Dentures Flashcards
1
Q
what are abutment teeth
A
teeth that will be adjacent to the RPD
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
3
Q
why do we survey models
A
to understand the undercut involvement of teeth to provide good retention with RPDs
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)
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.
6
Q
what is the saddle of an RPD
A
the base that holds the artificial teeth
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
8
Q
what are bounded saddles?
A
saddles bounded between natural teeth
9
Q
what is a free end saddle
A
a saddle where there are no natural teeth distal to it
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
11
Q
if a patient has badly controled OH what RPD do we provide
A
a cheap mucosa bound mainly PMMA RPD
12
Q
when do we provide a mucosa-teeth bourne RPD?
A
when free end saddles are required wit no distal supporting tooth
13
Q
why provide RPD?
A
- aesthetics
- function of mastication
- reduces alveolar bone loss
- maintain OVD
- prevent tooth drifting
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
15
Q
what are basker and davenports 8 criteria for designing an RPD
A
- Saddles: Number and extent
- 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 - 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? - Reciprocation: For each clasp
- Bracing: Resistance to lateral movements
- Connectors: Design criteria and options for connectors
- Indirect retention: For free end saddles
- Declutter and preparation work required
16
Q
what are basker and davenports 8 topics to think about when designing an RPD
A
- Saddles: Number and extent
- 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 - 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? - Reciprocation: For each clasp
- Bracing: Resistance to lateral movements
- Connectors: Design criteria and options for connectors
- Indirect retention: For free end saddles
- Declutter and preparation work required
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
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.
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.
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
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
22
Q
how does denture candidiasis present and occur
A
red speckled fungal markings
keeping dentures in over night and not washing
23
Q
how do we record the hamular notch on taking impressios
A
open and close mouth
24
Q
where does the back of the upper denture sit
A
hamular notch
25
shallow sulci lead to ...
less lateral resistance of dentures - instability
26
how do we use the incisive papilla on our mould for placement of teeth
distal border of IP should be 12mm (or 8mm??) from labial surface of upper incisors
27
where should the lower denture end posteriorly
1/2 - 2/3 above the retromolar pad
28
what signifies the peripheral borders of the posterior lower denture
internal (mylohyoid) oblique ridge and external oblique ridge
29
why does the patient have to move their tongue side to side whilst taking impressions
record the lingual frenum
if not recorded, this can catch on the denture and cause pain/dislodgment
Understand the neutral zone
30
why are genial tubercles relevant to denture production
highly resorbed mandibles lead to prominent genial tubercles
| can compress mucosa against denture causing pain
31
what is the function of primary impressions
to make a model to then form a secondary special tray for a more accurate impression
32
a patient has dentures already. How can we measure to know what sized impression tray they need
use calliper's to measure intra-hamular notch length
33
how do we increase the shape of stock trays so they record abnormal/excess tissue
add greenstick
| needs to be in hot water and to be heating for stick
34
for impressions we need impression material, trays and...
denture adhesive
35
what angle should the patient be sat at for impression taking
60 degrees
36
how do we take an impression
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
37
why do we not place impressions completey down and balanced?
