W3: Denture Base Materials Flashcards

1
Q

What impacts can tooth loss have on the quality of life?

A

The impact of tooth loss on the quality of life is emotional and psychological health problems, joint and jaw disorders, as well as premature aging.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is vulcanite?

A

Vulcanite was a rubber material that was hardended through a process and then used as a denture base (it was a successful material but had limitations).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the ideal properties for a denture base material?

A

Natural appearance (colour and translucency)
Easy processing (for consistent and good results)
Easy to clean
Easy to repair
Inexpensive
Long shelf life
Biocompatible (to the oral cavity)
Persistant to bacterial contamination
High strength, stiffness, hardness, toughness and
impact strength
Low density (not too heavy)
Radiopaque (to appear on radiographs)
High thermal conductivity
Dimensionally stable
Accurately reproduces surface detail

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What does PMMA stand for?

A

Polymethyl Methacrylate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

When are acrylic polymers used?

A

Acrylic polymers are used in prosthetic dentistry (articifcal teeth), denture repairs, crown and bridge facings, temporary crowns, impression trays, cleft palate obturators, and orthodontic devices

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are conventional dentures made of?

A

PMMA (highly crosslinked with polymer chains of varying lengths) and residual monomer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Why is PMMA the most popular base material for conventional dentures?

A

PMMA as a base material has advantages including good aesthetics, fit accuracy, stability in the oral cavity (biocompatible), easy to work with clinically and in the laboratory (easy manipulation), and is an inexpensive production.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the two forms PMMA can be supplied in?

A
  1. Powder and liquid
  2. Gel
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the composition of the powder in heat cure acrylic?

A

Powder composition:

PMMA granules/beads
Initiator (benzoyl peroxide)
Pigments/dyes (cadium salts)
Optical opacifiers (titanium dioxide/zinc oxide)
Radio opacifiers (Ba, bismuth, zirconyl dimethacrylate)
Plasticizers (ethyl acrylate, dibutyl phthalate)
Synthetic fibers (nylon)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What does benzoyl peroxide do?

A

Benzoyl peroxide (initator) starts the setting process

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What do cadium salts do?

A

Cadium salts (pigments/dyes) add colour to the material

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What does titanium dioxide or zinc oxide do?

?

A

Titanium dioxide/zinc oxide (optical opacifiers) are related to light. If the optical opacifiers are too translucent, there is an issue with light.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What do Ba, Bismuth, and zirconyl dimethacrylate do?

?

A

Ba, Bismuth, and zirconyl dimethacrylate (radio opacifiers) make the acrylic material visible on radiographs.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What do ethyl acrylate and dibutyl phthalate do?

A

Ethyl acrylate and dibutyl phthalate (plasitcizers) add flexibility to the acrylic material.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What does nylon do?

A

Nylon (synthetic fibers) add colour and strength?

?

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the composition of liquid in heat cure acrylic?

A

Liquid composition:
Methyl methacrylate monomer (MMA)
Inhibitor (hydroquinone)
Crosslinking agent (diethylene glycol dimethacrylate)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the boiling point of heat-cure acrylic?

A

MMA boiling point is 100.3°C

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the glass transition temperature of acrylic?

A

PMMA Tg is around 105°C

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the flexural strength range of PMMA?

A

70-127 MPa (ASTM D790)

*ASTM is a testing method that determines the flexural properties

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the flexural modulus of heat cure acyrlic?

A

More than 2 (>2) GPa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

How much residual monomer can be in heat-cure acrylic?

A

Less than (<) 2.2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is the water sorption of heat cure acrylic?

A

Less than (<) 32 μg/mm3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is the solubility of heat cure acrylic?

A

Less than (<) 1.6μg/mm3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Which type of PMMA form does vinyl acrylic present as?

