Dental Materials Lecture DMD-3L

Elastomers in Dentistry

• Elastomers are synthetic polymer-based impression materials with elastic properties similar to natural rubber.
• Common types of elastomers include Polysulfide, Polyether, and Silicone (condensation and addition).
• Used for making impressions in dentistry, particularly for partial and complete edentulous cases.

Polysulfide Impression Material

• First elastomeric impression material introduced, made from polysulfide polymer (mercaptan).
• Polymerization time (curing time) defines the time needed for the material to harden.
• Setting conditions lead to a flexible and paste-like state.

Composition of Polysulfide

• Base: Polysulfide polymer (contains mercaptan) which is cross-linked via oxidizing agents.
• Catalyst: Typically lead dioxide, which acts as an accelerator and is brown in color.
• Fillers: Lithopone or titanium dioxide enhance strength and prevent stickiness.
• Plasticizers: Include oleic or stearic acid (retarders) and dibutyl phthalate to adjust viscosity and workability.
• Sulfur: Present at 0.5%, enhances the reaction during curing.

Setting Reaction

• Chemical reaction involves lead dioxide and polysulfide polymer, producing polysulfide and water as a by-product.
• Working time for the material is approximately 4-7 minutes, with a setting time of 7-10 minutes.

Characteristics of Polysulfide

• No syneresis or imbibition occurs, maintaining the integrity of impressions.
• Hydrophobic nature ensures no change to the dental model, although it leads to longer setting times than other impression materials.

Advantages and Disadvantages

• Advantages: Long working time allows for detail capture; good for fixed appliances capturing necessary landmarks.
• Disadvantages: Requires a custom tray for application and has a longer setting time.

Elastomers in Dentistry

• Elastomers are synthetic polymer-based impression materials with elastic properties similar to natural rubber.
• Common types of elastomers include Polysulfide, Polyether, and Silicone (condensation and addition).
• Used for making impressions in dentistry, particularly for partial and complete edentulous cases.

Polysulfide Impression Material

• First elastomeric impression material introduced, made from polysulfide polymer (mercaptan).
• Polymerization time (curing time) defines the time needed for the material to harden.
• Setting conditions lead to a flexible and paste-like state.

Composition of Polysulfide

• Base: Polysulfide polymer (contains mercaptan) which is cross-linked via oxidizing agents.
• Catalyst: Typically lead dioxide, which acts as an accelerator and is brown in color.
• Fillers: Lithopone or titanium dioxide enhance strength and prevent stickiness.
• Plasticizers: Include oleic or stearic acid (retarders) and dibutyl phthalate to adjust viscosity and workability.
• Sulfur: Present at 0.5%, enhances the reaction during curing.

Setting Reaction

• Chemical reaction involves lead dioxide and polysulfide polymer, producing polysulfide and water as a by-product.
• Working time for the material is approximately 4-7 minutes, with a setting time of 7-10 minutes.

Characteristics of Polysulfide

• No syneresis or imbibition occurs, maintaining the integrity of impressions.
• Hydrophobic nature ensures no change to the dental model, although it leads to longer setting times than other impression materials.

Advantages and Disadvantages

• Advantages: Long working time allows for detail capture; good for fixed appliances capturing necessary landmarks.
• Disadvantages: Requires a custom tray for application and has a longer setting time.

Explore the essential concepts of dental materials, focusing specifically on elastomers and hydrocolloids in the context of DMD-3L. This quiz will test your knowledge of polysulfide materials and their applications in dentistry.