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
38
what can lead to impression material flowing out the back of the denture
over filling impression tray
| pressing down anterior first and material forced backwards
39
when the impression is done, what 2 steps do we do with a scalple
cut back sulcus depth by 1-2mm
| cut away space for frenum
40
where should the special tray extend to regarding the sulcus
1-2mm short of functional depth
41
after trimming back the primary denture, what do we do
use indelible pencil to outline where we want special tray : 1-2mm short of sulcus depth
Disinfect for 10 minutes
42
what instruction needs to be on primary impression report for lab
what tray they want e.g
perforated/ non-perforated
close fitting / loose fitting
material e.g. ZnEu
43
what instruction needs to be on primary impression report for lab
what tray they want e.g
perforated/ non-perforated
close fitting / loose fitting
material e.g. ZnEu
44
what must we do with a primary impression before sending it off
disinfect for 10 minutes in 'perform' and fill in sterilisation label
45
where do we place mandibular teeth in relation to the residual ridge and why
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
46
where do we place all maxillary teeth in relation to the residual ridge and why
labially/buccally to the residual ridge
| this is the weaker cortical plate
47
what is the neutral zone
a zone in which the teeth can be placed so the forces buccally/labially from the lips are balanced equally with the tongue
48
what is crossbite
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
49
give three reasons why mandibular resorption can lead to pain with dentures
1. irregular resorption leading to bumpy ridge accumulating pressure
2. mental nerve/foramen close to mucosa
3. genial tubercles prominent
50
when making a spaced tray, how do we make it 'spaced'
use 1mm spacers when making the tray
| fit 1mm or 2mm above the mucosa
51
what spacing do we use for alginate, ZnOE and silicone
silicone 1.5mm
ZnOE 2mm
alginate 3mm for deep undercuts
52
what do you tell the patient before taking a znOE impression
sill burn a bit and feel warm
| quick set and we will take out
53
we want to take an impression of someone with xerostimia, what do we do
mouth needs to be wet so impression material doesn't stick so rinse around with water
54
what allergy comes with ZnOE materials
elastoplast allergy
55
what should we ask to be added to our special trays
handlebar
| finger spcaes on premolars for even pressure
56
how do we take an impression of a flabby ridge when we want to use mucocompressive material
we must use mucostatic for flabby ridges
use a 'windowed' tray so we can inject boiled mucocompressive silicone into flabby area
therefor not compressed
57
after secondary impressions, if a patient has dentures already what readings do we take for the technicians
use alma gauge to find the vertical height to the incisive papillae and horizontal reading
58
after secondary impressions and the patient doesn't have an existing denture, what readings do we send to the technician with the impressions
standard readings of upper V = 22mm and lower V = 17mm from deepest part of sulcus
59
what are the standard tooth heights from the deepest part of the sulcus for upper and lower dentures
upper 22mm
| lower 17mm
60
what is the vibrating line
margin between hard and soft palate
61
where is the DBA for upper and lower dentures
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
62
why are secondary impressions necessary
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
63
what needs to be marked by an endogenous pencil on the secondary impression
the real sulcus depth by removing 2mm from the highest part of the sulcus
muscle attachements/frena
64
what will the difference between primary and secondary denture models be
primary white, secondary more yellow
primary less detail and less accurate
secondary more detail and more accurate
65
why do we remove undercuts from denture models
as if we built in any undercuts they would get stuck under the model
66
what do we block out of models for dentures
undercut
67
what are some patient factors leading to denture failure
motomusular disorders like Parkinson's not being able to control muscles well
abnormal anatomy such as tori or highly resorbed ridges
68
what checks must be made in the try in stage
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
69
in the try in stage, if the dentures are not RCP = ICP what do we do
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
70
what is the BULL rule regarding?
lateral excursions
| buccal upper lingual lower
71
how do we find pressure points on the denture base
PSI pressure spot paste
put on denture (all of DBA, half of palate)
ask to press down and border mould
72
if a denture has insufficient post dam, how can the operator alter this?
