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Operative Dentistry Y2 > Prosthetics > Flashcards

Prosthetics Flashcards

(101 cards)

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1
Q

What percentage of the UK population are edentulous ?

A

13

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2
Q

What are the stages of denture construction ?

A

Primary impression, primary cast, special tray, secondary impression, master cast, record block, occlusal registration, shade colour and size, set up teeth, try in, process trim and polish, fit, review

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3
Q

What preparations may be necessary for edentulous patients for dentures ?

A

Treat infection

Improve contour

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4
Q

What features of the denture should the dentist check at the try in stage?

A

Vertical height, midline, labial contour, aesthetics, occlusion

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5
Q

What factors does facial surface anatomy depend on ?

A

Skeletal form, muscles of mastication and facial expression, age, gender, race, disease, dentition

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6
Q

What is occlusal vertical dimension ?

A

The superior inferior relationship between the maxilla and mandible when in maximum intercuspation

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7
Q

What is resting vertical dimension ?

A

The superior inferior relationship between the maxilla and mandible when the mandible is at rest. This depends on posture and muscle tone

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8
Q

What is free way space ?

A

RVD-OVD, 2-3 mm in dentate adults

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9
Q

What is aesthetics ?

A

Recreating what is considered the norm

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10
Q

What is cosmetics ?

A

Creating aesthetics above the norm

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11
Q

What is the golden ratio ?

A

1:1.618 (phi)

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12
Q

Which factors affect the appearance of dentures ?

A

Tooth selection , modification, position, vertical height, flange colour and design, position and material of clasps

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13
Q

Which factors should be considered when positioning the teeth ?

A

Occlusal plane, interpupillary and alar tragus lines
Lip support
Arrangement

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14
Q

What alternative materials are there to stainless steel and cobalt chrome for clasps?

A

Gold
Nylon
Acetal
Sandblasting to give Matt finish

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15
Q

Why replace missing teeth ?

A

Improve aesthetics, function, speech, confidence, prevent drifting, over eruption, open contacts

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16
Q

What is the Frankfort plane ?

A

External auditory meatus to the lower border of the orbit

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17
Q

What are the advantages of gypsum ?

A

Good colour contrast
Dimensional stability
Cheap

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18
Q

What are the disadvantages of gypsum ?

A

Poor surface detail
Poor tensile strength
Poor abrasion resistance
Poor wetting of rubber based impressions

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19
Q

How is beta type I I gypsum made ?

A

Heat in open vessel 150-160 degrees

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20
Q

What is type II beta gypsum used for ?

A

Mount models on articulators, flask dentures, basing models

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21
Q

What is the structure of type II gypsum ?

A

Large irregular orthorhombic crystals

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22
Q

How is type III gypsum produced ?

A

Heat in autoclave under steam pressure 120-150 degrees

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23
Q

What are the uses of type III gypsum ?

A

Can be used 50/50 with white plaster for edentulous models

Used on its own for dentate models and denture flasking to minimise acrylic shrinkage

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24
Q

What structure is type III gypsum ?

