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133 Cards in this Set
- Front
- Back
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ADA specifications for alginate?
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<3% deformation with a 10% strain
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Calcination
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Dental gypsum products are manufactured by driving off part of the water of the calcium sulfate dihydrate to form calcium sulfate hemihydrate
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What are the chemical components of gypsum?
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dihydrate form of calcium sulfate
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The reverse direction of gypsum is endothermic or exothermic?
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Exothermic
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What is plaster composed of?
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beta form of calcium sulfate hemihydrate crystals
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What is type II gypsum used for?
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mounting casts
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Why is dental plaster weaker than dental stone?
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1.) porosity of the particles, requiring more water for a plaster mix
•2.) irregular shapes of particles prevent them from fitting together tightly |
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What form is stone?
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the alpha hemihydrate form
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What is type III gypsum used for?
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Diagnostic casts
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What is type IV gypsum used for?
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working models
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2 good reasons to use stone:
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require less water, and are approx. 2.5 times stronger than plaster
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What are type V gypsum products used for?
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with high expansion, it is especially suited for polyether or polyvinyl impression materials
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Principal difference between plaster, stone, and high-strength stone is:
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shape and form of the hemihydrate crystals
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The greatest disadvantage of gypsum products is?
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poor resistance to abrasion
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Directly proportional to W/P ratio?
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manipulation and setting times
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Inversely related to w/p ratio?
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strength and setting expansion
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raw hemihydrate used to produce stones and die stones have a higher inherent setting expansion in normal mixes than plaster, how do they fix that?
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This effect is masked by the additives used in their formulation
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physical properties? definition and name 5
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REVERSIBLE interactions with environment
1. Mass 2. Thermal 3. Electrical 4. Optical 5. Surface |
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Mass properties
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Density and specific gravity
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Density
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weight/unit volume
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High density?
Medium density? Low density? |
Metals
Ceramics polymers |
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High density?
Medium density? Low density? |
Metals
Ceramics polymers |
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Specific gravity
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relative density - density of material/density of water
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Density of water?
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1 g/cm cubed
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Material with a specific gravity of 1.2 has a density of what?
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1.2 g/cm cubed
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2 thermal properties?
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thermal expansion and heat flow
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How do you measure thermal expansion?
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LCTE- linear coefficient of thermal expansion ppm/degreesC
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which has highest thermal expansion? Ceramics, metals, or polymers?
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Polymers (30-600)
Metals (10-30) Ceramics (1-15) |
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which has highest thermal expansion? tooth, amalgam, composite?
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Composite (28-35)
Amalgam (25) Tooth (9-11) |
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Clinical consequence of thermal expansion?
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Percolation at restoration margins due to differences in contraction and expansion
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Specific gravity
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relative density - density of material/density of water
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Why are teeth insulators?
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High mineral content
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Density of water?
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1 g/cm cubed
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Material with a specific gravity of 1.2 has a density of what?
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1.2 g/cm cubed
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2 thermal properties?
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thermal expansion and heat flow
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How do you measure thermal expansion?
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LCTE- linear coefficient of thermal expansion ppm/degreesC
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which has highest thermal expansion? Ceramics, metals, or polymers?
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Polymers (30-600)
Metals (10-30) Ceramics (1-15) |
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High density?
Medium density? Low density? |
Metals
Ceramics polymers |
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which has highest thermal expansion? tooth, amalgam, composite?
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Composite (28-35)
Amalgam (25) Tooth (9-11) |
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Clinical consequence of thermal expansion?
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Percolation at restoration margins due to differences in contraction and expansion
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Specific gravity
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relative density - density of material/density of water
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Why are teeth insulators?
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High mineral content
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Density of water?
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1 g/cm cubed
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Material with a specific gravity of 1.2 has a density of what?
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1.2 g/cm cubed
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2 thermal properties?
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thermal expansion and heat flow
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How do you measure thermal expansion?