addition of autopolymerising resin
73
at the try in stage, how do we check for overextensions
press down denture in premolar regions and then pull lip out and up
if denture dislodges anywhere, there is an overextension
74
what should be told to a patient leaving with new dentures
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
75
what does a pt. need to do with their denture over night
do not wear sleeping
wash and soak
do not over soak or use bleach - discolouration and fractures
76
what is denture stomatitis
inflammation of the mouth after wearing dentures too much (usually over night)
77
how do we adapt POI for elderly patients
write down instructions so they remember
78
what cleaning instruction do we give denture patients
mechanically clean and rinse over sink after every meal
soak in denture cleanser overnight
never use boiling water or bleach
79
what is resting face height
distance between 2 set points of the maxilla and mandible (nose and chin) whilst pt is in resting habitual state, not in occlusion
80
what is occlusal face height
distance between a set point of mandible and maxilla (nose and chin) whilst in ICP
81
what should the relationship be between occlusal and resting face height and what is this called
they should be 2-4mm apart
| this is Free Way Space
82
what is free way space
the difference between resting and occlusal face height
| ~2-4mm
83
what stage do we ensure RCP = ICP
registration phase with wax blocks
| wax try in phase
84
how do we check that ICP = RCP
ask to put tongue to back of palate
slowly close jaw
ensure no slide from first contact, RCP, to maximum contact ICP
85
how do we measure OFH and RFH
with calipers
| between 2 set points of maxilla and mandible
86
if we see a hot plate that say 'hot 240V' what do we do
do not touch the plate
| seek assistance as it should have a sheild
87
how can we alter wax registration blocks
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
during registration, what angle do we look at on the outside of the mouth, what should it be and how do we alter it
nasolabial angle
should be ~90 degrees
add additive wax if over 90 degrees, remove wax if under 90 degrees
89
why is the RFH hard to measure
mentalis muscle over chin is mobile so changes
| pt has nothing to bite on so is subjective
90
how do we get pt into RFH
tell them to quietly say 1, 2, 3 and then keep still
| lips should be gently touching, no teeth contact
91
if a pt has old dentures, what should we consider with OFH
older patients struggle to adapt to new occlusal face heights
we should try to keep this the same
92
what two lines must the upper maxillary block be parralell to
```
foxes plane (paralell to alatragar line)
inerpapilalry line between pupils
```
93
during regestration phase, what order do we place the blocks in
upper block - get parallel to foxes plane and interpapillary line and nasolabial angle
then lower block to measure OFH, RFH. Adjust RCP
94
what is done during registration phase
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
what notches do we place in denture registration rims and why
premolar notches bilaterally and opposing
| to place silicone in
96
how and when do we decide tooth shape and colour
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
how do we use the shape of head to decide shape of teeth
tooth shape mimics the head
unisex - tapered (K)
female - oval (O)
male - square (S)
98
when allowing patients to decide tooth size what do we do
cover the cervical portion as patients often think teeth are too big, select smaller sizes and then they look too small
99
when is the post insertion review and what should they bring
1 week after final try in stage
| bring denture and what they are using to clean
100
what are the 6 main post insertion complaints
```
pain
dislodging - looseness
trouble with speech
trouble eating (food packing)
aesthetics
nausea
```
101
what causes this symptom at the 1 week review: pain at periphery
overextensions
102
what causes this symptom at the 1 week review: pain at midline
occlusal problems
103
what causes this symptom at the 1 week review: numbness
not enough freeway space - too much contact of teeth putting too much pressure on mental nerve
104
what causes this symptom at the 1 week review: pain increases throughout day and red whole ridge
lack of free way space - too much contact of teeth causing fatigue and pain
105
what causes this symptom at the 1 week review: pain cant tell if coming from top or bottom
ulceration on hamular notch
106
what causes ulceration around the lips/tongue/frenal attachmnets post insertion
poor border moulding at secondary impression stage
107
what causes this symptom at the 1 week review: blood blisters on side of tongue and common dislodgment of lower denture
lingually inclined molars
108
how do we find which part of the denture is causing ulceration at 1 week review
dry mouth and denture
place ZnOE white paste on ulcer
place denture in, move
remove and see where white patch it
109
what is the white spot test for post insertion review
using white znOE to test which part of the denture is causing ulceration
110
what causes this symptom at the 1 week review: posterior buccal blisters
not enough space between retromolar pads and maxillary tuberosity
avoid by removing 7s and 8s
111
what causes this symptom at the 1 week review: upper denture falling out easily
usually lack of post dam or dry mouth - autopolymerising resin
112
what causes this symptom at the 1 week review: speech problems and dislodging of lower denture
interference with tongue - lingually inclined teeth
| teeth not in neutral zone
113
why must teeth be in the neutral zone
to prevent muscular dislodgement
| aid speech with denture
114
what causes this symptom at the 1 week review: insecurity whilst eating
RCP does not = ICP
| cuspation of teeth too different to what pt is used to causing locking at lateral excursions
115
what causes this symptom at the 1 week review: insecurity whilst speaking
muscular interactions at periphery - teeth not in neutral zone
muscular attachments frenal not included in secondary impressions
116
if a pt gets dislodgment of the teeth, what questions should we ask
occur during eating or speaking?
