Flashcards in Dental Materials Part II, Test II Deck (76):
Name 4 advantages to Glass Ionomers
Inherent (chemical) adhesion to tooth
CTE - Coefficient of thermal expansion is similar to tooth
What does RMGI stand for?
What are 2 important characteristics of RMGI?
Resin-modified Glass Ionomer
light and/or chemical cure
What are the 3 phases of the Conventional Setting Reaction in Glass Ionomers?
What is formed in the Ion-Leaching phase of a conventional setting rxn for Glass Ionomers?
Name 2 importanat characteristics of this product:
Not native to Matrix
Physical properties aren't affected by depletion
What are the 2 types of rxn going on in the Setting of RMGI?
Acid-Base Rxn - traditional glass-ionomer
(proceeds more slowly)
(similar to composites - light/chemical initiated)
What are 3 properties of the Fluoride Release from Glass Ionomers?
Slow, long term
Doesn't affect physical properties (also doesn't take part in matrix formation)
How long does the initial burst of Fluoride Release from Glass Ionomers last?
The uptake and re-release process process that maintains Fluoride reservoirs can be supplemented with what?
In a glass ionomer, the Fluoride reservoir in the reservoir is _____ the initial burst.
A fraction of
What type of restoration cannot be used with RMGI - Resin Modified Glass Ionomers?
2 examples of an Elastic Impression Material:
What type are they?
Agar and Aginate
Describe the Syneresis process that occurs with Aqueous Hydrocolloids:
Fibril cross linking
What is the primary disadvantage to Alginate?
Single cast only
What are the Advnatages to Addition Silicones?
How does Polyether compare in stiffness to Addition Silicone?
Polyether > Addition Sillicone
*Polyether is the most rigid
List 5 Impression materials from the most to least rigid:
Polyether > Addition Silicone > Condensation Silicone > Polysulfide = Hydrocolloids
*Polyether most difficult to get out of pt's mouth
Why Amalgam? - 5 reasons
Easy to use
Proven (more than 100 years)
Resin-free (less allergies than composite)
What are 2 important functions of Cu in Amalgam?
Ties up tin by reducing Gamma-2 formation
Reduces creep by reducing marginal deterioration
What does Zinc do for the other elements in Amalgam?
*by sacrificial anode
If Amalgam is a brick wall, what fills the holes/voids of the cement?
Sn8Hg - Gamma 2
In an admixed high-copper alloy, what is added to the eutectic?
Gamma 1 (Ag2Hg3) surrounds eta phase (Cu6Sn5) and gamma alloy particles (Ag3Sn)
Gamma sphere (Ag3Sn) with epsilon coating (Cu3Sn)
Ag and Sn dissolve in Hg
Formula for Single Composition High-Copper Alloys
Ag3Sn + Cu3Sn + Hg > Ag3Sn + Cu3Sn + Ag2Hg3 + Cu6Sn5
In the SCS - Single Composition Spherical method of adding Copper to Amalgam, the less the condensation force, the ________.
Larger the Condenser
Most high-copper amalgams undergo a net contraction
What do high-copper amalgams leave once they have contracted?
What does this cause?
Initial leakage and post-op sensitivity
High-copper amalgams will have reduced corrosion over time
What does the net contraction of Amalgams depend on?
Type of alloy
What type of alloy has more contraction?
Greater condensation =
What does overtitration cause in an amalgam?
What type of Strength do amalgams have?
Higher compressive vs. Tensile
Corrosion reduces strength of Amalgam
What are the 2 ways Corrosion will seal margins
Low Cu: 6 months (SnO2, SnCl - gamma 2 phase)
High Cu: 6-24 months (SnO2, SnCl, CuCl - eta-phase Cu6Sn5)
Creep correlates with what?
How much Cu must be in amalgam before it can preven the Gamma-2 phase and have Creep Resistance?
12% Cu total
Overtrituration will have what 3 effects?
"hot" mix - sticks to capsule
Decreases working/setting time
Increases setting contraction
Undertituration will create what kind of mix?
What does Condensation of Amalgam do to Hg?
Reduces residual Hg in restoration
***this is what happens when packing preparation
A continuation of trituration
Adapts amalgam to cavity walls
REduces residual Hg in restoration
Increases strength and servicability to restoration
Dentists can specialize in treating purported Hg toxicity, and the removal of amalgam supposedly cures Leukemia, Hodgkin's disease, and MS
The lay population is unfamiliar with peer reviewed dental lit and relies on media/internet to get it right
How many Amalgam Restorations are there/yr?
*75 tons of Hg
Mercury vapor is released by chewing/brushing and it is difficult to determine vapor levels accurately
What is the average daily dose of Mercury from 8-10 amalgam surfaces?
What is the threshold level?
82 considered dangerous
Less than _____ % of elemental Mercury can be absorbed from the GI and the skin
*also non-toxic if swallowed
Mercury vapor from spills (thermometers, fluorescent light bulbs) accountf for most exposure
What is the most toxic form of Mercury?
Where is it absorbed?
95% absorbed in gut
*Minamata Bay - Hg methylated by marine animals and concentrated up food chain
Blood can reflect ______ of Hg
What is the half life of Hg in the blood
Hair is a reliable method for Hg monitoring
Studies found no relationship between Amalgam and MS
Studies have linked Hg from amalgam Hg to Hg found in Alzheimersf
*no link established
Studie show Renal Toxicity due to Amalgam restorations
Changing the Powder/Liquid ration will have a profound effect on Film Thickness and Consistency when it comes to cements, liners, and bases
What determines the Ultimate Film Thickness in Cements?
Particle size of powder
Conc. powder in liquid
Force applied at cementation
What 2 factors influence the ease with which cement is expressed from under the restoration?
Consistency of cement
Type of restoration
Self etching has no Etch and Rinse - all 3 components, the Etch, Primer, and Bonding Agent are combined
Etch and Rinse are generally 3 step or 2 step process
A 3 Step Etch and Rinse would be a ______ Generation
1 - etch and Rinse
2 - Primer
3 - Bonding/Adhesive agent
5th Generation 2 step has what 2 steps?
1 - Etch and Rinse
2 - Primer/Adhesive mixture
Self-etching can be 1 or 2 steps
Self Etching: conditioner, etch, and primer all mixed and either 1:
1: Bonding incorporated (1 step)
2: Etch and Primer mixed, Then mix Adhesive (2 steps)
With the exception of _________, most bonding is _______
Bonding to dentin locks into micropores created when etched - collagen fibers and dentinal tubules
Most anything bad about restorations is due to amount of polymer
More fillers, less matrix
Less fillers, more matrix
Biggest problem with polymerization shrinkage?
Bond failure at Interface
Sn8Hg (void filler in cement)
Cu added to Epsilon by:
Cu added to Silver-copper eutectic by:
Gamma (Ag3Sn), Ag and Sn dissolve in Hg
Spherical - Ag enters Hg from Ag-Cu spherical eutectic particles
Urine Hg testing for:
Blood Hg testing for:
Composites, Cu ionomers, Glassionomers, RMGI
which has the most F?
Similar for Conventional Glass-Ionomers and RMGI
Higher conc. of Cu reduces the Gamma-2 formation that reduces creep and corrosion and doesn't react with Hg because it attracts tin