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BDS 2 > Dentures > Flashcards

Dentures Flashcards

1
Q

what are abutment teeth

A

teeth that will be adjacent to the RPD

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2
Q

how do we survey a model?

A

use a surveyor with the model placed horizontal surface and with a pencil, draw on the line of highest bulbosity around the abutment teeth and other teeth to be implemented

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3
Q

why do we survey models

A

to understand the undercut involvement of teeth to provide good retention with RPDs

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4
Q

what is the path of insertion and what is it in relation to occlusal plane

A

path of prosthesis from first tooh contact to fully saddled on the teeth, usually 90 degrees to occlusal plane (+-10 degrees)

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5
Q

what is an RPD

A

An RPD is a removable appliance which replaces one or more missing teeth but not the entire arch.

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6
Q

what is the saddle of an RPD

A

the base that holds the artificial teeth

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7
Q

RPDs can be classified by their support, the pattern of tooth loss or by material type (relates to support). Classification by support:

A

Mucosa Borne - trasnfer load onto mucosa
Tooth bourne - transfer load throigh adjacent teeth through cingulum and occlusal rests
Tooth and Mucosa Borne - mixture

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8
Q

what are bounded saddles?

A

saddles bounded between natural teeth

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9
Q

what is a free end saddle

A

a saddle where there are no natural teeth distal to it

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10
Q

when do we provide tooth Bourne RPDs and why

A

with bounded saddles and when Oral hygiene and health is under good control as they take longer and are more expensive, cannot be modified so if OH reduces, a whole new one is needed

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11
Q

if a patient has badly controled OH what RPD do we provide

A

a cheap mucosa bound mainly PMMA RPD

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12
Q

when do we provide a mucosa-teeth bourne RPD?

A

when free end saddles are required wit no distal supporting tooth

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13
Q

why provide RPD?

A
  • aesthetics
  • function of mastication
  • reduces alveolar bone loss
  • maintain OVD
  • prevent tooth drifting
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14
Q

what are some disadvantages of RPDs

A
  • cause more tooth loss than other prosthesis as act as plaque retentive factor
  • can be gum stripping if forces are not equally balanced
  • food packing underneith
  • most issues can be avoided in manufacture
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15
Q

what are basker and davenports 8 criteria for designing an RPD

A
  1. Saddles: Number and extent
  2. Support: Decide if the denture is to be tooth or tissue borne, Extent of connectors
    and saddle for mucosa borne, Occlusal rests for tooth borne
  3. Retention: Physical muscular and mechanical retentive forces need to be considered.
    Surveying the model for undercut that may be used relative to path of
    displacement: Path of insertion different to path of displacement? Design options for
    clasps?
  4. Reciprocation: For each clasp
  5. Bracing: Resistance to lateral movements
  6. Connectors: Design criteria and options for connectors
  7. Indirect retention: For free end saddles
  8. Declutter and preparation work required
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16
Q

what are basker and davenports 8 topics to think about when designing an RPD

A
  1. Saddles: Number and extent
  2. Support: Decide if the denture is to be tooth or tissue borne, Extent of connectors
    and saddle for mucosa borne, Occlusal rests for tooth borne
  3. Retention: Physical muscular and mechanical retentive forces need to be considered.
    Surveying the model for undercut that may be used relative to path of
    displacement: Path of insertion different to path of displacement? Design options for
    clasps?
  4. Reciprocation: For each clasp
  5. Bracing: Resistance to lateral movements
  6. Connectors: Design criteria and options for connectors
  7. Indirect retention: For free end saddles
  8. Declutter and preparation work required
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17
Q

what is a circumferential clasp and where are they found

A

metal clasp that surrounds the whole teeth underneath its survey line - undercut
found at free end saddle on most distal natural tooth

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18
Q

what is an occlusal rest?

A

A rigid, usually metal, extension of a removable partial denture which rests on the occlusal surface of a posterior tooth for the support of a prosthesis.

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19
Q

what is a cingulum rest

A

A rigid, usually metal, extension of a removable partial denture which rests on the cingulum surface of an anterior tooth for the support of a prosthesis.

