Retraction cords and haemostatic pastes: haemostasis and sulcus opening are two different problems

Managing the gingival sulcus before an impression solves two problems that tend to be conflated: opening the space so material can enter, and stopping bleeding so it does not contaminate.

A dry cord opens but does not stop blood; a haemostatic paste stops blood but opens little. Confusing them leads to choosing the wrong tool for the problem at hand.

Cords differ by construction. Braided cords compress into the sulcus and expand slightly, conforming to its shape; twisted cords tend to unravel during insertion; knitted cords hold impregnating agents best.

Diameter is chosen relative to sulcus depth, not tooth size. Too thick a cord will not enter and pushes the tissue outward; too thin a cord disappears into the sulcus and cannot be retrieved.

Among impregnating agents, aluminium chloride has the best profile for adhesive prosthodontics. It acts by protein precipitation, controls light bleeding well and leaves no residue interfering with bonding.

Ferric sulphate is more effective against heavy bleeding, but leaves a dark precipitate and, above all, inhibits polymerisation of resin materials. Using it before adhesive cementation compromises the bond.

Epinephrine is now little used, owing to systemic risk in cardiac patients and to rebound: bleeding resumes when vasoconstriction ceases, often just as the material is setting.

The double-cord technique remains the best documented for subgingival margins. A thin cord stays in place during the impression and controls fluid; a thicker one, removed just before, has opened the space.

The moment of removal matters more than the cord chosen. Removing dry reopens bleeding because the clot adheres to the fibres: the cord must be moistened before withdrawal.

Retraction pastes in cartridges have gained ground because they require no instrumentation within the sulcus. They are injected, act for a few minutes, and are rinsed away.

Their limitation is the opening achieved: good in already wide sulci, insufficient where the margin is deep and the tissue tightly attached. They remain indicated in thin biotypes, where cord can cause permanent recession.

Contact time must be respected in both cases. A cord left beyond ten minutes can produce ischaemia and recession; a paste rinsed early has not acted.

In summary: aluminium chloride where adhesive cementation will follow, ferric sulphate only where no bonding is involved, cord to open and paste for delicate biotypes. And the cord is always moistened before removal.