Term
| What is Dental Amalgam made of? |
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Definition
Powdered Allow (silver-tin-copper) + mercury |
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Term
What is dental Amalgam used for and how is it mixed? |
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Definition
Used for filling caviteis in molars & premolars Mixed by mixing powder (titurate) with mercury to produce paste |
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Term
Dental Amalgam Precautions? |
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Definition
Mercury vapour is toxic avoid spillages (or collect them) Store amalgam under used X-ray fixer |
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Term
Handling of Dental Amalgam? |
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Definition
Pack amalgam paste (Ag-Sn-Cu) / Hg) into cavity and condense to force powder particles together |
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Term
How does dental amalgam set? |
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Definition
metallurgic reaction between Ag-Sn-Cu and Hg |
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Term
Properties of Dental Amalgam? |
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Definition
Slow to set stron & wear resistant when hard |
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Term
| Uses of Dental Composite? |
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Definition
Filling cavities mainly in ANTERIOR teeth |
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Term
What is the composition of Dental Composite? |
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Definition
Low molecular weight monomers with inert glass filler particles |
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Term
How is Dental Composite Mixed? |
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Definition
Only needed for 2 paste systems |
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Term
How should Dental Composite be handled |
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Definition
Pack paste into cavity & expose to visible blue light 470nm. |
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Term
How does dental composite set? |
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Definition
The monomers (contain double bonds) in the composite paste undergo polymerisation to yield a rigid high molecular weight polymer. |
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Term
Properties of Dental Composite? |
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Definition
Rapid setting command setting for light cured composites high strength reasonable wear resistance |
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Term
What is dental composite used for? |
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Definition
All types of anterior restorations & some posterior teeth |
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Term
Precautions to be observed when using dental composite... (7) |
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Definition
dental staff can become sensitised to unpolymerised material don't stare directly into the light the light guide is fragile, handle with care dental composites have limited depth of cure & only certain thicknesses can be cured. shades also have an impact on the depth of cure length of exposure is important poorly polymerised composite might have 'soggy bottom' with inferior properties |
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Term
Impression Materials: types? |
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Definition
elastomeric impression material : synthetic / natural origin alginates: polysaccharide obtined from seaweed |
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Term
What are impression materials composed of (3 'ingredients') and how do they react? (equation) |
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Definition
alginate salt (eg sodium alginate) calcium salt (eg calcium sulphate) trisodium phosphate Na alginate + Ca sulphate + H2O --> ca alginate + Na sulphate |
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Term
Good Properties of impression materials? (4)
General properties of impression materials? (2) |
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Definition
Good: 1. good surface detail 2. elastic enough to be drawn over the undercuts (but tears over deep undercuts) 3. non toxic 4. non irritant General: 1. reaction is faster at higher temperatures 2. setting time depends on mixing technique and operator handling |
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Term
Bad properties of dental impression materials? (5)
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Definition
1. not dimensionally stable on storage due to evaporation 2. unstable on storage in presence of moisture / in warm temperatures 3. poor dimensional stability. 4. Incompatibility with some dental stones 5. messy to work |
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Term
Precautions to be observed when using Impression Materials: |
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Definition
1. shake container of powder first to get even distribution of consituents 2. Measure powder & water to manufacturers instructions 3. Water should be at rtp (gives reasonable working time, few mins. Use warm / cold water for faster / slower stting respectively. 4. Once remove impression, rinse with cold water to remove saliva/ blood 5. over impression with damp gauze/napking to prevent syneresis (DONT place in water --> expansion) |
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