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20
Q

what is an eyebar clasp and where are they found

A

partial clasps under the undercut of teeth involved in the RPD found on natural teeth in the middle of dentition

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21
Q

what are the 6 stages to complete dentures

A 
primary impressions
secondary impressions
occlusal registration
wax try in
final try in
post insertion review
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22
Q

how does denture candidiasis present and occur

A

red speckled fungal markings

keeping dentures in over night and not washing

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23
Q

how do we record the hamular notch on taking impressios

A

open and close mouth

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24
Q

where does the back of the upper denture sit

A

hamular notch

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25
Q

shallow sulci lead to …

A

less lateral resistance of dentures - instability

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26
Q

how do we use the incisive papilla on our mould for placement of teeth

A

distal border of IP should be 12mm (or 8mm??) from labial surface of upper incisors

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27
Q

where should the lower denture end posteriorly

A

1/2 - 2/3 above the retromolar pad

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28
Q

what signifies the peripheral borders of the posterior lower denture

A

internal (mylohyoid) oblique ridge and external oblique ridge

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29
Q

why does the patient have to move their tongue side to side whilst taking impressions

A

record the lingual frenum
if not recorded, this can catch on the denture and cause pain/dislodgment
Understand the neutral zone

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30
Q

why are genial tubercles relevant to denture production

A

highly resorbed mandibles lead to prominent genial tubercles

can compress mucosa against denture causing pain

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31
Q

what is the function of primary impressions

A

to make a model to then form a secondary special tray for a more accurate impression

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32
Q

a patient has dentures already. How can we measure to know what sized impression tray they need

A

use calliper’s to measure intra-hamular notch length

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33
Q

how do we increase the shape of stock trays so they record abnormal/excess tissue

A

add greenstick

needs to be in hot water and to be heating for stick

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34
Q

for impressions we need impression material, trays and…

A

denture adhesive

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35
Q

what angle should the patient be sat at for impression taking

A

60 degrees

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36
Q

how do we take an impression

A

seat patient at 60 degrees
place filled tray in sideways to fit
place posteriorly first and then apply pressure gradually anteriorly
ensures excess comes to front, not back and prevents air bubbles

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37
Q

why do we not place impressions completey down and balanced?

A

this causes excess to move out of the tray via path of least resistance - backwards to throat
this doesn’t allow air to escape so forms bubble blows in material

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38
Q

what can lead to impression material flowing out the back of the denture

A

over filling impression tray

pressing down anterior first and material forced backwards

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39
Q

when the impression is done, what 2 steps do we do with a scalple

A

cut back sulcus depth by 1-2mm

cut away space for frenum

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40
Q

where should the special tray extend to regarding the sulcus

A

1-2mm short of functional depth

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41
Q

after trimming back the primary denture, what do we do

A

use indelible pencil to outline where we want special tray : 1-2mm short of sulcus depth
Disinfect for 10 minutes

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42
Q

what instruction needs to be on primary impression report for lab

A

what tray they want e.g
perforated/ non-perforated
close fitting / loose fitting
material e.g. ZnEu

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43
Q

what instruction needs to be on primary impression report for lab

A

what tray they want e.g
perforated/ non-perforated
close fitting / loose fitting
material e.g. ZnEu

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44
Q

what must we do with a primary impression before sending it off

A

disinfect for 10 minutes in ‘perform’ and fill in sterilisation label

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45
Q

where do we place mandibular teeth in relation to the residual ridge and why

A

anterior place in front of residual ridge
canines/premolars on residual ridge
first molars just inside residual ridge
second molar just outside residual ridge
on the weaker cortical bone to reduce resorption

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46
Q

where do we place all maxillary teeth in relation to the residual ridge and why

A

labially/buccally to the residual ridge

this is the weaker cortical plate

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47
Q

what is the neutral zone

A

a zone in which the teeth can be placed so the forces buccally/labially from the lips are balanced equally with the tongue

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48
Q

what is crossbite

A

where the lower/upper teeth overlap e.i. anterior uppers are in front of mandibular anterior however posteriorly, the maxillary teeth are inside the mandibular teeth

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49
Q

give three reasons why mandibular resorption can lead to pain with dentures

A
  1. irregular resorption leading to bumpy ridge accumulating pressure
  2. mental nerve/foramen close to mucosa
  3. genial tubercles prominent
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50
Q

when making a spaced tray, how do we make it ‘spaced’

