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REVISION BDS > RPD p622 > Flashcards

RPD p622 Flashcards

1
Q

support

definition

A

resistance of a denture to an occlusally directed load

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2
Q

kennedy classification

is

A

describes number and distribution of edentulous areas

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3
Q

kennedy class I

A

bilateral free end saddle

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4
Q

kennedy class II

A

unilateral free end saddle

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5
Q

kennedy class III

A

unilateral bounded saddle

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6
Q

kennedy class IV

A

anterior bounded saddle (crosses midline)

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7
Q

modifications to kennedy classes

A

take most posterior saddle as main classification each edentulous area in addition to this takes one mode point

e.g. upper arch with 2 posterior bounded saddles and 1 anterior bouneded saddle would be kennedy class III mod2

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8
Q

craddock classification

is

A

based on the support for the removable denture

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9
Q

options for craddock classification

A

tooth borne

mucosa borne

tooth and mucosa borne

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10
Q

tooth borne support

A

provides hard tissue resistance to occlusal loading i.e. when there is abutment teeth with support on bounded saddles

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11
Q

mucosa borne support

A

large covering provides resistance to occlusal loading

i.e. when the vertical biting force of the denture is resisted entirely by soft tissue

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12
Q

tooth and mucosa borne support

A

reduced number of teeth and large edentulous saddles

i.e. large free end saddle with mesial rest and mucosal support

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13
Q

what type of support is best

A

Tooth support is better as it transmits load through PD membrane, protects soft tissue, comfortable, more natural also doesn’t suffer
from muco-compressibility

Mucosal support may damage gingival margins and is more likely to displace, however large area=reduced occ. table

The best teeth for support are those with large root areas depending on PDL attachment
“A healthy tooth can carry 1.5x its own load”

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14
Q

rests

role

A

provide support against vertically opposing forces and can also be used for reciprocation

Best used as part of a cast metal base alloy
➡i.e CoCr Base= CoCr rests
➡i.e PMMA Base= Stainless steel rest (however can fracture base if thin)

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15
Q

5 functions of rests

A
  • Prevent movement of RPD towards mucosa
  • Distribute occ. load
  • Direct retention to work in correct way
  • Prevent overeruption
  • Determine axis of rotation for denture
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16
Q

factors for rest position

3

A

In tooth borne, rest should be nearest base

For tooth and mucosa should be on surface not near base

In free-end saddle rest is not placed immediately adjacent to saddle to prevent tilting

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17
Q

Every design

mucosal support

A

Contact points between Denture and abutment teeth
Wire stop at most posterior teeth to stop distal drift
Uncovered gingival margins

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18
Q

7 basic support guidelines

RPD

A

Tooth support first choice

Bounded saddles tooth supported unless longer than 3 teeth

Rests must direct forces down long axis

Occlusion must be taken into account incase tooth prep needed

Mucosal support must cover a large surface area

‘Every’ design is a less harmful mucosa borne dentue

Mandibular mucosa supported RPD not recommended unless as training for complete denture or overdenture

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19
Q

retention RPD

A

Resistance of a denture to lifting away from the tissues (vertical dislodging forces)

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20
Q

direct retention

RPD

A

resistance to vertical displacement of teh denture

clasps

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21
Q

modes of direct retention

A

mechanical - clasps

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22
Q

clasps in RPD

A

placed below bulbosity of the tooth in the undercut

occlusally or gingivally approaching

single arm, circumferential or ring clasps

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23
Q

RPD clasp design

A

section - round or half round

length - longer then length the greater the flexibility, must be at least 15mm

thickness - if reduced by 1/2 the flexibility inc by factor of 8

24
Q

clasp position and survey line

A

2/3 of clasp arm should be above the survey line

terminal 1/3 below the survey line engaging in the undercut

➡If not enough of an undercut it is possible to tilt the cast or use a composite build up *ONLY IN SMALL UNDERCUTS, OTHERWISE CLASP ARM WILL DE-BOND THE COMPOSITE
➡Alternatively you can prep an undercut with a crown bur

25
Q

RPD rest types

6

A

occlusal / incisal

ledge

onlay

inlay

hook

ring (if occlusion tight)

26
Q

CoCr clasp thickness

A

0.25mm

27
Q

Au clasp thickness

A

0.5mm

28
Q

Stainless steel clasp thickness

A

0.75mm

29
Q

length of clasp

A

longer the length the greater flexibility, therefore clasp arm on molar
must be 15mm at least

30
Q

frictional retention by

A

guide planes

31
Q

guide planes

A

provide frictional retention

boudned saddle - have 2 or more parallel axial surfaces on abutment teeth which limit the POI and improve stablity

can be natural or prepped

larger the guide surface = the more efficient it is

32
Q

altered path of insertion effect

A

eliminates undercuts (in common path of insertion) and creates new ones for retentive elements

common PoI = 90 degrees
tilt anterior or posterior to create new ones

33
Q

muscular retention

A

in resting position from orbicularis oris and buccinator

34
Q

RPI is a

A

stress reliving clasp system

35
Q

RPI used in

A

distal extension saddles

kennedy I and II

36
Q

RPI components

A

Mesial Rest (Occlusal), Rounded on impression surface

Proximal Plate (adjacent to saddle) guide surface of 2-3mm, with an undercut at tooth bulbosity to permit movement

