Dental Materials Quiz

Dental Materials and Laboratory Procedures

• Mouthwash is used for a pure and clean mouth.

Mechanical Properties

• Force: Causes physical changes via energy and strength, creating stress or strain.
• Stress: Reaction within the material causing distortion, creating stress and strain.
• Strain: Change in product in the result of stress.
• Tensile Stress: Pulling and stretching the material.
• Compressive Stress: Pushing materials together, such as chewing.
• Shear Stress: Breakdown over sliding of two materials.
• Ductility: Change shape via pulling force without fracturing.
• Malleability: Change shape into thinner sheet or plate via compressive force.

Thermal Properties

• Contraction/Expansion: Hot to cold food/drinks cause sudden contraction and expansion in seconds, causing restorative materials to pull away from teeth. This results in microleakage or cracked restorations.
• Microleakage: Separation of material from teeth due to temperature changes during hot or cold food/drinks, or through expansion and contraction, allowing fluids, debris and microorganisms to enter between the cavity preparation wall and material.
• Percolation: Process of liquid slowly passing through a porous substance.

Application Properties

• Flow: Dental material should possess a pliable(soft) consistency to fill the preparation of teeth.
• Adhesion: Proper adhesion prevents microleakage and loss of restorations. Force causes unlike materials to adhere to each other, affecting the adhesion process.
• Wetting: Ability of a liquid to flow over a surface.
• Viscosity: Liquids flow over surfaces; the resistance of a fluid flowing, described in terms of wetting and viscosity.

Retention

• Retention: Holding together two things that otherwise wouldn’t adhere to each other.

Curing

• Auto-cured: Materials harden through a chemical reaction, often triggered by light exposure in the blue wave spectrum.
• Light-cured: Harden only under light.

Electrical Properties

• Galvanic/Shock: Two dissimilar metals in the oral cavity with saliva causing electrical conduction can lead to galvanic shock.
• Saliva: containing salt acts as a good electrical conductor.

Solubility

• Solubility: Substance will dissolve in certain amount of another substance (liquid). For Example Material in oral cavity that dissolves easily will wash away and leave tooth structure exposed

Corrosive Properties

• Corrosion: Reaction of metals in contact with temperature, humidity, and saline.

Dental Amalgam

• 143-54% of mercury equal to 46-57% of alloy powder
• Alloy powder is mixed with mercury.
• Soft pliable mixture that's placed in the tooth, then condensed, carved and hardened to create a permanent amalgam filling.

Amalgam Composition

• Silver
• Tin
• Copper
• Zinc

Amalgam Indications

• Small to medium sized cavities in posterior teeth.
• Patients with poor oral hygiene.
• Foundation of metal-ceramic, cast metal and ceramic restorations.
• Severe destruction of tooth structure.

Amalgam Contraindications

• Allergy to mercury.
• Large restorations when other restorative materials aren't a significant factor for esthetics.

Composite Resin

• Properties: Withstand oral cavities. Matches natural tooth color. Easily shaped to tooth anatomy. Bonds directly to teeth.
• Indications: restorations for surface defects (hypocalcification, attrition, abrasion, and congenital abnormalities). Closure of diastema.
• Composition: Organic resin material (dimethacrylate), Inorganic fillers, Coupling agents, pigments.

Flowable Composite

• Properties: Wear resistance from sufficient filler, ability to flow into conservative restorations.
• Application: Extrusion into minute cavity preparations.

Acid Etch

• Steps: Dry cavity vigorously, apply acid etch to enamel wall, for 15-30 seconds, when prep is contaminated repeat for half the time.
• Precautions: Avoid contact with soft tissue; thoroughly rinse if contaminated.

Bonding Procedures

• Chemically bonds material to tooth structure (adds micro-mechanical retention)
• Light cured, so no mixing.

Protective Shield

• Protective shield needed when curing bonding agent.

Precautions

• Protective shield when curing bonding agent to protect eye hazard to provider and patient.
• Light should be positioned correctly on relevant surface.

Advantages (Composite Resin)

• Bonds further support to tooth structure, preventing damage.
• Matches natural tooth color. Fixes mishaped, chipped or discolored teeth in one procedure (6-12 years). Reduced sensitivity.
• Reduced need for extensive tooth structure removal compared to amalgam.