A

use 1mm spacers when making the tray

fit 1mm or 2mm above the mucosa

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51
Q

what spacing do we use for alginate, ZnOE and silicone

A

silicone 1.5mm
ZnOE 2mm
alginate 3mm for deep undercuts

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52
Q

what do you tell the patient before taking a znOE impression

A

sill burn a bit and feel warm

quick set and we will take out

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53
Q

we want to take an impression of someone with xerostimia, what do we do

A

mouth needs to be wet so impression material doesn’t stick so rinse around with water

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54
Q

what allergy comes with ZnOE materials

A

elastoplast allergy

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55
Q

what should we ask to be added to our special trays

A

handlebar

finger spcaes on premolars for even pressure

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56
Q

how do we take an impression of a flabby ridge when we want to use mucocompressive material

A

we must use mucostatic for flabby ridges
use a ‘windowed’ tray so we can inject boiled mucocompressive silicone into flabby area
therefor not compressed

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57
Q

after secondary impressions, if a patient has dentures already what readings do we take for the technicians

A

use alma gauge to find the vertical height to the incisive papillae and horizontal reading

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58
Q

after secondary impressions and the patient doesn’t have an existing denture, what readings do we send to the technician with the impressions

A

standard readings of upper V = 22mm and lower V = 17mm from deepest part of sulcus

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59
Q

what are the standard tooth heights from the deepest part of the sulcus for upper and lower dentures

A

upper 22mm

lower 17mm

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60
Q

what is the vibrating line

A

margin between hard and soft palate

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61
Q

where is the DBA for upper and lower dentures

A

upper: posterior to vibrating line and peripherally to deepest part of sulcus
lower: posterior 1/2-2/3 up retromoalr pad and outer limit of buccal shelf peripherally

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62
Q

why are secondary impressions necessary

A

primary impressions are inaccurate
overextensions due to improper fit of tray
buccal overextensions give false impression of buccal sulcus
alginate has low tear strength and distorts at different rates depending on thickness

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63
Q

what needs to be marked by an endogenous pencil on the secondary impression

A

the real sulcus depth by removing 2mm from the highest part of the sulcus
muscle attachements/frena

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64
Q

what will the difference between primary and secondary denture models be

A

primary white, secondary more yellow
primary less detail and less accurate
secondary more detail and more accurate

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65
Q

why do we remove undercuts from denture models

A

as if we built in any undercuts they would get stuck under the model

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66
Q

what do we block out of models for dentures

A

undercut

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67
Q

what are some patient factors leading to denture failure

A

motomusular disorders like Parkinson’s not being able to control muscles well
abnormal anatomy such as tori or highly resorbed ridges

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68
Q

what checks must be made in the try in stage

A

no rough parts on the denture and remove with bur, ask if patient feels anything sharp
check for too much undercut
check occlusion ensuring ICP = RCP in CR

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69
Q

in the try in stage, if the dentures are not RCP = ICP what do we do

A

put pt into CR and find RCP with GHM paper, mark and tell the lab
they will articulate and alter occlusion so that ICP = RCP

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70
Q

what is the BULL rule regarding?

A

lateral excursions

buccal upper lingual lower

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71
Q

how do we find pressure points on the denture base

A

PSI pressure spot paste
put on denture (all of DBA, half of palate)
ask to press down and border mould

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72
Q

if a denture has insufficient post dam, how can the operator alter this?

A

addition of autopolymerising resin

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73
Q

at the try in stage, how do we check for overextensions

A

press down denture in premolar regions and then pull lip out and up
if denture dislodges anywhere, there is an overextension

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74
Q

what should be told to a patient leaving with new dentures

A

try wear as much as possible in first week
will be pain and possibly post dam ulcers
if too much pain, record where the pain is and bring back in a week with cleaning equiptment
if returning, try wear dentures for 24 hours before dentist app

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75
Q

what does a pt. need to do with their denture over night

A

do not wear sleeping
wash and soak
do not over soak or use bleach - discolouration and fractures

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76
Q

what is denture stomatitis

A

inflammation of the mouth after wearing dentures too much (usually over night)

