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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
upper plate disadvantges
lose sense of taste speech effected chunky in mouth
26
how to decide on upper connector type
preference of dentist and patient
27
minimum space needed for no food trap
tooth and half
28
problem with complex RPD design
costly small windows can be food traps
29
advantage of upper ring dentures
wider bars, thinner so less tongue impact
30
disadvantage of upper ring design with narrower bars
narrower bars need thickness so less tongue space
31
bilateral upper RPD design
Bracing across arch Wide and thin Less palatal coverage - Patient tolerate
32
key to avoiding complications with RPDs
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
why do clinicians design the denture
``` 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
advantage and disadvantage of technician designing the denture
Technician are good on theoretical aspect - very experienced - But don’t have knowledge of abutment tooth and periodontal condition and patient motivation
35
2 factors needed for best success rate for dentures
Good oral hygiene - motivation | Good dental care
36
3 possible alternative treatments to RPDs
no active treatment - shortened dental arch fixed prosthesis - conventional - resin bounded implants
37
advantage of bridge (fixed prosthesis) over RPD for lower bilateral free end saddle (6s, 7s missing)
Free end saddle lower (6s, 7s) risking replacing 10 teeth for sake of 4 placed also consider SDA
38
why are implants and tooth supported RPD rarely mixed
Implant has no movement – no PDL | - No bounce in it unlike tooth supported RPD
39
what in montogomery consent
Need patient decision tell Options, benefits, disadvantages
40
saddles
the teeth being replaced
41
kennedy class I
bilateral free end saddle
42
kennedy class II
unilateral free end saddle
43
kennedy class III
bounded saddle
44
kennedy class IV
anterior bounded saddle crossing midline
45
how to decide on kennedy classification
always go for lowest classification possible most posterior saddle denotes the class can have modifications of additional anterior saddles
46
support
The resistant of the denture to occlusally directed load | - What stops the denture from going through the mucosa when patient bites
47
craddock class 1
tooth borne
48
why are patients with grade 3 mobility teeth not suitable for tooth borne support
teeth too mobile | need mucosa borne
49
craddock class 2
mucosa borne
50
craddock class 3
combination (tooth and mucosa)
51
retention
resistance of the denture to vertical displacement (lifting away from the tissues)
52
6 methods of retention
clasps soft tissue undercuts adhesion (maxillary plates) friction (guide planes) path of insertion - rarely alter (more complex), anterior most common precision attachments/implants
53
point of surveying
to identify suitable undercut locations for retention tilt the cast, more complex to see undercuts - Try to get as simple as possible
54
indirect retention
resistance to rotational displacement Have things on both sides of denture axis of rotation - balance
55
reciprocation
prevents a clap arm moving the clasped tooth
56
connectors types
major and minor
57
major connectors
connects all components
58
minor connectors
Connects rests, clasps and bracing arms | - All individual components to the major
59
3 types of maxillary major connectors
bar horseshoe plate (PMMA/CoCr)
60
3 positive features of a good maxillary bar design
clear gingival margin enough depth neat, tidy, uncomplex
61
maxillary strap bar design positives
Comfy for patient Efficient Mid palatal bar or strap
62
maxillary horseshoe design positives
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
why would an upper plate be used
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
consideration when replacing few natural teeth
compromising many more natural teeth – is a bridge for missing canine better option?
65
issue with unilateral connectors
not much bracing from other side, tend to rotate around
66
2 mandibular connector designs
CoCr bars - lingual, sub-lingual, dental Plates - CoCr, PMMA
67
flanged saddle advantages
- Helps with retention - stops food trapping - appearance constant over time
68
gum-fitted/open face saddle advantage and disadvantage
looks good initially resorption occurs and can see gap between alveolar and denture
69
things to consider when deciding on type of support to use (5)
- periodontal condition of abutments - size and position of saddle/abutments - condition of supporting mucosa - occlusion / chewing capability - aesthetics tooth preparation?
70
5 methods of direct retention
clasps engaging soft-tissue undercuts hydrostatic pressure path of insertion muscle control
71
importance of muscle control in complete dentures
Tongue - lower denture will try and displace Too square - knock sideways Triangular - push it down slightly
72
what to look for when deciding indirect retention sufficient?
Look at retention and look for rotation – see if support negates this Support on both sides
73
points to review when completed denture design
- Simpler - Less fussy - With less components No jaggy parts, food traps
74
7 stages in denture design
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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