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272 Cards in this Set
- Front
- Back
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How thick is the smear layer?
what four things are in it? |
.5 - 5 microns
1. Pulverized HA 2. Altered Collagen 3. Bacteria 4. Saliva/crevicular fluid |
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How do you get rid of the smear layer?
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Acid etching
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What does coupling agent do?
What are most made of? |
it's a bifunctional molecule that allows the inorganic filler particles to bond to the resin matrix.
Silanes |
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What two things are in a composite?
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Organic resin
Inorganic filler particles |
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What makes up the organic matrix of composites most of the time?
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Bis-GMA or UDMA
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What is the inorganic matrix of a composite composed of?
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Quartz, lithium aluminum silicate, zirconia, barium, strontium, zinc, or ytterbium glasses
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What are three characteristics that inorganic filler particles bring to a composite?
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1. Improve physical and mechanical properties of matrix
2. Reduces shrinkage of polymer (bc less resin) 3. Reduces water sorption 4. Reduces coefficient of thermal expansion |
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What is def'n of a composite?
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A compound of two or more different materials that has properties that are superior or intermediate to the properties of the individual constituents.
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How do you adhere composites to the underlying tooth structure?
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Bonding
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WHat is the inorganic filler size for each of the following:
1. Macro 2. Micro 3. Microfine 4. Nano |
1. 20-30 microns
2. .4-3 microns 3. .04-2 microns 4. 1-20 nanometers |
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What is % filler particles for Micro-filled composites?
What classes are they used for? |
32-50%
class III and VI |
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WHat is inorganic filler % in Microhybrid composites?
Which classes is it used for? |
60-70%
All classes |
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What is inorganic filler % in nano-filled composites?
Which classes is it used for |
78.5%
All classes |
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WHat provides bonding of the inorganic filler particles to the organic matrix in composites?
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Coupling Agent = silanes
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For chemical polymerization of composites, what is the initiator and what is the accelerator?
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Initiator = benzoyl peroxide
Accelerator = organic amine |
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For light polymerization of composites, what is the initiator and what is the accelerator?
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Initiator = Light/diketone (camphorquinone)
Accelerator = organic amine |
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What is the name of the process by which the resin of composites are formed?
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Polymerization
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what are the three steps of polymerization?
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Initiation
Propagation Termination |
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what is formed on top of composites during polymerization?
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Oxygen-inhibition layer
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What do you use to inhibit polymerization of composite reaction?
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Eugenol/peroxide
(bleaching) |
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Do composite resins shrink or expand during polymerization?
what two things determine the direction? |
Shrink
cavity shape and bonded surfaces |
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What is the c-factor, what does it pertain to, and is a high or low number better? Why
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The c-factor is used in composites
It is the number of bonded surfaces over unbonded surfaces A low number is better because it means less stress due to shrinkage |
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What three places does polymerization shrinkage cause micromechanical stress?
WHat three things does this lead to? |
In enamel/dentin
At interface In restoration Postoperative sensitivity Microleakage Decay (secondary caries) |
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3 ways to reduce polymerization shrinkage?
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Use smaller and more fillers
Use a soft-start curing light Add in small layered increments with small c-factor |
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What are the six techniques for layering composites?
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Horizontal
Vertical Oblique Cusp-build up three site technique centripetal |
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what are the three different types of curing lights?
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Plasma Arc
Quartz-Tungsten-Halogen LED |
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What is the name given to the substrate that is bonded to?
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Adherend
(enamel/dentin) |
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What is the name given to the material providing adhesion to the adherend?
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Adhesive
(bonding agent) |
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What are the three different bonding mechanisms?
WHich is most common/important for dental materials? |
Micromechanical
Chemical Van-der-Waals Micromechanical most important |
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Should a bonding agent have high or low wettability?
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High (because it needs to contact a large surface area to provide adequate adhesion)
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Which is more hydrophobic, enamel or dentin? WHy?
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Enamel because it has a higher inorganic %.
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What is the major component of etchants?
What percentage? What is physical property of etchant? |
Phosphoric Acid
37% Thixotropic gel (flows with vibration, hard otherwise) |
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WHat is composition of a primer?
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Hydrophilic monomer (it needs to contact the entire tooth to get it ready)
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WHat is composition of adhesives?
