dental materials Flashcards
what is light curing
: a dental curing light is a piece of dental equipment that is used for the polymerization of light cure.
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.
a substance which has a molecular structure built up chiefly or completely from many similar units bonded together. - best describes what
a polymer
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
: is the action of changing a mixture of monomers, oligomer and photo initiators that conform into a hardened polymeric material. - best describes what
curing
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
a solid or liquid synthetic organic polymer used as the basis of plastics, adhesive, varnishes, or other products. - best describes what
Resin
are certain materials that are placed in dental composites to reduce shrinking upon curing. - best describes what
fillers
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.
- 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
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
what is the name of the system that shows all possible combinations of an alloy
alloy system
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
The reaction between mercury and alloy when mixed together is termed an ?
amalgamation
the maximum degree of extension in response to an applied tensile force - is the definition of
ductility
the maximum degree of compression in response to an applied compressive force. - is the definition of what
malleability
alloy and mercury produces amalgam, what is this a process of
amalgamation
viable alternatives for material and concerns over safety and enviromnetal pollution has seen the reduction of which dental restoration material
amalgam
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
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
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
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
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
amalgam undergoes dimensional changes during the setting period.
how long does it take for amalgam placement to function
15-20 mins
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
no
can you apply dycal on cavity margins
no
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