A

Gel form

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What is the composition of gel form PMMA?
Same composition of powder-liquid PMMA **PLUS** light activator.
26
Which denture base is light-cure?
Gel form PMMA (i.e need to cure gel)
27
Which light is gel-form PMMA cured by?
Ultraviolet light
28
Are self-cure acyrlic resin and cold acrylic resin the same?
Yes Self-cured (cold) acrylic resin
29
What is the composition of self-cured acyrlic resin?
Same as that of heat cure acrylic resin **PLUS** a tertiary amine (e.g. sulfinic acid or dimethyl-p-toluidine)
30
What is the composition of self-cured acrylic resin?
Smaller bead size Shorter average chain length **High residual monomer** Lower strength properties Lower colour stability Lower glass transition temperature around (75-80ºc) compared to heat-cure acrylic resin
31
What are visible light-cure resins similar to in dentistry?
Restorative composite (because of the matrix)
32
What is the matrix of visble light-cure resin based on?
Urethame dimethacrylate (has colloidal silica which control material abilty to flow)
33
Which photoinitiator is included in the visible light cure resin?
Comphoroquinon (allows the material to set)
34
What are three more types of acyrlic resins?
Microwave cure acrylic resin Rapid heat-polymrtized resins Pour type denture resins
35
Which areas requirement of denture base materials does PMMA lack?
Strength, stiffness, hardness and toughness Inhibit bacterial growth Thermal conductivity Retention to other polymers, porcelain and metals Radio-opacity
36
What are the advantages of PMMA?
Excellent aesthetics Easy and cheap to process Low density
37
What are the disadvantages of PMMA?
Low strength and toughness Suceptible to distortion Prone to discolouration Low thermal conductivity Radiolucent
38
How can acrylic materials modified?
Rubber reinforced Fiber reinforced Paritculate reinforced
39
Give examples of rubber reinforced acrylic materials?
Rubber reinforce (high impac resin) includes rubber particle reinforcement (butadiene-syrene) and acrylic-elastomer copolymer (MMA-butadiene or MMA-buadiene-styrene).
40
Give examples of fiber reinforced acyrlic materials?
Carbon, acrylic, GF, Aramid, Nylon, PEF, and UHMWPEF
41
Give examples of particulate reinforced denture base materials?
Silica, alumina, glass flakes, nanoclay, titanium and zirconium oxide
42
What is Polyamide?
Nylon ## Footnote *1950s
43
What are the brand names for nylon dentures?
Valplast (Valplast Int. Corp., USA) and Flexiplast (Bredent, Germany)
44
What is the composition of Nylon dentures?
Crystaline polymers with weak bonding between chains
45
What are the advantageous properties of nylon dentures?
Non-brittle (high-toughness) Flexible Material Comfortable and aesthetic clasps **Less allergenic than PMMA**
46
What are the disadvantageous properties of nylon dentures ?
Low flexural strength Low fatigue resistance Low surface hardness Difficult to perform repairs and relines (have to completely replace denture often) Retains staining Retains biofilms Difficult to polish Lacks rigidity and occlusal rests (risks occlusal instability and sinking with Kennedy Class I and Class II cases as well as peridontally affecetd abutment teeth)
47
What is Polyoxymethylene?
Acetal Resin | Similar to nylon polymeric structure ## Footnote *1986
48
What are the advantageous properties of acetal resin dentures?
High modulus of elasticity High strength Heat resistant Organic solvent resistant Oil resistant Water resistant **Monomer-free**
49
What is acetal resin dentures a safe alternative for?
Acetal resin dentures are a **safe alternative** for patients **allergic to PMMA.**
50
What are the advantageus properties of acetal resin compared to nylon
Acetal resin material has minimal prosities therefore resisting the accumulation of biological material. This minimizes (lessens) the risk of bad odour and staining of the acetly resin material (unlike nylon).
51
What are Aryl Ketone Polymer (AKP) dentures?
AKP dentures attempt to bridge the gap between metal Removeable Partial Dentures (RPDs) that can be too rigid and other polymer frameworks that can be too flexible.
52
How are the clasps of AKP dentures compared to metal clasps?
AKP clasps are less retentive but more durable than metal clasps. This means that although clasp retention may not be as good to that of metal frameworks, the clasps may not break if moved out of design range (unlike metal clasps) and are more bendable/are more giving if needing adjusment (?).
53
How are AKP dentures manufacutred?
CAD-CAM
54
