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137 Cards in this Set

  • Front
  • Back
What is the primary objective of restorative dentistry?
primary objective of restorative dentistry is to replace diseased or lost tooth structure with materials that restore function and aesthetics
When should the restorative material be chosen?
Restorative materials should be chosen before the tooth is prepared for restoration
What 4 things are dental materials exposed to?
Dental materials are exposed to:
1. Oral environment
2. Biting Forces
3. Cleansed and polished by prophy procedures
4. different temperatures
What are the 7 considerations in the properties of dental materials?
Properties of dental materials
1. biocompatibility
2. dimensional changes
3. thermal conductivity
4. electrical properties
5. solubility and sorption
6. wettability
7. mechanical properties
What is biocompatibility?
Biocompatibility is a measure of the body's response to a specific material
What are some of the reactions involved in biocompatibility?
Biocompatibility Reactions:
1. chemical irritations
2. unpleasant tastes
3. localized allergic reaction
4. generalized allergic reaction
5. cytotoxicity
6. inflammatory reaction
What is dimensional change?
Dimensional change is the % shrinkage or expansion of a material as a result of chemical reaction
How is dimensional change expressed?
dimensional change is expressed as a % of an original volume or length
How is linear thermal expansion expressed?
linear thermal expansion is expressed as a coefficient of thermal expansion (ie. human teeth = 10-15, gold alloys = 12-15, porcelain =8 (can crack)
What is percolation?
Percolation is the contraction of restoration due to cool temperatures resulting in a small space at the jct between the two materials = fluid enters
When the temp returns to normal, the fluid is forced out of the space
Materials with high thermal conductivity values are good conductors of what?
Materials with high thermal conductivity values are good conductors of HOT & COLD
Amalgams with high metal content have _______ thermal conductivity
Amalgams with high metal content have HIGH thermal conductivity
Gold alloys have the _____ thermal conductivity
Gold alloys have the HIGHEST thermal conductivity
Enamel and dentin have ______ thermal conductivity
Enamel and dentin have LOW thermal conductivity
What are the 3 electrical properties in restorations?
3 electrical properties are:
1. Galvanism
2. Corrosion
3. Tarnish
What is galvanism?
Galvinism is the generation of electrical currents the patient can feel
What is the cause of galvanism?
Galvanism is caused by the presence of dissimilar metals in the mouth
What can prevent galvanism?
Galvanism is prevented by having the same type of restoration material in the mouth
What is corrosion?
Corrosion is the dissolution of metals in the mouth
What causes corrosion?
Corrosion is caused by galvanic currents
What are the consequences of corrosion?
The consequences of corrosion are:
1. Staining
2. Pigmentation of tissues
What is tarnish?
Tarnish is the surface reaction of metals in the mouth from components in saliva or foods
What is the consequence of tarnish?
Corrosion is the consequence of tarnish
Why is solubility and sorption of the restoration material important to consider?
Solubility and sorption are important to consider because the materials in the mouth are covered with plaque and therefore are exposed to various acids and organic materials
What is wettability?
Wettability is the measure of affinity of a liquid for a solid
How is wettability measured?
By placing a drop of water on the material and measuring the angle that is formed between the surface of the material and the angle formed at the edge of the drop (contact angle)
a. acute = hydrophilic
b. obtuse =hydrophobic
What is the major factor in the mechanical properties of dental materials?
The major factor in the mechanical properties is the biting force
What is a force?
Force is the external action that produces or tends to produce the motion of a body
What is the average biting force of a person with natural teeth in Kg?
The average biting force is 77 kg
What is the magnitude of the biting forces of the molars in newtons?
The magnitude of the biting forces of molars is 580 N
What is the magnitude of the biting forces of the cuspids in newtons?
Cuspids = 220 N
What is the magnitude of the biting forces of the incisors in newtons?
Incisor = 180 N
What is the magnitude of the biting forces of the bicuspids in newtons?
Bicuspids = 310 N
By how much are the biting forces decreased when a patient has restorations and prosthesis?
Decreased by 50-80 %
What are the mechanical properties to consider in a material?
Mechanical Properties
1. Stress
2. Strain
3. Elastic Modulus
4. Proportional Limit
5. Yield Strength
6. Ultimate Strength
7. Elongation and Compression
8. Resilience and Toughness
9. Hardness
What is stress?
Stress is the internal action to the external applied. When a force is applied to a material, the material inherently resists the external force
Formula for stress?