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LCTE- linear coefficient of thermal expansion ppm/degreesC
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which has highest thermal expansion? Ceramics, metals, or polymers?
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Polymers (30-600)
Metals (10-30) Ceramics (1-15) |
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which has highest thermal expansion? tooth, amalgam, composite?
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Composite (28-35)
Amalgam (25) Tooth (9-11) |
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Clinical consequence of thermal expansion?
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Percolation at restoration margins due to differences in contraction and expansion
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Why are teeth insulators?
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High mineral content
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measure of heat flow?
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thermal conductivity (rate of heat conduction)
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Thermal diffusivity
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heat conduction/ unit time
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Clinical consequence of heat flow?
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Pulps can withstand small temp changes for short times (42 C for 60 sec)
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Why can pulps withstand small temp changes for short times?
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restricted circulation of pulp cannot dissipate heat and carry it away
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Since metals have high thermal conductivity, what do they need?
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Thermal insulator, like a base
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Do composites have high or low thermal conductivity? why is that important?
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Do not need base for thermal conductivity, but do need it for other issues (sensitivity and pulp protection)
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Composites and ceramics are electrical insulators or conductors?
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Insulators
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If a patient complains of a shock when they put a fork to metal restoration, what does that mean?
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Galvanic reaction (electrical property)
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Name 4 optical properties
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Color, translucency, gloss, surface texture
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Hue
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wavelength, color (Roy G Biv)
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Value
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intensity, brightness
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Chroma
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purity, density or concentration
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Metamerism
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2 objects appear the same color under one light source and different under andother light source
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How do you measure surface properties?
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contact angle used to measure how liquid interacts with solid
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Good wetting?
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low contact angle (approach 0)
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Poor wetting
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high contact angle (approach 180
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Wetting can be anticipated on the basis of what too things?
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hydrophobicity and hydrophilicity
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4 characteristics of Hydrophilic primers?
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Allow penetration into areas with water
Usually mixed w/a solvent Very low viscosity Allows for attachment to composite |
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Chemical properties
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Properties that change the primary and secondary bonding of material
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Primary bonding
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generally affected by chemical and electro chemical reactions
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Secondary bonding
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generally affected by processes such as adsorption (onto) and absorption (into)
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Corrosion
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spontaneous destructive oxidation of metals
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Do all metals corrode?
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YES except gold, platinum, and palladium (noble metals)
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Active corrosion?
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Leads to destruction
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Passive corrosion?
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produce corosion film that prevents further corrosion
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Active corrosion needs:
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An anode, cathode, an electrolyte, and a cirtuit
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2 Biologic properties?
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Toxicity, sensitivity
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Stress
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load/unit area (MPa)
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Strain
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deformation per unit of length (length/length)
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Elastic strain
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still able to be converted back
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plastic strain
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permenant deformation
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elastic limit
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point of onset plastic strain
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Ultimate strength
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stress before fracture
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Elastic modulus
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measure of stiffness of material (more stiff = higher slope on graph)
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Resilience vs. toughness
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resilience- before deformation occurs
toughness- before failure or fracture |
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ADA specifications for deformation and strain?
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<3% deformation with a 10% strain
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Our jaw is what class of lever?
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Class III
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T/F Teeth are rigid
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F teeth are not rigid
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Abfractions are usually associated with what?
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heavy wear facets
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Cyclic tension and compression of enamel rods lead to what?
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microfractures
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Example of sincle cycle overload?
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bite on cherry pit or bone and tooth unexpectedly fractures
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Example of fatigue?
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eating something soft and tooth breaks = slow crack propagation over time
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What type of bonds are associated with ceramics?
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Ionic and covalent (both stronger than metal bonds)
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Ionic bond
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electron donor and electron acceptor
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covalent bond
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equally shared electrons
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What are the 3 most common ceramics in dentistry?
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Metal oxides...SiO2, Al2O3, K2O
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Crystalline vs. Noncrystalline?