What are 3 other advantageous properties of AKP dentures?
Fully biocompatible Lightweight (increase patient satisfaction) Heat reistant (can be autoclaved)
55
What are the advantages PEEK?
Highly bicompatible (no free monomer) Good mechanical properties High-temperature resistant Chemical stability Increased colour stability (better than PMMA) Milled/heat pressed
56
What can PEEK dentues be used an alternative for?
PEEK dentures can be used as alternative to Chobalt-Chrome (Cr-Co) dentures. This denture base material has clasps more flexible than Cr-Co and can be used in areas where there are deeper undercuts. This means that PEEK dentures can be designed to benefit tooth support.
57
What are the clinical applications of PEEK dentures?
Implant abutments, crowns, fixed bridges and removable dentures.
58
Which arch and which instance are Every Denture used for?
Every Denture is an upper acrylic partial denture that is used for the replacemet of anterior teeth (Kenndy IV classification).
59
What are characteristics of Every Denture?
Every Denture has: -Artifical teeth with a smaller occlusal table and wide embrassures -Point contact between abutment and denture teeth (reduces lateral stresses) -Posterior wire stops (to prevent distal drifting of posterior teeth and to increase denture retention) -Flanges (to increase bracing and open design between tooth/saddle)
60
What are the adverse reactions to PMMA?
Irritant contact dermatitis Allergic contact dermatitis
61
Describe in detail irritant contact dermatitis (include where it is most common, how it occurs, and protection measures) Which type of Allergy is irritant contact dermatitis to PMMA?
Irritant conact dermatitis is most **common** in dental laboritories. It may be **associated** (occur) with regular contact of handiling the monomer and powder dough. **Protection measures** include avoiding direct contact, rubber gloves (but may not provide sufficent protection), barrier creams, and utilizing the dust exhaust fans. Type I
62
Describe in detail allergic contact dermatitis (include, where it is most common, how it occurs, and protection measures)
Allergic contact dermatitis may be common with patients (?), is usually associated (occurs) with the **release of residual monomer**. Protective measure include ensure full denture cure.
63
Which type of PMMA does allergic contact dermatitis worsen with?
Self (cold) - cure acrylic resisns
64
Which type of Allergy is allergic contact dermatitis?
Type IV (delayed hypersensitivity)
65
If a patient has allergic contact dermatitis to PMMA, what ther materials can be considered?
Polycarbonate, nylon
66
Which 3 instances are denture lining materials used?
To restore denture fitness (**hard relining**) To relieve pressure over inflammed tissues or make functional impressions (**tissue conditioner**) To provide patient comfort with a soft liner (**soft reline**)
67
When are hard lining denture materials indicated?
When the denture **has a lack of fitness**
68
Which material can be used as a denture hard reline?
Conventional denture base resin ## Footnote *often PMMA
69
What are the methods to performing a denture hard reline?
Direct (chair side)- chemical-cure Indirect (lab)- heat-cure
70
What are the two types of chemical-cure denture hard liners?
1. Powder + MMA (+ Di-n-butylphtalate) (tissue irritant) 2. Powder + BMA less (tissue irritant)
71
What are the disadvantages of direct (chair side) hard lining denture materials?
Disadvantages of the direct method: Low glass transition temperature of chemical-cure resin High porosity of chemical-cure resin Tends to increase vertical dimension (VD) Tends to decrease the Free Way Space Can change the anterio-posterior position of the denture
72
When are tissue conditioners indicated?
Healing after extraction or surgery (cushioning) Relining of immediate dentures (cushioning) Recovery of traumatized tissues (cushioning) Making functional impressions
73
What is the composition of tissue conditioners?
Powder + liquid Powder- PMMA (no initiator) Liquid- alcohol (ethyl alcohol) + plasticizer (e.g. buthylphthalyl buthylglycolate) NO MONOMER, NO CHEMICAL REACTION, NO IRRITATION
74
How long after do tissue conditioners harden and why?
Tissue condtioners become hard after 3-14 days due to loosing plasticizer and alcohol
75
How often should tissue conditioners be replaced?
Every 2-3 days when used as a tissue conditioner
76
Should tissue conditioners be used for short-term use or long-term use only?
SHORT-TERM USE ONLY
77
What are the two different types of soft liners?
