Dental Materials: Gypsum Products

Setting Reactions

• Gypsum products undergo a hydration reaction when mixed with water, resulting in the formation of gypsum crystals.
• The setting reaction involves the reaction of calcium sulfate hemihydrate (CaSO4·0.5H2O) with water to form dihydrate (CaSO4·2H2O).
• The reaction is exothermic, releasing heat as it sets.

Composition

• Gypsum products typically consist of:
  • Calcium sulfate hemihydrate (CaSO4·0.5H2O) as the primary component.
  • Water.
  • Additives such as:
    • Retarders (e.g., potassium sulfate) to slow down the setting reaction.
    • Accelerators (e.g., sodium chloride) to speed up the setting reaction.
    • Fillers (e.g., silica) to improve strength and durability.

Properties

• Gypsum products exhibit:
  • High compressive strength (up to 2000 psi).
  • Low tensile strength (around 100-200 psi).
  • High density (around 2-3 g/cm³).
  • Low thermal conductivity.
  • Good dimensional stability.

Manipulation

• Gypsum products can be manipulated by:
  • Mixing with water to achieve the desired consistency.
  • Vibration or tapping to remove air bubbles.
  • Carving or shaping to achieve the desired form.
  • Investment materials can be added to improve strength and durability.

Clinical Applications

• Gypsum products are commonly used in dentistry for:
  • Making impressions and molds for dental restorations.
  • Creating dental models and casts.
  • Fabricating dental appliances, such as dentures and orthodontic devices.
  • Manufacturing dental implants and surgical guides.

Setting Reactions

• Gypsum products undergo hydration reaction when mixed with water, forming gypsum crystals.
• The reaction involves calcium sulfate hemihydrate reacting with water to form dihydrate, releasing heat as it sets.

Composition

• Gypsum products primarily consist of calcium sulfate hemihydrate (CaSO4·0.5H2O) and water.
• Additives can be included, such as:
  • Retarders (e.g., potassium sulfate) to slow down the setting reaction.
  • Accelerators (e.g., sodium chloride) to speed up the setting reaction.
  • Fillers (e.g., silica) to improve strength and durability.

Properties

• Gypsum products exhibit high compressive strength (up to 2000 psi).
• They have low tensile strength (around 100-200 psi).
• They have high density (around 2-3 g/cm³).
• They have low thermal conductivity.
• They exhibit good dimensional stability.

Manipulation

• Gypsum products can be manipulated by mixing with water to achieve desired consistency.
• Air bubbles can be removed through vibration or tapping.
• Gypsum products can be carved or shaped to achieve desired form.
• Investment materials can be added to improve strength and durability.

Clinical Applications

• Gypsum products are commonly used in dentistry for making impressions and molds for dental restorations.
• They are used for creating dental models and casts.
• They are used for fabricating dental appliances, such as dentures and orthodontic devices.
• They are used for manufacturing dental implants and surgical guides.

Composition of Gypsum Products

• Composed of calcium sulfate dihydrate (CaSO4·2H2O), water, retarders, accelerators, coloring agents, and fillers
• Retarders (e.g., sodium citrate) slow down the setting reaction
• Accelerators (e.g., potassium sulfate) speed up the setting reaction
• Coloring agents (e.g., pigments) and fillers (e.g., silica) are added for specific purposes

Setting Reactions of Gypsum

• Involves the hydration of calcium sulfate hemihydrate to form gypsum
• Exothermic reaction, releasing heat as it sets
• Divided into three stages: initial setting (minutes 1-10), intermediate setting (minutes 10-30), and final setting (after 30 minutes)

Properties of Gypsum Products

• Exhibits high compressive strength (up to 10,000 psi)
• Exhibits moderate tensile strength (up to 500 psi)
• Has low thermal conductivity, making it a good insulator
• Low cost and easy to manipulate
• Can be colored and shaped to mimic natural teeth
• Used as a model material for dental restorations

Manipulation of Gypsum Products

• Can be mixed with water to create a workable consistency
• Vibration or spatulation can be used to remove air bubbles and improve consistency
• Can be carved or shaped to create the desired form
• Investment materials can be used to create a mold around the gypsum model

Clinical Applications of Gypsum Products

• Used in various dental applications, including dental models and casts for restorative dentistry and orthodontics
• Used for impressions and molds for dental restorations
• Used for temporary restorations (e.g., temporary crowns)
• Used for study models for diagnosis and treatment planning
• Used for educational models for dental education and training