Deck 13: Polymers in Prosthodontics

Question 1

The denture base resin mixture should be _______ when it is used to pack the denture flask.

A) sticky
B) grainy
C) doughy
D) rubbery

Answer 1

doughy

Question 2

During denture fabrication, a custom impression tray is typically used to obtain a final impression during the _______ appointment.

A) first
B) second
C) third
D) fourth
E) fifth

Answer 2

second

Question 3

Which term is used to describe the extent to which all monomer is polymerized in a polymer?

A) Modulus of elasticity
B) Degree of conversion
C) Threshold level
D) Bond strength

Answer 3

Degree of conversion

Question 4

Orthodontic appliances use ________-linked poly(methyl methacrylate) homopolymer.

A) unfilled; non-cross
B) unfilled; cross
C) filled; non-cross
D) filled; cross

Question 5

What do short-term lining materials consist of?

A) Silicone-based polymers
B) Methacrylate-based polymers
C) Butadiene-styrene rubber-reinforced polymers
D) Polyethylene methacrylate powder and liquid plasticizers

Question 6

Which statement(s) is(are) correct when contrasting chemical-cured and heat-cured polymers?

A) Residual monomer levels are lower in chemical-cured acrylic polymers.
B) The clinical fit of heat-cured dentures is somewhat superior to those cured chemically.
C) Both heat- and chemical-cured acrylic polymers have residual stresses that result from polymerization shrinkage.
D) A, B, and C
E) A and C

Question 7

Removable partial dentures use _______-linked poly(methyl methacrylate) homopolymer.

A) unfilled; non-cross
B) filled; non-cross
C) unfilled; cross
D) filled; cross

Question 8

Cross-linked acrylic polymers are __________ than their non-cross-linked counterparts.

A) less rigid
B) more soluble
C) more temperature resistant
D) A, B, and C
E) A and C

Question 9

Which of the following statements is true concerning denture acrylic polymers and water sorption?

A) Denture acrylic polymers have low water sorption.
B) Months are necessary for full water sorption to occur.
C) Water sorption causes denture expansion of as much as 10%.
D) Sorption-mediated expansion compensates to some degree for polymerization shrinkage.

Question 10

High degrees of polymerization lead to _____ rigid, _____ soluble polymer networks.

A) more; more
B) less; less
C) more; less
D) less; more

Question 11

Which of the following is correct about acrylic polymers used for most dentures?

A) Are low in strength
B) Have a low modulus of elasticity
C) Have a high modulus of elasticity
D) A and B
E) A and C

Question 12

Which of the following statements is true of the process of polymerization?

A) Polymerization is a chemical reaction that links small inorganic compounds called monomers into long chains of repeating monomer subunits.
B) Polymers that form by simple addition may not shrink as much as those that form by condensation.
C) Polymers with high degrees of conversion have high levels of residual monomer.
D) Most prosthodontic polymers expand significantly as polymerization proceeds.

Question 13

Which of the following is the most common type of chemical reaction used to form polymers used for dental restorations?

A) Condensation to form epoxy polymers
B) Ring opening to form epoxy polymers
C) Ring opening to form silicone polymers
D) Condensation to form silicone polymers
E) Free-radical addition to form acrylic polymers

Question 14

How should dentures be cared for when removed from the mouth?

A) Stored in water
B) Stored in rubbing alcohol
C) Boiled and then air dried to kill bacteria and fungi
D) Desiccated with acetone to prevent ingress of bacteria

Question 15

Which of the following is the most common monomer found in acrylic polymers used in dentistry?

A) Hydroxyethyl methacrylate
B) Poly(methyl methacrylate)
C) Methyl methacrylate
D) Butyl methacrylate
E) Octyl methacrylate

Question 16

The polymerization reaction shrinkage of acrylics approaches _____ vol %.

A) 1
B) 3
C) 6
D) 12

Question 17

Increased salivary viscosity does not allow good wetting of the denture polymer. Increased salivary viscosity leads to impaired retention of the denture.

A) Statement 1 is correct; statement 2 is correct.
B) Statement 1 is correct; statement 2 is incorrect.
C) Statement 1 is incorrect; statement 2 correct.
D) Statement 1 is incorrect; statement 2 is incorrect.

Question 18

What do chemicals such as dibutyl phthalate cause a poly(methyl methacrylate) to become?

A) Stiff
B) Porous
C) Greasy
D) Rubbery
E) Slippery

Question 19

Which of the following statement(s) is(are) true of denture soft liners?

A) They may be used for patients with severe undercuts of the edentulous ridges.
B) Silicone liners harden as time passes, because they contain plasticizer.
C) The hardness of the long-term acrylic materials increases slowly as the plasticizer is leached out by exposure to oral fluids.
D) A, B, and C are true statements.
E) A and C are true statements.

Question 20

During fabrication of removable partial dentures, the acrylic bonds ___________ to the denture teeth and ____________ to the alloy framework.

A) chemically; chemically
B) chemically; mechanically
C) mechanically; mechanically
D) mechanically; chemically

Question 21

Why are filler particles often bonded to the polymer network?

A) Increase strength
B) Reduce water sorption
C) Stabilize the color or transparency
D) Only A and B are correct.
E) Only A and C are correct.

Question 22

Why are denture teeth made of acrylic and modified acrylic polymers replacing ceramic denture teeth?

