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4th Year Revision > Removable Prosthetics > Flashcards

Removable Prosthetics Flashcards

1
Q

What are the indications for rebasing a successful complete denture? (5)

A
  • the patient reports that it has been worn successfully but a deterioration in retention has been noticed since it was first made
  • the oral tissues are healthy
  • there is no significant loss of occlusal vertical dimension or gross tooth wear
  • the occlusal relationships remain satisfactory
  • the polished surface shapes are successful
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2
Q

What is retching?

A

Involuntary contraction of the muscles of the soft palate or pharynx

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3
Q

What can you use to secure a denture firmly? (4)

A
  • locator abutments
  • ball abutments
  • gold bar
  • CAD CAM titanium bar
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4
Q

What are the powder constituents of acrylic? (3)

A
  • polymer- PMMA beads
  • initiator- benzoyl peroxide
  • pigments- salts of cd/fe or organic dyes
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5
Q

What are the liquid constituents of acrylic? (4)

A
  • monomer- MMA
  • cross linking agents- ethyleneglycodimethacrylate
  • inhibitor- hydroquinone
  • activator- only self cure N,N dimethyl- p- toluidine
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6
Q

How do you process acrylic using a water bath/electrical oven? (3)

A
  • cycle 65*C to decompose benzoyl peroxide
  • do not exceed 100.3*C (BP of monomer)
  • e.g 7 hours at 70C and then 100C for 3 hours
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7
Q

What are the disadvantages of acrylic? (4)

A
  • low impact resistance
  • poor resistance to fracture fatigue
  • poor impact strength
  • water absorption and candida growth
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8
Q

What are the constituents of a cobalt chromium alloy? (5)

A
  • cobalt 35-65%
  • chromium 25-35%
  • molybdenum <4%
  • nickel 0-30%
  • traces of Be, Si, C
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9
Q

What are the affects of carbon? (3)

A
  • hardness
  • strength
  • ductility
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10
Q

What are the advantages of CoCr? (4)

A
  • stronger
  • thinner
  • low corrosion
  • high biocompatibility but nickel allergies
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11
Q

What are the disadvantages of CoCr? (3)

A
  • difficult to polish
  • clasp fractures- work hardening
  • in laboratory high casting temperature
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12
Q

What is steel?

A

An alloy of iron and <2% carbon

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13
Q

What are the additions of stainless steel? (2)

A
  • addition of 18% chromium improves corrosion resistance

- addition of 8% nickel improves corrosion resistance and strength

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14
Q

What is the processing of stainless steel? (3)

A
  • work hardening
  • can be soldered or welded
  • cannot heat treat
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15
Q

How are acrylic denture teeth produced?

A

In reusable moulds by dough moulding or injection moulding

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16
Q

What is a tissue conditioner?

A

Temporarily applied to permit a more equal distribution of load and assumption of more normal mucosal distribution. Helps to get an ill fitting denture to more closely fit the ridge

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17
Q

What is a soft (resilient lining)?

A

Applied as a shock absorber to avoid pain from movement of the denture upon nerves, chronic ulceration, flabby ridges. Useful occasionally when large undercuts can flex in and out

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18
Q

What temperature do tissue conditioners and soft linings work at? (2)

A
  • soft at mouth temperature

- glass transition temperature at < or =37*C

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19
Q

What are the types of materials of tissue conditioners/soft linings? (3)

A
  • acrylic polymers with solvent
  • acrylic polymers or co polymers with an inert ester to act as a plasticiser
  • silicones
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20
Q

What are the requirements of tissue conditioners? (4)

A
  • non irritant
  • non toxic
  • when set tissue conditioners should be soft but not capable of undergoing substantial permanent deformation
  • many are visco elastic
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21
Q

What are the problems with soft linings? (4)

A
  • in time food can become embedded within soft liner
  • plasticisers of the acrylic lost with time > hardening and dimensional changes
  • silicones susceptible to candida
  • sometimes difficult to achieve bond between silicone and PMMA denture base
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22
Q

What are the types of precision attachments? (2)

A
  • ball on post and diaphragm

- tubelock

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23
Q

When is a two part denture useful?

