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BDS2 CDS Prosthodontics Removable > Design Principles for RPD > Flashcards

Design Principles for RPD Flashcards

1
Q

7 parts of a system for design

A
  1. Saddles
  2. Support
  3. Retention
  4. Bracing/reciprocation
  5. Connectors
  6. Indirect retention
  7. Review design/simplify
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2
Q

bounded saddle support to aim for…..

A

aim for tooth support

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3
Q

why is tooth support best for bounded saddle?

A

Not as much alveolar resorption - less load on alveolus

Teeth move a bit, but less than mucosa - denture will move with the teeth if just tooth borne

Support as close to bounded saddle as possible

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4
Q

what may you need to do if occlusion is tight on the site closest to the bounded saddle?

A

may need to put rest on the opposite side

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5
Q

what type of support is needed for a free end saddle

A

tooth and mucosa support

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6
Q

why is tooth and mucosa support utilised in a free end saddle RPD

A

Need mucosa at distal end of free end

Teeth Support on the mesial aspect of the abutment in a free-end saddle
- Distal aspect - risk of tooth tipping backward

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7
Q

3 reasons for tooth preparation on posterior teeth

A

prevent rough to tongue feeling,

interfere with occlusion

can ensure the denture is fully seated

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8
Q

caution for tooth preparation with metal crowns

A

When preparing a rest seat if pure metal can perforate the crown as don’t know the thickness
- dentist cost as their mistake

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9
Q

in which scenario is support closest to the bounded saddle not appropriate

A

Posterior molar is tilted due to mandible

  • Place rest seat on mesial - whole tooth will tilt
  • As load not down long axis of the tooth

Place on distal won’t further tilting
- good for ring clasp goes round mesial lingual surface

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10
Q

where should the load be direct

A

down the long axis of the tooth

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11
Q

alternative way to prepare anterior teeth

A

add composite ledge instead of drilling with a bur

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12
Q

advantage and disadvantage of incisal rest

A

Good indirect retention

Metal showing - unfavourable

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13
Q

4 methods of retention

A

Clasps

Guide planes

Path of insertion

Precision attachments
- Useful in certain circumstances with few teeth (later years)

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14
Q

what is the ideal pattern of retention to aim for

A

triangular

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15
Q

advantage and disadvantage of RPI system

A

Efficient, works well

Leaves small windows for food traps
- Patient dislikes especially if poor oral hygiene

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16
Q

how do clasps act to prevent functional displacement/ aid retention

A

clasps go deeper into the undercut and curvature of the tooth

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17
Q

bracing

A

lateral resistance to the movement of the denture

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18
Q

reciprocation

A

Actively pushing the tooth in, need to reciprocate to stop the tooth moving

Remember Newton’s 3rd law - equal and opposite force for every one

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19
Q

how can lower connectors act in indirect retention

A

Rotate around distal teeth
- Try to lift up at free end saddle

Got clasps to prevent backwards movement

Plates good for indirect retention- but clunky in mouth

Clasps on canines can leave incisors free, get some indirect but not as much but more comfy

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20
Q

advantage of clasps on lower canines rather than incisors

A

Clasps on canines can leave incisors free, get some indirect but not as much but more comfy

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21
Q

advantage and disadvantage of plates on lower RPD

A

Plates good for indirect retention - but clunky in mouth

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22
Q

advantage and disadvantage of dental bar

A

not on mucosa at all

over gingival margin so harder oral hygiene

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23
Q

advantage of sublingual bar

A

can be made thinner for indirect retention

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24
Q

upper plate advantages

A

lots of retention from palate

bracing

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25
Q

upper plate disadvantges

A

lose sense of taste
speech effected
chunky in mouth

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26
Q

how to decide on upper connector type

A

preference of dentist and patient

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27
Q

minimum space needed for no food trap

A

tooth and half

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28
Q

problem with complex RPD design

A

costly

small windows can be food traps

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29
Q

advantage of upper ring dentures

A

wider bars, thinner so less tongue impact

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30
Q

disadvantage of upper ring design with narrower bars

A

narrower bars need thickness so less tongue space

31
Q

bilateral upper RPD design

A

Bracing across arch

Wide and thin

Less palatal coverage - Patient tolerate

32
Q

key to avoiding complications with RPDs

A

If the patient doesn’t maintain excellent oral hygiene and/or there is poor maintenance the patient will get caries, endodontics, periodontal issue - complications

33
Q

why do clinicians design the denture

A 
We have seen the patient
- tooth condition
- periodontal condition
- motivation
- cost
technician in commercial lab will design a denture with lots of clasps, rests and connectors
- we can simplify it to keep cost low
34
Q

advantage and disadvantage of technician designing the denture

A

Technician are good on theoretical aspect

  • very experienced
  • But don’t have knowledge of abutment tooth and periodontal condition and patient motivation
35
Q

