Materials FINAL.txt

• Any elements that ionizes positively in solution
• Constitute ~ ¾ of the periodic table

• Au, Pd, Pt, Ir, Rh, Os, Ru, Ag
• ruthenium (Ru)
• rhodium (Rh)
• palladium (Pd)
• silver (Ag)
• osmium (Os)
• iridium (Ir)
• platinum (Pt)
• gold (Au)

Au, Pd, Pt, Ir, Rh, Os, Ru,

Ni, Cr, Co, Mn, Fe

Imperfections involving the absence of one or a few atoms

Linear imperfections through the crystal

2D imperfections involving external surface or internal boundar

• missing atom
• 

• 2 missing atoms
• 

• Schottky defect
• pairs of ions of opposite charge
• 

• extra atom if APF is low
• 

• Frenkel defect
• extra self-interstitial atom
• 

• important to the clinical performance of dental alloys
• Grain boundaries block the movement of dislocations
• Small grains (larger grain boundary) improve the elongation and tensile strength of cast gold alloys

• Cooling rate of solidifying alloy
• Quenching the hot invested casting in cold water (slower cooling = larger grain size)

larger grain size (bad)

Adding ruthenium, iridium and rhenium to the alloy

• High melting and boiling points
• High thermal energy is required to separate the ions which are bound by strong electrical forces
• Low electrical conductivity
• No free electrons causes the ions to be firmly bound and cannot carry charge by moving

good thermal insulating bases for the pulp under the metal restoration

• Force per unit area within a structure subjected to an external force or pressure
• Applied area ↓ -> stress ↑
• Unit: N/m2 = Pa
• 

• Dissimilar restoration
• Dental amalgam ↔ Gold inlay
• Silver fork (Tin) ↔ Gold inlay
• Aluminum foil ↔ Gold inlay
• Electrolyte
• Saliva, tissue fluids
• Anode: Amalgam
• Cathode: Gold
• Electrolyte: Saliva

• 
• Resilience=comparison of area under elastic portion curve (Straight line)Toughnesss=comparison of area under entire curve (More Ulitmate tensile Strength

• 
• Stress=Y-axis
• Strain=X-axis
• Elastic Modulous = Slope of straight line portion
• Yield Strenth = Maximum Stress (y-axis value)
• Ultimate Tensile Strength = Total Area under curve
• Elongation = Maximum strain (x-axis value)
• Resilience=comparison of area under elastic portion curve (Straight line)
• Toughnesss=comparison of area under entire curve (More Ulitmate tensile Strength
• 

• Strength
• Workability
• Corrosion susceptibility (Inc. if grain boundary Inc.)

• usually desirable in a dental alloy
• Smaller grain -> more grain boundaries -> higher resistance to deformation
• Rapid cooling of dental gold alloys
• Addition of grain refiners in the gold alloys
• e.g 0.005% iridium in gold alloys
• Nucleation site ↑ -> # of grains ↑ (125 times more grains/unit volume) -> size of individual grain ↓

Glass modifier

• Simulate natural teeth
• Iron or nickel oxides: brown
• Copper oxides: green
• Titanium oxides: yellowish brown
• Manganese oxide: lavender
• Cobalt oxide: blue

Cerium oxide, zirconium oxide, titanium oxide, tin oxide

Lanthanide earth

• Easy manipulation of the powders
• Starch, sugar

• Recreation of all of the aesthetic features of a tooth
• Opaque shade
• Mask color of the underlying structure (amalgam, metal)
• Dentin shade
• Enamel shade
• Procedure
• 1) Condensation
• 2) Firing
• 3) Glazing and shading ceramics

• Porcelain jacket crown
• Lack of strength and toughness
• 

Aesthetic ceramic is supported by a strong and tough metal

• Aesthetic ceramic is supported by another ceramic materials
• High strength and toughness
• Lack of aesthetics

• (veneer)
• Supported by the tooth structure itself
• Bonding the aesthetic ceramic directly to the enamel and dentine
• Strength depends on the quality of the bond

• Alumina
• Stronger particles than the glass
• Effective at preventing crack propagation  crack stoppers
• Flexural strength: 60 MPa (feldspathic porcelain) vs. 120~150 MPa (aluminous core porcelain)
• 

• Opaque shade
• Use with the weaker dentine and enamel shades of the feldspathic porcelains
• Anterior teeth restoration

• The ceramic should have a coefficient of thermal expansion slightly LESS than that of the alloy in most cases
• ~14 ppm / deg. celcius

