Dental Materials Quiz

Calcium Hydroxide

• Used for indirect pulp capping, when a cavity preparation leaves little dentin covering the pulp
• Used for direct pulp capping when a micro pulp exposure is suspected
• Supplied in paste-paste system
• One paste contains calcium hydroxide in distilled water
• Second paste contains salicylate (weak acid similar to eugenol), titanium oxide
• Paste 1 contains calcium hydroxide, zinc oxide, zinc stearate and ethyl toluene sulphonamide
• Paste 2 contains glycol salicylate, titanium dioxide, calcium sulfate, and calcium tungstate

Varnish

• Applied to surface of new metallic restorations to reduce galvanic action
• Composed of natural gum (copal, rosin or synthetic resin) and organic solvent (acetone, chloroform or ether)
• Varnish protects underlying tooth structure by acting as a film after solvents evaporate
• Two applications are required

Thermal Barrier

• Materials designed to be used as dental restorations, to restore tooth structure loss
• Thin residual layer of dentin puts the pulp at risk for thermal shock when tooth is exposed to hot/cold food
• Thermal injury to the pulp may occur due to heat from filling material liberated during setting, or a base that sets by an exothermic reaction

Chemical Barrier

• Phosphoric acid in silicate materials and acrylic monomers present in some resin-based restorative materials can act as a barrier
• The cements themselves can contain irritants
• Cements are designed to create an adhesive bond at the tooth/restoration interface, to eliminate or reduce leakage at the margins

Electrical Barrier

• Insulating cement helps prevent galvanic shock but is not an ideal electrical insulator
• Varnish consisting of less polar resins (polysterene) can be used to provide electrical barrier

Cement Based on Phosphoric Acid

• The setting reaction of Zinc Phosphate Cement is: Zinc Oxide + Phosphoric Acid → Zinc Phosphate + Heat
• The setting reaction of Silicophosphate Cement is: Silica + Phosphoric Acid → Silicophosphate + Heat
• Copper Cement contains copper and inhibits bacterial growth

Cement Based on Organometallic Chelate Components

• Zinc Oxide Eugenol has obtundent properties, useful for sedative and temporary fillings
• Zinc Oxide Eugenol has bactericidal properties
• Zinc Oxide Eugenol is not suitable for luting, due to the presence of free eugenol - causes discoloration and softening of composite surfaces
• Ortho-ethoxybenzoic Acid (EBA) Cements are stronger and less soluble than Zinc Oxide Eugenol
• Calcium Hydroxide Cements are commonly used as liners and bases, and have biocompatible properties

Cement Based on Polyacids

• Polycarboxylate Cements provide minimal irritation to the pulp
• Glass Ionomer/ Polyalkenoate Cement has a pH of 1.7, bonds chemically with stainless steel

Zinc Oxide Eugenol Cement

• Used as sedative and temporary fillings, due to its obtundent property
• Can withstand amalgam condensation forces
• Setting Reaction for Zinc Oxide Eugenol is: H2O + Zinc Oxide + Eugenol → Zinc Eugenolate
• Unreinforced ZOE used when strength and solubility are not critical; for temporary restorations; has compressive strength of 20 MPa
• Reinforced ZOE used for temporary and intermediate bases; contains additives like alumina, rosin and polymethyl methacrylate resin; compressive strength of 40 MPa
• ZOE is not suitable for luting due to free eugenol being replaced by water, which causes hydrolysis of zinc eugenolate and disintegration of cement structure.

Polycarboxylate Cement

• Has a good biocompatibility for the pulp
• Mix is completed in 30-40 seconds
• Clean up is performed before material sets