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dentures > RPDs > Flashcards

RPDs Flashcards

1
Q

saddle

A

edentulous area

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2
Q

flange

A

replacement tissue extending to vestibular sulcus

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3
Q

two choices of saddle

A

flanged
- don’t see gaps under false teeth, replace some of missing tissue
gum-fitted/open face
- straight after ext can get better fit w gum-fitted but over time get resorption

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4
Q

sequence of design

A 
prosthesis - fixed or removable
saddles
support
retention
connector
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5
Q

support

A

resistance of a denture to occlusally directed load
options
- use hard tissues
- large surface coverage

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6
Q

Kennedy classification

A

anatomical - describes number and distribution of edentulous areas
- doesn’t describe type of support required

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7
Q

Kennedy classification rules

A

3rd molars generally ignored unless have direct part in denture design
most posterior saddle defines classification
modifications of each class
- numerical count of number of additional edentulous saddle areas present
- can’t modify class 4

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8
Q

kennedy class 1

A

bilateral free end

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9
Q

kennedy class 2

A

unilateral free end

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10
Q

kennedy class 3

A

unilateral bounded

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11
Q

kennedy class 4

A

anterior bounded (crossing midline)

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12
Q

Craddock classification

A

gives type of support, doesn’t give info about number or distribution of teeth

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13
Q

craddock class 1

A

tooth supported

- teeth provide a hard tissue resistance to occlusal loading

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14
Q

craddock class 2

A

mucosa

- a large coverage provides resistance to occlusal loading

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15
Q

craddock class 3

A

tooth and mucosa

  • a combination of hard tissue and large coverage when there are reduced number of teeth and large edentulous saddles
  • FES always class 3
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16
Q

which are the best teeth for support?

A

ones with the largest root area

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17
Q

what load can a healthy tooth support?

A

its own load plus 1.5 similar teeth

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18
Q

compare PD membrane mucosal coverage of a lost tooth for support

A

> x4

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19
Q

what ratio is important in working out support?

A

crown to root ratio

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20
Q

where should a rest transfer load through?

A

the long axis of tooth

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21
Q

tooth support

A

bone and root area provides wide distribution of load
transmits load via PDL - feels more natural
more comfortable
protects ST from trauma
likely to stay in close contact with supporting structures over time
bounded saddle cases are tooth supported unless saddles are longer than 3 teeth

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22
Q

mucosal support

A

cover large area
allows denture base to move slightly
- possible damage to adjacent gingival margins
lose area periodontium
- quantitative difference of 75% supporting tissue
approx 33% of natural tooth load
avoid base within 3mm of gingival margins
L mucosa supported dentures generally not recommended - insufficient area to provide support

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23
Q

where should the base in mucosa borne dentures be avoided?

A

within 3mm of gingival margins

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24
Q

why are L mucosa supported dentures generally not recommended?

A

because insufficient area to provide support

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25
Q

maxilla - primary support areas

A

hard palate

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26
Q

maxilla - secondary support areas

A

residual alveolar ridge

buccal vestibule?

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27
Q

mandible - primary support areas

A

buccal shelf

RM pad

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28
Q

mandible - secondary support areas

A

residual alveolar ridge

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29
Q

what is the overall fct of a rest?

A

provide support for denture from vertical opposing forces

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30
Q

rests incorporated into acrylic

A

can weaken surrounding acrylic - get internal stresses

but can be used when opposing forces are light

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31
Q

why aren’t small rests recommended?

A

apply large forces per unit area

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32
Q

functions of rests

A 
prevent movement of RPD towards mucosa
assist in distribution of occlusal load
direct retentive elements to work in planned manner
prevent over-eruption of unopposed teeth
provide bracing on anterior teeth
determine axis of rotation for FES RPDs
reciprocation and indirect retention
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33
Q

where should rests be placed on bounded saddles?

A

rest placed adjacent to saddle

additional rests e.g. on next tooth can be placed to help distribute load if abutment tooth has a smaller root area

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34
Q

where should rests be placed on FES?

A

have it furthest side of tooth away from saddle to avoid rotation

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35
Q

why should you avoid placing a rest in an occlusal centric stop?

