Test 5 Flashcards
What kind of restoration is amalgam?
Direct
How long has amalgam been used in restoring teeth successfully?
Over 165 years
approximately 50 million placed each year.
What has stimulated the rise in tooth color restorations?
Due to the less than .01% adverse reactions and the concerns of patients, plus the lack of esthetics
there is still a great concern over the sensitivity experienced with tooth color restorations in posterior teeth
What is the most durable, easy to handle and has physical characteristics that are compatible in the mouth?
Amalgam
What is Alloy?
a mixture of two or more metals
What is the definition and composition of amalgam?
Metallic restoration material composed of silver based alloy with mercury
composition- high copper alloy
Characteristics of amalgam
tarnish
corrosion
creep
high copper alloy
What is tarnish?
Surface discoloration by oxidation
What is corrosion?
breakdown by CHEMICAL reaction
What is creep?
gradual change in the shape of a restoration due to compression
what is a high copper alloy
admixed or spherical types require less mercury
What equipment is used to mix amalgam?
Amalgamator
What is the act of mixing amalgam?
trituration
What are the types of mixes of amalgam?
capsules (primary packaging today)
pellets (mercury)
powder (mercury)
what two ways can amalgam be manipulated?
hand (no longer in existence)
mechanical
what does mulling mean?
to bring to a uniform mass
What are the three ways mercury can enter the body?
inhalation
swallowing
careless use of mercury
when placing or removing amalgam restorations:
take precaution to prevent swallowing of amalgam or inhaling mercury. HVE and rubber dam minimize swallowing/inhaling of amalgam
what is the safe level of mercury in a 40 hour work week at the threshold limit value (TLV)
.005mg/m3
what main organ does mercury accumulate?
kidneys
what organs retain mercury the longest?
brain, kidneys, and testicles
what kind of test is done for mercury levels?
urine analysis
What are casting alloys?
indirect restorations
What did Taggart invent?
in the 1900’s, the lost wax technique restorations made from metal and cast into a mold
why is pure metal hardly used?
due to weakness and being too soft
Gold dental casting alloy classification
high noble
noble metals
wrought metals
High Noble
Does not corrode or tarnish contains 40% gold and 60% noble metals
classified by its content;
karat-measure of gold content
fineness-is the % of gold x10
Noble metals
precious metals, due to high monetary value
pt: platinum- increased in price due to shortages
pd: palladium- corrosion resistance, hardness, less expensive
base metals
(non precious) (due to low cost)
most common are- chrome cobalt and nickel chrome
primary base metals are- copper, nickel, silver, zinc, tin and titanium
wrought metals
formed after the metal is casted
example- wire clasps
what are noble metals more compatible with?
oral tissues
What is the allergy rate to nickel?
9%-12% for the general population
women have a higher rate of allergy to nickel than men (10-1)
where is the allergic response to nickel seen?
around free gingival tissues
what is the inhalation of berrylium known to contribute?
to lung disease called berylliosis
ventilation and proper PPE should be worn
how are lab techs at risk with nickel and beryllium?
due to casting, grinding and polishing metals
what are solders?
alloy used to join metals together
3 processes-
solders
brazing
welding
what are the 2 types of solders?
gold based- used in crown and bridge work
silver based- used in orthodontics and pediatric dentistry
what metals are used in orthodontics?
composed of base metals nickel and titanium called nitinol and is used because of the spring back effect for the arch wires due to the gradual tooth movement
what are endodontics?
files and reamers are made from wrought metals. they are used from this metal to maintain the twisting motion involved while removing pulpal tissue with the hand instruments- files and reamers
What are composites composed of?
