Dental Materials Exam 1
what can happen when you disinfect the impression material?
imbibition
what is the incorrect manipulation: unpredictable water/powder setting and properties.
incorrect ratio
what are the different types of impression material?
inelastic (plaster, wax and ZOE), aqueous elastomeric (alginate, agar) and nonaqueous elastomeric (polysulfides, silicones, etc).
What is retention/bonding/adhesion?
joining together of objects using a cement or glue.
low-viscosity resin - polymerization of the resin can be activated by ________________.
light or chemical reaction.
Bond is strength is measured in ?
mPA = megapascals / 1mPa is =145 pounds per square inch (psi)
what kind of trays require tray adhesive?
non-perforated.
Give an example of an indirect restoration:
onlay, inlay, crown, bridge and denture
what is the incorrect manipulation: sets before seating tray.
overmixing
How does a Dual-Cured material work?
polymerization begins with curing light but is completed by chemical activation
Exothermic reaction can vaporize monomer and cause...
porosity (low boiling point temp)
Hydroquinone...
reacts or destroys the first free radicals that are produced during the initiation process. Once it is used up polymerization can continue but this delay has allowed the clinician working time with the mateiral
what gets the initiator going?
the activator
Setting time is defined as?
the length of time for a mixed preparation of materials to reach a state of hardness.
etchant removes what?
the smear layer
T/F: critical objects that penetrate or touch broken mucous membranes/skin must be sterilized in steam, dry heat or saturated chemical vapor.
true
T/F: non-critical objects that do not contact mucous membranes but are touched should be disinfected appropriately by intermediate level of disinfectants.
true
T/F: semi-critical objects that come in contact with mucous membranes but done penetrate can be either heat or chemical (6-10 hours) sterilized.
true
T/F: you should fluff powders.
true!
what is the incorrect manipulation: a grainy mix, poor surface detail, inconsistent setting.
undermixing
what is the incorrect manipulation: distortion, inaccuracy, tears.
wiggling the impression during removal
how do you mix alginate?
with a stropping motion against bowl while rotating.
the following is an advantage/disadvantage for what type of impression material: accurate, less deformation, slightly stronger. A: Agar - advantage B: Alginate - disadvantage C: Agar - disadvantage D: Alginate - advantage
A: Agar - advantage
Acrylic resins are not used as a restorative material due to susceptibility to recurrent decay (statement 1). However, they are widely used for fabrication of dentures bases and teeth. (statement 2). A: Both statements are True B: Both statements are False C: First statement is true and second is false D: First statement is false and second is true
A: Both statements are True
Which of the following is the strongest type of retention/bonding/adhesion? A: Chemical B: Physical
A: Chemical
The following is what classification from G.V. Black: Pits and fissures of teeth (particularly posterior) A: Class I B: Class II C: Class III D: Class IV E: Class V F: Class VI
A: Class I
What step of polymerization does light and chemical activation occur? A: Initiation B: Propagation C: Termination
A: Initiation
The following is always a powder. A: Polymer B: Monomer
A: Polymer
An unwaxed car is an example of: A: low contact angle, good wetting B: low contact angle, poor wetting C: high contact angle, poor wetting D: high contact angle, good wetting
A: low contact angle, good wetting
What materials are set by addition polymerization?
Acrylic resins and composites.
__________ is a material that can stick to a flat surface or bond two flat surfaces together.
Adhesive
What is adhesion/bonding used for in dentistry?
Retention of restorations, reduction of microleakage and recurrent decay.
_________ polymers can be easily heated and re-shaped due to linear chains.
Thermoplastic
A bond strength of _______________ is necessary for clinical success in high-stress areas of the mouth.
20-25mPa (2900-3400 psi)
What percent of etchant is Phosphoric acid?
37%
If an area is contaminated, how long do you re-etch for?
5 seconds
what is the removable part of the cast that is exteremly accurate replica of a single tooth and is used to make crowns or inlays?
A Die
What is Chemical retention/bonding/adhesion?
A chemical bond with tooth structure (glass ionomer & polycarboxylate cement)
What can help the clinician to keep saliva and biofilm from the adherend?
A rubber dam
Modified Polymers
Compounds can be added that do not enter into the polymerization process-oily organic esters, rubbers and fillers
Co-Polymers
Formed by two or more different monomers
______________ is a current flow caused by dissimilar metals in contact or in a circuit
Galvanism
what type of strength is measured just after it sets?
Wet strength
Thermoset polymers
cross-linked chains, cannot be reshaped, final shape after polymerization; most dental resins.
do you dispense by equal lengths or volumes?
equal lengths!
what forms irregularities and is 37% phosphoric acid?
etchant
what is the purpose of impression material?
fabrication of restorations and prostheses and evaluation of the rendition for orthodontic, occlusal or other reasons.
what is an advantage to using Co-Polymers?
flexibility can be gained
Cross-linked polymers
formed by different monomer units with reactive double bonds on each end (dimethacrylate)
Sealants use what kind of polymers?
