dental materials Flashcards by Rohmat Ali

what is light curing

: a dental curing light is a piece of dental equipment that is used for the polymerization of light cure.

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describe polymerization in dentistry

In polymer chemistry, polymerization is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks.

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a substance which has a molecular structure built up chiefly or completely from many similar units bonded together. - best describes what

a polymer

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is a polymer that changes its properties when exposed to light, often in the ultraviolet or visible region of the electromagnetic spectrum. - best describes what

a photopolymer

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: is the action of changing a mixture of monomers, oligomer and photo initiators that conform into a hardened polymeric material. - best describes what

curing

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is a material made from two or more different materials that, when combined, are stronger than those individual materials by themselves. - best describes what

composite

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a solid or liquid synthetic organic polymer used as the basis of plastics, adhesive, varnishes, or other products. - best describes what

Resin

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are certain materials that are placed in dental composites to reduce shrinking upon curing. - best describes what

fillers

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what is the purpose of a coupling agent in a resin composite

The coupling agents act as an adhesion promoter. Coupling agents are activated when activated by a light curer.

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Hard and lustrous (shiny)
Closely packed crystalline structures
Opaque
Conductors of heat and electricity except mercury (Hg)

features above best describe metal at what state

metals at ambient temperature

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alloys are a mixture of two or more metals

what is the name of an alloy with two and three metals

two metals - binary alloy

three metals - ternary alloy

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what is the name of the system that shows all possible combinations of an alloy

alloy system

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the initial process that occurs in the formation of a crystal from solution, a liquid, or a vapour, in which small number of ions, atoms, or molecules become arranged in a pattern characteristic of a crystalline solid. Forming a site upon which additional particles are deposited as the crystal grows. - is known as what

nucleation

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The reaction between mercury and alloy when mixed together is termed an ?

amalgamation

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the maximum degree of extension in response to an applied tensile force - is the definition of

ductility

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the maximum degree of compression in response to an applied compressive force. - is the definition of what

malleability

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alloy and mercury produces amalgam, what is this a process of

amalgamation

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viable alternatives for material and concerns over safety and enviromnetal pollution has seen the reduction of which dental restoration material

amalgam

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65% Ag, 29% Sn (tin), 6% Cu, 2% Zn, 3% Hg (mercury) represents the composition of which amalgam, the conventional or the more typical one.

conventional

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40% Ag, 32% Sn (tin), 30% Cu, 2% Zn, 3% Hg (mercury) represents the composition of which amalgam, the conventional or high copper resolution?

high copper resolution

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40% Ag, 32% Sn (tin), 30% Cu, 2% Zn, 3% Hg (mercury) is the composition for amalagam

what purpose does the Ag and Sn have

undergoes setting reaction

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40% Ag, 32% Sn (tin), 30% Cu, 2% Zn, 3% Hg (mercury) is the composition for amalagam

what purpose does the Cu have

strengthening effect on amalgam

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40% Ag, 32% Sn (tin), 30% Cu, 2% Zn, 3% Hg (mercury) is the composition for amalagam

what purpose does the Zn have

Zn (zinc) acts as a scavenger, preventing oxidation of other metals.

zinc oxide

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amalgam undergoes dimensional changes during the setting period.

how long does it take for amalgam placement to function

15-20 mins

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amalgam undergoes dimensional changes during the setting period. how long does it take for amalgam placement to undergo final strength

24 hours

amalgam is at its strongest under compression. but when is amalgam at its weakest

tension and shear

what is defined as a time dependant plastic deformation under constant stress occuring in crystalline materials

creep

how does creep affect the margins of the cavity

creep causes the amalgam to flow, such that unsupported amalgam protrudes out from the margins of the cavity

creep results in unsupported amalgam protruding out from the margins resulting in unsupported edges. these edges become weak what other factor may weaken them.

corrosion

the formation of a ditch around the margins of amalgam restorations are caused by what

crosion of the unupported edges through creep.

a marginal seal between the margins of the cavity and the amalgam is sealed by what

corrosion products

what reacts with the exposed amalgam to cause corrosion

electrolytes of saliva

why is it important to place a varnish, liners or a base in the cavity before an amalgam restoration

amalgam is 2.5\* more thermal conductive than normal tooth. this ensures the pulp is protective.