A

When gross tissue loss and different paths of insertion

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24
Q

What is the design of a two part denture? (2)

A
  • split pins on cobalt chrome denture

- acrylic slots into pins on different path of insertion

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25
Q

What kind of denture would you use for bruxists? (4)

A
  • metal backing to teeth
  • cobalt chromium reduces fracture
  • use of cross linked teeth as better wear resistance
  • acrylic post dam increases retention
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26
Q

What is digital dentistrys application to prosthodontics?(4)

A
  • digital dentures
  • implants
  • CAD CAM crowns and bridges
  • digital smile design
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27
Q

What are the advantages of digital dentures? (4)

A
  • improved aesthetics
  • digital record so can produce another
  • no need for articulators
  • time saving in laboratory
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28
Q

What are the disadvantages of digital dentures? (4)

A
  • cost very expensive
  • bond of teeth to base (potential weakness)
  • software updates and system becomes obsolete
  • clinical techniques (learning curve)
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29
Q

How can digital technology be used with implants? (3)

A
  • planned surgery with CBCT
  • guided surgery
  • milled titanium frameworks
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30
Q

What is the NICE definition of frailty?

A

A state of increased vulnerability to poor resolution of homeostasis after a stressor event

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31
Q

What is the legislation protecting a vulnerable adult?

A

Adult support and protection (scotland) act 2007

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32
Q

What are the pathological changes relating to dentures? (3)

A
  • acute or chronic reactions to microbial denture plaque
  • a reaction to constituents of denture base materials
  • mechanical denture injury
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33
Q

What is the bacteria in angular cheilitis? (3)

A
  • candida albicans
  • staph aureus
  • beta haemolytic streps
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34
Q

What can denture irritation hyperplasia be treated with?

A

Tissue conditioner e.g coe comfort

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35
Q

What are the solutions to flabby ridges?

A

New denture covering whole denture bearing area with good peripheral seal and opposing arch denture giving posterior support

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36
Q

What are the allergic reactions in dentistry?

A

Nickel containing Co/Cr or PMMA especially self cure relines as higher monomer

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37
Q

What is the definition for a reline?

A

Adding new base material to the tissue surface of an existing denture in a quantity sufficient to fill the space which exists between the original denture contour and the altered tissue contour

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38
Q

What are the indications for a temporary reline? (3)

A
  • tissue conditioning when grossly ill fitting dentures
  • post immediate dentures
  • after implant surgery
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39
Q

When is a soft reline useful?

A

If parafunctional habits, very atrophic ridges and in cancer/cleft patients

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40
Q

What are the disadvantages of soft relines? (3)

A
  • plasticiser leaches
  • deteriorates with time
  • harbours microorganisms
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41
Q

What are the uses of permanent relines? (4)

A
  • peripheral seal problems
  • correction of errors following inadequate master impression
  • immediate dentures
  • prolongs lifespan of some older dentures
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42
Q

What are the common types of denture fractures? (5)

A
  • midline
  • tooth detaches from denture base
  • loss of flange
  • acrylic saddle detaches from co/cr baseplate
  • clasp fracture
43
Q

Why do dentures fracture? (4)

A
  • impact
  • acrylic in thin section
  • work hardening of metal
  • parafunctional habits
44
Q

How do you do a simple repair?

A

If fractured pieces can be located together, disinfect and send to lab, cast poured, fractured area removed, new acrylic processed

45
Q

How do you do a repair if a piece of denture is missing?

A

Impression taken with fractured denture in mouth, disinfected, cast poured and new acrylic processed into defect

46
Q

How do you do a repair on an acrylic cobalt chrome denture?

A

May need to add retentive tags. Solder on tags and/or use 4-META or silicate co/cr to retain acrylic on co/cr

47
Q

What are the materials for temporary repairs? (2)

A
  • self cure acrylic

- cyanoacrylate glue

48
Q

What are the types of additions? (3)

A
  • immediate addition
  • post immediate addition
  • retention
49
Q

What is a post immediate addition?

A

When a tooth is lost after denture construction and at a later date a tooth is added

50
Q

What is retention addition?

A

When denture retention is inadequate a clasp is added to try to improve retention. Usually a wrought stainless steel clasp

51
Q

What are the clinical issues with additions?

