NEET MDS Lessons
Dental Materials
Temporary Filling Materials
Applications / Use
While waiting for lab fabrication of cast restoration
While observing reaction of pulp tissues
Objectives
Provide pulpal protection
Provide medication to reduce pulpal inflammation
Maintain the tooth position with an aesthetic restoration
Classification
Temporary filling cements
Temporary filling resins
Components
Temporary filling cements
1. Zinc oxide-eugenol cement with cotton fibers added
2. Polyme r powder-reinforced zinc oxide eugenol cement
Temporary filling resins
• MMA / PMMA filling materials
• Polyamide filling materials
• BIS-GMA filling materials
Gypsum Products
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Characteristics |
Plaster |
Stone |
Diestone |
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Chemical Name |
Beta-Calcium Sulfate hemihydrate |
Alpha-Calcium sulfate hemihydrate |
Alpha-Calcium sulfate hemihydrate |
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Formula |
CaSO4 – ½ H2O |
CaSO4 – ½ H2O |
CaSO4 – ½ H2O |
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Uses |
Plaster Models ,Impression Plasters |
Cast Stone, Investment |
Improved Stone, diestone |
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Water(W) Reaction Water Extra Water Total water Powder (P) W/P Ratio |
18ml 32ml 50ml 100g 0.50 |
18ml 12ml 30ml 100g 0.30 |
18ml 6ml 24ml 100g 0.24 |
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PROPERTY |
INGREDIENT |
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Silver |
Tin |
Copper |
Zinc |
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Strength |
Increases |
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Durability |
Increases |
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Hardness |
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Increases |
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Expansion |
Increases |
Decreases |
Increases |
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Flow |
Decreases |
Increases |
Decreases |
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Color |
Imparts |
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Setting time |
Decreases |
Increases |
Decreases |
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Workability |
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Increases |
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Increases |
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Introduction
The science of dental materials involves a study of the composition and properties of materials and the way in which they interact with the environment in which they are placed
Selection of Dental materials
The process of materials selection should ideally follow a logical sequence involving
(1) analysis of the problem,
(2) consideration of requirements,
(3) consideration of available materials and their properties, leading to
(4) choice of material.
Evaluation of the success or failure of a material may be used to influence future decisions on materials selection.
Manipulation
Mixture of powder and liquid is painted onto working cast to create shape for acrylic appliance à After curing of mixture, the shape and fit are adjusted by grinding with burrs and stones with a slow-speed handpiece .Acrylic dust is irritating to epithelial tissues of nasopharynx and skin and may produce allergic dermatitis or other reactions. Grinding may heat polymer to temperatures that depolymerize and release monomer vapor. which may be an irritant
Investment Materials
Investment is mold-making material
Applications
a. Mold-making materials for casting alloys
b. Mold-making materials for denture production
Classification
a. Gypsum-bonded investments (based on gypsum products for matrix)
b. Phosphate-bonded investments
c. Silicate-bonded investments
Components
a. Liquid-water or other reactant starts formation of matrix binder by reacting with reactant powder
b. Powder-reactant powder, filler, or modifiers
Manipulation
a. P/L mixed and placed in container around wax pattern
b. After setting, the investment is heated to eliminate the wax pattern in preparation for casting
CASTING: casting is the process by which the wax pattern of a restoration is converted to a replicate in a dental alloy. The casting process is used to make dental restorations such as inlays, onlays, crowns, bridges and removable partial dentures.
Objectives of casting
1) To heat the alloy as quickly as possible to a completely molten condition.
2) To prevent oxidation by heating the metal with awell adjusted torch .
3) To produce a casting with sharp details by having adequate pressure to the well melted metal to force into the mold.
STEPS IN MAKING A CAST RESTORATION
1. TOOTH PREPARATION
2. IMPRESSION
3. DIE PREPARATION
4. WAX PATTERN FABRICATION
5. SPRUING