A

Small irregularly shaped prismatic particles

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25
What are the properties of alginate ?
Mucostatic Viscoelastic Inexpensive Susceptible to syneresis and imbition Dimensional stability depends on humidity Satisfactory reproduction of hard and soft details
26
What are the uses of alginate ?
Full and partial dentures - use 3 mm spaced special tray | Duplicate denture moulds
27
What are the constituents of alginate ?
``` Sodium alginate Calcium sulphate dihydrate Sodium phosphate Potassium sulphate Filler Sodium silicoflouride ```
28
What are the relative amounts of the constituents of alginate (%) ?
``` Sodium alginate 18 Calcium sulphate dihydrate 14 Sodium phosphate 2 Potassium sulphate 10 Filler 52 Sodium silicoflouride 4 ```
29
What is The purpose of each of the constituents of alginate ?
``` Sodium alginate - hydrogel former Calcium sulphate dihydrate - calcium ions Sodium phosphate - control working time Potassium sulphate - setting Filler - consistency Sodium silicoflouride - control pH ```
30
What is the setting equation for alginate ?
Sodium alginate + calcium sulphate ------> sodium sulphate and calcium alginate (insoluble )
31
What is dental wax ?
Thermoplastic material that melts without decomposition and is usually composed of two or more natural or synthetic compounds
32
What is modelling wax ?
Tough, used for occlusal rim and try ins
33
What is beading wax ?
Soft, easily distorted at room temperature, used for adjusting impression trays
34
What is casting wax ?
Used for patterns on metal castings
35
What is sticky wax ?
Rigid, brittle, used to fix things together
36
What are the thermal properties of dental wax ?
Coefficient of thermal expansion that minimises dimensional change Well defined melting point Softening point above the mouth Poor thermal conductivity meaning that the outer surface hardens before the inner mass
37
What are the mechanical properties of dental wax ?
Flows well at moulding point Little or no flow at mouth or room temperature Brittleness which allows it to be removed from undercuts
38
What are the constituents of dental wax ?
Paraffin wax Bees wax Synthetic materials eg carnauba to improve toughness and melting range
39
What is the melting range of dental wax ?
49-58 degrees
40
What are the special tray design principles ?
2 mm from sulcus | Relief for frenae
41
What angle should the handle be at for an upper special tray ?
45 degrees
42
What angle should the handle be at for the lower special tray ?
10 degrees
43
When might a finger rest be included in a special tray ?
For close fitting lower trays a finger rest may be placed on the crest of the ridge in the premolars region
44
What are the properties of light cured special tray wafer ?
Transverse strength 80 mpa | Shelf life 3 years
45
What are the uses of the special tray wafer ?
Special trays Occlusal rim and try in baseplate Neutral zone base plates
46
What are the constituents of the special tray resin wafer ?
``` Glass filler Additives Catalyst Pigment Pyrogenic resin Vinylic ester resin UDMA TEDMA ```
47
Which factors influence dimensional stability?
Continuation of setting reaction after setting time Slow elastic memory Internal stress from mouth to room temperature Loss of volatile products leading to shrinkage
48
When is plaster used as an impression material ?
Edentulous, mobile soft tissue
49
Describe plaster as an impression material
Similar to Dental plaster with higher water to powder ratio to record fine detail Additives increase working time and reduce setting expansion May give patient dry mouth
50
How is plaster disinfected ?
Places in sodium hypochlorite for 10 mins
51
What is impression compound used for ?
Primary impressions for full dentures | Base for wash impression
52
What types of impression compound are there ?
Type 1 low fusing impression material | Type 2 high fusing tray material
53
For how long is impression compound heated and under what temperature ?
Several minutes 55-60 degrees | Flow rate for type 1 is substantial over 45 degrees but poor below 37
54
What are the properties of impression compound ?
Muco displasive Non elastic High viscosity Can be re adapted
55
What causes internal stress in impression compound ?
High coefficient of thermal expansion Change in temperature from softening to room Poor thermal conductivity
56
What are the constituents of impression compound ?
47 % thermoplastic material eg wax or raisin characterises softening temperature 50% filler eg limestone increases viscosity and reduces Thermal contraction 3% lubricant eg stearin acid or gutter percher improves flow properties
57
Which other material are impression waxes most commonly used with?
Zinc oxide eugenol
58
What so zinc oxide eugenol impression material used for ?
Edentulous master casts
59
What are the properties of zinc oxide eugenol impression material ?
``` Non toxic Irritant Persistent taste Good dimensional stability Good detail reproduction Moco displasive ```
60
What are the constituents of paste 1 of zinc oxide eugenol impression material ?
Zinc oxide Water Olive oil Zinc acetate
61
What are the constituents of paste 2 of zinc oxide eugenol impression material?
