Base, Liner, and Varnish in Dentistry: Functions, Applications, and Precautions

Base, Liner And Varnish

Cavity varnish is a solution of one or more resins in a volatile solvent which when applied onto the cavity walls, evaporates leaving a thin resin film that serves as a barrier between the restoration and dentinal tubules.

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Compositions of Cavity varnish:

• Natural gum such as copal, rosin, or synthetic resin dissolved in an organic solvent like alcohol, acetone, or ether.
• Medicinal agents such as chlorobutanol, thymol and eugenol may be added. Some varnishes also contain fluorides

Applications of Cavity varnish:

• Cavity varnish reduces microleakage around the margins of newly amalgamed restorations.
• Cavity varnish reduces the passage of irritants into the dentinal tubules from the overlying restorations or base.
• Cavity varnish also prevents the penetration of corrosion products into the dentinal tubules in case of amalgam restorations, thus minimizing the tooth discoloration.
• Varnish may be used on the surface of metallic restoration as a temporary protection in case of galvanic shock.
• Varnish may be used as a surface coating over certain restorations to protect them from dehydration or contact with oral fluids, for example
• Glass Ionomer Cement (GIC) and silicate restorations.

Precautions of Cavity varnish:

• Varnish should be tightly capped immediately after use to prevent loss of solvent by evaporation.
• Cavity varnish should be applied in thin consistency.
• Excess varnish should not be left on the margins of restorations as it prevents proper finishing of the margins of restorations

Placement of Cavity varnish:

• Apply varnish by small cotton pledget or by applicator tip.
• The solvent gets evaporated and leaves a thin layer of resin behind with porosities.
• Now a second layer is applied to get a uniform thin layer of varnish.

Disadvantages of Cavity varnish:

• Varnish should not be used under composites as it interferes polymerization process of composites.
• Under the GIC and polycarbonate cement, it interferes with chemical bonding and fluoride release.