does it cause pain
how often
what time of day
117
why is important that we do not change the steepness of cusps too much for older patients
too much change to chewing lateral excursions
| leads to locking of the jaw
118
what may cause problems with aesthetics what factors of a new denture affect aesthetics
colour of teeth
shape of teeth
soft tissue support
119
what causes this symptom at the 1 week review: nausea
overextending posterior margins/post dam
| stimulating gag reflex at back of tongue/throat
120
how can we help a patient with nausea with dentures
training plates
add teeth slowly
if pt doesn't get used to training plates, they wont get used to dentures
121
what causes this symptom at the 1 week review: ulcers on both sides and burning over night
overextensions causing ulcers
probably putting bonjela on ulcer over night
bonjela contains aspirin - salicylic acid causing burning
122
why does bongela cause burning of uclers
bongela contains aspirin
derivative of salyclic acid
causes burning
123
how does resorption of the jaw affect denture making (5)
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
if a patient has near to no residual ridge, what can be done
titanium implants in lower 3 area to clip denture
| sulcus deepening
125
what is the problem with primary impressions
Tray not correct size for patient
over extended
shrinkage due to thickness
distortion due to uneven thickness
126
is ZnOE mucostatic or mucocompressive
mucostatic
127
what is an impression
acurate negative imprint of hard and soft tissues of the mouth
128
what are ideal properties for impression material
```
cheap
non-toxic
set relatively quick
easy fast mixing
neutral taste and odour
simple to reproduce
accurate
minimal shrinkage/contraction
```
129
how far should maxillary incisors dip below lip in RFH
a few mm
130
if we can see the occlusal plane of the upper posterior teeth, what needs to be adjusted
maxillary occlusal plane is not on Foxes plane - alatragar line
move posterior teeth lower into denture
131
what is gothic arch tracing
very accurate way of measuring CR and vertical dimensions of edentulous patients
132
what are the vertical dimensions of upper and lower dentures
upper: 22mm from deepest sulcus to incisal edge
lower: 18mm from deepest sulcus to incisal edge
40mm all together
133
how do we make a registration wax block denture
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
what material is used as the denture base of registration rims
thermoplastic shellac
135
what 2 materials form a wax registration rim
shellac and wax
136
how do we find the centre line and canine lines
centre line is down from centre of nose
| canine lines come down from lateral borders of alar of the nose
137
what lines do we mark when finishing the registration phase
midline
canine line
premolar line
smile line (when smiling - where lips cover denture)
138
What is bracing, in partial dentures
Resistance to anterior and lateral dislogment
139
What is the minimum thickness needed for incisal occlusal rest seats and what happens if this is not followed
0.5 mm
| Fracture likely if under 0.5mm
140
why can the midline suture of the maxilla cause problems during dentures
can be indented or convex
| as bone resorbs, this can act as a see saw affect
141
is ZnOE used for mucostatic or mucocompressive impressions
mucostatic
142
when is a face bow helpful
helpful for measuring the relationship of the teeth with the mandible
143
why is it useful to mark the lowest part of the mandibular ridge on a denture model
this is the place where we should add highest occlusal load e.g. 6's
144
what is angles classification
classification of mandibular first molar and its antagonist
145
from labial view, how should upper 1's 2's and 3's be positioned
1s and 3s should be perpendicular to occlusal plane
| 2's should be tilted medially with incisal edge parallel to occlusal plane
146
from a distal view how should upper 1s 2s and 3s be positioned
1s proclined
2s more proclined
3s vertical
147
why should the upper incisors on a denture be slightly proclined
so when we come into protrusion, we get anterior guidence
148
how can we use facial features to help placement of upper anterors
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
how do we specifically place the upper and lower 6's
lower 6 in lowest pat of the residual ridge
| upper 6 mesiopalatal cusp should fit within lower mesiobuccall groove
150
how much overjet is ideal for incisors
1mm
151