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Hydrophobic, dimethacrylate monomers
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What are the two major classifications of primers?
Which is better? |
Etch and rinse
Non-rinse Etch and Rinse |
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How long do you etch for?
Longer or shorter for virgin, primary, uncut enamel? |
15-30 seconds
Longer |
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What are the different types of enamel?
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Type I enamel (core)
Type 2 enamel (periphery) |
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What two things does Etchant do?
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Dissolves HA to provide mechanical undercuts for adhesion
Removes Smear layer |
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FOr dentin bonding,
How long do you etch? WHat does it do to the dentin? |
15 seconds (less than enamel)
Exposes of collagen network and dentin tubules |
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FOr dentin bonding, do you want the tooth wet or dry? WHy?
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Moist bonding-
keep the tooth wet but not too wet to prevent the collagen network of the dentin from collapsing |
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When the primer goes into the dentin, what does it form? Does it form this in enamel? WHy?
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Hybrid layer
Enamel does not ever form hybrid layer because it does not have dentinal tubules or intertubular dentin! |
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For testing, what does dye penetration show?
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Microleakage and gaps
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what type of bond does dentin bonding provide?
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Micromechanical interlocking.
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what is objective of an impression material?
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to record the dimensions and spatial relationships of the hard and soft tissues
(teeth, gums and vestibule) |
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does an impression give a positive or negative reproduction of the oral tissues?
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Negative reproduction (the cast and die and model is a positive reproduction)
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what are the two major groups of impression materials?
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Rigid and Elastic impression materials
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what are the three rigid impression materials?
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Impression dental compound
Impression plaster zinc-oxide eugenol |
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what are the two major categories of elastic impression materials?
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Hydrocolloid
Non-aqueous elastomers |
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what are the two hydrocolloid impression materials?
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Agar
Alginate |
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What are the 4 non-aqueous elastomers for impressions?
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Polysulfides
Addition Silicones Condensation Silicones Polyethers |
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which two types of impression materials do we use at case?
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alginate
Addition silicone |
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For what two main purposes is impression dental compound used?
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Preliminary impressions of edentulous patients
Checking impressions to determine whether cavity prep has undercuts |
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what are the four components of impression dental compound?
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Fillers andorganic pigments - 50%
Natural resins - 40% Waxes - 7% Steric acid - 3% |
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what does the steric acid do in an impression dental compound?
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lubricant and plasticizer
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WHat is primary use of impression plaster?
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Mounting casts on articulators
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is zinc-oxide eugenol used much for impressions?
what type? |
not really (replaced by rubber materials)
used for final impressions of edentulous patients |
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does alginate or agar have more surface detail?
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agar
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what are the three major disadvantages of alginate?
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1. not as much surface detail as agar or rubbers
2. Needs immediate pour-up 3. can only be used with Gypsum for models and dies |
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What is the working time of regular alginate?
Fast set alginate? |
4 mins
2 mins |
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for alginate, does increasing water temp. increase or decrease working time?
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Decreases working time (up to 37.5 celsius, then it increases working time and slows rxn)
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what is the purpose of sodium phosphate in alginate
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Retarder (increases working time) NaPO4
"Nap"s can make you slow when you wake up? |
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WHat are the main two ingredients in alginate powder and what do they form?
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Sodium or Potassium Alginate
Calcium Sulfate Form insoluble Calcium Alginate |
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What is the retarder in alginate powder?
How does it work? |
Sodium Phosphate
Reacts preferentially with Calcium Sulfate to prevent it from reacting with the Sodium or Potassium Alginate |
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what do you mix with the fat spatula (gorda)?
Skinny spatula (pequena)? |
alginate
Gypsum and stone |
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WHat is the reaction for alginate?
What happens to the physical properties of it? |
Calcium Sulfate + Sodium Alginate + H2O => Calcium Alginate + (Na, Sulfate, H20)
Goes from a paste to a gel |
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WHat is the permanent deformation of alginate?
When does it occur? How do you decrease it? |
2-4%
Occurs when being removed from mouth Pull the impression out fast |
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HOw do you make alginate more flexible?
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higher water to powder ratio
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how do you decrease the chance of tearing an alginate impression?