what is the danger of Hg in the human body

Hg known to be toxic to the CNS

polymerisation of resin composites undergo the 4 following stages

activation initiation propagation terminationn

during polymerisation composite material contracts to bring about an exothermic or endothermic reaction

exothermic reaction

which material is better for matching tooth shade. resin composite or acrylics

acrylics

what is the purpose of using a inert filler

to reduce shrinking

what reduces the mobility of the unreacted monomers

resin matrix

what are siloraines used for

used to lower shrinking during polymerisation

glasses silica quartz are all examples of what

types of fillers in resin composite

how does the increase in percentage of filler content by volume, affect the surface hardness

increases surface hardness

how does the increase in percentage of filler content by volume affect the "percentage of volume setting contraction"

increase in filler volume decreases setting contraction

how does the increase in percentage of filler content by volume affect the "cofficent of thermal expansion"

as the filler volume increases this decreases coefficent of thermal expansion

what is the name given to something that is a **photoinitiator** used in curring dental composites

camphorquinone

what affect does camphorquinone have on free radicals

it yields the necessary free radicals to start polymerisation

at what spectrum does dental composite get excited

460-480 nm (blue light)

resin and filler are completley useless without which agent

coupling agent

what does the coupling agent convert the brittle filler to

flexible and ductile polyermer matrix

what would type 1 resin composites be used for

restoration of cavities involving occlusal surfaces

porosity is the air bubbles present in dental materials what does the increase of porosity have on the strength and fatigue of resin composites

decrease in strength and fatigue

if there is a decrease in coupling agent, how does this affect the strength and fatique

decreases strength and fatique by 30%

does cavity shape influence the overall success of restoration

yes C factor = _number of bonded surfaces_ number of un-bounded surfaces

how does food and plaque acid affect the resin matrix

initiates chemical softening

crack propagation is brought about by stress concentrations where

at the surface resin composite or fillers

how does increase in porosity affect rate of crack propagation

increases crack propagation

glass polyalkenoate is formly known as what

glass ionomers

polycarboxylate cement has been used as a filling material as alternative to which restoration material

amalgam

powder and liquid, powder mixed with water and encapsulated form are example of how a particular material is supplied. what is the name of the material

glass polyalkenoate

what would increase the porosity of fluid cements if mixed by hands or mixed mechanically

more porosity if mixed mechanically think froth development

glass polyalkenoate setting reaction has two phases initial set final set what are the times for each set

initial set - first few minutes final set - 24 hours after completion

what are the implications for clinicians when working with glass polyalkenoate

delay final finishing for atleast 24 hours material sensitive to moisture until final set is complete

how does polyalkenoate properties thermal diffusivity relate to dentine

close to dentine

what effect does polyalkenoate have on fluride

polyalkenoate releases and uptake

varnish and adhesive sealers are examples of what

cavity sealers

glass ionomer is an example of a cavity sealer or liners

cavity liners

zinch phosphate cement reinforced zinc oxide zinc polycarboxyl cement glass ionomer cement the above are examples of liners or bases

bases

provides a protective coating and barrier to leakage coats walls of the cavity the above is describing what

cavity sealers

seals the dentinal tubules and reduces the leakage around a restoration provides no thermal insulation the above best describes what type of sealer?

varnish sealer

provides sealing as well as bonding at the interface between restoration and cavity preparation walls the above best describes which type of cavity sealer?

adhesive sealers

it is a liquid in which CaOH are suspended in a **solution** of natural or synthetic **resin** the above is a definition of what

cavity liners

is dycal a cavity sealer or cavity liner

liner

dycal acts as a thin barrier between the restoration and the remaining dentine. this prevents irritation in the form of **physical, mechanical, biological and chemical** to what part of the tooth

pulpal tissue

does dycal provide thermal insulation

can you apply dycal on cavity margins

dycal stimulates the production of dentine, which type of dentine does it stimulate be specific

stimulates secondary dentine stimulates tertiary dentine - **reparative dentin**

in terms of restorative material, what is the benefit of using dycal as a liner

it is compatible with all type of restorative material

what is the most common direct pulp capping agent

calicum hydroxide CaOH

what is the purpose of direct pulp capping

to seal communication between the root cancal system and the external tooth surface at all levels

phosphoric acid based cements setting reaction time is rapid or slow

rapid

phosphoric acid based cements reaction is exothermic or endothermic

exothermic

phosphoric acid based cements take how long to fully solidify

4-7 minutes

phosphoric acid based cements, can they be seen in an x-ray

no they are radiolucent

is the pH of phosphoric acid based cements high or low

low

if a cavity sealer or liner has a non obtundant effect what does that mean

it means that the material doesnt blunt the irritation or lessens the pain.