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Crystalline = (long range order) more order, crystalline silicate quartz or cyrstobilite
Noncrystalline (short range order, not long range) amorphous silicate glass |
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Most dental ceramics are?
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semicrystalline or polycrystalline
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Does porcelain use noncrystalline or crystalline products?
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Both
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name 4 mechanisms in adhesion
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1. mechanical
2. diffusion 3. adsorption and surface reaction 4. electrostatic |
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Mechanical adhesion
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most important in dentistry, impermeable surface, lock and key effect (enamel bonding)
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Diffusion adhesion
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solubility of one material into another (dentin bonding)
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Adsorption and surface reaction
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chemical bonding (covalent, ionic, hydrogen) ex: glass ionomer adhesion
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Electrostatic adhesion
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least important and weakest
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Micro or macro tags will provide major retention?
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Micro
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Macrotags
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IntERprism resin penetration
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Microtags
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IntRAprism resin penetraction
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What type of etch do we use?
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optibond solo plus
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Steps in wet bonding technique?
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1. 30 sec. etch
2. Solubilize smear layer 3. Rinse for 10 sec. 4. Remove excess (DO NOT DESSICATE) 5. Apply adhesive 6. 15 second scrub motion 7. remove solvent 8. apply composite |
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Composite
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Physical mixtures of metals, ceramics, and/or polymers
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Matrix phase vs. Dispersed phase
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Matrix (continuous) monomer resin, photoinitiators, pigments
Dispersed (discontinuous) glass fillers, silane coating |
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What do silicate glasses do in composite?
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They are reinforcing fillers that strengthen
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Advantage of using hybrids over microfills for composites?
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Hybrids have a mixture of glass and colloidal compounds so it is stronger
Microfills are smoother, but weaker |
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What are most filler sizes?
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Minifilled
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Modern composites use crystalline or non-crystalline?
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non
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3 examples of hydrophobic monomers?
and level of viscosity? |
Bis-GMA (high viscosity
UDMA- moderate biscosity TEGDMA- low viscosity |
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What will a silane do to a surface?
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change it from hydrophilic to hydrophobic
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Another name for proportional limit?
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elastic limit
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What is a crown?
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A restoration that covers all the coronal surfaces
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4 different crown types?
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CVC (complete veneer crown)- strongest
MCC (Metal ceramic crown)-most common ACC (all ceramic crown) FRC (fiber reinforced composite |
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Partial veneers
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restoration that covers all but one portion of the coronal part of the tooth
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Onlays
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Restoration that covers entire occlusal surface of tooth and retained by mechanical or adhesive features
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What happens on the first visit to make a crown?
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Diagnostic casts, restoration under crown
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What happens on the second visit to make a crown?
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Prepare tooth to specifications
Fabricate provisional restoration Make final impression |
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What does the provisional restoration do (crown process) 4 things
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Protects pulp (sensitivity)
Maintains tooth position and periodontal health Prevents tooth fracture Provides function and esthetics |
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Sprue
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A channel or hole through which metal is poured (used when making a wax pattern for crown)
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Why do teeth need root canals?
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Remove bacteria and infected pulp tissues
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Two stages of root canal therapy?
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1. prepare canals
2. fill canals |
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Steps in preparing root canal:
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1.Access opening (use high speed handpiece)
2.Clean and debride canals to apical area 3. Guta-percha coated with cement is placed into canals and sealed tightly 4. fill remainder of canal with gutta-percha up to floor of chamber 5. Fill access opening with temporary material (IRM) |
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What do you need to do for minimal tooth destruction?
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Direct restoration only, no crown needed on anterior teeth. May need to crown posterior due to higher stresses
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What do you need to do for a moderate tooth destruction?
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Coronal Radicular Buildup
Must have good size chamber Good on molars, not premolars |
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What do you need to do for severe tooth destruction?
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Post and core
Cast metal Cemented post and direct filling core |
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Diagnostic casts are not made from what type of plaster? Why?
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Type II stone, model plaster b/c it has poor physical properties
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