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remove it quickly from mouth
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what is compessive strength of alginate?
tear strength? |
5000-9000 gm/cm^2
380-700 gm.cm |
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WHen does alginate expand?
when does it shrink? |
when in water (absorbs the water)
when in air (water evaporates) |
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what is the longest time you can leave alginate wrapped in wet paper towel before pour up?
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1 hour - pour right away!
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what is the most common way to disinfect an alginate impression?
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10 minute wait after spraying with 0.5% Sodium Hypochlorite
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which hydrocolloid impression material is reversible?
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Agar
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Do we use agar much for impressions?
What do we use most |
Alginate and rubber materials
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what is contact angle of a hydrophobic material?
Hydrophilic? |
>90 degrees (obtuse)
<90 degrees (acute) |
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WHat is another name for Polysulfide impression material?
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Mercaptan
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Which impression material has the best tear strength?
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Polysulfide
(Sulfur in gas => farting = tearing; therefore, poly"sulf"ides have best tear strength) |
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what are the two main ingredients in polysulfide impression material
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Polysulfide polymer
Lead dioxide |
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how many times can you pour polysulfides?
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Only once
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what are the two types of silicone impression materials?
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Addition and condensation
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what is main ingredient in base of condensation silicone?
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Poly(dimethylsiloxane) with terminal OH groups
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what is the number one disadvantage of condensation silicones?
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Poor dimensional stability
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what are the two main addition silicones?
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PVS (polyvinylsiloxane)
VPS (Vinylpolysiloxane) |
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what is activator of addition silicone?
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Platinum salt
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what is the most accurate impression material
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Addition silicone
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which impression material is most susceptible to contamination?
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Addition silicone
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Which impression material is the most expensive?
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Addition silicone
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What shouldn't you wear when handling putty of addition silicone?
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Latex gloves (they can contaminate it)
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for putty wash addition silicones, what two things can cause a distortion of the impression?
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if it's held under pressure
if set putty is used in the two stage technique |
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what is the impression material with the highest rigidity?q
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PolyEthers
(PE like phys ed where you get athletically fit and rigid as a board) |
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which impression material has highest tear strength?
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Polysulfides
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Which impression material has the least dimensional stability?
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condensation silicones
(condensation on a glass is not stable - sometimes it's there sometimes its not) |
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what are the main two disadvantages of polyether impression materials?
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1. could be too stiff (and cause extraction)
2. could cause allergic rxn to sulphonic acid ester. |
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Rank the non-aqueous rubber impression materials based on flexibility (greatest first)
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Polysulfides
Condensation silicones Addition silicones Polyethers (very stiff) PCAP - Pen CAPs are flexible |
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Rank the non-aqueous rubber impression materials based on elastic recovery (greatest first)
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Addition silicones (most accurate
Condensation silicones Polyethers Polysulfides (very flexible but doesn't bend back) |
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WHat makes up an alloy?
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Metals and nonmetals
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how are alloy restorations made?
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casting
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For ADA classification of alloys, what are the three categories and what is the gold and noble metal concentration of each?
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High-noble alloys: at least 60% noble metals and 40% gold
Noble-alloys: at least 25% noble metals and no gold stipulation Base metal alloys: anything with less than 25% noble metal by weight |
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what is the alloy classification based on the alloy's yield strength and elongation?
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Class I: soft
Class II: medium Class III: hard Class IV: extra hard |
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What two things do noble metals possess?
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1. good and retained metallic luster in dry air
2. Excellent resistance to tarnish and corrosion during heating, casting, and soldering |
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what are the three main noble metals and the melting point of each?
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Gold: 1063 Celsius
Palladium: 1555 Celsius Platinum: 1755 Celsius |
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which noble metal has the highest ductility?
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Gold
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what four ways can gold content be expressed?
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Percentage
Karat Fineness Color |
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What is the formula for gold Karat?
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(% gold/ 100) x 24
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What is the formula for fineness of gold? what't the highest fineness you can get?
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% gold x 10
1000 is highest |
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What is the fineness system used to rate?
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Gold-based dental solders
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what are the specific gravities of the noble metals?
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Gold : 19
Palladium: 11 Platinum: 21 |
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what two things do platinum and palladium increase to gold alloys?
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strength and hardness
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what three characteristics do base metals add to alloys?