A

because it will interfere with occlusion

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36
Q

how much prep should be done for an occ rest seat and how can you measure?

A

1mm

bite on soft wax

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37
Q

disadvantages of prepping occ rest seats

A

loss of occlusal stop when denture isn’t worn
destruction of tooth surface
exposure of D

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38
Q

advantages of prepping occ rest seats

A

doesn’t annoy pts tongue

direct forces down LA

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39
Q

every partial denture design

A

mucosa borne denture which restores dental arch
contact points between denture and abutment teeth
ensure most distal tooth doesn’t drift posteriorly - wire stop
gingival margins not covered by denture design
weak bases
- narrow
- metal inserted into acrylic

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40
Q

difference in compressibility between tooth and mucosal support and consequence

A

periodontium - vertical displacement of tooth attachment 0.1mm within its socket
mucoperiosteum - 2mm
denture will rock if surfaces are of unequal compressibility

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41
Q

some ways to reduce load on teeth

A

use stress relieving clasp system (RPI)

use an altered clasp technique

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42
Q

rest seat teeth

A 
periodontal condition
size and position of saddle and abutments
condition of supporting mucosa
occlusion
aesthetics
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43
Q

types of rest

A 
incisal
onlay
crown
overlay
ledge
ring
cingulum
occlusal
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44
Q

incisal rest

A

L anteriors

poor aesthetics

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45
Q

ring rest

A

recommended to direct forces down LA
all of rest must be above survey line
used for single standing teeth or if occlusion prevents occ rest

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46
Q

cingulum rest

A

likely need prep
canines, can be used on U incisors
apply stress at lower level, less rotational forces

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47
Q

retention

A

resistance of denture to vertical dislodging forces away from tissues

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48
Q

types of retention

A

mechanical: clasps, guide surfaces, precision attachments
muscular forces: on polished surface
physical forces: coverage of mucosa, adaptation, forces on imp surface - cohesion, adhesion, atm pressure, surface tension

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49
Q

direct retention

A

resistance to vertical displacement

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50
Q

indirect retention

A

resistance to rotational displacement

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51
Q

guide planes

A

2 or more parallel axial surfaces on abutments which limit PofI
resists displacement
supplementary retention
close to base and parallel to PofI

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52
Q

where should guide planes be placed related to gingiva?

A

3mm

far from gingiva as possible

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53
Q

what type of retention do clasps provide?

A

mechanical - engages undercut

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54
Q

when are clasps most efficient?

A

when used with a rest

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55
Q

above survey line what do clasps provide?

A

support (except I-bar) - stops it pushing down

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56
Q

2 ways of making clasps

A

make in wrought metal and incorporate into denture base

include as part of cast denture base

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57
Q

gingivally approaching I-bar clasp

A

need on premolar/canine for desired length
only tip contacts tooth - terminal end engages UC
ideally originates from a saddle
doesn’t provide support
infrabulge
length of tooth doesn’t have to be ≥15mm to accommodate 15mm clasp arm

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58
Q

occlusally approaching/suprabulge clasp

A

single arm or circumferential
terminal 1/3 in UC - rest must be above survey line
say which UC it engages - best usually linguals lower molars
length of tooth has to be ≥15mm to accommodate a 15mm clasp arm

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59
Q

reciprocation

A

when clasp flexes over bulbosity it applies load on tooth
have something on other side of tooth so as clasp flexes over bulbosity it prevents movement
e.g. connector up onto lingual surface

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60
Q

clasps have 2 components

A

retentive arm
reciprocation component
- counteracts the force of the retentive component with an equal and opposite force

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61
Q

what does the flexibility of the retentive arm of the clasp depend on?

A

material
length - longer = more flexible
thickness - thinner = more flexible

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62
Q

how difficult it is to dislodge clasp depends on:

A

flexibility of retentive arm
placement of retentive arm
depth of UC

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63
Q

what space do you need between the terminal end of a clasp and the gingiva and why?

A

1-2mm to avoid irritation to gingiva

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64
Q

what is indirect retention provided by?

