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Prosthetics Flashcards

1
Q

What is Kennedy class I saddle

A

Bilateral distal extension saddle

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2
Q

What is Kennedy class II saddle

A

Unilateral distal extension saddle

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3
Q

What is Kennedy class III saddle

A

Unilateral bounded saddle

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4
Q

What is Kennedy class IV saddle

A

One saddle which crosses mid-line anterior to remaining teeth

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5
Q

What is Craddock class I saddle

A

Tooth supported

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6
Q

What is Craddock class II saddle

A

Mucosal supported

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7
Q

What is Craddock class III saddle

A

Tooth and mucosal supported

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8
Q

What are 6 ideal features of indirect retainers

A
  1. Be rigid
  2. Prevent rotation of the denture
  3. Not interfere with the occlusion of the patient
  4. Be readily tolerated by the patient
  5. Prevent food packing
  6. Be placed as far as possible from the rotation point
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9
Q

What are 4 features influencing a clasps resistance to deformation

A
  1. Length of the clasp arm
  2. Diameter of the clasp arm
  3. Cross-sectional form of the clasp
  4. Type of alloy of the clasp
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10
Q

Where should a indirect retainer be placed

A

Anterior to the axis of rotation

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11
Q

2 types of occlusally approaching clasps

A

Circumferential clasps
3-arm clasps

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12
Q

3 types of gingival approaching clasps

A

T-bar
Reverse L-bar
I-bar

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13
Q

5 ideal features for connectors

A
  1. Cover the minimum area compatible with strength
  2. Be rigid enough to prevent flexure
  3. Prevent food packing
  4. Be readily tolerated by the patient
  5. Not cover the gingival margins
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14
Q

How much free space is required from the gingival margins for lower connectors

A

Minimum of 2 mm from gingival margins

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15
Q

How much free space is required from the gingival margins for upper connectors

A

Minimum of 5 mm from gingival margins

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16
Q

Name 4 upper connectors

A

Palatal plate
Palatal strap
Skeletal
Horseshoe

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17
Q

Name 5 lower connectors

A

Lingual bar
Sub-lingual bar
Lingual plate
Dental bar
Labial bar

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18
Q

5 benefits of replacing teeth

A

Aesthetics
Speech
Mastication
Maintenance of dental health
Physiological benefits

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19
Q

4 means of replacing teeth

A

Removable prostheses
Fixed prostheses
Implants
Orthodontics

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20
Q

4 benefits to oral health by replacing teeth

A

Maintain stability of the remaining dentition to prevent over-eruption and drifting
Reduce risk of tooth wear
Provide adequate masticatory function
Reduce risk of TMD or TMJ pathology

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21
Q

4 structures to record in preliminary impressions

A

All surfaces of all teeth
All of the palate back to junction of hard and soft palate
Bounded saddle areas: alveolar ridge, full depth of buccal, labial, lingual sulci
Distal extension saddle areas: hamular notch (upper), 2/3 retromolar pad (lower), full functional depth and width of buccal, labial, lingual sulci

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22
Q

How to record a preliminary impression

A

Select an impression tray with sufficient extension
Customise tray with compound to record palatal surface and distal extension
Add adhesive to tray and allow to dry
Add handle to tray
Load tray with aliginate
Take impression
Disinfect impression

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23
Q

Describe the jaw relationship to which you would restore a patient requiring a partial denture when using the conformative approach to occlusal rehabilitation

A

Intercuspal position (ICP) /centric occlusion

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24
Q

3 benefits from changing the path of insertion

A
  1. Improve aesthetics
  2. Improve retention
  3. Avoids interferences from large undercuts
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25
Q

Describe the jaw relationship to which you would restore a patient requiring a partial denture when using the reorganised approach to occlusal rehabilitation

A

Retruded contact position (RCP)

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26
Q

What is path of insertion

A

Path followed by denture from first contact with teeth until fully seated

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27
Q

What is path of displacement

A

Direction in which the denture tends to be displaced in function which is assumed to be at right angles to the occlusal plane

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28
Q

7 functions of guide planes

A

Horizontal stability
Increased retention
Reciprocation
Prevention of clasp deformation
Prevent food packing
Definitive path of insertion
Improved aesthetics

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29
Q

Describe 2 reasons for rest seat preparations

A

Provide more suitably inclined bearing surface for the occlusal rest

Provide space between the occlusal surface of the upper and lower teeth to allow a rest of adequate thickness and strength to be used