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strength
flexibility wear |
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what is the major disadvantage of base metals?
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they can corrode in mouth
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what is zinc used as in alloys?
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a scavenger (deoxidizing agent)
-it scavenges around and steals all the oxygen |
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what are the five most common base metals in alloys?
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Copper
Zinc Silver Nickel Titanium |
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what metal causes the most allergic rxns? what percentage of population is allergic?
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Nickel
8-15% |
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Is silver a noble metal in dentistry? Why?
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no, it corrodes!
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in an alloy, what are the grains between the crystals called?
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grain boundaries
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What size grains give the best properties to the alloy? What are they called and what are the two most common ones?
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Small
Grain refiners Ruthenium and Iridium |
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what is the hardness of enamel?
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343 kg/mm^2
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WHich alloy type is the most expensive?
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high noble alloys
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Which alloy type is the easiest to manipulate?
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High noble alloys
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how do the yield strengths and hardness of noble alloys compare to high noble alloys?
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equal to or greater than
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WHat is main use of Noble Alloys?
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crowns and fixed partial dentures
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What is main advantage of base metal alloys?
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extremely hard yield strengths and hardness
cheap |
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What is main disadvantage of base metal alloys?
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most difficult to manipulate
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what are the three major metals in base metal alloys?
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Nickel, cobalt, titanium
(NCT - base metal alloys are cheap so they "Never Cost Tons") |
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what is biocompatability of metals based on?
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their corrosion, which produces unpleasant tastes, irritation, and allergies
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are all of today's dental alloys safe?
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For the most part, but make sure to buy from a reputable company
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what is a wrought alloy?
What is their grain structure described as? |
An alloy shaped into another form by mechanical force
Fibrous grain structure |
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what are the three uses of Wrought alloys?
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Orthodontic wires
Endodontic files RPD clasps Wrought iron is made from "ORE" |
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what is composition of ceramic bonding alloys? what are the extra ingredients used for?
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High noble or noble alloys plus Galium Indium and Tin
they help form the oxide layer ("GIT" oxide) |
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what is melting range of ceramic bonding alloys?
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850-1350 Celsius
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what is the amount of expansion or contraction called?
For ceramic bonding alloys, should the alloy or ceramic have a higher one? |
coefficient of thermal expansion
Metal should have a higher one by .5 x 10^-6 to form tension on the ceramic when they contract during cooling |
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what are the three major problems of ceramic bonding alloys?
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Color
Greening (those with high silver or copper) Debonding |
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What does soldering involve the use of, and what does it do?
What temperature is it done at? |
Flux - cleans the alloy and removes surface oxide on the alloy
greater than 425 Celsius |
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What are the five uses of solders?
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1. Join ortho wire to band
2. Join clasp wire to RPD 3. Join two parts of a FPD 4. Add proximal contact 5. Repair an occlusal defect in casting |
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what three ways can the heat during soldering be supplied?
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Blow torch
traditional oven laser |
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What are the two categories of all-ceramic systems?
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1. Glass based
2. High Strength (oxide ceramics) |
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what are the two subcategories of glass based ceramics?
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Feldspathic
Reinforced feldspathic |
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every crown that has tooth-color is made of what on the outside?
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Feldspathic porcelain
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what are the three main ingredients of feldspathic porcelain and what are their chemical formulas?
|
1. Kaolin (least important) Al2O3.2SiO2.2H2O
2. Silica SiO2 3. Feldspar K20 Al2O3 6SiO2 (Alkaline alumina silica) |
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The silica in the feldspathic porcelain is added in what form to do what?
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in the form of pure quartz to keep material stable and prevent it from collapsing in furnace
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What did kaolin used to be added to feldspathic porcelain for?
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to increase stickiness and opacity (we use somethign else now)
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What happens to the particles in feldspathic porcelain when the temperature is raised above melting?
|
they fuse into one continuous disorganized lattice
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what is definition of glass?
what is another term for it? |
a material that solidifies without an organized crystalline structure
super cooled liquid ( because liquids do not have a crystalline structure) |
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what is the #1 characteristic of glass-based restoration (feldspathic and reinforced feldspathic)?
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High translucency due to lack of crystalline structure to refract/reflect light
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What are the two main disadvantages of glass based porcelain?
