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DENTAL MATERIALS
AMALGAM
Question | Answer |
---|---|
GAMMA PHASE | This is the silver alloy phase. This is the STRONGEST phase and has the least corrosion. |
GAMMA-1 PHASE | This consists of mercury reacting with the silver. It is also strong and corrosion resistant, although not as resistant as the Gamma Phase. |
GAMMA-2 PHASE | This consists of the reaction with mercury and tin. This is the WEAKEST phase and corrodes readily. This phase is eliminated with high copper alloys. |
What phase is eliminated with high copper alloys? | GAMMA-2 PHASE |
What material is used to control the rate of set of amalgam? | Tin. |
What materials dissolve into and absorb Mercury until the solution becomes saturated? How long does this process take? | Silver and Tin. 24 hours |
What type of amalgams have much more corrosion because of the chemical reaction of tin and mercury? | LOW COPPER AMALGAMS |
What type of amalgam has no GAMMA-2 PHASE? | HIGH COPPER AMALGAMS, which is why they are superior in performance |
What factors contribute to dimensional changes? | *ratio of mercury to alloy *Compostion of alloy particles *Salivary/moisture contamination while manipulation and insertion *perspiration on fingers contribute to moisture if amalgam is touched |
Hom much Cu is in a low copper alloy? | Less than 5% Cu |
How much Cu is in a High Copper Alloy? | More than 12% Cu, superior to low Cu. |
What results from undertrituration? | Low strength. |
Define Creep | Gradual dimensional change of amalgam caused by compression from occlusion |
Lower Creep | Better marginal integrity |
When does setting time of amalgam begin? | At trituration |
Define Percolation | Movement of fluid in a microscopic open margin between tooth and restoration caused by constant thermal changes. Causes irritation to pulp and recurrent decay. |
Scales commonly used to determine hardness of a material: | Moh's scale, Brinnel and Knoop |
When bonding what is considered a wetting agent for the preparation? | Etch |
bis-GMA | most commonly used resin for composites as well as sealants. Also known as the MONOMER of the mixture. |
Over manipulation of sealants creates... | air bubbles |