I-bar clasp (gingivally approaching) at the greatest prominence of tooth contour

37
Q

how does RPI work

A

Mesial rest is loaded

Proximal plate rotates into the distal undercut

I-bar clasp rotates into mesial undercut and isn’t touching tooth (it lies on largest bulbosity of crown before loading)

38
Q

5 methods of direct retention in RPD

A

mechanical retention - clasps

frictional retention - guide planes

altered PoI

muscular retention

RPI

39
Q

indirect retention

definition

A

resistance to rotational displacement of teh denture

40
Q

types of indirect retention

6

A
  • Indirect Retainers
  • Major Connectors
  • Minor Connectors
  • Rests
  • Saddle
  • Denture
41
Q

indirect retainers principles

A

resists rotation around a ‘fulcrum axis’.
* (fulcrum axis = the line of rotation – it is an imaginary line between the most posterior rest seats on the end of each arch)
* ( clasp axis = imaginary line between clasps on opposite sides of the arch)
When there are multiple clasp axes, use the one closest to the saddle, this is the MAJOR one.

Rests should be 90 to their potential path of movement in order to behave as indirect retainers

42
Q

reciprocation in RPD design

A

resistance to side to side movement

Reciprocation is placed opposite to retentive clasp to assist in preventing unwanted movements/stresses of abutment teeth:
* Reciprocating arms provide some resistance but also allow flexure so that the retentive arm does not get put under too much pressure and break.
* Reciprocating clasps still need to engage undercut
* Try and encircle the tooth by 180 degrees

Guide planes
* Place suitable rigid components of the denture to resist horizontal and vertical forces.

RPI system – minor connector on mesial rest of tooth prevents excessive distal movement.

Bracing = general resistance to lateral movements exerted on the denture by tissues:
* Maxilla – palate and alveolar ridge can be taken advantage of
* Flatter ridge = more movement
* Major connector and flanges can be useful to help with bracing – this should be incorporated into the design.

43
Q

indirect retention principles

A

Principles
* Retentive clasps should always be between the saddle and indirect retainer
* Retentive clasps should be as close to saddle as possible, whilst the indirect retainer is as far away from saddle as possible.
* Try not to have movements that will force pressure on a tooth/ortho movement.

44
Q

maxillary major connectors options

A

can be open (better OH) or closed (greater retention)

45
Q

mandibular major connecotrs options

A

plate or bars

46
Q

mandibular plates

A

Can be thin in cross section and maintain rigidity
* 0.5mm

only recommended in mandibular arch where there is no space for a bar
(because they will have to cover gingival margins)

When less tooth support plates will confer mucosal support

leave free gingival margin where possible (3mm from GM for > 1.5 teeth)

47
Q

mandibular bar

A

Less coverage of gingival margins

Must be thick to maintain rigidity
* 2mm thickness

Default connector in mandibular arch

48
Q

lingual bar space requirements

A

8mm total

➡3mm- Distance from gingival margin
➡4mm- Height of the bar
➡1mm- Above floor of the mouth

49
Q

mandibular major connector options

A

lingual bar (needs 8mm, 2mm thickness)

sublingual bar (4mm thickness)

kennedy bar/continual lingual clasp - on 2/3 of teeth

lingual plate - 0.5mm thickness, but gingival coverage

50
Q

minor connectors definition

A

join components such as rests to the major connector

tranfer functional stresses to and from teh abutment teeth

51
Q

requirements for minor connectors

4

A

rigid
finish above the survey line
cross gingival margin at right angles (easily cleaned)
cover as little of gingival tissue as possible

52
Q

checklist for RPD setting teeth

A
  • Contact points
  • Use existing teeth to guide in 3 dimensions
  • ICP for posterior teeth, make sure they are as centric as possible
    - Occlusal dimension maintained (pin on table w/ articulator)
    - Artificial teeth set to conform with existing occlusion
  • Refinement must be done in occlusion intra-orally (at chairside)
53
Q

components used to survey casts

A

Analysing rod

Undercut gauges
* 1 line- 0.25mm- CoCr
* 2 lines- 0.5mm- Au
* 3 lines- 0.75mm- Stainless Steel

Surveying table

Surveying arm

Graphite marker

54
Q

curve of spee

A

curvature of the mandibular occlusal plane beginning at the tip of the lower
incisors and following the buccal cusps of the posterior teeth, continuing to the terminal molar

55
Q

curve of wilson

A

The curve of Wilson is the across arch curvature or posterior occlusal plane. Arc of the curve, which is concave for mandibular teeth and convex for maxillary teeth are defined by a line drawn from left mandibular first molar to right mandibular first molar

56
Q

sphere/curve of monson

A

The curve of occlusion of natural teeth in which each cusp and incisal edge touches or conforms to a segment of the surface of a sphere, with its centre in the region of the glabella.

REVISION BDS (43 decks)

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