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77
Q

how do we adapt POI for elderly patients

A

write down instructions so they remember

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78
Q

what cleaning instruction do we give denture patients

A

mechanically clean and rinse over sink after every meal
soak in denture cleanser overnight
never use boiling water or bleach

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79
Q

what is resting face height

A

distance between 2 set points of the maxilla and mandible (nose and chin) whilst pt is in resting habitual state, not in occlusion

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80
Q

what is occlusal face height

A

distance between a set point of mandible and maxilla (nose and chin) whilst in ICP

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81
Q

what should the relationship be between occlusal and resting face height and what is this called

A

they should be 2-4mm apart

this is Free Way Space

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82
Q

what is free way space

A

the difference between resting and occlusal face height

~2-4mm

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83
Q

what stage do we ensure RCP = ICP

A

registration phase with wax blocks

wax try in phase

84
Q

how do we check that ICP = RCP

A

ask to put tongue to back of palate
slowly close jaw
ensure no slide from first contact, RCP, to maximum contact ICP

85
Q

how do we measure OFH and RFH

A

with calipers

between 2 set points of maxilla and mandible

86
Q

if we see a hot plate that say ‘hot 240V’ what do we do

A

do not touch the plate

seek assistance as it should have a sheild

87
Q

how can we alter wax registration blocks

A

sterile hot plate for adjusting planes
sterile hot wax knife for removing over extensions
wax burs to remove rough patches and smoothen
rim inclinator for adjusting planes and occlusion

88
Q

during registration, what angle do we look at on the outside of the mouth, what should it be and how do we alter it

A

nasolabial angle
should be ~90 degrees
add additive wax if over 90 degrees, remove wax if under 90 degrees

89
Q

why is the RFH hard to measure

A

mentalis muscle over chin is mobile so changes

pt has nothing to bite on so is subjective

90
Q

how do we get pt into RFH

A

tell them to quietly say 1, 2, 3 and then keep still

lips should be gently touching, no teeth contact

91
Q

if a pt has old dentures, what should we consider with OFH

A

older patients struggle to adapt to new occlusal face heights
we should try to keep this the same

92
Q

what two lines must the upper maxillary block be parralell to

A 
foxes plane (paralell to alatragar line)
inerpapilalry line between pupils
93
Q

during regestration phase, what order do we place the blocks in

A

upper block - get parallel to foxes plane and interpapillary line and nasolabial angle
then lower block to measure OFH, RFH. Adjust RCP

94
Q

what is done during registration phase

A

measure RFH
upper block in
-use hot plate to get parallel to foxes plane and interpapillary line
-alter nasolabial angle to 90 degrees

lower block in

  • measure OFH and ensure 2-4mm FWS
  • bring to CR and check RCP
  • alter lower block to ensure balanced RCP = ICP

find rough patches and over extensions and alter
add center, canine and premolar lines and bind together with silicone
chose teeth size and colour

95
Q

what notches do we place in denture registration rims and why

A

premolar notches bilaterally and opposing

to place silicone in

96
Q

how and when do we decide tooth shape and colour

A

at end of registration phase
use old dentures, shape of head and old pictures
colour is down to patient, may want staining - use old pictures

97
Q

how do we use the shape of head to decide shape of teeth

A

tooth shape mimics the head
unisex - tapered (K)
female - oval (O)
male - square (S)

98
Q

when allowing patients to decide tooth size what do we do

A

cover the cervical portion as patients often think teeth are too big, select smaller sizes and then they look too small

99
Q

when is the post insertion review and what should they bring

A

1 week after final try in stage

bring denture and what they are using to clean

100
Q

what are the 6 main post insertion complaints

A 
pain
dislodging - looseness
trouble with speech
trouble eating (food packing)
aesthetics
nausea
101
Q

what causes this symptom at the 1 week review: pain at periphery

A

overextensions

102
Q

what causes this symptom at the 1 week review: pain at midline

A

occlusal problems

103
Q

what causes this symptom at the 1 week review: numbness

A

not enough freeway space - too much contact of teeth putting too much pressure on mental nerve

104
Q

what causes this symptom at the 1 week review: pain increases throughout day and red whole ridge

A

lack of free way space - too much contact of teeth causing fatigue and pain

105
Q

what causes this symptom at the 1 week review: pain cant tell if coming from top or bottom