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They are brittle and weak (they fracture easily and the fracture propagates easily)
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What slows down crack propagation in feldspathic porcelain?
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NOTHING! it goes right through
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What indirect material has the lowest flexural strength? what is it?
|
Feldspathic porcelain
60-90 MPa |
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Is the modulus of elasticity of feldspathic porcelain high or low? what does this mean?
|
High,
It is very stiff/won't bend when you apply stress to it. It'll just break. When you apply it to tooth, it gets stronger because it can't bend or flex |
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How do you bond silica based ceramics?
|
etch the tooth AND PORCELAIN with hydrofluoric acid
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WHat initiates the chemical bond between porcelain and cement?
|
Silane coupling agent
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what is the application for feldspathic based all porcelain systems?
|
Laminate veneers (can't take much force because of low flexural strength (60-90 MPa)
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WHat are the three most popular crystals used to reinforce feldspathic porcelain?
|
Leucite
Alumina Lithium Leucite is the most important as it is a popular way of making restorations. |
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WHat is flexural strength of Leucite reinforced porcelain?
|
220 MPa
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What does the leucite do to reinforce the porcelain material?
|
Increases flexural strength to 220 MPa because the crack has to go around the filler crystal (leucite)
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What are the fabrication steps of pressable ceramics?
|
Wax
Burn out wax pattern Press ceramic with high force (cannot be cast because it's too viscous) |
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Why can't ceramics be cast?
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they are too viscous (must be pressed)
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WHat is another name for pressable ceramics?
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Reinforced porcelain
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what are the four applications for pressable ceramics (Reinforced Feldspathic)
|
1. Onlays - to first molar
2. single units (full coverage crowns) - to first molar 3. Porcelain laminate veneers Less work than feldspathic porcelain because it doesn't require powder-liquid approach (you just press it in wax burn out) 4. Inlays |
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What glass system porcelain has the highest flexural strength? what is it?
|
Lithium reinforced feldspathic porcelain
360 MPa |
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In what type of appliance does Lithium reinforced feldspathic porcelain have the highest tendency to break?
|
Fixed partial dentures
(Feldspathic Porcelain Degraders) |
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What is the form of lithium used to reinforce Feldspathic porcelain?
|
Lithium disilicate
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Which type of ceramics need to be bonded?
Which don't? |
Glass based need to be bonded
High strength (Oxide ceramics) dont need to be because they are strong enough |
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How do you attach Oxide ceramics to teeth?
|
Just cement!
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What are the two main categories of high strength ceramics (Oxide ceramics)
|
Alumina (aluminum oxide)
Al2O3 Zirconia (Zirconium oxide) ZrO2 |
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What is another name for high strength ceramics?
|
Oxide ceramics (bc made of aluminum or zirconium OXIDE)
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What part of the restoration is made with oxide ceramic?
what is the rest made of? |
Just the core
Feldspathic porcelain (for translucency) |
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What happens to densely sintered alumina or zirconia when fired to full sintering?
|
It shrinks significantly
(so much so that we have to use CAD/CAM to control it) |
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When alumina (Al2O3) is fired, what happens to it?
|
It becomes densely sintered and LOSES POROSITY
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What is flexural strength of alumina?
|
700 MPa (10x glass)
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What can densely sintered alumina be used for?
|
A single unit Anywhere in the mouth (because flexural strength is high = 700 MPa)
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What are 4 applications of Densely sintered alumina?
|
1. Single units
2. Veneers (not common) 3. Implant abutments 4. Anterior Fixed Partial Dentures (bridge) |
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What is the strongest dental ceramic material?
What is its flexural strength? |
Zirconia (zirconium oxide)
over 1000 MPa (1 gigapascal) |
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Does zirconia ceramic framework stand the test of time?
|
Don't know yet, not enough science
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What are the three different types of zirconia crystals?
High temp? As it cools? Room temp? |
Cubic
Tetragonal Monoclinic |
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What is added to zirconia systems to prevent stress in material as it cools (due to crystals changing form)
|
Yttrium oxide (yytria Y2O3)
|
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How does zirconia stop crack propagation?