A

Additions usually require an impression of the arch with the denture to be added to in the mouth during an impression

52
Q

What is bracing?

A

The resistance of a denture to displacement by functional forces

53
Q

What are the clinical uses of permanent soft lining materials? (3)

A
  • atrophic ridge and mucosa
  • undercut ridges
  • obturators
54
Q

What is the advantage of acrylic soft lining materials?

A

Good bonding between denture base and lining material

55
Q

What are the advantages of silicone based materials?

A

Maintains softness

56
Q

What are the disadvantages of silicone based materials? (5)

A
  • failure of acrylic/silicone bond
  • rough surface which is difficult to modify
  • susceptible to candida colonisation
  • risk of denture fracture
  • more complex laboratory technique required for soft lining materials
57
Q

What are the components of temporary soft lining materials? (2)

A

Powder- polyethyl methacrylate

Liquid- ethanol, plasticiser

58
Q

What are the clinical uses of temporary soft lining materials? (3)

A
  • temporary relines
  • tissue conditioner
  • functional impressions
59
Q

What are temporary relines used for? (3)

A
  • used for dentures undergoing modification during the transitional phase after implant placement
  • oncology patients
  • used in ill fitting dentures to allow recovery of inflamed tissues in the denture bearing area
60
Q

What materials do we use on the atrophic ridge? (2)

A
  • soft lining materials

- molloplast B

61
Q

How do we reduce trauma to the atrophic ridge? (2)

A
  • reduce the number of posterior teeth on the denture

- over denture abutments

62
Q

What methods ensure a good base fit? (2)

A
  • valves

- precision attachments

63
Q

How do you do the neutral zone technique for tooth position? (4)

A
  • record the jaw relationships in the normal way
  • construct a stable mandibular base in acrylic and build occlusal stops to the correct vertical dimension
  • patient carries out functional movements such as speech and swallowing to record the shape of the neutral zone
  • the technician will make buccal and lingual indices around the neutral zone impression. This will identify the area where the teeth can be placed
64
Q

What are the indications for implants? (3)

A
  • atrophic ridge and poor ability to control prosthesis
  • reconstructive phase after surgery e.g oncology
  • loss of bone following trauma e.g. RTA
65
Q

What are the local risk factors for implants? (4)

A
  • insufficient depth or width of bone
  • bone disease e.g osteoporosis
  • bisphosphonates
  • pts have received radiography for oral malignancy
66
Q

What are the complications around bar retained prosthesis?

A

Soft tissue hyperplasia

67
Q

Describe how you would test for the following features of a complete denture:

  1. retention,
  2. stability,
  3. support,
  4. adaptation
  5. extension
A
  1. tug on incisor teeth,
  2. move side to side,
  3. apply pressure,
  4. rock denture in different axes,
  5. border mould
68
Q

What is the interfacial surface tension?

A

Thin layer of fluid present between two parallel planes of rigid material. Ability of fluid to wet the rigid material

69
Q

What is interfacial viscous tension?

A

The force holding two parallel planes together that is due to the viscosity of the interposed liquid

70
Q

What is the management for an irregular occlusal plane on natural teeth? (5)

A
  • no adjustments
  • minimal localised occlusal grinding
  • radical occlusal adjustment
  • extraction of teeth
  • overlay appliances
71
Q

How do you make replica blocks in the construction of a replica denture? (3)

A
  • 1st impressions
  • melt shellac over the impression as a base
  • wax poured into sprue holes with shellac inside
72
Q

What is the material for the second impression in the replica technique?

A

Wash impression using a light bodied material e.g aquasil, rapid liner

73
Q

How do you assess labial fullness?

A

Assessed side on, should be 90*C angle between base of nose and lip
Nasal philtrum and upper lip

74
Q

How do you assess the incisal level?

A

1-2mm below upper lip at rest

75
Q

What kind of putty do you use in the replica technique?

A

Condensation cured silicone putty

76
Q

Name 5 biometric guides to tooth position

A
  • incisive papilla (5mm posterior to incisal edges),
  • overbite,
  • overjet,
  • smile line,
  • buccal corridor
77
Q

What tool can be used to check if the horizontal plane is even?