A

support elements of denture: connectors, rest, saddle, base

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65
Q

principles of indirect retention

A

provided by support elements of denture: connectors, rest, saddle, base
rest has to be on opp side of clasp axis to saddle
should happen at 90 degrees to clasp axis on opposite side to saddle

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66
Q

retention guidelines

A

not required on every adjacent tooth to saddle
ideally 3 clasps
- or one each side of arch
triangular pattern of retention ideal
altering PofI gives you retention at saddle but not indirect

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67
Q

what is the RPI stress relieving clasp system used for?

A

used in FES to prevent stress on last abutment tooth (mostly L)

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68
Q

components of RPI system

A

occlusal rest - mesial of tooth
proximal plate - adjacent to saddle
I-bar clasp - can disengage on load

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69
Q

RPI system occlusal rest

A

mesial of tooth

rounded on imp surface

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70
Q

RPI system proximal plate

A

adjacent to saddle
guide surface of 2-3mm
UC to permit movement

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71
Q

RPI system I-bar clasp

A

can disengage on load

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72
Q

why don’t you need the RPI system with a maxillary plate?

A

stress on abutment tooth is negligible

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73
Q

which connector can’t you use the RPI system with and why?

A

lingual plate
have contact on back of that tooth
- unless transition at canine

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74
Q

ways of minimising stress on abutment if you can’t use RPI system e.g. if lingual plate?

A

make supporting connector wider
consider less teeth at saddle area
altered clasp technique

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75
Q

major connectors

A

part of RPD that connects components on one side of arch to components on other side of arch

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76
Q

guidelines for major connectors

A

rigid (no mods)
avoid covering gingival margins
comfortable - few edges as possible
cover as little tissue as is consistent with rigidity

77
Q

modifications to guidelines for major connectors

A 
base distribution
need for tissue support
need for indirect retention
anatomical limitations
prognosis of dentition
prev denture influence
78
Q

minor connectors

A

join components to major connector

transfer fct stress to and from abutment teeth

79
Q

guidelines for minor connectors

A

rigid
finish above survey line
cross gingival margin at right angle (easier to clean)
cover as little gingival marginal tissue as possible

80
Q

modifications to guidelines for minor connectors

A

cover gingival margins instead of lots of small windows - OH

81
Q

plates

A 
mucosa borne dentures
CS thickness only 0.5mm
may cover gingival margins therefore only recommended in mandibular arch where no space for bar
could add pin dam for rigidity
cover more tissue
82
Q

finishing lines

A

groove at end of polished metal

don’t have acrylic just overlapping chrome as fluid can ingress

83
Q

mandibular connectors

A 
dental bar
lingual bar
lingual plate
sublingual bar
labial bar
84
Q

lingual bar contraindication

A

if you think incisors will be lost

85
Q

space required for lingual bar

A

height of bar 4mm
space gingival margin 3mm
above raised fct depth of FOM 1mm

=8mm

86
Q

lingual plate

A

covers gingival margins and cingulums

87
Q

sublingual bar

A

hard to record fct depth at chairside

uncomfy

88
Q

labial bar

A

only use when L anteriors lingually inclined so can’t do lingual bar

89
Q

maxillary connectors

A 
anterior and posterior ring bar
palatal plate
 - anterior, midpalatal, posterior
horseshoe bar/plate
posterior bar - offers less support to FES
90
Q

acrylic connectors

A

anterior/mid palatal plate, full coverage or horseshoe
not strong enough for bar
spoon - flaps up and down, quite small - choke hazard
modified spoon - wings come up onto palatal surfaces above survey line
every - wire stops

91
Q

bars

A

more likely choice for tooth supported
less coverage of mucosa and gingival margins
need to be thick in CS to maintain rigidity
- lingual bar 2mm
less space available in L arch so default choice

92
Q

why shouldn’t you alter the PofI to create and undercut for a clasp?