Stress = force / area
So, for a smaller area the stress increases
What are 3 types of stress?
types of stress
1. tensile
2. compressive
3. shear
What is tensile stress?
tensile stress is the pulling apart of 2 materials
What is compressive stress?
compressive stress is pushing against a material
What is the objective of an impression material?
The objective of an impression material is to accurately record the dimensions and spatial relationships of the hard and soft oral tissues
Does an impression give a positive or negative reproduction of the oral tissues?
The impression gives a negative reproduction of oral tissues
What are the two major classifications for impression materials?
Impression materials are Rigid or Elastic
What are the 3 types of rigid impression materials?
The 3 types of rigid impression materials are
1. Impression dental compound
2. Impression plaster
3. Zinc oxide-eugenol
What are the 2 major classifications of elastic impresssion materials?
The 2 major classifications of elastic impression materials are HYDROCOLLOID & NON-Aqueous ELASTOMERS
What are 2 types of hydrocolloid?
The 2 types of hydrocolloid are Reversible hydrocolloid and Irreversible hydrocolloid
Under what category of impression materials do agars fall into?
Agars fall into the reversible hydrocolloid in the elastic impression materials group

THERMOPLASTIC = AGAR
Under what category of impression materials does alginate fall?
Alginate falls into the irreversible hydrocolloid in the elastic impression materials group
What are the 3 principle applications for impression dental compound?
The 3 principle applications for impression dental compound are:
1. Preliminary impressions of edentulous patients (type I)
2. Border molding of impressions (type II)
3. Check impressions to determine whether the cavity preparation contains undercuts
What are the 4 components and their percentages of impression dental compound?
The 4 components of impression dental compound are:
1. 50% fillers and organic pigments
2. 40% natural resins
3. 7% waxes
4. 3% steric acid (lubricant and plasticizer)
What is the primary use for impression plaster?
The primary use for impression plaster is to mount casts on an articulator
What are the 3 uses for impression plaster?
The 3 uses for impression plaster are:
1. mount casts on an articulator
2. to take preliminary impressions for edentulous patients
3. used for intraoral records
What is zinc oxide-eugenol used for?
Zinc oxide-eugenol is used for to take final impressions of edentulous patients
T/F Rubber impression materials have eliminated the use of zinc oxide-eugenol.
True
T/F Zinc oxide-eugenol is used frequently in the dental office.
FALSE IT IS RARELY USED
Name the 5 advantages to alginate hydrocolloid.
The 5 advantages of alginate hydrocolloid are:
1. Easy to mix and manipulate
2. Minimum equipment is required
3. Flexibility of the set impression
4. Accuracy if it is properly handled
5. Low cost
Name the 3 disadvantages to alginate hydrocolloid.
The 3 disadvantages of alginate hydrocolloid are:
1. Does not transfer as much surface detail to gypsum as rubber or agar
2. Restrict the choice of model and die materials to gypsum type
3. Need quick pour-up of impression
List the 3 ways that alginate can be mixed.
The 3 ways that alginate can be mixed are:
1. By hand
2. Alginator
3. Mechanical spatulator (vacuum mixer)
What is the normal setting time and the working time for alginate?
The normal setting and working time for alginate are:
Setting time = 3-4.5 min
Working time = 1-2 minutes
What is the setting time and working time for fast setting alginate?
The setting time and working time for fast setting alginate are:
Setting time = 1-2 minutes
Working time = 30-45 seconds
Increasing the temperature of the water used to prepare the alginate _______ the working and setting times.
Shortens working and setting times
What is the reaction for alginate?
The reaction for alginate is
Sodium Alginate + CaSO4*H2O --> Calcium Alginate + Na+ + SO4 = H2O
What is the definition of permanent deformation?
Permanent deformation is deformation that occures during the removal of the impression
What % of permanent deformation and recovery should occur during an alginate impression?
Permanent deformation = 2-4%
Recovery should be 96-98%
Typical values of flexibility for commercial alginates are between __% and __%
Typical values of flexibility for commercial alginates are between 5% and 18%
When mixing alginate, more water = (more/less) flexibility?
When mixing alginate, more water = MORE flexibility
What is the compressive strength of alginate?
The compressive strength of alginate is 5000 - 9000 gm/cm2
What is the tear strength of alginate?