Soft liners (temporary) Soft liners (permanent)
78
What are the indictions for temporary soft liners?
- When frequent replacement is difficult - Provisional improvement of fitness before defenitive denture constructures - Assesment of patient response to soft liners
79
Describe the viscoelasticity property of temporary soft liners and its added benefit
The viscoelasticity property is harder at setting but remain soft for 2-3 months. This allows the temporary soft liner to be used as a permanent soft cushion for patients unable to tolerate hard dentures.
80
What are two types of permanent (long lasting) soft liners?
Acrylic Silicone
81
What is the composition of acrylic permenent (long lasting) soft liners?
Acrylic: can be chemical-cure or heat-cure Composition: **Powder** (polyethyl) or polybutyl-mathacrylate (+BPO) and **Monomer** butyl-mathacrylate + plasticizer
82
What are two forms of curing silicone permanent (long lasting) soft liners?
Chemical cure Heat cure
83
What is the composition of heat cure silicone permanent (long lasting) soft liners?
Composition of heat cure: Single paste- vinyl terminated polydimethylsilxane + silica + filler particles + heat activated peroxide
84
What is the composition of chemical cure permanent silicone (long lasting) soft liners?
Composition of chemical cure: condensation and addition polymerization
85
What are the relative merits of silicone based soft liners?
Highly resilient Retains softness longer Weak bond to acrylic Suceptible to candida growth Poor tear strength Poor wettability No permanent deformation Requires regular replacement High water sorption More elastic
86
What are the relative merits of acrylic based soft liners?
Not as resilient as silicone Harden with time due to plasticizer leaching Resistant to bacerial growth Excellent bond to acrylic Acceptable tear strength Suceptible to creep Good wettability Requires regular replacement More vicoelastic
87
What is the contraindication to silicone liners
Xerostomia -> chaffing and irritation
88
What is a polymer?
Polymer is a distinc repeating group of atoms called monomer
89
What is addition polymerization?
Addition polymerization occurs when a reaction between two molecues produces a larger molecule **WITHOUT** the elimination of a smaller molecule or by prodcut.
90
What are the steps of addition polymerization?
Activation Initiation Propagation Termination
91
What is a commonly used free redical producer and an INITIATOR in addition polymerization?
Benzoyl peroxide
92
What are activators in addition polymerization?
Heat Chemical compounds (tertiary amines) Light (radiation) | = produce free radicals describes
93
What is condensation polymerization?
Condensation polymerization occurs when a reaction between two molecures produces a larger molecule **WITH** the elimination or production of a smaller molecule
94
What controls the properties of polymers?
Molecular strength of repeating units Molecular weight (average MW) Chain length Degree of chain branching Crosslinking Filler or plasticizer
95
What are the benifits of cross-linking a polymer?
Cross-linking can make the polymer rigid, brittle, and strong.
96
What are two different types of polymers?
Thermoplastic Thermosetting
97
Describe thermoplastic polymers
Thermoplastic polymers are softened at glass transition temperature (Tg) and molded to shape when required.
98
Describe thermosetting polymers
Thermosetting polymers are manufactured partly polymerized (powder). Heating after molding will complete polymerzation. These polymers are highly cross-linked and cannot bet softened.
99
What is glass transition temperature (Tg)?
Glass transition temperature (Tg) is the temperature at which polymer chains flow past each other. ## Footnote * relates to thermoplastic polymers
100
What are two different polymer structures?
Amorphous polymers Crystalline polymers
101
Describe amorphous polymers?
Amorphous polymers are polymers that contain amorphous regions where molecules are randomly arranged.
102
Describe crystalline polymers?
Crystalline polymers are polymers with crystalline regions where molecules are arranged in a partial pattern
103
Which polymer structure has a limited use in dentistry and why?
Crystalline polymers have a limited used in dentistry because of opacity and processing conditions.
104
Which type of structure are dental polymers mostly?
Amorphous
105
What are the dental applications of polymers?
PMMA (hompolymer) Polyacrylic acid/Hydroxy Methylmethacrylate (copolymer) pure resin e.g PMMA composute e.g. restorations (tooth fillings) ## Footnote ?