A

no undercut in common PofD so would just fall out

only utilise UCs

93
Q

open

A

try if ≥2 teeth between saddle areas
no gingival coverage, greater clearance
possible reduced irritation to gingival tissues
ideal but not always possible

94
Q

metal backing

A

when occlusion means limited space between incisors

provide an occlusal contact therefore prevent pressure on upper artificial tooth from debonding to denture base

95
Q

combination syndrome

A

only some L anterior teeth remain functioning against a complete U denture
makes ST loose and flabby

96
Q

dimensions of rests

A

0.5-1mm thick

97
Q

dimensions of lingual bar

A

height 4mm, thickness 2mm, oval or half pear shape

98
Q

dimensions of sublingual bar

A

thickness 4mm kidney shaped

99
Q

clearance of U connectors from gingival margin

A

5mm

100
Q

cast CoCr clasp

A

15mm to engage 0.25mm UC

101
Q

beading

A

all the way round border but stops 3mm from gingival margin

facilitate intimate contact - prevent food impaction

102
Q

closed

A

more contact, greater retention, guide planes
possible increased irritation to gingival tissues
don’t stop connectors at gingival margins - don’t strip gingiva e.g. bring up onto cingulum of canines to protect gingiva

103
Q

denture history

A 
why teeth lost
how long worn dentures
how many dentures
fav denture/preferred design
prefer metal/acrylic
104
Q

special investigations for abutments

A

periapicals
sensibility testing
surveyed study models
clinical photos

105
Q

pros of RPDs

A 
simple, restore fct and appearance
less £
min tooth prep
can restore longer edentulous spans
can replace missing alveolar ridge tissues
remove for cleaning/adjustment/repairs
106
Q

cons of RPDs

A 
aesthetics
denture stomatitis
compromise abutments
may be bulky and plaque retentive
gagging
retention and stability
107
Q

RPD indications

A 
multiple missing teeth
no suitable bridge abutments
implants contraindicated
immediate after extraction
provisional during implant tx
transitional to complete denture
108
Q

RPD contraindications

A 
untreated dental disease
chronic poor OH
pt acceptance
SDA pt can fct with
mobile teeth (unless transitional to complete)
109
Q

consequences of missing teeth

A

anatomical
- EO: change in facial appearance, TMJ problems
- IO: alv resorption, tooth movement, toothwear
aesthetics - lose hard and soft tissues which support face
fct - mastication, speech
psychological

110
Q

SDA indications

A

missing posterior teeth with 3-5OU
sufficient occ contacts to provide a large enough occ table
favourable prognosis for remaining anterior and premolar teeth
pt not motivated to pursue a complex Rx plan
limited financial resources on dental care

111
Q

occlusal stability

A

absence of tendency for teeth to migrate other than normal psychologic compensatory movements occurring over time

112
Q

SDA

A

where most posterior teeth missing
satisfactory oral fct without RPD (compliance can be low)
priority - maintain anterior and premolar dentition in one/both jaws
sufficient adaptive capacity when 3-5OU
- pair of occluding premolars 1
- pair of occluding molars 2
only works long term if remaining natural dentition can be preserved for the life of pt

113
Q

SDA contradindications

A 
poor prognosis for remaining dentition
untreated/advanced PDD
pre-existing TMD
signs of pathological toothwear
significant malocclusion
 - class 2 or class 3
114
Q

determining factors for occlusal stability

A 
PD support
number of teeth
interdental spacing
occlusal contacts 
tooth wear
get distal tooth migration in SDAs
115
Q

pouring up

A

pour alginate imps in 100% dental stone
25-30ml H2O to 100g stone
saturate - softens particles of stone and reduces spatulation time
agitation
base - 30ml H2O to 110g stone - thicker to support weight
trim periphery (5mm from sulcus depth)

116
Q

articulators

A

mechanical elements corresponding to anatomic structures

reproduces recorded relationships of M to M (and movements)

117
Q

facebow

A

locate maxilla on articulator to correspond with hinge axis

118
Q

types of articulators

A 
simple hinge
semi-adjustable
average value
virtual/digital
fully adjustable
ARCON
NON-ARCON
119
Q

simple hinge articulator

A

can’t reproduce mandible movements
open and close
hinge axis has smaller radius path of closure - can get discrepancies in occlusion

120
Q

semi-adjustable articulator

A

some dynamic movement but pre-set by manufacturer

121
Q

average value articulator

A

condylar guidance track fixed at average value (30%)