Slight (COMPRESSION, tension)

• High fusing: 1300° C: Denture Teeth
• Medium FUsing: 1101 – 1300° C: PJC, All ceramic crown
• Low Fusing: 850 – 1100° C: P/M restoration
• 

between the metal and the ceramic will produce stresses depending upon the type of mismatch

• Ideal = porcleain<metal
• a little so that compression fit will give room for tensile stress

• Chemical
• Mechanical
• Thermal Contraction
• 

• Fewer polymer chains
• Longer polymer chains
• More rigid, less soluble
• 

• More polymer chains
• Shorter polymer chains
• Less stiff, more soluble
• 

• The extent to which all monomer is polymerized
• Percentage of (Mers in polymer)/(Total initial Mers)
• Each monomer has at least one chemical group that participates in the polymerization reaction
• Unreacted residual monomer
• Not all monomers may be able to react completely
• High degree of conversion =Fewer residual monomers

• 
• Two molecules (not usually the same) react to form a larger molecules
• Production of low molecular weight byproducts
• Water, alcohols, halogen acids, ammonia
• Dimensional shrinkage
• Condensation silicone, polysulfide rubber
• Silicone byproduct is WATER

• 
• Free-radical polymerization
• Most commonly used in dentistry
• Most prosthodontic polymers, direct restorative materials
• Carbon-carbon double bond
• Polymerization reaction sites
• No byproduct

• 
• Blue light (λ = 470 nm)
• Light sensitive initiator
• Camphoroquinone (CQ) as the initiator in combination with dimethaminoethyl methacrylate (DMAM) accelerator
• Direct restorative materials

• Low Mw substance is added to a polymer to modify the physical properties of the polymer
• Used to reduce the brittleness of cross-linked polymers
• Do not participate in the polymerization reaction
• Do not become part of the polymer chains

• Reduce the forces of attraction between the polymer chains
• Brittle polymer -> Soft, flexible, tough polymer

• PMMA + dibutyl phthalate  Denture soft liners
• No leaching out of the polymer to oral tissues
• Low vapor pressure
• Low diffusion rate

Attachment of dissimilar materials by atomic or molecular attraction

Attraction between similar atoms or molecules within a material

• Characteristic of a material to flow over a surface
• Need strong adhesive joint, which requires good wetting (flow in undercuts)

• Angle formed when a drop of liquid is placed on a solid surface
• High contact angle - poor wetting
• Low contact angle - good wetting ->good bond

• Extra energy of surface atoms or molecules over those in interior
• High surface energy - good attachment
• Low surface energy (contaminated surface) - poor attachment

• Continuous layer - strong joint
• Discontinuous layer - weak joint
• Want THIN CONTINUOUS LAYER

• Thin layer - strong joint
• Thick layer - weak joint

• material dependent
• Leave intact
• Partial removal and alteration
• Complete removal
• 1. If you leave smear layer, plug up tububles, drier surface = better for hydrohobic dental stuff
• 2. Leave some of smear layer (smear plug) intact – plugging up tubules, keep dentin relatively dry, get some etching into dentin, improve MICRO of dental agent to tooth
• 3. Stronger etching, remove smear layer – deeper penetration of dental bonding agents with tooth sturcture – improved MICRO attachment

• Formed by permanent deformation of tooth structure during cutting and abrasion
• Accentuated by lowering of modulus and yield strength at elevated temperatures
• Deformed material contains hydroxyapatite particles, microorganisms
• Lowered permeability, altered properties

• acid etch - usually 37% phosphoric acid for 15 sec to 1 min
• Produces spaces between rods for micromechanical attachment
• Increases surface energy + cleans surface = better wetting

• Left: minor smear layer when you cut enamel. Enamel smear layer is smaller than dentin b/c enamel has LOW ORGANIC CONTENT (HIGHER ORGanic, more smearing)
• Right: etching removes smear layer, puts undercuts into layer
• When you put adhesive/resin on surface of undercuts, micromechanical attachment
• 
• 

• Absorbed heat energy increases vibration of the atoms or molecules -> material expansion
• Thermal expansion of the restorative material does not match that of the tooth structure
• Differential expansion/contraction -> leakage of oral fluids between the restoration and the tooth
• Percolation
• Decrease with time with dental amalgam
• Space being filled with corrosion products

• Change in length for a 1°C change in temperature
• Unit: ppm(x10-6)/°C
•