Eugenol | Kaolin
62
What is agar ?
15% colloidal suspension of agar in water | Includes borax to give body and potassium sulphate to increase setting of gypsum as this is retarded by borax
63
What is agar susceptible that could compromise its dimensional stability?
Imbition | Syneresis
64
What should the casting of addition cured silicone impression materials be delayed ?
They release hydrogen which could cavitate the gypsum
65
What chemical on some synthetic gloves can retard the setting of some silicone impression materials?
Dithiocarbonate
66
Do addition cured silicones have a high or low setting shrinkage ?
Low so no space for cement
67
What is the by product of condensation cured silicone ?
Alcohol
68
Do condensation cured silicones have a high or low setting shrinkage ?
High so allows space for cement
69
What sis a disadvantage of condensation cured silicone impression materials ?
TES is hydrolysed easily and can become inactive if contacts water
70
To which component of a poly ether can patients be allergic ?
Sulphonic acid catalyst system
71
What is any advantage of poly ether imoression materials ?
Less hydrophobic than silicones
72
How long does poly sulphide impression material take to set ?
10 mins
73
What are the advantages of polysulphides?
Can be electroplated | Highest tear strength
74
What are the disadvantages of polysulphides?
Bad smell and taste Humid and temperature dependent Erratic setting
75
What are the main types of articulators ?
Simple hinge Average value articulators Semi adjustable Fully adjustable
76
What are the 2 types of average value articulators called ?
Ash freeplane 75 and dentatus ARS
77
What are the average vales for average value articulators and what plane are they in ?
Incisal plane 10 degrees, horizontal Condylar plane 30 degrees horizontal Bennett angle 15 degrees Saggital
78
What are the 2 types of semi adjustable articulators called ?
Dentatus ARH non arcon | Denar mark 2 arcon
79
What are the angles and planes for a semi adjustable articulator ?
Incisal, angle custom table, horizontal Condylar, set to patients protrusive wafer, Frankfort Bennett, set to patients lateral wafer, Saggital
80
What is the type of fully adjustable articulator called ?
Denar D5A
81
What are the angles and planes for the fully adjustable articulator ?
``` Incisal, custom table, horizontal Condylar, set to pantograph , Frankfort Bennett , set to pantograph , Saggital Inter condylar distance, adjustable width Pantograph, recordings are transferable ```
82
What are the uses of heat cured acrylic resin ?
Denture bases Splints Artificial teeth Rebases
83
What are the physical properties of acrylic resin ?
Thermal conductivity Radiopaque Low specific gravity and density High glass transition temperature to prevent distortion
84
What are the mechanical properties of acrylic resin ?
Flexural and impact strength High modulus of elasticity High elastic limit
85
What are the chemical properties of acrylic resin?
Does not absorb water Inert Insoluble
86
What are the biological properties of acrylic resin?
Non toxic Non irritant Resists bacteria and fungi
87
What Is the boiling point if the acrylic resin monomer ?
100.3 degrees
88
What is the monomer in acrylic resin ?
Methylmethacrylate
89
What is the ideal ratio of powder to liquid for acrylic resin ?
2.5 to 1
90
What is the ideal polymerisation shrinkage for acrylic resin?
5-6 %
91
What are the transitional stages of the polymerisation of acrylic resin ?
``` Sand Sticky Dough Rubber Hard ```
92
What should be taken into consideration regarding the polymerisation of acrylic resin?
Above 65 degrees benzoyl peroxide evaporates forming free radicals Above 100.3 degrees the monomer boils in the hottest parts of the denture leading to gaseous porosity The polymerisation is very exothermic High conversion rate of monomer to polymer
93
Describe a typical polymerisation cycle for acrylic resin ?
Heated to 70 degrees over several hours then 100 degrees for 3 hours Majority of polymerisation occurs at 70 degrees, 100 degrees at end ensures thinnest parts of denture polymer missed as less exothermic heat is generated in these areas
94
How many times greater is the coefficient of thermal expats nil of acrylic than gypsum ?
Ten
95
What is the powder on acrylic resin composed of ?
``` Polymer - polymethylmethacrylate Initiator benzoyl peroxide Pigment, slats of iron or organic dyes Synthetics eg acrylic or nylon Plasticiser dibutyl phthalate ```
96
What is in the monomer of acrylic resin ?
Methyl methacrylate Inhibitor hydroquinone Cross linking agent ethylenglycoldimethacrylate
97
What lowers the flexural modulus in high impact acrylic resin ?
Butadiene styrene
98
What are the ideal properties of denture base materials ?
High thermal conductivity, Low density, Resistant to bacterial growth and absorption of oral fluids, Radio opaque
99
What amount of undercut is required for a cobalt chrome clasp ?
0.25mm
100
What amount of undercut is required for stainless steel or cast gold clasps ?
0.5 MM.
101
What amount of undercut is required for wrought gold claps ?
0.75mm

Operative Dentistry Y2 (7 decks)

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