25 degrees

122
Q

ARCON

A

condylar representation on lower arm of articulator
mimics what happens naturally
condylar track on maxillary component

123
Q

NON-ARCON

A

condylar representation on maxillary element
condylar track on mandibular component
not anatomical
can lead to inaccuracies during protrusive movements

124
Q

stability

A

the resistance to horizontal/lateral movement of the denture

125
Q

abutments

A

structurally sound
good alignment and position
prev Rxs and endo txs satisfactory
roots and supporting alveolar bone functionally adequate
alveolar bone of ridge between or distal to the abutment teeth is adequate in quantity and quality
ST of ridge adequate in quantity and quality

126
Q

when to record occlusion

A

when designing denture
- if can’t hand articulate/unstable - after primary imp but before design stage

help technician set up teeth

  • if can hand articulate and stable - after master imps
  • if do before - risk occlusal record blocks won’t fit on master casts
127
Q

split cast mounting

A

easy removal of mounting - sodium silicate
mount upper cast first
pin on table
incisal post at 0

128
Q

UC

A

areas below max contour

129
Q

stages of surveying

A 
occlusal plane horizontal
 - use flat ruler, common PofD
tripod
 - 3 lines
analysing rod
 - 'eyeball' for UCs, choose PofI
graphite marker
 - tip lined up with gingival margin
 - long side of chiselled edge used against cast
 - survey all abutments and relevant STs
 - U and L survey lines

rotate platform to view from every angle
mark position where UC gauge contacts tooth surface - where terminal head of clasp can be placed

130
Q

instructions to pt

A 
insertion/removal
coping with new dentures
pain
denture cleansing
speech
eating
refer to clinic info leaflet
131
Q

common PofD

A

90 degrees to occlusal plane - horizontal

132
Q

tripoding

A

3 lines

mark PI/W (red) and PD (black)

133
Q

prepping the cast after surveying before duplication

A

parallel surfaces for the denture are provided where required to the PofI
unwanted UCs eliminated using wax and trimming knife

134
Q

altering PofI

A 
provide retention
 - using guide surfaces of teeth
improve appearance
 - close unsightly gaps
eliminate interference
 - tooth or ridge UCs preventing a satisfactory PofI
135
Q

what does the survey line indicate and what must be done with this?

A

indicates extent of UC

must be used or eliminated by blocking out

136
Q

conformist

A

maintaining same occlusion

137
Q

reorganised approach

A

altering occlusion

e.g. toothwear, every complete denture

138
Q

master imps

A

greenstick to get imp of sulci and FES
alginate for U
silicone med-body for L

139
Q

how to block out casts - options

A

wax and chisel on surveyor

plaster and chisel

140
Q

blocking out - wax and chisel on surveyor

A

will be duplicated in “refractory” material for a CoCr framework
duplicated again to give a stone “working” cast
+ master cast not destroyed
- time

141
Q

blocking out - plaster and chisel

A

ONLY PMMA
trial and process on this master cast
+ quicker
- cast may be broken after

142
Q

post dam

A

groove in posterior of HP of master cast
posterior periphery of U RPD, in front of palatine fovea
cut on compressible tissue on the HP close to the jct of the hard/soft palate
not cut on SP - moves in fct
polished surface of the denture in this region is prepared to enable the denture to merge with the tissue
less obtrusive

143
Q

record blocks

A

identify index teeth
adjust one block to keep index teeth in occlusion
adjust second block with first one still in to keep index teeth in occlusion
record occlusion
mark centre line
correct occlusal plane

144
Q

blocking out

A

prep master cast
prevent a part of RPD entering an area that it shouldn’t
- rigid connector can’t enter UCs
- clasp arms should only engage UCs to a depth suitable for the material they are made from

so the processed denture will fit - however there will always be a space

145
Q

in relation to survey lines only block out:

A

in relation to PofI and PoR
between high and low survey lines where a connector is being placed
from UC gauge mark to lower survey line where a clasp is being placed

146
Q

RPDs made on master cast

A

blocked out in plaster - can process in heat-cured acrylic
wax - self-cured acrylic
good to consider a duplicate of blocked out cast