The tear strength of alginate is 380-700 gm/cm2
When alginate impressions are removed ____, they are less likely to tear
When alginate impressions are removed RAPIDLY, they are less likely to tear
T/F Alginate impressions do not lose accuracy with increased time of storage?
False they do lose accuracy with increased time of storage
What happens to an impression when stored in air?
It shrinks
What is the best environment for storing impressions?
The best environment for storing impressions is in humid air approaching 100% relative humidity results in the least dimensional change
For what length of time can alginate impressions be stored in an optimal environment?
No more that 1 hour in 100% humidity
What are 5 methods for disinfecting alginate and the appropriate lengths of time needed for disinfection?
The 5 methods for disinfecting alginate are:
1. 10 min after spraying with 0.5% sodium hypochlorite
2. 10 minute soak in 0.5% sodium hypochlorite
3. 10 min soak in an iodophor solution diluted 1:213
4. 20 min soak in 2% glutaraldehyde diluted 1:4
5. 20 min soak in phenylphenol diluted 1:32
What was the first successful elastic material used in dentistry?
Agar hydrocolloid was the 1st successful elastic material used in dentistry
Can agar hydrocolloid impressions be used multiple times without repouring?
yes agar hydrocolloid may be reused
T/F Agar hydrocolloid is very flexible, allowing for impression of undercut areas
True
T/F agar hydrocolloid has largely been replaced by alginate and rubber impression materials
True
What is the definition of viscosity?
viscosity is the property of a fluid that tends to prevent it from flowing when subjected to an applied force
What happens to an impression if it is placed in water?
It expands
High viscosity fluids ______ flow, low viscosity fluids flow _______.
High viscosity fluids RESIST flow, low viscosity fluids flow EASILY.
What is the biggest advantage to polysulfides?
The biggest advantage to polysulfides is they have the best tear strength
What are some disadvantages to polysulfides?
Some disadvantages to polysulfides are
1. Unpleasant odor and taste
2. Poor recovery from deformation
3. Poor dimensional stability - should be poured within one hour
4. CANNOT BE REPOURED
5. Should be used with custom trays
6. Staining of clothes due to the lead oxide
How are polysulfide impressions disinfected?
Polysulfide impressions are disinfected by immersion in sodium hypochlorite, iodophors, complex phenolics, glutaraldehydes, or phenolic gluteraldehydes
What are two types of silicones?
2 types of silicones are:
1. condensation
2. addition
What are the 3 components to the base of a polysulfide in addition to the catalyst?
1. polysulfide polymer
2. fillers
3. plasticizers
What are the 7 advantages to condensation silicone?
The 7 advantages to condensation silicone are:
1. good recovery from deformation
2. good tear strength
3. good accuracy
4. adjustable working times
5. No unpleasant odor or taste
6. Stable in disinfectant solution
7. Relatively inexpensive
What are the 4 disadvantages to condensation silicone?
The 4 disadvantages to condensation silicone are:
1. Hydrophobic
2. POOR DIMENSIONAL STABILITY
3. Immediate pour required
4. Poor bond to tray adhesive
What are 2 types of addition silicones?
2 types of addition silicones are
1. Vinyl polysiloxane materials (VPS)
2. Polyvinylsiloxane (PVS)
What are the components to the base of an addition silicone?
1. Polymethyl hydrogen siloxane
2. Platinum salt activator
3. Fillers
4. Retarders
What are other advantages to polysulfides?
Long working time and set time
2. Good reproduction of surface detail
3. good flow before setting
4. good bond with tray adhesive
5. stable in disinfectant solutions
6. relatively inexpensive
What are the components to the catalyst for an addition silicon?
1. Divinyl polydimethyl siloxane
2. Platinum salt activator
3. Fillers
4. Retarders
What are some of the advantages to addition silicones?
1. MOST ACCURATE MATERIAL AVAILABLE
2. Good tear strength
3. Excellent recovery from deformation
4. Long term dimensional stability
5. Hydrophilic
6. No unpleasant taste or odor
7. Stable in disinfectant solutions
8. Available in automixing devices
What are some of the disadvantages to addition silicones?
1. Some are hydrophobic
2. Relatively expensive
3. Materials are sensitive to contaminants
What are some ways that addition silicones can be contaminated?
