Dental Materials Part II, Test I Flashcards
Class I cavities include what?
5 points here
All pit and fissure cavities
Occlusal Surfaces
Premolars/Molars
Occlusal 2/3 of Facial/LIngual surfaces
LIngual Max Incisors
Define Class II cavities
Proximal surfaces
Premolars/Molars
Class III cavities:
Proximal surfaces
Incisors/Canines
Do NOT involve incisal angle
Class IV cavities:
Proximal surfaces
Incisors/Canines
Involve Incisal angle
Class V cavities:
Gingival 1/3
Facial/Lingual
All teeth
*non pit/fissure cavities
Class VI cavities:
Incisal edge Anterior teeth
Occlusal cusp heights Posterior teeth
In enamel bonding, what 2 structures are identifiable after etching with phosphoric acid gel?
Microtags
Macrotags
What are the 3 procedures of Dentin Bonding?
Etching
Priming
Bonding
What % of Dentin is water?
25%
What are 4 functions of Etching in Dentin Bonding?
removes 2 things, exposes 2 things
Removes the smear layer
Removes HA from outer dentin layer
Exposes a collagen sponge layer
Exposes dentin tubules
During the Etching process, what must be done to keep the collagen sponge layer from collapsing?
Prevent drying
In Dentin Bonding, the resin component part of the primer’s attachment to the dentin is called what?
Hybrid Layer Formation
4 principles of adhesion in Dentin Bonding:
Hybrid Layer variable thickness
Mechanically weak if incomplete adherence with primer
Primer Solvents enhance wetting (monomers > tags)
To get monomers deep, many primer layers may be needed (as solvent evaporates)
What are the 2 parts of Primer that make it a Bifunctional Monomer?
Hydrophilic collagen
Hydrophobic resin
What is an example of a Bifunctional monomer?
HEMA
The self-etch two-step process has combined what?
Conditioner and Primer
Most bonding is a result of ________ retention
Micro-mechanical
Currently the best bonding takes place on a _____ surface and agents containing ______ and ______.
Moist
MDP and Ethanol
What are the 4 Major Components of Resin Composite restorative material?
Organic polymer matrix
Inorganic filler particles
Coupling agent
Initiator-accelerator system
The Organic Polymer Matrix that make up resin composite are made up of what?
Oligomers
What are 3 examples of Oligomers?
Bis-GMA
U-DMA
TEG-DMA
What is the most common photoinitiator in Visible-Light Activation?
What wavelength does it absorb?
Camphorquinone
Blue light (400-500 nm)
*reacts w/ activator, forms free radicals, polymerization
T/F
The surface layer of resin composite’s exposure to air may inhibit double bonds
True
What percentage of resin composite may be unreacted double bonds at the air contact surface layer?
75%
What is present in bond failure interface in resin composite?
Microgap formation
In resin composite, what is Polymerization Shrinkage a direct function of?
Volume Fraction of Polymer
Because Microfilled composite has a higher volume percentage of polymer, there is more/less shrinkage?
More
Why does Microhybrid composite have less shrinkage?
Less polymer matrix
Thermally speaking, why does Microfilled resin composite have More Expansion?
More polymer present
Compared to highly filled Fine Particle Composites, what is the E value of Microfilled composites?
1/4 to 1/2 E value
*microfilled not as good as highly filled fine particle
How is Irradiance (radiate exitance) measured?
photos per second per unit area
mW/cm2
How is Energy Density measured?
Irradiance x time
J/cm2
What is the most common photo-absorbing material?
Camphorquinone
What is the maximum spectrum sensitivity of Camphorquinone?
465-47- nm
Blue range
What are 5 factors that determine how long it takes to adequately cure a composite?
Energy Density (irradiance of light x time)
Distance from composite
Collimation of light (focusing/narrowing)
Wavelengths emitted and absorbed
Composite type
What is the Reciprocity principle in terms of Total Energy Density?
Increase irradiance, Decrease time
Decrease irradiance, Increase time
What 2 types of light will lower irradiance and therefore increase curing time?
LED
Halogen
What type of light will increase irradiance and therefore decrease curing time?
Plasma arc
Other than lowering Irradiance, name 5 factors that will Increase curing time
Microfil composites
Darker shades
Flowable composites
greater distance
poor collimation
Other than increasing irradiance with plasma arc, name 4 factors that will Decrease curing time
Hybrid composites
Lighter shades
Close distance
Good collimation
What instrument part fits into the handpiece and provides the rotary motion to the bur?
Shank
What connects the head to the shank?
Neck
*usually tapers
What is the working part of the instrument?
Head
How are Rotary Cutting Instruments classified?
2
Shape
Number (which I think is size)
If the rake face is ahead of the radius, the bur has a ….
Negative Angle
A negative rake angle is used for cutting hard brittle materials because it…
Minimizes fracture of the cutting edge
Increasing the Clearance Angle ________
Decreases the Edge Angle
What provides space for the chips formed ahead of the following blade?
Clearance Angle
Why are Carbide burs at around 90 degrees and need more of a rake angle?
This angle is considered?
Carbide is brittle
Negative
T/F
Clearance angles are either curved or have 2 surfaces to provide low clearance angles and greater clearance space ahead of the following blade.
True
What does a Coupling Agent ensure?
Bond forms between Inorganic filler and Oligomer during setting
What is an example of a Coupling Agent?
Silane
T/F
Coupling Agent like Silane is applied to the surface of the filler before it is mixed with Oligomer
True
When the Oligomer sets, the double bonds from the Silane react with the Oligomer to bridge a link between what?
Filler > Coupling Agent > Oligomer > polymer matrix
Compared to a Microhybrid, a Microfil will have more Matrix Resin in it. What are 5 consequences for Microfil?
Take up more water
More soluble in mouth
More polymerization shrinkage
Higher rate of Thermal Expansion
Lower Elastic Modulus
***overall, decreased properties
Where would Microfils most likely be used?
Where would Microhybrids most likely be used?
*one Doesn’t go into heavy load-bearing areas
Aesthetics
Load bearing
***Microfils shouldn’t be used on load bearing interface - will stress tooth-composite bond because of “squishyness”
Round burs are measured from ____ to _____
Pear shaped bur common measurement:
Tapered fissure burs common measurement:
1/4 to 8
330, 329 (230-232)
169 (700-703)
What happens to the edge angle if you increase the clearance angle?
Edge angle decreases
What happens when we etch dentin?
What happens when we etch enamel?
Prevent drying, hybrid layer, collagen
Microtags/Macrotags
What are the 4 components common to all bonding?
Etching
Primer
Adhesive
Initiator
How is the Hybrid layer formed?
Resin in Primer > Etched Dentin
Look at HEMA molecule
OK
hydrophobic/hydrophilic
Polymerization of composites:
Initiation, Propagation, Termination
T/F
Microhybrids are blends of fine materials
True