Precautions (Composite Resin)

• Ensuring proper use of protective shield.
• Ensuring correct dispensing of material before exposure to light. For large restorations, increments should be cured before next application.

Micro-mechanical Retention

• Bonding agents use microscopic interlocking with enamel porosities, tubules, and other structures.

Macro-mechanical retention

• Undercuts in dentin to retain non-bonded amalgams and self or auto cure compounds.

Application of Composite versus Amalgam

• Composite resin cavity prep designed for micro-mechanical retention.

Glass Ionomer (GIC)

• Versatile dental material.
• Excellent biocompatibility with oral environment. Adaptable for various uses.
• Used for permanent restorations (liners, bonding agents, and cements) for primary (children) teeth and minor restorations of adults.
• Not suitable for high-stress areas.

Types of GIC

• For cementing metal restorations and direct-bonded orthodontic brackets.
• Restoring areas near gingiva.
• Used as liners and dentin bonding agents.
• Reinforced GIC, using silver and tin, for high-stress situations.

Supply of GIC

• Powder and liquid
• Pre-mixed paste tubes and mechanically triturated capsules that dispense through dispenser.

Precautions (GIC)

• Avoid exposure to water.

Temporary Restorative Materials

• Maintain, restore and function to keep patient comfortable for a limited time.

Temporary Restorative Materials Applications

Tooth Whitening Materials

• Bleaching. Cost-effective method of tooth restoration using peroxide-based ingredients.

Indications (Tooth Whitening)

• Removal of staining.
• Peroxide breaks down and oxygen enters enamel and dentin removing discoloration.

Indirect Restorative Materials

• Restorations created outside the mouth by dental technicians. Restorative materials are placed after preparing the tooth and taking an impression.

Indirect Restorative Materials Types

• Castings.
• Noble metal alloys.
• Base metals.
• Ceramic castings.

Dentinal Liners and Bases

• Insulating the pulp tissue to protect from sensitivity caused by procedures.
• Protect tooth from thermal shock.

Dental Cements

• Permanent, intermediate, temporary restorations.
• Luting for indirect and orthodontic procedures.
• Thermal insulator of metallic restorations.
• Periodontal packs with zoe sedation.

Affecting Cements

• Mixing time
• Humidity
• Powder to liquid ratio
• Temperature

Luting Agents

• Permanent temporary
• Zinc phosphate, polycarboxylate, and glass ionomer (GIC)

Zinc Oxide Eugenol

• Types (1 (ZOE, IRM, temporal bond): for temporary cementation (putty); lacks strength and long-term durability, and Type II (Relyx): has reinforcing agents; for permanent restorations of cast restorations or appliances)

Zinc Phosphate

• Types 1 (fine grain) for permanent cementation (e.g., inlays, crowns, onlays, bridges, and thin film layer for castings); and 2 (medium grain) as insulating base for cavities
• Properties - viscosity, strength, bonding to enamel.

Zinc Polycarboxylate

• Properties - viscosity, strength, bonding to enamel (useful for temporary applications)
• Powder and liquid for use in crowns and orthopedic bands and restorations.

Guidelines for Mixing Dental Cements

• Powder towards one end of glass or paper pad; liquid on opposite end.
• Use explorer, mouth mirror, and spoon excavator for cement removal. Clean instruments right away.

Articulator

• Replicates the movement of the TMJ (temporomandibular joint)

Sandblaster

• A device that blasts sand and air to polish dental castings.

Dental Lathe

• Used for trimming dental castings and appliances

Model Trimmer

• A device for trimming study models.

Heat Source

• Used to heat waxes.

Impression Trays

• Metal, plastic, polystyrene.

Sizes

• Quadrant (half of arch)
• Section (anterior)
• Full arch (covers full arch)

Custom Trays

• Designed to fit specific patient needs, often for patients with high palates.

Block Out Material

• Soft, light-cured dental material to protect undercuts of soft tissue procedures. It is placed on the cast to make space for impression materials.

Seperating Medium

• Liquid used to separate casts and impression materials for proper set.

Hydrocolloid Impression Materials

• Includes Alginate or Reversible hydrocolloid for preliminary impressions.