1. Rubber dams (sulfur inhibition)
2. Latex gloves (DO NOT WEAR LATEX GLOVES WHEN MANIPULATING THE PUTTY!!)
3. Acrylic temp residues
4. Air inhibited methacrylate
5. Heat
T/F When using addition silicones, the putty-wash is a very popular handling technique
True
When using the putty-wash handling technique for addition silicones, what are the two things that can produce an inaccurate impression?
1. If it is held under pressure
2. If set putty is used in the two stages technique
How can an addition silicone be disinfected?
Immersion for 10-15 minutes in 10% hypochlorite, or 2% glutaraldehyde solutions
What constitutes the base of a polyether impression material?
Low molecular weight polyether with ethylene-imine terminal groups
What constitutes the catalyst for polyether impression material?
1. Aromatic suldonic acid ester
2. Thickening agent
What are some of the disadvantages of polyether?
1. Unpleasant taste and odor
2. Poor recovery from deformation
3. Unstable in some Disinfectant solutions
4. CAN BE TOO STIFF AND CAN CAUSE BREAKAGE
5. Difficult to mix
6. May cause allergic reaction due to sulphonic acid ester
Rank the 4 elastomeric impression materials in terms of flexibility
Polysulfides > condensation silicone ≥ addition silicone ≥ polyether
Rank the 4 elastomeric impression materials in terms of elastic recovery
Addition silicone ≥ condensation silicone ≥ polyether > polysulfides
Which of the elastomeric impression materials has the best tear strength?
Polysulfides
Which of the elastomeric impression materials has the poorest dimensional stability?
Condensation silicones
Which of the elastomeric impression materials is very rigid?
Polyether
Which of the elastomeric impression materials is the most accurate?
Addition silicones
what is type I Gypsum?
mounting plaster
what is type III Gypsum?
microstone
what is type IV Gypsum?
silky rock
(more working time)
what is type II Gypsum?
Model Plaster
How is the hemihydrate created from dihydrate for Type II gypsum?
Open Kettle
How is the hemihydrate created from dihydrate for type III gypsum?
Hi-pressure Steam
How is the hemihydrate created from dihydrate for Type IV and V gypsum?
Boil with CaCl2
What are chemicals that decrease the rate of setting for gypsum products?
Retarders like BORAX
What are the chemicals that increase the rate of setting for gypsum products?
Accelerators like Potassium Sulfate and Terra Alba
What does excess water in gypsum cause?
1. Increased Setting Time
2. Reduced Strength
3. Reduced Expansion
4. Reduced Hardness
What is the term for gypsum's ability to absorb water out of the air?
Hygroscopic
What is the main component of Hardening solutions, which increase the hardness and the abrasion resistance of the gypsum?
Colloidal Silica 30%
T/F
Investment is mixed with water.
FALSE
NOT mixed with water
What is the composition of investment?
1. Binders - Gypsum that holds investment together
2. Silica (SiO2) - Resists the heat of burnout and casting
What are the investments used here at CASE?
Novocast (gypsum bound)
Hi-Temp
What are the types of investment?
Gypsum-bonded investments (lower melting point <1200 deg C)
Phosphate-bonded investments (higher melting point <12000 deg C)
How much do casted metals shrink when they cool from the solid state at a high temperature to room temperature?
1-2.5% shrinkage when cooling
What causes expansion of the investment material?
Hygroscopic and thermal expansion
What is the term for expansion of investment material by addition of the mixing water or submerging the ring in water container?
Hygroscopic expansion
What is the term for when the silica refractory expands when heated?
Thermal expansion
What type of waxes come from minerals, plants or animals?
Natural Waxes
What type of waxes come from gums, fats, fatty acids, oils, and various resins?
Synthetic Waxes
What is the term flow used for when describing the melting wax?
Flow is a change in shape or dimension in response to an applied force
What type of dental material has the highest coefficient of thermal expansion?
Waxes
What is Reported as parts per million of expansion per Celsius degree of the rise in temperature (ppm/degree C) and the greater thi is the greater the expansion as the wax is heated?
Coefficient of thermal expansion of the wax
What are the steps in the lost wax technique?
Pattern is attached to a wax sprue
covered in investment
wax burned out
casting filled in
What category does wax for inlays, casting, and baseplates fall into?
Pattern Wax
What category does wax for boxing, utility, and sticky wax fall into?
Processing Wax
What category does wax for bite registration and corrective fall into?
Impression Wax
What impression materials should we use on edentulous patients?
Any of the Rigid Impression materials

1) Impression dental compound
2) Impression plaster
3) Zinc oxide-eugenol