A

ulceration on hamular notch

106
Q

what causes ulceration around the lips/tongue/frenal attachmnets post insertion

A

poor border moulding at secondary impression stage

107
Q

what causes this symptom at the 1 week review: blood blisters on side of tongue and common dislodgment of lower denture

A

lingually inclined molars

108
Q

how do we find which part of the denture is causing ulceration at 1 week review

A

dry mouth and denture
place ZnOE white paste on ulcer
place denture in, move
remove and see where white patch it

109
Q

what is the white spot test for post insertion review

A

using white znOE to test which part of the denture is causing ulceration

110
Q

what causes this symptom at the 1 week review: posterior buccal blisters

A

not enough space between retromolar pads and maxillary tuberosity
avoid by removing 7s and 8s

111
Q

what causes this symptom at the 1 week review: upper denture falling out easily

A

usually lack of post dam or dry mouth - autopolymerising resin

112
Q

what causes this symptom at the 1 week review: speech problems and dislodging of lower denture

A

interference with tongue - lingually inclined teeth

teeth not in neutral zone

113
Q

why must teeth be in the neutral zone

A

to prevent muscular dislodgement

aid speech with denture

114
Q

what causes this symptom at the 1 week review: insecurity whilst eating

A

RCP does not = ICP

cuspation of teeth too different to what pt is used to causing locking at lateral excursions

115
Q

what causes this symptom at the 1 week review: insecurity whilst speaking

A

muscular interactions at periphery - teeth not in neutral zone
muscular attachments frenal not included in secondary impressions

116
Q

if a pt gets dislodgment of the teeth, what questions should we ask

A

occur during eating or speaking?
does it cause pain
how often
what time of day

117
Q

why is important that we do not change the steepness of cusps too much for older patients

A

too much change to chewing lateral excursions

leads to locking of the jaw

118
Q

what may cause problems with aesthetics what factors of a new denture affect aesthetics

A

colour of teeth
shape of teeth
soft tissue support

119
Q

what causes this symptom at the 1 week review: nausea

A

overextending posterior margins/post dam

stimulating gag reflex at back of tongue/throat

120
Q

how can we help a patient with nausea with dentures

A

training plates
add teeth slowly
if pt doesn’t get used to training plates, they wont get used to dentures

121
Q

what causes this symptom at the 1 week review: ulcers on both sides and burning over night

A

overextensions causing ulcers
probably putting bonjela on ulcer over night
bonjela contains aspirin - salicylic acid causing burning

122
Q

why does bongela cause burning of uclers

A

bongela contains aspirin
derivative of salyclic acid
causes burning

123
Q

how does resorption of the jaw affect denture making (5)

A

highly resorbed:

  • cross bite formed due to widening of posterior mandible
  • very little resistance to lateral movements for dentures
  • mental foramen and genial tubercles exposed and cause pain
  • irregular resorption leads to pressure pain
  • very hard to take impressions
  • resorption happens rapidly and then slows down so may need new dentures

not resorbed atall:
-leads to very thin dentures with high midline fracture incidence

124
Q

if a patient has near to no residual ridge, what can be done

A

titanium implants in lower 3 area to clip denture

sulcus deepening

125
Q

what is the problem with primary impressions

A

Tray not correct size for patient
over extended
shrinkage due to thickness
distortion due to uneven thickness

126
Q

is ZnOE mucostatic or mucocompressive

A

mucostatic

127
Q

what is an impression

A

acurate negative imprint of hard and soft tissues of the mouth

128
Q

what are ideal properties for impression material

A 
cheap
non-toxic
set relatively quick
easy fast mixing
neutral taste and odour
simple to reproduce
accurate
minimal shrinkage/contraction
129
Q

how far should maxillary incisors dip below lip in RFH

A

a few mm

130
Q

if we can see the occlusal plane of the upper posterior teeth, what needs to be adjusted

A

maxillary occlusal plane is not on Foxes plane - alatragar line
move posterior teeth lower into denture

131
Q

what is gothic arch tracing

A

very accurate way of measuring CR and vertical dimensions of edentulous patients

132
Q

what are the vertical dimensions of upper and lower dentures

A

upper: 22mm from deepest sulcus to incisal edge
lower: 18mm from deepest sulcus to incisal edge
40mm all together

