops that absorb fluids well and resist unravelling during packing.
• Braided Cords: Constructed from multiple woven strands, offering good strength but may fray if not handled carefully.
• Packing Depth: Avoid placing the cord deeper than 1-2 mm into the sulcus to protect the biological width.
• Removal: Always wet the cord thoroughly with water before removal to prevent tearing the sulcular lining and initiating new bleeding.

Cordless retraction pastes and gels offer an atraumatic alternative, functioning via hydraulic pressure and chemical astringency. Containing kaolin clay for expansion and aluminum chloride for hemostasis, these are syringed into the sulcus. A compression cap applies pressure for 1-2 minutes, widening the sulcus mechanically while the chemical agent controls moisture.

These pastes are most effective in healthy, shallow sulci (<2 mm). They suit anterior restorations, veneers, and Class V fillings where minimal trauma is paramount. Displacement is less than cords, making them unsuitable for deep subgingival margins or significant hemorrhage. Thorough rinsing post-use is mandatory, as residual paste inhibits PVS impression setting. Explore various prosthodontic products.

• Mechanism: Physical expansion of paste combined with astringent effect of active ingredient.
• Placement Time: Typically 1-2 minutes under compression cap pressure.
• Best Use Case: Single-unit anterior crowns, veneers, or shallow Class V restorations.
• Limitation: Less lateral displacement than cord, unsuitable for deep margins.

Safest chemical agents for hemostasis during gingival retraction are astringents: aluminum chloride and ferric sulfate. These work locally by precipitating proteins, forming a mechanical plug that occludes capillaries without significant systemic effects. This makes them safer than vasoconstrictors like epinephrine, which carry adverse cardiovascular risks.

Aluminum chloride (15-25% concentrations) provides good hemostasis with minimal tissue irritation, but residual amounts can inhibit PVS polymerization. Ferric sulfate (15.5-20%) is a more potent hemostatic, yet can cause temporary, dark gingival staining and is highly acidic. Epinephrine offers profound hemostasis via vasoconstriction but is contraindicated in patients with heart conditions, hypertension, or hyperthyroidism due to systemic risks.

• Aluminum Chloride: Safe and effective, but requires thorough rinsing to prevent PVS inhibition.
• Ferric Sulfate: Excellent hemostasis, especially for problem bleeding, but can cause transient tissue discoloration.
• Epinephrine: Offers superior vasoconstriction but carries significant systemic risks (e.g., tachycardia, elevated blood pressure).
• Rinsing Protocol: Sulcus must be vigorously rinsed with water spray for at least 15 seconds and dried before impression making.

The two-cord technique offers maximum gingival displacement for deep subgingival margins or thick, fibrotic biotypes. It provides superior vertical and lateral tissue deflection versus single cords, creating a 'V'-shaped sulcular trough for impression material flow without tearing.

This technique involves placing a small-diameter primary cord (e.g., 000 or 00) deep into the sulcus, which remains during the impression. A larger secondary cord (e.g., 1 or 2) is then packed on top for bulk displacement. Before injecting impression material, the secondary cord is wetted and removed, leaving the primary cord to prevent sulcus collapse and control crevicular fluid seepage, ensuring clear, accurate margin capture.

• Deep Subgingival Margins: Essential when finish line is >1.5 mm below gingival crest.
• Thick Gingival Biotype: Provides necessary force to displace dense, resistant tissues effectively.
• Hemorrhage Control: Primary cord can be soaked in hemostatic agent for targeted bleeding control.
• Prevents Tearing: Primary cord acts as barrier, preventing thin impression material sections from tearing.