Pulp Protection in Dentistry

Pulp Protection

• Pulp protection is crucial in operative dentistry to preserve the health of the dental pulp.
• The remaining dentinal thickness (RDT) is the single most important factor in protecting the pulp from insult.
• RDT of 2 mm or more reduces pulpal reaction.

Functions and Importance of Pulp Protection

• Thermal protection: preventing thermal and electrical conductivity of metallic restorations.
• Electrical protection: preventing electrical conductivity of metallic restorations.
• Chemical protection: preventing acids and monomers in restorative materials from affecting the pulp.
• Mechanical protection: withstanding the force of condensation.
• Biological protection: preventing bacteria from saliva.

Ideal Requirements of Liners and Bases

• Non-irritant to the pulp.
• Compatible with the restorative material.
• Strong enough to withstand the force of mastication and condensation.
• Reduces thermal conductivity of metallic restorations.
• Improves marginal seal of restorative material and adaptation to cavity walls and margins.
• Prevents chemical exchange between the restoration and tooth.
• Reduces galvanic action of certain metallic restorations.
• Resists degradation in oral fluids.
• Enhances the formation of reparative dentin.
• Easy to manipulate and apply.

Cavity Sealers

• Provide a protective coating (2-5micron thick) to the walls of the prepared cavity.
• Act as a barrier to leakage at the interface of the restorative material and the walls.

Pulp Protection Materials

• Cavity varnish: provides thermal and electrical protection.
• Liners and bases: provide pulpal protection or pulpal response protection.

Zinc Oxide Eugenol (ZOE) Cement

• Advantages:
  • Perfect initial sealing.
  • Effective thermal insulating capacity.
  • Capable of blocking the penetration of metallic ions and acids.
• Disadvantages:
  • Low crushing strength.
  • Slow setting.
• Indications:
  • Temporary filling material to seal up cavities between visits.
• Contra-indications:
  • Cannot be used as base material due to low crushing strength.
  • Cannot be used as sub-base material due to slow setting.
  • Cannot be used with resinous materials as it retards or prevents polymerization.
  • Cannot be used for direct pulp capping as it leads to pulp necrosis.

Glass Ionomer Liner

• Advantages:
  • Adhesive to tooth structure.
  • Anticariogenic due to fluoride release.
  • Biocompatible with the pulp.
  • Thermal and electrical insulator.
  • Compatible with all restorative materials.
  • Semi-translucent color.
  • Higher modulus of elasticity.
• Disadvantages:
  • Water sorption leading to leakage, discoloration, and penetration of microorganisms.
  • Low wear or abrasion resistance.

Zinc Polycarboxylate Cement

• Advantages:
  • Chemical adhesion to teeth.
  • Minimally irritating to the pulp.
  • Good thermal insulator.
• Disadvantages:
  • Twice as soluble as zinc phosphate cement.
  • Lower compressive strength than zinc phosphate cement.

Cavity Bases

• Used as dentin replacement materials and for blocking out undercuts for indirect restorations.
• Protect pulp against thermal injury, galvanic shock, and chemical irritation.
• Should provide support for the restoration subjected to occlusal loading.
• Used in a thickness of greater than 0.75mm (1-2mm).

Zinc Phosphate Cement

• Material of choice as base under metallic restorations.
• Excellent thermal and electrical insulator.
• Good compressive strength.
• Low solubility in water.
• Composed essentially of zinc oxide powder and aqueous solution of phosphoric acid.
• Acidic in nature when placed (pH 3-4) and for a short time until the reaction is completed.
• After one hour, pH comes to 6.
• Acidity is detrimental to the pulp dentin organ.
• Requires a cavity liner under the cement in deep cavities and varnish.

Reinforced Zinc Oxide Eugenol Cement

• Modified zinc oxide/eugenol cement with additives to overcome disadvantages.
• Composition: zinc oxide and zinc acetate, resins (e.g. polystyrene, polycarbonate), alumina, and ethoxy benzoic acid (EBA) and eugenol.
• Advantages: higher strength and faster setting time.