133
Q

how do we make a registration wax block denture

A

use heated shellac to form base - not into peripheries
use wax around peripheries
trim
add large occlusal wax block on top of residual ridge
remove block from positions of 7’s and 8’s
mark 22mm and 18mm accordingly and use a hot occlusal inclinator
smear shellac and wax together and smoothen edges

134
Q

what material is used as the denture base of registration rims

A

thermoplastic shellac

135
Q

what 2 materials form a wax registration rim

A

shellac and wax

136
Q

how do we find the centre line and canine lines

A

centre line is down from centre of nose

canine lines come down from lateral borders of alar of the nose

137
Q

what lines do we mark when finishing the registration phase

A

midline
canine line
premolar line
smile line (when smiling - where lips cover denture)

138
Q

What is bracing, in partial dentures

A

Resistance to anterior and lateral dislogment

139
Q

What is the minimum thickness needed for incisal occlusal rest seats and what happens if this is not followed

A

0.5 mm

Fracture likely if under 0.5mm

140
Q

why can the midline suture of the maxilla cause problems during dentures

A

can be indented or convex

as bone resorbs, this can act as a see saw affect

141
Q

is ZnOE used for mucostatic or mucocompressive impressions

A

mucostatic

142
Q

when is a face bow helpful

A

helpful for measuring the relationship of the teeth with the mandible

143
Q

why is it useful to mark the lowest part of the mandibular ridge on a denture model

A

this is the place where we should add highest occlusal load e.g. 6’s

144
Q

what is angles classification

A

classification of mandibular first molar and its antagonist

145
Q

from labial view, how should upper 1’s 2’s and 3’s be positioned

A

1s and 3s should be perpendicular to occlusal plane

2’s should be tilted medially with incisal edge parallel to occlusal plane

146
Q

from a distal view how should upper 1s 2s and 3s be positioned

A

1s proclined
2s more proclined
3s vertical

147
Q

why should the upper incisors on a denture be slightly proclined

A

so when we come into protrusion, we get anterior guidence

148
Q

how can we use facial features to help placement of upper anterors

A

central incisors should be width of philtrum of nose
canines should be in-between corner of nostril and corner of eye
occlusal line should follow lip
incisal margin should be slightly hidden during smiling by the lip

149
Q

how do we specifically place the upper and lower 6’s

A

lower 6 in lowest pat of the residual ridge

upper 6 mesiopalatal cusp should fit within lower mesiobuccall groove

150
Q

how much overjet is ideal for incisors

A

1mm

151
Q

what percent of the population have dentures

A

6%

152
Q

what are the three curves of compensation to which the posterior teeth of a denture must sit on to prevent dislodgement

A

curve of spee
curve of monson
curve of wilson

153
Q

what is the curve of spee

A

saggital
the curve that follows the anterior-posterior line of mandibular teeth
along the buccal cusps of molars and incisal edges of anteriors

154
Q

what is the curve of Wilson

A

coronal plane

curve connecting LHS posterior occlusal surface with RHS posterior occlusal surface

155
Q

what is the curve of monson

A

combination of curve of spee and wilson
In Centric relation, 4inch radius sphere with centre at glabellar
lower concave portion of sphere sitting on all occlusal/incisal surfaces

156
Q

why are the compensating curves important

A

teeth must sit on these curves to ensure balanced occlusion and eccentric movements

157
Q

does the buccal or lingual cusp ‘leave’ the occlusal plane first on mandibular teeth following curve of spee

A

buccal

158
Q

where should we place denture teeth

A

ideally where teeth used to be so they are in neutral zone
Take cortical bone resorption into account
along curves of compensation - Monson, Wilson, Spee
so that ICP = RCP

159
Q

what pattern do we see with the upper teeth against the occlusal plane

A

they follow the curve of spee
come away from the occlusal plane at the molars
buccal cusp leaves first