2 factors needed for best success rate for dentures

A

Good oral hygiene - motivation

Good dental care

36
Q

3 possible alternative treatments to RPDs

A

no active treatment
- shortened dental arch

fixed prosthesis

  • conventional
  • resin bounded

implants

37
Q

advantage of bridge (fixed prosthesis) over RPD for lower bilateral free end saddle (6s, 7s missing)

A

Free end saddle lower (6s, 7s) risking replacing 10 teeth for sake of 4 placed

also consider SDA

38
Q

why are implants and tooth supported RPD rarely mixed

A

Implant has no movement – no PDL

- No bounce in it unlike tooth supported RPD

39
Q

what in montogomery consent

A

Need patient decision

tell Options, benefits, disadvantages

40
Q

saddles

A

the teeth being replaced

41
Q

kennedy class I

A

bilateral free end saddle

42
Q

kennedy class II

A

unilateral free end saddle

43
Q

kennedy class III

A

bounded saddle

44
Q

kennedy class IV

A

anterior bounded saddle crossing midline

45
Q

how to decide on kennedy classification

A

always go for lowest classification possible

most posterior saddle denotes the class

can have modifications of additional anterior saddles

46
Q

support

A

The resistant of the denture to occlusally directed load

- What stops the denture from going through the mucosa when patient bites

47
Q

craddock class 1

A

tooth borne

48
Q

why are patients with grade 3 mobility teeth not suitable for tooth borne support

A

teeth too mobile

need mucosa borne

49
Q

craddock class 2

A

mucosa borne

50
Q

craddock class 3

A

combination (tooth and mucosa)

51
Q

retention

A

resistance of the denture to vertical displacement (lifting away from the tissues)

52
Q

6 methods of retention

A

clasps

soft tissue undercuts

adhesion (maxillary plates)

friction (guide planes)

path of insertion
- rarely alter (more complex), anterior most common

precision attachments/implants

53
Q

point of surveying

A

to identify suitable undercut locations for retention

tilt the cast, more complex to see undercuts
- Try to get as simple as possible

54
Q

indirect retention

A

resistance to rotational displacement

Have things on both sides of denture axis of rotation
- balance

55
Q

reciprocation

A

prevents a clap arm moving the clasped tooth

56
Q

connectors types

A

major and minor

57
Q

major connectors

A

connects all components

58
Q

minor connectors

A

Connects rests, clasps and bracing arms

- All individual components to the major

59
Q

3 types of maxillary major connectors

A

bar

horseshoe

plate (PMMA/CoCr)

60
Q

3 positive features of a good maxillary bar design

A

clear gingival margin

enough depth

neat, tidy, uncomplex

61
Q

maxillary strap bar design positives

A

Comfy for patient
Efficient

Mid palatal bar or strap

62
Q

maxillary horseshoe design positives

A

keep palate clear for patient

High up prosthetic teeth

  • habit of breaking plastic acrylic denture or teeth came away from metal
  • Patient bites of metal backing instead so not breaking denture due to heavy bite
63
Q

why would an upper plate be used

A

Compromised natural teeth - longevity poor
- Can add on to plate relatively easy to it

Plate extended distally to give indirect rotation around rotation axis

64
Q

consideration when replacing few natural teeth

A

compromising many more natural teeth – is a bridge for missing canine better option?

65
Q

issue with unilateral connectors

A

not much bracing from other side, tend to rotate around

66
Q

2 mandibular connector designs

A

CoCr bars
- lingual, sub-lingual, dental

Plates
- CoCr, PMMA

67
Q

flanged saddle advantages

A
  • Helps with retention
  • stops food trapping
  • appearance constant over time
68
Q

gum-fitted/open face saddle advantage and disadvantage

A

looks good initially

resorption occurs and can see gap between alveolar and denture

69
Q

things to consider when deciding on type of support to use (5)

A
  • periodontal condition of abutments
  • size and position of saddle/abutments
  • condition of supporting mucosa
  • occlusion / chewing capability
  • aesthetics

tooth preparation?

70
Q

5 methods of direct retention

A

clasps

engaging soft-tissue undercuts

hydrostatic pressure

path of insertion

muscle control

71
Q

importance of muscle control in complete dentures

A

Tongue - lower denture will try and displace

Too square - knock sideways

Triangular - push it down slightly

72
Q

what to look for when deciding indirect retention sufficient?

A

Look at retention and look for rotation – see if support negates this

Support on both sides

73
Q

points to review when completed denture design

A
  • Simpler
  • Less fussy
  • With less components

No jaggy parts, food traps

74
Q

7 stages in denture design

A
  1. saddle
  2. support
  3. retention
  4. indirect retention
  5. reciprocation
  6. connectors
  7. review

BDS2 CDS Prosthodontics Removable (10 decks)

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