Resin matrix
filler particles (macro, micro, hybrid, microhybrid, nanohybrid, nanocomposites)
coupling agent
pigments
resin matrix
bis-GMA or UDMA
(bisphenol a glycidyl dimethacrylate)
(urethane dimethacrylate)
filler particles
fillers make the composite stronger and more resistant
by size
macro-filled
larger filled (the very first composite material contained these particles)
an early generation of composites that contain filler particles ranging from 10-100 microns
micro filled
very small particles
composites that contain very small filler particles averaging 0.04
hybrid
(combination of micro and macro)
composites that contain both fine fill (2-4) and microfill(0.04-0.2) particles to obtain the strength of macrofilli and polishability of microfilli
microbybrid
even smaller particles contain higher filler content
0.04-1
nanohybrid
small hybrids, polish, less resin
nanocomposites
composites that contain all nanosized fillers to enhance physical properties
coupling agent
silane (this helps bind organic filler and resin matrix to adhere to tooth structure)
pigments
organic and offer different shades to the matieral
Polymerization (modes of cure)
chemical
light cured
dual cure
chemical mode of cure
two pastes, syringes or cartridges (self cure)
light cured
by a visible light (VLC)
dual cure
combination of both chemical and light to activate the material to set
flowable composite
used to fill spaces that cannot be reached by packable composite
low viscosity, light cured resins may be lightly filled (40%) or more heavily (up to 70%)
pit and fissure sealants
low viscosity resin that prevent dental decay
bulk fill composites
these were developed to speed up the placement process of the composite restoration
used to fill with larger amounts of material, less time (flowable-and viscous nano hybrids, less fillers, not suitable for class 2)
Packable composites
used in posterior restorations
highly viscous micro hybrid that contain high volume of filler particles
class 1 and class 2 restorations
smart composite
material has not been proven to be as effective as thought
core build up material
used in place of amalgam or composite build up tooth structure that is badly broken down
what is one very important factor when restoring a tooth with a composite materials?
layer in increments and cured (polymerize) each layer. this hardens the materials with in turn and cuts down on severe sensitivity in the restored tooth
What are the physical and mechanical properties of composites?
composite materials wear faster
bispheonal A may have been linked to mimic the effects of estrogen and cause the development of secondary female characteristics which stimulate certain cancer cells
formaldehyde may also be formed in a by product of polymerization which in turn can cause tissue reaction which resemble lichens planus
composite is weak
water softens the material which causes shrinkage
what classes are made up of composite restorations?
classes I through class VI
what are suited for anterior restorations?
microfill and microbybrid
what should you do before you begin a procedure for composites?
take an accurate shade before
what is a must when placing a composite?
incremental placement and curing. this reduces sensitivity as well as making sure the margins are sealed
what is one thing you should never use on a composite material?
alcohol because it weakens the material. the same applies for bonding material, do not use on the instrument this weakens it
what can contaminate and must be removed from the tooth structure and re etched?
saliva, blood and fluid from the gingival sulcus
what is another issue with composite material?
cross contamination
all delivery systems as well as syringes should not be cross contaminated/ disposable tips are packaged in the material to prevent this from occurring
what factors effect the cure of restoration?
short curing times
inadequate light output
strong wavelength of light
incorrectly positioned light guide
what factors affect the mechanical and physical properties of light cure?
not receiving the correct amount of radiant energy at the right exposure time and the right wavelength in order for them to polymerize completely
types of light curing units
quartz-tungsten-halogen (QTH or halogen)
Light emitting diode (LED)
argon laser
plasma arch curing (PAC)
what kind of damage does the lights cause on the eye?
aging of the retina, low level light over a period of time can lead to macular degeneration
infection control procedure for light curing
barriers on wands, also acts as purpose to keep material from building up on lights
two most common reason for failure of light cured composites
fracture of restoration and recurrent caries
what operator errors occur with the failing of composites?