Name and mechanism |
Transformation Toughening
as a crack forms it builds enough pressure on the surrounding crystals making them change from tetragonal to monoclinic. The monoclinic crystals are 4% larger so they push the crack and stop it from propagating at its apex. |
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WHat does yytria do to the crystal type of zirconia?
|
Prevents the crystals from changing from tetragonal to monoclinic as it cools (so all are tetragonal)
Allows for transformation toughening if a crack forms later |
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Transformation toughening means more for...?
|
thicker zirconia structures (not necessarily relevant to crown copings (frameworks/cores)
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What are 5 applications for zirconia?
|
1. Single units
2. teeth supported FPD 3. Implant supported FPD (screw/cement) 4. implant abutments 5. adhesively retained FPD |
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How do we bond glass ceramics?
|
Micromechanical bond (etching)
Chemical bond (silanes) |
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Why can't alumina or zirconia be bonded (even though they are strong enough to not need to be)?
|
they are too hard to be etched with hydrofluoric acid
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What is def'n of cementing?
In dentistry? |
THe bonding or uniting of two or more items with cement.
The attachment of a restoration to a tooth/abutment with cement |
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What are the three applications of cement?
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1. Luting Agents - to bond preformed restorations and orthodontic agents.
2. Cavity liners and bases - to protect the pulp and foundations from restorations 3. Restorative materials cement "Lines Car Roads" |
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What are the three broad categories of cements?
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Water based
Oil based Resin based |
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What are the water based cements?
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Glass ionomer
Hybrid ionomer Zinc Polcarboxylate Zinc Phosphate |
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What are the oil based cements?
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Zinc Oxide Eugenol
Non-Eugenol Zinc Oxide Calcium Hydroxide (self-cured) |
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WHat are the resin based cements?
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1. Composites and adhesive resin
2. compomers 3. Calcium Hydroxide (light cured) |
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What cements do we use for provisional restorations?
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1. Non-Eugenol Zinc Oxide (ZONE at case)
2. Zinc Oxide Eugenol (not used at case) |
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What is the only temporary cement we use at CWRU?
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ZONE
(Zinc Oxide Non Eugenol) |
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What is the main powder and main liquid ingredient in glass ionomer cement?
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Powder: Aluminosilicate glass
Liquid: Polycarboxylate copolymer |
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Is glass ionomer cement radiolucent or radiopaque?
Hybrid Ionomer? |
Radiolucent
Radiopaque |
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What is def'n of cementing?
In dentistry? |
THe bonding or uniting of two or more items with cement.
The attachment of a restoration to a tooth/abutment with cement |
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What are the three applications of cement?
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1. Luting Agents - to bond preformed restorations and orthodontic agents.
2. Cavity liners and bases - to protect the pulp and foundations from restorations 3. Restorative materials cement "Lines Car Roads" |
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What are the three broad categories of cements?
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Water based
Oil based Resin based |
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What are the water based cements?
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Glass ionomer
Hybrid ionomer Zinc Polcarboxylate Zinc Phosphate |
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What are the oil based cements?
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Zinc Oxide Eugenol
Non-Eugenol Zinc Oxide Calcium Hydroxide (self-cured) |
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WHat are the resin based cements?
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1. Composites and adhesive resin
2. compomers 3. Calcium Hydroxide (light cured) |
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What cements do we use for provisional restorations?
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1. Non-Eugenol Zinc Oxide (ZONE at case)
2. Zinc Oxide Eugenol (not used at case) |
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What is the only temporary cement we use at CWRU?
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ZONE
(Zinc Oxide Non Eugenol) |
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What is the main powder and main liquid ingredient in glass ionomer cement?
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Powder: Aluminosilicate glass
Liquid: Polycarboxylate copolymer |
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Is glass ionomer cement radiolucent or radiopaque?
Hybrid Ionomer? |
Radiolucent
Radiopaque |
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Does Glass ionomer cement bond to dentin or enamel?
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BOTH
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What is film thickness of glass ionomer cement?
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22-24 Microns
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What is major disadvantage to working with Glass ionomer cement?
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It is susceptible to moisture contamination
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what are the five indications of glass ionomers?
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1. Class V restorations
2. Retention of alloy, zirconia, and alumina restorations 3. Retention of orthodontic bands 4. High strength bases 5. provisional restorations |
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What is composition of hybrid ionomer cement powder and liquid?