147
Q

pin dams

A

much shallower groove than post dam
anterior aspect of finished edge
aids in ensuring flush fitting and deflection of food material not slipping under the denture
scribed onto master cast approx 5mm from gingival margins

148
Q

clinical stages

A 
primary imps (primary jaw reg if required)
(survery, mount, design)
tooth prep and master imps
jaw reg
trial
delivery
review
149
Q

mouth prep

A 
initial prosthetic tx
 - repairs and additions
 - temporary relines
 - occ adjustment
 - tx denture stomatitis
pre-prosthetic surgery
PD tx
ortho tx
 - optimise space and abutment alignment
fixed pros and endo
150
Q

rest seats for upper anteriors

A

well-developed cingulum - prep stays within enamel

151
Q

rest seats for lower anteriors

A

lingual surface too vertical and cingulum too poorly developed to avoid penetrating E
incisal rest seats

152
Q

duplicating casts

A

reversible hydrocolloid - agar

condensation cured silicones

153
Q

tooth prep

A

provide rest seats
establish guide surfaces
modify unfavourable survey lines
create retentive areas

154
Q

rest seat prep

A

produce favourable tooth surface for support
prevent interference with occlusion
reduce prominence of rest

155
Q

rest seats for posteriors

A 
reduce MR (rest at least 1mm)
'saucer' shaped - allow some horizontal movement and dissipation of occlusal forces
if no space occlusally for a clasp to extend buccally from an occ rest, the prep should be extended as channel onto buccal
156
Q

alternatives to tooth prep

A

produce a rest seat in composite applied to cingulum area

bond a cast metal cingulum to tooth

157
Q

tooth modification

A

unfavourable survey lines
clasp would be positioned too close to occlusal surface - occlusal interference - annoyance
deformation of clasp

158
Q

creating retentive areas

A

addition of composite
need broad area of attachment of the restorations to the enamel
use ultrafine or hybrid composites

159
Q

plastic/acrylic teeth

A 
chemical bond with base
natural appearance
silent in function
soft - low abrasion resistance
tough
easily trimmed/polished/customised
cold flow under pressure
insoluble in mouth fluids - some dimensional change
160
Q

modified acrylic/composite/polymers teeth

A

chemical bond with base
partial bonding - recommended mechanical and/or bonding agent (4-META)
higher abrasion resistance

161
Q

guide planes

A

≥2 parallel axial surfaces on abutment teeth which limit the PofI of a denture
may occur naturally but often need to be prepared
surfaces parallel to each other and the PofI

162
Q

what do guide planes provide?

A

increased stability
reciprocation
prevention of clasp deformation
improved appearance

163
Q

preparing guide surfaces

A

should extend vertically 3mm but be kept as far away from the gingival margin as possible
≤0.5mm E removal

164
Q

5 stages of setting teeth

A 
choosing artificial teeth
matching natural teeth
customising artificial teeth
setting to existing dentition
trial dentures
165
Q

what type of tooth is the most popular?

A

acrylic

166
Q

compare posterior tooth moulds used for RPDs vs complete

A

RPDs generally wider/larger

167
Q

info from tooth/mould chart

A 
shape - square, ovoid, tapered
length anterior teeth
height and width of central incisor
occlusal tooth form
length C-C (remember 2D)
168
Q

porcelain teeth

A

mechanical attachment with denture base (silane coupling agent)
- metal pins anterior teeth
- holes (diatorics) manufactured into posterior teeth. Fill with the denture base
natural appearance
possible noise in fct
brittle
friable - grinding removes the surface glaze
hard - high abrasion resistance
- sometimes not recommended for occlusion opposing natural teeth
inert in mouth fluids - no dimensional change
high heat distortion - no permanent deformation under masticatory forces
can’t easily be customised by trimming ridge lap area or polished surface

169
Q

setting anterior teeth

A

symmetry

  • set to LA of corresponding tooth
  • contact points
170
Q

setting posterior teeth

A

central fissures conform
teeth set according to available space
- can set a premolar in a space occupied by a molar
marginal ridges same level as existing teeth
palatal cusp in contact with the central fissure of its antagonist on the opposing arch