A) Do not wear natural opposing teeth
B) Mechanically bond to the acrylic denture base
C) Better absorb occlusal forces and preserve the edentulous ridge
D) A, B, and C
E) A and C

Question 23

What advantage(s) do/does light-cured urethane dimethacrylate material have versus powder-liquid acrylic material?

A) Lower polymerization shrinkage
B) Quicker fabrication time
C) Lower cost
D) A and B
E) A and C

Question 24

Which of the following is correct regarding cross-linked acrylic polymers?

A) More rigid
B) Less soluble
C) Less temperature resistant
D) Only A and B
E) Only B and C

Question 25

Which of the following statements is correct about plasticizers?

A) Liquid oils such as dibutyl phthalate will cause a PMMA to become rigid.
B) The chemicals in plasticizers do not participate in the polymerization process.
C) The chemicals do not become part of the polymer strands but are trapped in the network.
D) Only A and B are correct.
E) Only B and C are correct.

Question 26

How long does it take for a chemically cured custom impression tray to polymerize?

A) 2 to 4 minutes
B) 4 to 7 minutes
C) 6 to 10 minutes
D) 8 to 10 minutes

Question 27

Chemical-cured denture materials are initiated using ________ in the monomer liquid that mixes with the benzoyl peroxide in the polymer powder.

A) fillers
B) plasticizers
C) accelerators
D) free radicals

Question 28

Which of the following statements is correct regarding addition polymerization?

A) It has a high exothermic reaction.
B) It has a low exothermic reaction.
C) It does not create by-products.
D) All of the above are correct.
E) Only A and C are correct.

Question 29

Soft liners are used for patients with minimal undercuts of the edentulous ridges. They are also used for those patients whose ridges are continually sore.

A) Statement 1 is correct; statement 2 is correct.
B) Statement 1 is correct; statement 2 is incorrect.
C) Statement 1 is incorrect; statement 2 is correct.
D) Statement 1 is incorrect; statement 2 is incorrect.

Question 30

Which of the following statement(s) is(are) true regarding acrylic denture teeth?

A) The coronal portion of the tooth is constructed of minimally cross-linked polymer to provide resistance to crazing when the teeth are exposed to solvents during eating.
B) Polymers in the gingival portion of the plastic teeth have maximal cross-linking to ensure the denture base can bond to the polymer of the denture tooth.
C) Cross-linking provides better wear resistance and a more solid feel when the patient chews food.
D) A, B, and C are true statements.
E) A and C are true statements.

Question 31

Which of the following is not a by-product produced during polymerization?

A) Water
B) Alcohol
C) Free radicals
D) Hydrogen gas

Question 32

What is a homopolymer?

A) Contains multiple types of monomers
B) Contains one type of monomer
C) Contains no monomer
D) Does not polymerize

Question 33

Which of the following statements is true of Bis-GMA-based polymers used to fabricate temporary crowns or bridges?

A) Lower cost than non-cross-linked acrylic polymers
B) May be light-cured, chemical-cured, or dual-cured
C) Are more difficult to trim than acrylic polymers
D) Do not wear as well as acrylic polymers

Question 34

Which method of polymerization uses monomers that have a carbon-carbon double bond as their reactive group?

A) Poly(methyl methacrylate)
B) Residual monomer
C) Free radical
D) Addition

Question 35

Small organic compounds called ____________ chemically link into long chains of repeating subunits called ____________.

A) monomers; methacrylates
B) polymers; methacrylates
C) polymers; monomers
D) monomers; polymers

Question 36

Not all monomers may be able to participate in the polymerization reaction. Any unreacted residual monomer in the polymer will not have significant clinical consequences.

A) Statement 1 is correct; statement 2 is correct.
B) Statement 1 is correct; statement 2 is incorrect.
C) Statement 1 is incorrect; statement 2 is correct.
D) Statement 1 is incorrect; statement 2 is incorrect.

Question 37

Which of the following is correct about maxillofacial prostheses?

A) They are inflexible and difficult to retain.
B) The edges are thick and esthetics are poor.
C) Difficult to match a person's skin tone and coloring.
D) Materials with better properties have not been developed since the late 1980s.

Question 38

The denture base material should be _________ before packing into the flask.

A) doughlike
B) grainy-sandy
C) sticky-stringy
D) viscous-flowing

Question 39

Co-polymers contain three or more different polymers. Copolymers are used in dentures, mouth protectors, and restorative composites.

A) Statement 1 is correct; statement 2 is correct.
B) Statement 1 is correct; statement 2 is incorrect.
C) Statement 1 is incorrect; statement 2 is correct.
D) Statement 1 is incorrect; statement 2 is incorrect.

Question 40

Custom impression trays are essential for the appropriate construction of __________________ prostheses.

A) removable but not fixed
B) fixed but not removable
C) both removable and fixed
D) neither removable nor fixed

Question 41

Resin composite temporary materials are chemical cured. Resin composite temporary crowns wear better than their acrylic counterparts.

A) Statement 1 is correct; statement 2 is correct.
B) Statement 1 is correct; statement 2 is incorrect.
C) Statement 1 is incorrect; statement 2 is correct.
D) Statement 1 is incorrect; statement 2 is incorrect.

Question 42

Apply the steps to acceptable denture care.

Question 43

Compare and contrast methyl methacrylate polymers with cross-linked polymers.