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Powder: raidopaque fluoroaluminosilicate glass
Liquid: Polycarboxylate and tartaric acid 2- HEMA Pendant methacrylate groups |
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WHich cement is contraindicated for all-ceramic restorations?
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Hybrid Ionomers (except for zirconia and alumina)
-tendancy to fracture |
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WHat is a positive of hybrid ionomer cements compared to glass ionomer?
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Less susceptible to moisture contamination
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What are the four indications of Hybrid ionomer cements?
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1. Class V restorations
2. Retention of alloy, zirconia, and alumina restorations 3. Retention of orthodontic bands 4. High Strength bases (same as glass ionomer except for provisional restorations) |
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WHat is the maximum distance allowed between restoration and abutment before it can be detected by explorer?
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25 microns
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what is film thickness of hybrid ionomer cement?
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25 microns (the limit)
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What is composition of powder and liquid components in zinc polycarboxylate?
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Powder: zinc oxide
Liquid: Polyacrylic acid |
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what is film thickness of zinc polycarboxylate?
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25-48 microns
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Which provides more retention: zinc phosphate or zinc polycarooxylate?
WHich is more difficult to remove? |
Zinc phosphate
Zinc polycarboxylate |
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what is viscosity of zinc polycarboxylate?
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High (Difficult to mix)
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What are three indications for zinc polycarboxylate?
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1. Retention of alloy restorations
2. Retention of ceramic bands 3. High Strength bases (glass ionomer's - provisionals and class V) |
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What is powder and liquid composition of zinc phosphate?
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Powder: zinc oxide and magnesium oxide
Liquid: Phosphoric acid |
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what is the most common cement for cast restorations?
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zinc phosphate
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what is film thickness of zinc phosphate cement?
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25 microns
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what is major disadvantage of zinc phosphate cement?
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high acidity (phosphoric acid) can cause sensitivity
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What are the indications of zinc phosphate?
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1. Retention of alloy restorations
2. Retention of orthodontic bands 3. High-strenth bases 4. Provisionals |
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with which cement is the frozen slab technique used? WHat does it do?
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Zinc Phosphate
increases working time while allowing a 50% increase in powder/liquid ratio |
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what cement was shown to be a successful luting agent for 20 yr restorations with no marginal leakage?
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Zinc phosphate
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what is powder and liquid composition of zinc oxide eugenol
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powder: zinc oxide, zinc acetate, rosin
liquid: Eugenol |
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What are physical characteristics of zinc oxide eugenol?
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inferior
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what is film thickness of zinc oxide eugenol cement?
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25-35 microns
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what are the indications of zinc oxide eugenol cements?
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1. low and high strength bases
2. Provisional restorations 3. temporary and permanent retention of restorations |
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what is a major substitution for non-eugenol zinc oxide cements?
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2- ethoxybenzoicacid (2-EBA)
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what is disadvantage of non-eugenol zinc oxide?
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excess material is difficult to remove
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what are indications of non-eugenol zinc oxide cements?
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1. Temporary retention of restorations
2. root canal sealers 3. gingival tissue packs 4. surgical dressings |
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WHich temporary cement do we use at case? what is its composition?
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ZONE (zinc oxide non eugenol)
powder: zinc oxide zinc acetate and rosin liquid: 2-EBA (non-eugenol) |
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What is composition of self cured calcium hydroxide?
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Base paste:
Calcium tungstate Calcium Phosphate Zinc oxide glycol salicylate Catalyst paste: Calcium hydroxide Zinc Oxide |
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Are calcium hydroxide's mechanical properties low or high?
what does it stimulate? what is its major use? |
Low
Formation of reparative dentin pulp capping and lining |
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what's stronger? zinc oxide eugenol or calcium hydroxide cement?
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calcium hydroxide
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is thermal conductivity of calcium hydroxide cement high or low?
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Low -> it's used as a pulp liner to protect it from high temps
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what are indications for calcium hydroxide?
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1. low strength base
2. temporary retention of restorations 3. direct and indirect pulp capping 4. protective barrier beneath composite restorations |
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what is the composition of composite and adhesive resin cements?
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Dimethacrylate resin
glass filler (microhybrid and microfilled) |
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which cement is capable of chemical bonding to dentin?