171
Q

aesthetics

A

available space - may need to compromise
not advisable to have large areas blocked out ‘dead spaces’ - food impaction
artificial teeth must conform to existing tooth surface wear, and follow natural tooth guidance

172
Q

adjusting tooth mould

A

remove from ridge lap - part that contacts residual ridge
because if you remove from the length of a tooth (cervical margin or incisal tip) it can affect the shade
adjusting the tooth can affect the denture base and tooth bond

173
Q

trial base

A

rigid acrylic/shellac with wax saddle

modelling wax to attach teeth

174
Q

lost wax technique

A

precision metal casting
wax denture made on cast, mould made to surround shape, wax removed by melting, shape filled with molten metal
involves refractory model

175
Q

sticky wax

A

ensure fully adheres to light cured base

contains a gum resin

176
Q

refractory cast

A

no survey lines
heat resistant duplicate of master cast
made in phosphate-bonded investment material
- stronger than gypsum ones on heating
subject to surface wear - must be treated by hardening the surface of the model
- beeswax, resin, aerosol - model hardner

177
Q

tooth debonding

A

more the ridge lap is reduced the less bonding area is available
if softer bonding area is reduced in area it can affect the bond with the ‘enamel’ layer having a harder surface
at least 2 layers of material
- ridge lap made up of a more heavily cross-linked acrylic, specifically to bond with the denture base

178
Q

preventing debonding - heat cured dentures

A

adhesive failure
grind teeth with diamond cutters - rougher abraded surface (microabrasion)
no wax/grease on tooth surface (use detergent when boiling out to remove)
ensure no residue of mould seal on the tooth surface
use a post for retention when space is limited for PMMA

179
Q

preventing debonding - self cured dentures

A

cohesive failure
grind teeth with diamond cutters - rougher abraded surface (microabrasion)
no wax/grease on tooth surface (use detergent when boiling out to remove)
ensure no residue of mould seal on the tooth surface
use a post for retention when space is limited for PMMA

+ add a drop of monomer to the tooth surface and allow to soak into the tooth before adding the self-cure PMMA
+ try to avoid heavy contact on the denture teeth - cuspal interference

180
Q

sprue attachment

A

conducts molten metal into the mould
attached to the thickest and closest to the ingress of metal part of the casting
casting should progressively cool from the exterior to the centre of the metal inflow
- should prevent cooling shrinkage producing voids in the casting
placement and number of sprues also important to prevent air turbulence or air being trapped which would cause voids or porosity within the casting
sprue attached to a plastic cone which will be aligned in the casting machine
other wax - stabilise cone
cone and sprue attachment must be higher than any part of the wax pattern
to avoid air pressure - use air gates (1mm diameter) - carry air away from the casting

181
Q

packing

A

pack PMMA under pressure

can do trial

182
Q

3 types of porosity

A

granular
contraction
gaseous

183
Q

0.25mm clasp

A

CoCr

184
Q

0.5mm clasp

A

wrought gold

185
Q

0.75mm clasp

A

SS wire

186
Q

constructing denture - retention

A

wax retention pattern for FES
external finishing line
can use posts for anterior/single teeth
fill clasp from thickest part not from mesh

187
Q

flasking

A

waxed denture on cast embedded in plaster
set
evacuate wax
- heat
- detergent
hooded method
- easiest way to flask a partial denture to avoid the UC
- artificial teeth and clasps held in investing plaster following flasking

188
Q

post-processing

A

place on definitive cast
check occlusion
finish - burs - remove excess and any oxides
polish
- non-imp surface
- electropolishing - place wax over any thin areas e.g. wax to protect it
- polish with silicone rubber bur

189
Q

mechanism of action of RPI

A

Rest mesially acts as axis of rotation. As the proximal plate and I-bar rotates downwards and mesially (respectively) around the axis of rotation during occlusal load. The I-bar and proximal plate disengage from the tooth/undercuts. Thus, potential traumatic torque is avoided
prevents stress on abutment tooth in FES

dentures (2 decks)

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