properties of amalgam

52 terms by gracel05 

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the ability to be molded, upon mixing allows us to place it into the cavity preparation with rentetive features while it is moldable, and have it set up hard so it is held in place, like two puzzle parts fitting togeher

plasticity

streght of amalgam to withstand forces that would crush it

compressive forces

is teh strenght of amalgam that resists being pulled apart, such as the proximal box of amalgam being broken off of teh occlusal portion by pulling it apart at the thines area

tensile strenght

narrower portion of a preparation that connects the occlusal portion with a proximal box or extension

isthmus

tensile strenght of amalgam is only about ___of compressive strenght

1/8

amalgam must be well____and not over carved especially in the isthmus in order to maintain excellent bluk, thereby improving properties that would resist being broekn apart

condensed

amalgam is strong when bulky or thin?

bulky

does not bend udner foces, will break easilty when chewe on if is___

brittle

thin layer of excess amalgam that extends beyond the cavosurface margins

flash

Who must removed flash sinc it would break under occlusal forces and result in rough margins that would collect plaque?

EFDA

amalgam undergoase dimensional changes about___and ___times that of a tooth when subjected to changes in temperature, which is clinically tolerable

3 and 1/2 times

the tooth does not change in size to the same extent as the dental amalgam, so an___ and ___of a space between the tooth and filling can suck in and then push out oral fluids into the small space

opening and closing

the process of pulling in and pushing out fluids into this space is called

percolation

this also contributes to tooth sensitivity

percolation

the dimensional changes that occur upon temperature changes can be measured as a number called the

coefficient of thermal expansion

the greater the number of coefficient, the__the amount of dimensional change

greater

the more difference between the coefficient of expanison for the tooth and the coefficient for the filling, the moer likely___and ____ will occur

percolation and subsequent sensitivity will occur

the generally undesirable chemicla breakdown of amalgam similar to the rusting of exposed car metal

corrosion

the difference in oxygen concentrations sets up a condition that is doncutive for what to occur

corrosion

oral fluid found in small, microscopic pit of amalgam have less or more oxygen thatn fluid elsewehre on the amalgam surface

less oxygen

the negative result of corrosion may be______of the amalgam surface, the poorer physical properties resulting in teh need to replace the amalgam

blackening

corrosion products also provide a benefit by___

slowly filling in teh microscopic gap that exists between amalgam and tooth, reducing post operative sensitivity over time

corrosion is reduce when using

high copper alloys

polishing result in a ___surface, thus reducing surface corrosion

smoother surface

this is poor between the tooth and amalgam, which allows fluids and bacteria into and out of the dentinal tubules resulting in irritation

seal at the margin

a thin protective layer of insoluble material called____ is used to protect the tubules when dentinal procteciton is required

copal varnish

amalgam resists _____or wearing away with rubbing froces from opposing teeth or restorations

abrasion , abrasion resistance

a quality of amagalm that is not desirable since hot and cold conducted through the amalgam toward the pump may result in discomfort

thermal conductivity, is a good thermal conductor

thick layer of thermal insulating base may be used in deep preparation under metallic restorations that are lcose to the pulp, what is the thermal insulating base

zinc oxide, eugenol, glass ionomer

under repeated on/off biting foces, amaglam resists this

creep

is a deforming of metal over time when constant forces are placed upon it

creep

when plaed under foce, amalgam deofrms to become thinner and iwder so it appears to ____of the preparation

grow out , creeping out

how can creep be minimized

selecting and using high copper alloys

occurs when dissimilar metal in the mouth are connecte dthrough a lyaer of saliva and act like a battery

galvanism

when the teth with these dissimilar metals come together during fucntion, an electrical current is conducted through _____between two different metal and inot the pulp. resulting in sharp immediate nerve irritation

saliva

when does galvanism occur

newly placed restorations but usually diminishes as teh surface of restorations change chemicall over a few weeks

mixing speed and mixing time affect the characteristics of amalgam, results in cohesive ball of velvety, shiny amalgam

trituration effect

what is the liquid and what is the powder when mixing amalgam with mercury

mercury is the liquid, amalgam is the powder

what will amgalm look if under triturated

will appear dry and grainy not cohesive

porosity will contribute to what other undesirable properties

corrosion and less strength

if over triturated what will happen

the amalgam will be hot, crumbly, quick setting, but properties are not affects as much as undertrition

what is needed to decrease voids between amalgam layers, thus improving all properties, and decreasing corrosion

adequate condesation

lathe cut or admixed amalgams need to be what

adequately condensed

the force applied to eh amagam is related to the_____of the condenser nib

diameter

much more force is given by what size condenser

smaller

burnishing the amgalm, immediately after carving improves ___by reducing ____ ____

surface properties

is critical to obtaining the best amalgam properties

the correct amount of mercury

is too much or too little mercury bad for strenght of amalgam

too much

too much mercurty will exhibit increased___,___and ___

increased setting expansion, increased corrosion, and increased creep

mercury rich layer

plash

tbhis occurs during condensation results in udnersirable delayed expansion of amalgam since zince and water yileds hydrogen gas

mosture contamination

zinc free amalgam reduces

delayed expansion

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