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Gypsum/certified fixed orthodontic courses by Indian dental academy /certified fixed orthodontic courses by Indian dental academy
 

Gypsum/certified fixed orthodontic courses by Indian dental academy /certified fixed orthodontic courses by Indian dental academy

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The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.

The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.


Indian dental academy provides dental crown & Bridge,rotary endodontics,fixed orthodontics,
Dental implants courses.for details pls visit www.indiandentalacademy.com ,or call
0091-9248678078

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    Gypsum/certified fixed orthodontic courses by Indian dental academy /certified fixed orthodontic courses by Indian dental academy Gypsum/certified fixed orthodontic courses by Indian dental academy /certified fixed orthodontic courses by Indian dental academy Document Transcript

    • CONTENTS: • INTRODUCTION • GYPSUM • CLASSIFICATION • MANUFACTURE • SETTING PROCESS • PROPERTIES • MANIPULATION • COMPATIBILITY • INFECTION CONTROL • RECENT DEVELOPMENTS • CONCLUSION • REFERENCES
    • INTRODUCTION • Auxiliary dental material. • Glossary of Prosthodontic terms: • Model: Facsimile used for display purposes, a miniature representation of something. • Dental Cast: A positive life size reproduction of a part or parts of the oral cavity. • Die: The positive reproduction of the form of a prepared tooth in any suitable substance. • Direct link between the clinical phase of treatment and the technical laboratory procedures. • Contributes significantly to the ultimate success of the prosthesis. GYPSUM: • Originates from the Greek word ‘Gypos’ which means chalk. • Dihydrate of calcium sulfate. • Chemical formula CaSO4.2H2O. • Sulfate mineral most commonly found. • Usually white to yellowish white in color. • Large beds of gypsum were formed when seawater evaporated, leaving dissolved Calcium and Sulfate ions to form deposits of gypsum. • United States is the largest producer as well as the biggest consumer of gypsum. Others are Canada, France, Japan and Iran. Gypsum mineral can be found in various forms: 1. ROCK–GYPSUM: widely occurring massive dull coloured rocks. 2. ALABASTER: Large fine-grained white stones. Often used for carving into vases and ornaments. Also used in building of King Solomon’s Temple 3. SELENITE: as transparent crystals 4. SATIN SPAR: as fibrous crystals. SYNTHETIC GYPSUM: • • Also produced as a by-product of manufacture of phosphoric acid. CHEMICAL GYPSUM. 3 H2SO4(l) + Ca3(PO4)2(s) + 6 H2O(l) 2 H3PO4(s) + 3 CaSO4·2H2O(s)
    • PROPERTIES:  Found as prismatic, curved or twisted monoclinic crystals of vitreous luster.  Specific gravity: 2.3  It cleaves perfectly in one direction.  Moh hardness no: 2, which means that it can be scratched by a fingernail. USES: 1. As a raw material for making Plaster of Paris. Plaster of Paris is called so, because the gypsum that was used to manufacture it came from a village called Montamarte, near Paris. It is used extensively in construction purposes. 2. Grounded gypsum (land plaster) is sometimes used as a fertilizer for soil that needs calcium. 3. Raw gypsum is also used to keep Portland cement from hardening too quickly. 4. It is also used to make paint (as a filler), filters, insulation and wall plaster. 5. Alabaster is used for carving ornaments and vases. 6. Selenite is sometimes used as an optical material. Gypsum produced for dental application is nearly pure calcium sulfate dihydrate. DENTAL USES OF GYPSUM PRODUCTS: • Impression plaster is used to make the impression of the edentulous mouth. • For preparation of study models of oral and maxillofacial structures. • To form cast and dies on which dental prosthesis are constructed. • As a mold material for processing complete dentures. • For mounting of casts on the articulator. • Also used as a binder for silica, gold alloy casting investment, soldering investment and investment for low melting point nickel-chromium alloys.
    • GYPSUM PRODUCTS: • Refers to the various forms of calcium sulfate, hydrous and anhydrous. • Manufactured by the calcination of calcium sulfate dihydrate. • Calcination can be controlled to produce partial or complete dehydration. ADA No: 25. ISO No: 6873. Gypsum products can be classified into five types: GYPSUM PRODUCTS IMPRESSION PLASTER ( ISO TYPE I ) PLASTER ( ISO TYPE II ) HIGH STRENGTH PLASTER STONE ( ISO TYPE III ) STONE, HIGH STRENGTH, LOW EXPANSION ( ISO TYPE IV ) STONE, HIGH STRENGTH, HIGH EXPANSION ( ISO TYPE V )
    • CHEMISTRY OF GYPSUM: In the temperature range of 20º to 700ºC that is important in dental manipulation of gypsum products, three phase changes occur in the CaSO4-H2O system. 40º – 50ºC 1) CaSO4.2H2O CaSO4.1/2H2O + Water (Calcium Sulfate Hemihydrate) 90º – 100ºC 2) CaSO4.1/2H2O γ-CaSO4 + Water (Hexagonal Form) (Soluble anhydrite) 300º – 400ºC 3) γ-CaSO4 CaSO4 (Orthorhombic CaSO4) (Insoluble anhydrite) MONOCLINIC HEXAGONAL ORTHORHOMBIC Calcium Sulfate Hemihydrate Soluble anhydrite Insoluble anhydrite Calcium Sulfate Dihydrate
    • MANUFACTURE: From the conversion temperature given before, it can be seen that calcium sulfate hemihydrate would be produced by heating gypsum to temperatures in the range of 50o to 90 oC. However, at these temperatures the reaction is slow; even at 90oC substantially complete conversion takes about 12 hours (Khalil et. al., 1971). Therefore, in commercial processes temperatures higher than this are used, for shorter times. The stable phase at these higher temperatures is hexagonal calcium sulfate, so the initial product of calcination is partly of very largely this anhydrous form. However, on cooling to temperatures below 85 oC and exposure to atmospheric moisture, the hexagonal calcium sulfate rehydrates to form the hemihydrate. In the production of plaster, the gypsum is ground to a fine powder, impurities such as sulphur (S) and quartz (SiO2) are removed, and then it is subjected to calcination. dehydration by heat or other means Mineral Gypsum Plasters Synthetic Gypsum formulation Dental plaster Hydrocal Densite Dental Stone High strength dental stone
    • MANUFACTURE: From the conversion temperature given before, it can be seen that calcium sulfate hemihydrate would be produced by heating gypsum to temperatures in the range of 50o to 90 oC. However, at these temperatures the reaction is slow; even at 90oC substantially complete conversion takes about 12 hours (Khalil et. al., 1971). Therefore, in commercial processes temperatures higher than this are used, for shorter times. The stable phase at these higher temperatures is hexagonal calcium sulfate, so the initial product of calcination is partly of very largely this anhydrous form. However, on cooling to temperatures below 85 oC and exposure to atmospheric moisture, the hexagonal calcium sulfate rehydrates to form the hemihydrate. In the production of plaster, the gypsum is ground to a fine powder, impurities such as sulphur (S) and quartz (SiO2) are removed, and then it is subjected to calcination. dehydration by heat or other means Mineral Gypsum Plasters Synthetic Gypsum formulation Dental plaster Hydrocal Densite Dental Stone High strength dental stone