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composite and adhesive resins
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what is film thickness of composites and adhesive resin cements?
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13-20 microns (the least of all)
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Are composites and adhesive resin cements radiolucent or radiopaque?
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radiopaque
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which cement can be recharged with fluoride?
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compomer cement
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which cements are contraindicated for all-ceramic restorations?
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Hybrid ionomers
compomers |
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where do restorations usually fail?
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at the cement!
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what cement has the highest compressive strength?
Tensile strength? what has the second highest compressive strength? |
Resins
Resins Glass ionomer |
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what two cements do we usually use for long lasting restorations?
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glass ionomer
resin |
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can a tooth be dessicated where you are applying cement?
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NEVER
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what are steps to cementing?
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1. isolate area
2. no contamination from blood, saliva, etc. 3. clean and dry tooth 4. don't dry too much and damage odontoblasts 5. air-abrade surface with 50 micron alumina for restoration 6. cavity varnish or dentin bonding resin (for non-adhesive cements |
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steps for cementation of ceramic veneers and inlays?
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1. Air-abrade restoration
2. etch restoration 3. Apply silane coupling agent to ceramic 4. etch enamel (phosphoric acid) 5. Apply resin bonding agent 6. Seat restoration with resin luting agent |
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What type of resin luting agent should you use for:
Veneers Inlays/Onlays Full ceramic crowns |
light cure material (because veneers are thin and light can penetrate them)
Dual cure or chemical cure material dual cure or chemical cure material |
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which two dental materials have the highest thermal conductivity?
WHich has the least? Which two are comparable to enamel? |
GOld Alloys and Amalgam
Unfilled acrylic plastics Porcelain and composites |
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Which two materials have the highest coefficient of thermal expansion?
WHich has the lowest? Which is comparable to human teeth? |
WAX and unfilled acrylic plastics
Porcelain Gold Alloys |
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What is the average biting force?
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77 kg
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what happens to biting force when dentures are in?
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decreases by 50-80%
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What are biting forces of:
Molars Bicuspids Cuspids Incisors |
580 N
310 N 220 N 180 N |
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what is yield strength of enamel?
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344 MPa
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Which material has highest tensile strength?
Lowest? |
Gold Alloys
Human enamel |
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What is compressive strength of human enamel?
Dental Amalgam? |
400 MPa
310-483 MPa |
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for what two things is resilience especially important?
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Orthodontic wires
Acrylic denture teeth |
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Rank the top three materials in terms of hardness and give their knoop hardnesses
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1. Porcelain - 460 kg/mm^2
2. Human enamel - 343 3. Nickel Chromium alloy - 330 |
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what is the formula of gypsum? what is overall reaction to form it?
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CaSO4 . 2H2O
CaSO4 . 1/2H2O + 11/2H2O -> CaSO4 . 2 H2O + heat |
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Rank the four gypsum materials based on % expansion (Low-high)
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1. Mounting Plaster .09%
2. Silky Rock .09% 3. Microstone .12% 4. Snap stone .15% |
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Rank the four gypsum materials based on working time (Low-high)
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1. Snap stone 60-90 s
2. Mounting Plaster 60-90 s 3. Silky rock 3-6 min 4. Microstone 5-7 min |
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Rank the four gypsum materials based on compressive strength (Low-high)
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1. Mounting plaster (4-12 MPa)
2. Microstone (31-59) 3. Silky Rock (41-90) 4. Snap stone (41-97) |
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WHat is the name of the material that can resist the high temps and forces of burn out and casting?
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Investment
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what is the name of the material that resists the heat during burnout and casting and what is the form of it?
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Refractory material
SiO2 (silica) |
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What are the two basic components of an investment?
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Binder (Gypsum, Phosphate, Silica)
Refractory material (SiO2) |
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what is the gamma phase?
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Ag3Sn (Silver-tin)
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what is the amalgamation reaction?
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gamma + mercury -> gamma + gamma1 + (Sn-Cu) (epsilon)
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what constitutes 75% of all restorative materials used by dentists?
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Amalgam
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what is the least expensive long term restorative material?
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amalgam
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what material wears at a similar rate to tooth?
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amalgam
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what three advantages does a high copper alloy have?
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Higher strength
Better Longevity at margins Less corrosion |
