composite and amalgam Flashcards
name 4 prop of composite
esthetically pleasing, strong, wear resistant, but have low to no fluoride release
what classes are composite recommended for
III to V
name the three phases of which composite is made of
resin matrix
dispersed inorganic filler particles
silane coupling agent
suggest a method to overcome or minimize the effect of polymerization shrinkage
insert and polymerize composite in layers
compressive and flexural strengths and elastic modulus or stiffness of microhybrid composites are dominated by what
the amount of filler and increases exponentially with the volume fraction of filler
name a downside to composite
loss of surface contour, which results from a combination of abrasive wear from chewing and toothbrushing and erosive wear from degredation of the composite in the oral environment
how to manipulate composite
with fourth abd 5th generation bonding agents:
1.enamel and dentin are etched with phosphoric acid
2.acid is flushed away with water
3.surface is dried gently with a steam of air
with 6th and 7th generation bonding agents:
etching and priming are accomplished at the same time and no rinsing is required
how are single paste composites activated
light activated thats why they come in an opaque plastic syringe to protect the material from exposure to light and thus provide adequate shelf life
name 4 direct esthetic restorative materials and name the date in which each one appeared
composite 1960
glass inomer 1972
Hybrid inomers 1990
compomer 1995
classify each material from the most releasing of fluoride to the least
- conventional glass inomer
- resin modified glass inomer
- compomer
- conposite
classify from most wear resistant to least
- composite
- compomer
- RMGi
- conventional glass inomer
what are Bis gma or UDMA (oligomers) characterized by
carbon double bonds
define an oligomer and give examples
it is a moderate molecular weight organic molecule made up of 2 or more molecules قليلة الحيدات
what is the principle system to achieve polymerization(setting) of composite
the visible light curing system
what is the exposure time to blue light
20 to 40 sec
what must be avoided when dealing with self-curing systems
the initiator and acceleratot must be kept separated and not mixed until just before the restoration is placed
describe the process of visible light curing systems
the composite is polymerized by exposure of it to intense blue light, the light absorbed by the diketone, which in tthe presence of an organic amine, starts the polmerization rxn.
what are the two types of composite
anatomical تشريحي
opaque كتيم
explain: the more the resin matrix, the higher the linear coeff of thermal expansion
because the polymers that are present i the resjn matrix have a hugher value than that of filler particles (molecules of filler particles are almost inert)
fill in the blank
most comosites are cosidered radiopaque when comapred with _____, and radiolucent when comapred with____
- dentin
2 .enamel
in class V caries do we use a composite with less or more filler particles
less, because we want it to be somewhat elastic
difference between coupling agents and bonding agents
coupling agents are used to bond resin matrix to inorganic filler particles while bonding agents are used to bond composite to prepared tooth
why is the sixth and seventh generation bonding agents very practical,require no rinsing and are called self-etching
because they are self etching, as in the acid the primer and the bonding agent all come in one bottle so etching and priming are essentially done simultaneously
not that the acid used for etching is not phosphoric acid but a weaker acid beacause no rinsage will be done
if a patient has sensitive teeth what bond generation is best to use and why
6th and 7th because the etchant is a weak acid which has a large molecular weight and thus a low likelihood of going into the dentinal tubules and to the pulp
the silane bond is essentially bifunctional so it bonds to both composite and the prepared tooth,name the type of bonding with each
with the composite: chemical
with the tooth:micromechanical
with time, how has amalgam developed
with time the percentage of copper in silver alloys increased, creating high-copper alloys which provied amalgam with higher strength and higher resistence to corrosion
what is responsible for the superior properties of high cu amalgam over low-cu amalgam
the absence of gamma-2 product
what is amalgamation
the rxn of the silver alloy with Hg
what product results from the amalgamation of low-cu alloys with mercury
gamma-2 or (Sn-Hg) tin mercury which corrodes and leads to restoration failure
write the amalgamation rxn of high-cu alloy with Hg
Hg + gamma= gamma + gamma-1 + eta
what is gamma,gamma-1. and eta respectively,gamma-2
gamma: the silver alloy
gamma-1 : silver-mercury
eta: copper-tin
gamma-2: tin-mercury
what are the 5 properties of amalgam with most clinical relevance
strength,dimensional change,creep,tarnish, corrosion
how does amalgam manipulation attribute to its strength
inadequate condensation results in voids, which weaken the set mass.mixing the amalgam for too long or too short a time also weakens the final strength.
define dimensional change
the net contraction(negative) or expansion(positive) of an amalgam during setting
define creep, which has a higher creep range, high-copper or low-copper amalgams
progressive deformation of a material at constant stress(chewing). it occurs in positive dimensional change 9expansion of amalgam)
low copper amalgams
what is the effect of negative dimensinal change of amalgam
means shrinkage of the restoration-aps at the margins-microleakage of oral fluids and bacteria,pulpal pain,and possibly recurrent decay
what is the effect of positive dimensional change of amalgam
means expansion-pain,creep(deformation) of dentin,and fracture of the tooth
clinical difference between tarnish and corrosion of amalgamn
tarnish-or the discoloration of amalgam with time-will not often cause the restoration to fail
whereas corrosion-or the dissolution of amalgam in moth- leads to failure of the restoration
what is trituration
the process of mixing silver alloys with mercury
does the amalgam bond to tooth structure
no, they have been retained by undercuts in the cavity design
https://pocketdentistry.com/wp-content/uploads/285/img0481.jpg
ما هو الأملغم التقليدي
الفقير بالنحاس low-copper amalgam
what form does the amalgam take if we are using an amalgamator(جهاز المعايرة الآلي)
capsules
what is the percentage of both silver alloy and mercury in
- manual mixing
- mechanical mixing
- 40 % silver alloy, 60%mercury
2. 50 50
which particles take up mercury more irregular or spherical
spherical
what is the importance of adding 1 to 2 % of zinc in the silver alloy
to prevent oxidation of other metals
Ag2o (oxided silver) is highly unwanted
what ia the importance of Sn or tin قصدير in the silver alloy
very important for الانسيابية/اللدونة
what is the average condensation force
20N
what is the purpose of polishing الصقل
removing excess Hg