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30
Q

6 functions of occulsal rests

A
  1. Transmits vertical load along the long axis of the tooth
  2. Prevents horizontal movements
  3. Maintains saddle/clasps components in correct position so that they don’t sink toward the mucosa
  4. Deflects food impaction
  5. Prevents tooth over eruption
  6. Improves occlusion by restoring occlusal tooth contacts and avoid premature occlusion
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31
Q

2 materials used for master impressions

A
  1. Polyvinylsiloxane type II medium viscosity
  2. Alginate
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32
Q

4 common faults that may occur in an impression

A
  1. Tray not in correct position: not seated fully or tray offset
  2. Impression material already set before seat or removed too early
  3. Tray extension errors: under/over
  4. Voids /defects due to air, debris, saliva, blood, drags, insufficient
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33
Q

Dimensions required for mid-palatal strap

A

0.5mm thick x 15 mm wide

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34
Q

Dimensions required for acrylic plate connector

A

2mm thick

35
Q

Dimensions required for palatal plate

A

0.5-0.6mm thick

36
Q

Dimensions required for skeletal connector

A

0.75mm thick

37
Q

Dimensions required for lingual bar

A

> 8mm: 2mm clear of gingival margin, 2mm clear of floor of mouth, 4mm bar width

38
Q

Dimensions required for sub-lingual bar

A

5mm: 2mm clear of gingival margin, 3mm bar width

39
Q

Dimensions required for lingual plate

A

< 4mm

40
Q

Undercut dimensions required for colbalt-chrome clasp

A

0.25mm

41
Q

Undercut dimensions required for gold alloy clasp

A

0.5mm

42
Q

Undercut dimensions required for wrought clasp

A

0.75mm

43
Q

Suggest 10 possible oral health risks associated with RPD wear

A

Caries
Abrasion of teeth with clasp
Fracture of restorations
Inflammation of periodontal ligament
Tooth mobility
Gingival inflammation
Denture-induced stomatitis
Denture-induced hyperplasia
Possible increase of resorption of alveolar bone
Muscles of mastication dysfunction

44
Q

Describe how wax occlusal registration rims are modified

A

Try in wax occlusal registration rims and ensure no overextension of borders and reduce as necessary with wax knife

Ask patient close into maximum intercuspation with the wax rims in position and trim wax rim with hot plate and wax knife until no contacts remain and there is 2 mm space apparent between wax and opposing teeth

45
Q

Outline the 3 different physical processes that produce gypsum product and give each product their common name

A

Heated in open oven 115 - 120c forms b-hemihydrate plaster of Paris

Heated in autoclave under steam pressure 120 - 130c forms hydrocal

Boiled in 30% calcium chloride forms improved dental stone (densite)

46
Q

What are the 3 pieces of advice should be given with new RPD’s

A

Oral and denture hygiene instruction

RPD care and maintenance instruction

New dentures nearly always cause some discomfort and that they will feel awkward to start

47
Q

What are the oral/denture hygiene instructions given to patients after receiving RPD

A

No night wear
Regular cleaning
Soaking dentures in a suitable cleaner - never use sodium hypochlorite on metal dentures

48
Q

What 4 ways can you optimise support when designing RPD’s

A
  1. Occlusal rests
  2. Occlusal onlays
  3. Embrasure hooks
  4. Denture base
49
Q

What is support

A

Resistance to the vertical load applied to prosthesis during function

50
Q

Describe how to prepare a mesial rest seat on a lower molar tooth

A

Use round diamond bur to cut occlusal rest of about one half of the bucco-lingual cusp-cusp width and one third of the mesiodistal width of the tooth

51
Q

Describe how and where you would prepare a guide plane on a premolar tooth when using a vertical POI

A

Use straight bur about to cut guide plane of about 2mm surface area at survey line to create parallelism

52
Q

5 things to do when assessing a newly produced denture framework

A

Ask patient if it feels comfortable
Check that the partial denture seats completely
Check retention and stability and ensure that clasp tips are activated
Check denture appearance at rest and smiling
Check occlusion

53
Q

How to respond when patient believes denture is loose

A

Check that clasp tips touch the tooth surfaces as designed and adjust as necessary

Reassure that dentures with distal extension saddles may feel especially loose until muscular control is gained and an improvement occurs

54
Q

Advantages of lingual bar

A

Covers minimum surface area of teeth and tissue

Relatively small, minimally interferes with functions

55
Q

Disadvantages of lingual bar

A

Not as rigid as the lingual plate or sublingual bar

Requires minimum 8mm space

56
Q

What is the preferred choice of impression material for master impressions and 4 reasons why

A

Polyvinylsiloxane type II medium viscosity
1. Allows for highly accurate impression
2. Good dimensional stability
3. Good tear resistance
4. Impressions may be repoured