what would cause coronal leakage

if the liner material has no adhesive affect, this would **NOT FORM** a coronal seal

is phosphoric acid based cements adhesive or not

non adhesive

zinc oxide eugenal cements come in the form of 2 paste what are they

zinc oxide and **accelerator**

zinc oxide eugenal cements is bacteriocidal. what property causes this

the zinc in zinc oxide eugenal cements is bacteriocidal

can zinc oxide eugenal cements be seen in x-rays

no they are radiolucent

zinc oxide eugenal cement are compatible with resin composites yes/no?

no they are incompatible

are zinc oxide eugenal cements adhesive

no they are not, so therefore no coronal seal

calcium hydroxide cements come in the form of 2 paste what are they

paste 1 - a glycol salicylate paste 2 - zinc oxide with calcium hydroxide

calcium hydroxide cements are activated by what

light

calcium hydroxide cements has a high pH, what affect does this have on bacterias

bacteriocidal affect

can calcium hydroxide cements been seen in x-rays

no radiolucent

why would calcium hydroxide cements not be used for amalgam restorations

insufficient strength to withstand amalagam condensation/packing

can calcium hydroxide cements provide a coronal seal

no, calcium hydroxide cements are not adhesive

polycarboxylates comes in the form of what powder or liquid

powder

what is the powder form of polycarboxylates

zinc oxide

polycarboxylates has the ability to release fluroride, what affect does this have on bacteria.

bacteriostatic

can polycarboxylates provide a coronal seal

yes, polycarboxylates are adhesive

what does RMGIG also known as

vitrebond

glass ionomers have a bacteriostatic property, what must glass ionomers have or do to have that bacteriostatic property

release fluoride

are glass ionomers adhesive or not

they are adhesive

the advantage of adhesion of a restorative material would be the absence of marginal gaps between the restoration and tooth surface what would this minimise

microleakage and development of secondary caries

the state in which two surfaces are held together by interfacial forces: is the definition of what

adhesion

is a material, frequently viscous fluid, that joins two substrates together and solidifies, and is able to transfer koad from one surface to the other is an example of what: adhesion adhesive adherend

adhesive

this referrs to the surface or substrate that is adhered to

adherened

there are three nechanism of adhesion what are they:

mechanical adhesion adsorption adhesion diffusion adhesion

interlocking of the adhesives with irreularities in he surface of the substrate or adherent: is an example of what mechanism of adhesion

mechanical adhesion

chemical bonding between the adhesive and adherent: is an example of what mechanism of adhesion

adorption adhesion

interlocking between mobile molecules: is an example of what mechanism of adhesion

diffusion adhesion

penetration of resin and formation of resin tags within the tooth surface: is an example of what mechanism of adhesion

mechanical

chemical bonding to the inorganic compound (hydroxyapattite) or organic components (type 1 collagen): is an example of what mechanism of adhesion

adsorption

precipitation of substances on the tooth surfaces to which resin monomers can bond mechnically or chemically: is an example of what mechanism of adhesion

diffusion

by having a **clean surface** **good coverage of adhesive on all surfaces** **and adhesive should be well cured** will enable what

the following were requirements of achieving good adhesion

the transformation of the smooth enamel to irregular surface, resulting in increase in surface energy is achieved by what

acid etch

when a fluid resin-based material is applied to the etched surface, the resin penetrates on to the surfaces, aided by what?

capillary action

what must the monomers undergo for the material to be interlocked with the enamel surface

polymerised

factors affecting etch time: why must adequate drying be done after washing the etch

this would enable the hydrophobic resin to penetrate and attach to the demineralised dentine

_dentine bonding problems_ why is the dentine being hydrophilic a problem

adhesives are hydrophobic - the use of primers helps with composite materials

what is the name of the acid that works as a dentine conditioner

primer

what is the fucntion of a primer

alters surface appearance and characterisitics of dentine

what is the function of sealers

flow in to the dentinal tubules seals dentine with a surface layer ensures bonding to resin in the composite

how do dentine conditioners work

they perform an acid base reaction with hydroxyapatite open dentine tubules demineralize surface detine to a depth of 4 microns

what bonds hydrophobic composites to hydrophilic dentine

primers they act as adhesives

children under 15 years pregnant women breast feeding these are all contraindications of what

uses of dental amalagam no longer used for

where is amalagam natrually occuring from

volcanic eruptions