Cavity Varnish, Liners, Bases – Differences and Uses

Cavity Varnish, Base, liner or Sealer are an integral part of Operative Dentistry which has the main goal of Preserving the health of Dental Pulp. In Operative Dentistry, the main objective is to restore the tooth affected by either caries, trauma etc with Restorative materials. These Permanent Restorative materials are harmful to the pulp when exposed to it, here is when the Pulp Protective agents come in. They act as a barrier between the restorative material or pulpal irritants and the Vital Pulp. Cavity Liners and Bases are used to prevent damage to the pulp which might result in irreversible pulpitis and might require Root Canal Treatment.

What are the Various Pulpal Irritants:

• Pulpal irritants are the substances or factors which lead to damage of the pulpal tissue.
• Caries, trauma, erosion, attrition etc
• Heat, Pressure, desiccation etc.

Cavity Varnish: Uses, techniques, advantages

It is a liquid that is applied on the surface of the teeth as a thin layer and later converted into a solid layer by using either a chemical or any physical process. Liquid-based or solvent-based varnish is used to help in making it easy to apply on the irregular surface of the tooth equally. It is usually a natural gum like copal resin or synthetic resin dissolved in organic solvents such as ether, alcohol or chloroform to help in ease of application.

The ideal requirements of a Dental Varnish is Bio compatibility, ease of application, patient comfort, ease of activation.

Uses of Cavity / Dental Varnish:

• Protection of Teeth from Dental Caries: Teeth are protected from future caries activity by the release of active substances such as fluoride or antimicrobial substances
• Desensitizing teeth: Varnish helps in decreasing sensitivity by forming a physical layer on top of the tooth which blocks the Dentinal tubules.
• Whitening of Teeth: Dental Varnishes sometimes contain bleaching agents in them which help in whitening of the teeth acting as indirect bleaching agents.

Varnishes are used in moderate to high-risk caries cases, as a preventive measure, dentinal hypersensitivity, post-operative sensitivity cases.

Types of Dental Varnish:

There are multiple types of Varnish depending on the ingredients it contains and the purpose of the Varnish. Fluoride Varnish, Tooth whitening Varnish, Desensitizing varnish, Antimicrobial varnish. The other types are depending on how they are cured – Physically cured or Chemically cured.

Most commonly used varnishes are:

• Duraphat: Fluoride varnish with 22,600 ppm fluoride in the form of Sodium fluoride
• Carex: Fluoride Varnish with lower concentration of fluoride but equivalent efficacy as that of duraphat in preventing caries.
• Fluoroprotector: Polyurethane based product with 7000 ppm fluoride as Silane fluoride. Clinical efficacy has been under question as it is mentioned as 1% to 17%.
• Duraflour: it consists of 5% NaF in alcoholic suspension of natural resins.
• Zarosen: Anti-microbial varnish, reduces the bacterial growth in the oral cavity. Commonly used is Chlorhexidine thymol varnish as it prevents growth of both gram negative and gram positive organisms.

Dental Varnish is applied in dental clinic easily without much use of dental equipment, complete oral prophylaxis followed by drying and isolation of the teeth to be applied. An applicator tufted small brush is used to apply the material on the proximal surfaces. Patient should be asked to wait for 5 mins with open mouth and all saliva should be suctioned out with the liquid applied on the surface of the tooth.

Patient is asked not be rinse of drink anything for the next one hour and should be advised not to chew anything solid on the teeth which have undergone application. It takes anywhere between 18-20 hours for the varnish to have the fluorides desired effect on the enamel. The only disadvantage with Varnish is that it leaves yellowish discoloration on the tooth for a few days along with a bad taste.

To prevent discoloration and bad taste – Duraflor Halo has been introduced keeping in mind Children.

Dental Liners of Cavity Liners:

A Cavity Liner is defined as a liquid containing CaOH and zinc Oxide (occasionally) suspended in a solution of synthetic or natural resins. Commonly used agents clinically are – Dycal and Life which is available in two paste system containing CaOH and Accelerator. The Cavty liner helps in providing thermal and physical insulating properties from the restorative material on the surface of the tooth. Resin Modified Glass Ionomer cement is also being used as a liner.

There are two types of Liners based on the suspension – Solution Liners or Varnish which are Copal or natural resin dissolved non-aqueous volatile solvent which dry after application to produce a thin layer over the tooth surface. Suspension Liner is the second type of Liner where the suspension is water and hence dry’s slowly and leavers a thicker layer (20-25 um) on the tooth surface helping in thermal protection.

Composition of Cavity Liners:

1. Therapeutic agent: Calcium Hydroxide and Zinc Oxide
2. Solvent: Ethyl alcohol
3. Thickening Agent: Ethyl cellulose
4. Radiopacifier: Barium sulfate
5. Anticariogenic: Fluoride

Functions of Cavity Liner:

Protection of Pulp from Thermal, Electrical (Amalgam Restoration) and Mechanical forces. The degree of insulation depends on thickness of remaining dentin, for pulpal protection 2mm of liner needs to be placed. Ca (OH)2 is used as a suspension or chemically cured of Light cured material in cases of deep caries with caries extending into the Dentin.

Manipulation and Application of Cavity Liners:

Liners (Dycal) are available in two paste system – one containing CaOH and ZnO and the other an Accelerator. Both the materials are dispensed in equal quantities on a mixing pad or glass slab and by using a Probe or a periodontal probe both are mixed to obtain a homogeneous mix and color and is carried using the same instrument to the cavity and applied on the base of the cavity.

A Cavity Liner is applied as thin layer on the floor of the cavity which acts as a barrier between the restoration and the dentin. Its main purpose is to protect the pulpal tissue from any irritants like thermal, physical, chemical or mechanical agents. It acts as a pulp capping agent along with having anticariogenic properties as it helps in formation of secondary Dentin or repairative dentin.

Dental or Cavity Bases:

These are placed similar to Liners but are indicated in cases where the amount of remaining dentin is low and a thicker Base is required for protection of pulp under the restoration. Minimum thickness of a Dental base to achieve thermal protection is 0.75mm. Bases are of two types based on the strength required –

Sub or Low Strength Base: Ca (OH)2, Zinc Oxide Eugenol, Glass Ionomer cement

High Strength Base: Glass Ionomer, Resin Modified Glass Ionomer, Reinforced Zinc Oxide Eugenol, Zinc Phosphate, Zinc Polycarboxylate.

Ideal Requirements of Dental Base:

• Should has high strength in low thickness which will not affect the thickness of the Restoration
• Compatible with the Dentin, Pulpal tissue and the overlying Restoration
• Should not irritate the Pulpal Tissue
• Should not Discolor
• Easy to manipulate and place in the cavity to help reduce working time
• Setting time should be short to help in placing the permanent restoration in immediate succession
• Should prevent Dentin permeability

For Thermal Insulation: ZOE, Ca (OH)2, Zinc Polycarboxylate are used

For Chemical Insulation: ZOE, Ca (OH)2 are considered ideal while GIC and Zinc Polycarboxylate can also be used

The main criteria of using a Liner or a Base is to protect the Pulpal and Dentinal tissues from external factors and the overlying restoration as well. While Varnish has varied purposes all these are used to protect the tooth from further damage and come under either preventive or restorative treatment plans in Dentistry.