A

Fox’s bite plane

78
Q

What are the advantages of immediate dentures? (4)

A

What are the advantages of immediate dentures? (4)

79
Q

What are some contraindications to immediate replacement dentures?

A
  • financial,
  • physical coping,
  • sedation or GA Xs,
  • surgical extractions
80
Q

What are the advantages of over dentures? (3)

A
  • can be used to support denture
  • preserve alveolar bone
  • retain proprioception
81
Q

What are the advantages of immediate dentures? (2)

A
  • maintenance of vertical and horizontal jaw relationships

- covering of x socket may protect blood clot and promote early healing

82
Q

What are the contraindications to immediate replacement dentures? (4)

A
  • financial
  • physical coping
  • sedation or GA Xs
  • surgical extractions
83
Q

What are the functions of flanges? (4)

A
  • retention
  • healing
  • undercuts
  • aesthetics
84
Q

When are open face flanges considered? (3)

A
  • bulky upper anterior alveolar ridge
  • undercuts too deep to be utilised for retention
  • flange would give too much support to upper lip
85
Q

What are the disadvantages of open flange IRDs? (3)

A
  • resorption of ridge leads to gap
  • difficult aesthetic transition to flange
  • reduced retention
86
Q

Where are stops placed in lower and upper trays?

A

lower: incisal region and retromolar pads,
upper: incisive papilla and along post dam area

87
Q

What is the spacing and material, and technique for spaced special tray impressions?

A

3mm spacing,
low/medium viscosity alginate,
placement of stops,
mucostatic technique

88
Q

What is the spacing and material, and technique for close-fitting special tray impressions?

A

1mm spacing,

thin layer of wash impression

89
Q

What impression technique must you avoid for a flabby ridge?

A

avoid mucocompression - use 2 stage technique (or single stage with low viscosity material and perforated tray)

90
Q

How can you fix a broken denture where the 2 pieces fit together closely?

A

Cold cure acrylic resin

91
Q

Name 2 materials that can be used for soft linings and the pros and cons of them

A

Ester (mma + plasticizer): good bond to denture but short clinical life,

Silicone: better performance but poorer bond to pmma

92
Q

name 2 methods on implant denture retention and a problem associated with each

A

Retentive anchors: poor OH

Bar-retained prosthesis: soft tissue hyperplasia

93
Q

What is the depth of undercut for:

a) cobalt chrome
b) stainless steel
c) gold

A

a) 0.25mm
b) 0.5mm
c) 0.75mm

94
Q

For a lingual bar:

a) how much should it clear gingival margins by?
b) width
c) minimum depth of lingual sulcus
d) height

A

a) 3mm
b) 3.5mm
c) 7mm
d) 4mm

95
Q

For a sub lingual bar:

a) width
b) minimum depth of lingual sulcus
c) height

A

a) 4mm
b) 5mm
c) 2mm

96
Q

What are the advantages of using cobalt chromium as a saddle? (4)

A
  • strong
  • less bulky
  • more hygienic if designed well
  • high abrasion resistance
97
Q

What are major connectors? (4)

A
  • unites partial denture saddles
  • provides bracing
  • provides indirect retention
  • acts as a splint
98
Q

What does the force required to displace a clasp vary with? (4)

A
  • depth of undercut engaged
  • length/cross section
  • flexibility of arm
  • angle of approach
99
Q

What is the definition of support?

A

Resistance to vertical load directed through denture to underlying mucosa

100
Q

What are the problems with casts? (3)

A
  • air bubbles
  • distorted impressions
  • heel interfaces
101
Q

How do you reduce the load of a free end saddle? (4)

A
  • decrease the size of the occlusal table
  • use narrow teeth
  • use fewer teeth
  • reduce cusp interference on lateral loading
102
Q

When does the cast usually need tilted?

A

For a bilateral free end saddle

103
Q

What bacteria are in denture debris? (4)

A
  • s aureus
  • e coli
  • k pneumoniae
  • alpha streps
104
Q

What are the disadvantages of alkaline peroxides as a denture cleaner? (2)

A
  • does not effectively deal with calculus or darker stain

- not for soft linings

4th Year Revision (12 decks)

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