160
Q

how do we flask and pack a denture

A

put vasaline on all flasking surfaces
fill shallow half of flask with plaster
wet denture and model and place into plaster (if not the moulds will dry out plaster)
let set for a minute and remove excess around edges
run under water and smoothen plaster off
let set and smear vasaline on plaster surfaces
fill other half of mould with plaster (harder plaster) and spread plaster into fine detail of denture
press two halves together, lining up hooks and let set. put in boiling water
open flasks and remove shellac plate and pop in boiling water to remove excess wax, teeth should be in
using very clean hands, form acrylic dough and pack denture
put moulds together and press with mechanical press. Flash will come out of sides and hold dentures apart increasing OVD
put in curing bath (undulating temps, 5-6 hours)
knock out of moulds

161
Q

why do we put vasaline on surfaces when flasking

A

prevent plaster sticking together and causing moulds to stick together, damaging the dentures

162
Q

why does a film of alginate form against the plaster when flasking

A

sodium alginate reacts with calcium sulphate in plaster

163
Q

why do we slightly wet wax denture before flasking

A

if dry, it will dry out the surrounding plaster too quick

164
Q

why do we remove excess plaster from around the denture when flasking

A

to reduce any fake undercut

165
Q

why do we use different plasters in denture flasking

A

softer plaster to set base in place as base is already plaster so doesn’t need added strength
harder plaster on top of denture as this will be put under strong mechanical load and needs extra support

166
Q

why do we put flask moulds in boiling water

A

to melt away wax, leaving teeth in plaster with space left for acrylic

167
Q

why is there an increased OVD after flask and packing

A

when we put moulds in press, acrylic dough leaks out as flash
separates the moulds slightly leading to increased vertical dimensions

168
Q

how do we deflask a flasked denture

A

use saw around teeth and then use gentle hammering to break apart the plaster

169
Q

what finishing touches do we make when we have a deflasked acrylic denture

A

remove any flash plaster
polish with pumice
smoothen any sharp ridges
incorporate stippling for increased aesthetics

170
Q

how do we repair dentures

A

use wax to replace soft tissues
place in cast, boil away wax and use cold setting acrylic
finish

171
Q

how would we replicate a denture

A 
clean and wet with cold water 
place in flask
use vasaline on surfaces
pour alginate and press
let set and remove hard denture
172
Q

what classes as a shortened dental arch SDA

A

when we leave a mouth with reduced amount of occluding pairs of teeth
SDA = 10 occluding pairs (1-5)
extreme SDA = 8 occluding pairs (1-4)

173
Q

what happens if we heat PMMA too quick when setting and how do we prevent this

A

vasodilation of monomer
setting reaction is exothermic and how relatively low BP
increased porosity
heat slowly under high pressure

174
Q

what are 2 procedural errors whilst making a denture and how can we avoid the,

A

porosity due to fast heating : avoid by heating slowly under high pressure
polymerisation shrinkage causing poor retention : slow cure under high pressure, use polymerisation beads

175
Q

how can we reduce polymerisation shrinkage of denture whilst curing

A

heat and cure slowly over long period of time under high pressure
use polymerisation beads
incorporate post dam to combat the shrinkage at the posterior palatal aspect

176
Q

how else could we produce dentures to reduce polymerisation shrinkage

A

milling from a PMMA block

use 3D printing

177
Q

what is found in the powder and liquid mixture of PMMA

A

powder:
- MMA monomer
- inhibitor - hydroquinonee
- cross linking agent

liquid:

  • PMMA crystals
  • initiator benzoyl peroxide
  • plasticizer
  • pigments, opacifiers
178
Q

compare cold and hot cure PMMA

A 
cold cur is:
weaker
more porous
less dense
softer
more prone to discolouration
quicker 
used chairside
179
Q

what side affects of contacting PMMA in high amounts have on lab technicians

A

contact dermatitis

acquired asthma

180
Q

what side effects (allergerns) can be caused by PMMA dentures

A

unreacted monomers of MMA can dissolve and cause burning mouth for pt
PMMA can cause contact dermatitis and acquired asthma for technician

181
Q

what fungi are involved with dentures and how and what affect does it have

A

candida albicans
bond to polymeric surface via Wander Vaals forces, to high sucrose diets, rough surfaces, other microbes
cause colonies of fungus causes denture stomatitis

182
Q

why must we avoid cracks and rough detail on denture base

A

Candia albicans and other microbes can inhabit these areas as PFT and cause denture stomatitis