57
Q

4 differences between tooth and mucosal supported

A

Directed down long axis to PDL rather than directly to alveolar bone

Via occlusal rests placed on natural teeth rather than via saddles and mucosa

Craddock classification I rather than II

Different casting technique as altered cast technique can be used for mucosal supported dentures

58
Q

4 ways in which clasp retainers can be attached to a denture base

A

Laser welded
Embedded
Soldered
Incorporated

59
Q

Which lower distal extension saddle denture design feature dictates using a vertical POI

A

RPI system

60
Q

4 situations where it is most appropriate to use alginate for master impressions

A

Gross undercuts (tilted teeth)

Large interdental spaces between contiguous teeth

Periodontally involved teeth: gross recession, mobile teeth

Patients with poor tolerance/compliance of impressions in general

61
Q

Which Kennedy class has no modifications and why

A

Kennedy IV because when classifying dentures always start at most posterior missing tooth

62
Q

Requirement for a shortened dental arch

A

At least 2 posterior occluding units either side

63
Q

5 requirements for an impression tray

A

Be rigid in use

Have sufficient extension to support an impression of all structures

Incorporate occlusal stops

Have a robust, preferably integral handle

Be capable of withstanding autoclave or be single use

64
Q

What 3 features of dentures are likely to cause premature contact

A

Occlusal rests

Clasp shoulders

Major / minor connectors

65
Q

What material are master casts poured in

A

Improved dental stone (densite) high strength type 4

66
Q

4 benefits of occlusal rather than gingival clasps

A

Provides bracing
Reduced caries risk especially if root cementum exposed
Better for gingival health
Better tolerated

67
Q

A benefit of of gingival rather than occlusal clasps

A

Better aesthetics as can tuck into an anterior distal u/c

68
Q

What is reciprocation

A

Resistance to displacing forces in the lateral direction on abutment teeth when clasps move up and over the maximum bulbosity

69
Q

What is bracing

A

Resistance to displacing forces in the horizontal direction when the denture is fully seated

70
Q

3 reasons RPD’s must be designed on articulated casts

A

Allows visualisation of space available between the dental arches

Prevention of premature occlusion with: clasps, rests, connectors

Ensure tooth-tooth centric occlusal stops are maintained

71
Q

Give 3 examples of dental application of different curing (activation) methods

A

Visible light activation: light 470 nm releases free radicals e.g. composite resin, triad tray material

Heat activation: > 650C benzoyl peroxide decomposes to release free radicals e.g. heat-cured methylmethacrylate denture base material

Chemical activation: chemical activating agent acts on benzoyl peroxide to release free radicals e.g. auto-polymerisation acrylic for orthodontic plate or denture repair materials

72
Q

Advantages of sub-lingual bar

A

Rigid
Well toleranced
Good aesthetics
Requires only 5mm

73
Q

Disadvantages of sub-lingual bar

A

Requires border molded impression of floor of the mouth

Not compatible with prominent lingual frenal attachments

74
Q

What is direct retention

A

Components used to prevent displacement

75
Q

What is indirect retention

A

Components that change the axis of rotational displacement and make clasps operate as intended

76
Q

7 clinical stages in RPD construction

A

Preliminary impressions for production of study casts
Recording occlusal/jaw relationships for articulation of study cats
Master impressions for working casts
Castings trial, occlusal/jaw relationship records
Trial prosthesis
Insertion
Review

77
Q

3 functions of preliminary impressions

A

Allow study cast production
Assess the occlusion
Enable custom tray construction

78
Q

4 tooth modifications required prior to taking master impressions

A

Rest seat preparation
Guide planes
Survey line reduction
Undercut augmentation

79
Q

2 ways to provide undercut augmentation

A

Composite: added to tooth to augment and create an undercut which would allow correct positioning of a clasp

Indirect restorations: design restoration with augmented undercuts

80
Q

What 4 things are assessed at castings trial

A

Prescription was followed and is correct

Denture fit

Position of components

Occlusion

81
Q

4 reasons study casts are surveyed

A

Identifies optimum path of insertion: for appearance, retention

Identifies guide planes

Allows design, material selection and positioning of clasps

Allows blocking out of unwanted undercuts

82
Q

4 surveyor tools

A

Analysing rod

Carbon marker

Trimmer

Undercut gauge

83
Q

3 components of the RPI system

A

Mesial rest
Distal proximal plate
GAC I-bar to mid-buccal convexity

84
Q

7 things to check in trial dentures

A

Aesthetics
Tooth position
Occlusion
Polished surfaces
Mould
Shade
Flange

prosthetics (1 decks)

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