Cross-linked
the following is an advantage/disadvantage for what type of impression material: inexpensive, easy to use, does not require special equipment. A: Agar - advantage B: Alginate - disadvantage C: Agar - disadvantage D: Alginate - advantage
D: Alginate - advantage
In the context of dental hygiene, the reason/s we study dental materials is to: A: Understand the behavior of materials B: Handle materials properly C: Educate patients with regards to homecare instructions D: All of the above
D: All of the above
Reaction of polymerization can be activated by all of the following methods EXCEPT one. Which one is the exception? A: By heat B: By using light C: By adding tertiary amines D: By adding hydroquinone
D: By adding hydroquinone
The following is what classification from G.V. Black: A lesion that involves the incisal angle of an anterior tooth A: Class I B: Class II C: Class III D: Class IV E: Class V F: Class VI
D: Class IV
What property is demonstrated when a gummy bear candy swells after soaking in the water over night? A: Elongation B: Syneresis C: Adsorption D: Sorption
D: Sorption
Acid etching was introduced in 1950s by who?
Dr. Buonocore (for P&F sealants)
What type of strength is the measured strength once excess water is not present?
Dry strength
What are the 2 common materials to pour impressions?
Gypsum and epoxy
What are the important steps in polymerization?
Initiation, Propagation and termination
What are the most common types of gypsum?
Model plaster, Dental Stone and high-strength dental stone (also known as die stone)
What are some advantages of using Cross-linked polymers?
More resistant to surface cracking, easier to grind and polish and less likely to vaporize (porosity)
What is the most common plastic?
Polyethylene
Chemical adhesion in dentistry started in ???
1970's
the following is an advantage/disadvantage for what type of impression material: not dimensionally stable, low tear strength A: Agar - advantage B: Alginate - disadvantage C: Agar - disadvantage D: Alginate - advantage
B: Alginate - disadvantage
The following is what classification from G.V. Black: The area of the tooth just below the interproximal contact posteriorly A: Class I B: Class II C: Class III D: Class IV E: Class V F: Class VI
B: Class II
The following is always a liquid. A: Polymer B: Monomer
B: Monomer
What step of polymerization does the process continue with free radicals to form chain? A: Initiation B: Propagation C: Termination
B: Propagation
Heat activation typically uses...
BPO - Benzoyl Peroxide (is the initiator)
Chemical activation of addition polymerization uses...
BPO - Benzoyl peroxide (is the initiator)
The following is what classification from G.V. Black: The gingival third of the facial and lingual surface of both anterior and posterior teeth. A: Class I B: Class II C: Class III D: Class IV E: Class V F: Class VI
E: Class V
the following is an advantage/disadvantage for what type of impression material: not dimensionally stable-shrinks, uncomfortable for patient, requires special equipment. A: Agar - advantage B: Alginate - disadvantage C: Agar - disadvantage D: Alginate - advantage
C: Agar - disadvantage
The following is what classification from G.V. Black: The area of the tooth just below the interproximal contact anteriorly A: Class I B: Class II C: Class III D: Class IV E: Class V F: Class VI
C: Class III
T/F: Using unit dose supplies is preferred in dentistry because it prevents cross contamination (1). Moreover, supplies that are sold in bulk are more expensive(2). A: Both statements are True B: Both statements are False C: First statement is true and second is false D: First statement is false and second is true
C: First statement is true and second is false
What step of polymerization does 2 free radicals at end of each chain reacting occur? A: Initiation B: Propagation C: Termination
C: Termination
Thermoplastic polymers
Can be easily recycled due to linear chains, can be heated and re-shaped after polymerization
What kind of activation of addition polymerization uses tertiary amines as the activator?
Chemical
Composite material is placed after bonding resin and is ___________ to resin
Chemically bonded
Heat that is given off when the hemihydrate powder is mixed with water that leads to crystal formations is called?
Exothermic reaction
The following is what classification from G.V. Black: The cusp tip or incisal edge of a tooth (very rare) A: Class I B: Class II C: Class III D: Class IV E: Class V F: Class VI
F: Class VI
T/F: Dental materials set slower in warm and humid environment of the mouth.
False
T/F: Lower denture has a better seal due to a better preservation of an alveolar ridge.
False
T/F: etchant needs longer to etch permanent teeth than deciduous teeth.
False
T/F: the lower denture has a better seal, larger surface bearing area and better alveolar ridge.
False - the upper does!
what is dimensional stability?
Loss off accuracy with storage so best to pour model quickly.
Bonding that can be seen and felt is ______.
Macromechanical
Joining two pieces of wood and repair of broken toys is an example of micromechanical or macromechanical?
Macromechemical
What is physical retention/bonding/adhesion?
Mechanically retained through micropores in enamel/dentin-etched (composites, cements and sealants)
Bonding that cannot be seen with the naked eye or felt with a dental explorer is _____________.
Micromechanical
When superglue is used it is an example of macromechanical or micromechanical?
Micromechanical
______________ is the opening and closing of the gap between tooth structure and a restoration due to differences in coefficients of thermal expansion.
Percolation
Of the 3 most common types of gypsum which on is the weakest and most expensive?
Plaster
What are the different type of chemical adhesions?
Polycarboxylate and Glass ionomer cement
T/F: Reaction of polymerization is an exothermic reaction.
True
T/F: Shelf-life is extended by inhibitors
True
T/F: When tooth fractures, the tooth materials reached their ultimate strength.
True
T/F: When using curing light you never overcure but can undercure.
True
Polymer
a naturally occurring or synthetic compound consisting of large molecules made up of a linked series of repeated simple monomers.
What are the 2 types of polymerization in dentistry?
addition and condensation polymerization
Low-viscosity resin is set via?
addition polymerization
Calcination is the process of ?
after mining, gypsum is ground into powder and heated in an oven to dry.
what is known as "irreversible hydrocolloid"?
alginates
What is the initiator?
an organic peroxide
Chemically, gypsum is known as?
calcium sulfate dihydrate (CaSO4 *2H20)