183
Q

what is CAD and CAM

A

computer aided design and computer aided manufacture - milling of PMMA to form denture base

184
Q

what programmes can we use for denture miling

A

CAD and CAM

185
Q

when would we use a flexible denture base

A

high undercut

presence of Tori

186
Q

how do we reline dentures

A

remove undercuts from denture base, fill with ZnOE or silicone and take impression
send to lab with ideal OVD measurements
lab make a model
add denture to model and add wax to build up
replace wax with PMMA by flasking and packing

187
Q

when are soft liners given

A

at point of production to put at base of denture to resolve pain e.g. above mental foramen, genial tubercle

188
Q

what types of soft liners are there

A

PMMA

silicone

189
Q

when is relining done to a denture

A

after immediate dentures or during time
bone resorbs and soft tissues change, altering the fit and retention of denture
needs new base or replacement

190
Q

compare a model and a die

A

model shows a whole ridge

a Die is part of a model that shows only part of a ridge

191
Q

what are some dental modelling material properties

A 
cheap
heat resistant up to 100 degrees 
hard and robust
don't react with impression materials, wax, PMMA
resistant to wear
192
Q

for secondary impressions what do we use for no undercut

A

Zinc Oxide Eugenol with Close fitting tray

193
Q

for secondary impressions what do we use for undercuts

A

alginate with a spaced tray of 2-3mm perforated

194
Q

POI for try in week of complete denture

A

If loose = use fixatives
Dry mouth = biotene
Clean with a non-abrasive toothpaste or soap. Excessive soaking is destructive
Pain is common and often expected If they are painful then only use when needed and either 24 hours before next appointment or 1 hour each day

195
Q

if a pt has a dry mouth with dentures, what do we reccomend

A

biotene

196
Q

if a patient has large undercuts, what impression do we use for secondary impressions

A

mucocompressive, flexible, 2mm spaced perforated tray with alginate
spaced + alginate for undercut
perforated for retention of alginate

197
Q

if a patient has no undercuts, what do we do for a secondary impression

A

mucostatic, nonflexible zinc oxide eugenol with not spaced tray
doesn’t need to be flexible to be taken out of undercuts
no space because no undercut

198
Q

what material do you use for flabby ridges or soft tissue excess

A

ZnOE mucostatic so the flabby ridges are not compressed or distorted

199
Q

why do we add spacers to some denture impression bases

A

spacers are used if undercut is present (for alginate - 2mm, silicone 1mm, ZnOE none
help form a thicker layer that can elastically deform on removal but not distort

200
Q

what is the cause of a midline fracture

A

resorbed ridges puts pressure on the peripheries with no support
puts tense stress on the midline causing fracture
thin base
old denture
cleaning with the wrong equipment
High residual ridges causing need for very thin denture base which is weak

201
Q

what is a short term and long term treatment of pt with broken denture

A

short term - fix chair side with cold curing PMMA
long term depends on reason for fracture
-if broken: make new pair of dentures
-remake dentures with different more flexible material like nylon
-if going to break again - surgical intervention like frenal reduction
-could line the denture to make less stress on midline

202
Q

if a pt has a broken denture what checks do we make and why

A

check for any missing parts
ask when and how the denture broke
how old the denture is
identify the cause of fracture before providing long term/short term treatment as the problem may re-occur and we need to treat the problem

203
Q

how do we clean dentures

A

non abrasive using soap, not toothbrush
soak in denture cleaner to manufacture instruction
do not wear overnight
do not oversoak as this affects mechanical properties

204
Q

What determines the Kennedy classification of a edentolous area and why does class 4 not have any modifications

A 
The most posterior edentolous area determines
So class 4 is anterior bilateral, if there was a more posterior saddle then this would make a new classification
205
Q

What is the ideal overjet to overbite ratio

A

1:2
Overbite is vertical
Overjet is horizontal

206
Q

what type of tray do we use for a ZnOE impression

A

rigid mucocompressive material

close fitting custom tray

207
Q

what two ways can we prepare alginate for impressions

A

stiff mix with less water - mucocompressive, compress

alginate wash - mucostatic, higher surface detail this is used on a already set hard mix alginate to finish

BDS 2 (13 decks)

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