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Dental Materials
Fichas del conjunto (14)
- 1Why are dental restorations and appliances polished?- Aesthetically pleasing
- Comfort
- Prevent the adhesion of food debris - 2Define: Abrasion and PolishingAbrasion - A process where the surface of the material being abraded is removed mechanically by the sharp particles of the abrasive.
Polishing - A process where the surface irregularities are reduced without any cutting action to produce a smooth surface. - 3What makes abrasives effective?- The particle size
- Particle shape
- Particle hardness
- Particle speed
- Hand pressure/heat/lubrication - 4What are the requirements of a denture base?-Bio-compatible
- Insoluble and impermeable to oral fluids
- Aesthetically pleasing
- Dimensionally stable
- Should possess adequate strength
-Weight, Low specific gravity
- Thermal coductivity
- Cleanliness
- Softening temperature
- Ease of manipulation
- Ease of repair
- Radio-opacity - 5What is acrylic resin?The polymerised form of Methyl Methacrylate (PMMA)
- 6What are the constituents of Acrylic Resin?Polymer - Powder (Poly methyl methacrylate) Consists of:
Catalyst - Benzoyl Peroxide
Plasticiser - Buthyl Phthalate
Pigments - Red/White
Monomer - Liquid (Methyl methacrylate) Consists of:
Inhibitor - Hydroquinone
Cross-linking agent - Ethyl Glycol Dimethacrylate
Chemical activator (Auto Polymerising monomer only) - 7What are the two groups of polymerisation?Condensation polymerisation - The reaction between two or more molecules to form a larger molecule with the elimination of water.
Addition polymerisation - The reaction between two or more molecules to form a larger molecule with out the formation of by-products. - 8What are polymers?Polymers are long chain molecules consisting of many repeating units,
- 9Describe Heat cureWhen polymerisation is achieved by the exposure to external heat which converts the monomer into polymer.
- 10Describe Self cure/cold cure/auto-polymerisationWhen polymerisation is achieved by the action of a chemical activator within the monomer.
- 11The polymerisation process - Describe: InitiationWhen mixing monomer and polymer, some of the catalyst (benzyl peroxide) dissolves in the monomer where it can initiate polymerisation. On heating or by chemical activation, the benzyl peroxide splits into two radicals, which react with the monomer molecules to create acrylic radicals.
- 12The polymerisation process - Describe: PropagationAn acrylic radical can react with another acrylic monomer unit, producing two unit radicals. Propagation is the growth of these chains by successive additions of the monomer units to the radical end of the chain. This process may occur over 500 times resulting in a high molecular weight polymer.
- 13The polymerisation process - Describe: TerminationThe chain growth finally stops by mutual termination and the radicals are transformed into a stable group.
- 14—
Información
- Descripción
- dental technology Fichas sobre Dental Materials , creado por mahsa rahnavardi el 22/05/2018.
- Creado por
- mahsa rahnavardi · may 2018
- Actualizado
- 22 may 2018
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- Historial
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- Creado por Abigail Withers · 6 dic 2017
- Copiado por mahsa rahnavardi · 22 may 2018
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