poor cavity preparation, inadequate isolation, over or underetching, improper rinsing and drying of tooth, poor incremental placement techniques, open proximal contacts, over heating pulp and inadequate curing of the bonding agent or composite resin
Glass Ionomer Cements (GIC’s)
introduced in the early 1970’s by Wilson and Kent. GIC’s are self cured, fluoride releasing materials that bond to tooth structure directly without a bonding agent
Classifying of GIC materials:
Type 1: luting (cementation) agents
Type 2: restorative materials
Type 3: liners and bases for cavity preparations
Packaging of GIC’s
hand mixed powder and liquid
encapsulated powder and liquid
two paste systems
syringes
Physical and Mechanical properties of glass ionomers
biocompatibility
bond to tooth structure
fluoride release
solubility thermal expansion and extraction
thermal protection
compressive and tensile strength
wear resistance
radiopacity
color
bond to tooth structure
bond to enamel and dentin thru chemical ion exchange mechanism that allows the material to bing with calcium ions in the tooth
fluoride release
they release an initially high level of fluoride for the first few days and then the fluoride levels fall to low levels. absorb fluoride from in office applications, fluoride rinses, or fluoride tooth paste and re release it, thereby acting as a fluoride reservoir
solubility
highly soluble during this time for the first 24 hours
thermal expansion and contraction
similar to tooth structure and stiffness (modulus of elasticity) comparable to dentin
thermal protection
they are good insulators against temperature extremes
compressive and tensile strength
moderately high but weaker in tension and brittle in sections. should not be used in stress bearing areas such as occlusal surfaces and incisal im edges for permanent teeth
wear resistance
wear faster than composite resins. surface gets rougher into time.
radiopacity of GIC
more radiopaque than dentin
color of GIC
more opaque than composites. translucency and the number of colors available have improved over the years
hybrid ionomers
contain HEMA (stronger than resin)
have nano particles (micro particles)
used mainly to restore primary teeth
compomers
resins that are modified with poly acid mainly used for class 3 and 5 restorations
giomers
combination of composite materials and glass ionomers
release fluoride slower
very beneficial for cervical carious or non carious
types of ceramics
glass based
non glass based
ceramics
materials composed of inorganic metal oxide compounds, including porcelain and similar ceramic materials that require baking at high temperature to fuse small particles together
porcelain
a tooth colored ceramic material composed of crystals of feldspar, alumina and silica that are fused together at high temperature to form a hard, uniform, glass like material
sintering
fusion of ceramic particles at their borders by beating them to the point that they just star to melt
CAD/CAM
computer assisted design / computer assisted matching applies technology that uses computers to design and milling device to cut restorations from blocks of dental materials
veneer
thin layer of ceramic or composite resin material that is bonded to the fronts of teeth to improve their appearance
porcelain metal restoration
restoration that has metal core over which porcelain is fused at high temperature. commonly referred to as porcelain-fused-to metal (PFM) or porcleain bonded to metal (PBM)
hue
the basic color of an object (red, yellow, green, blue)
chroma
the intensity of the color (hue) (pastel blue is less intense and has less chroma than a royal blue)
value
the brightness of a color, it’s lightness or darkness
glass based ceramics
main ingredient is silica, glassy matrix
feldspathic porcelains, leucite-reinforced ceramics, and lithium disilicate ceramics
non glass based ceramics
simple or complex oxides
no glassy matrix, alumina zirconia
all ceramic restorations
advantages- no metal substance one day crown
disadvantages- very brittle, hard to repair
glass based ceramics
porcelain describes tooth colored materials
non glass- zirconia presently used less expensive as porcleain
processing tech. of ceramics
sintering, slip casting, heat processing
slip casting
ceramic powder is mixed with a water based liquid to form a mass or slip to soak up die
heat processing
same as lost wax tech. heated at high temperature and casted
type of anterior restorations for ceramics
porcelain
veneers
porcelain fused to metal
types of posterior restoration for ceramics
inlay
onlay
gold crown
failure in ceramics
small crack from being under a load
heating during processing
shade taking in ceramics
very critical
shades might very from the cervical line, middle third, and occlusal third
hue, chroma and value revisiting these terms
uses of glass ionomers
bases
liner
cements
restorative materials
coping
thin covering like a thimble that serves as a substructure for a porcelain bonded to metal crown