what percent of the population have dentures
6%
152
what are the three curves of compensation to which the posterior teeth of a denture must sit on to prevent dislodgement
curve of spee
curve of monson
curve of wilson
153
what is the curve of spee
saggital
the curve that follows the anterior-posterior line of mandibular teeth
along the buccal cusps of molars and incisal edges of anteriors
154
what is the curve of Wilson
coronal plane
| curve connecting LHS posterior occlusal surface with RHS posterior occlusal surface
155
what is the curve of monson
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
why are the compensating curves important
teeth must sit on these curves to ensure balanced occlusion and eccentric movements
157
does the buccal or lingual cusp 'leave' the occlusal plane first on mandibular teeth following curve of spee
buccal
158
where should we place denture teeth
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
what pattern do we see with the upper teeth against the occlusal plane
they follow the curve of spee
come away from the occlusal plane at the molars
buccal cusp leaves first
160
how do we flask and pack a denture
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
why do we put vasaline on surfaces when flasking
prevent plaster sticking together and causing moulds to stick together, damaging the dentures
162
why does a film of alginate form against the plaster when flasking
sodium alginate reacts with calcium sulphate in plaster
163
why do we slightly wet wax denture before flasking
if dry, it will dry out the surrounding plaster too quick
164
why do we remove excess plaster from around the denture when flasking
to reduce any fake undercut
165
why do we use different plasters in denture flasking
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
why do we put flask moulds in boiling water
to melt away wax, leaving teeth in plaster with space left for acrylic
167
why is there an increased OVD after flask and packing
when we put moulds in press, acrylic dough leaks out as flash
separates the moulds slightly leading to increased vertical dimensions
168
how do we deflask a flasked denture
use saw around teeth and then use gentle hammering to break apart the plaster
169
what finishing touches do we make when we have a deflasked acrylic denture
remove any flash plaster
polish with pumice
smoothen any sharp ridges
incorporate stippling for increased aesthetics
170
how do we repair dentures
use wax to replace soft tissues
place in cast, boil away wax and use cold setting acrylic
finish
171
how would we replicate a denture
```
clean and wet with cold water
place in flask
use vasaline on surfaces
pour alginate and press
let set and remove hard denture
```
172
what classes as a shortened dental arch SDA
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
what happens if we heat PMMA too quick when setting and how do we prevent this
vasodilation of monomer
setting reaction is exothermic and how relatively low BP
increased porosity
heat slowly under high pressure
174
what are 2 procedural errors whilst making a denture and how can we avoid the,
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
how can we reduce polymerisation shrinkage of denture whilst curing
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
how else could we produce dentures to reduce polymerisation shrinkage
milling from a PMMA block
| use 3D printing
177
what is found in the powder and liquid mixture of PMMA
powder:
- MMA monomer
- inhibitor - hydroquinonee
- cross linking agent
liquid:
- PMMA crystals
- initiator benzoyl peroxide
- plasticizer
- pigments, opacifiers
178
compare cold and hot cure PMMA
```
cold cur is:
weaker
more porous
less dense
softer
more prone to discolouration
quicker
used chairside
```
179
what side affects of contacting PMMA in high amounts have on lab technicians
contact dermatitis
| acquired asthma
180
what side effects (allergerns) can be caused by PMMA dentures
unreacted monomers of MMA can dissolve and cause burning mouth for pt
PMMA can cause contact dermatitis and acquired asthma for technician
181
what fungi are involved with dentures and how and what affect does it have
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
why must we avoid cracks and rough detail on denture base
Candia albicans and other microbes can inhabit these areas as PFT and cause denture stomatitis
183
what is CAD and CAM
computer aided design and computer aided manufacture - milling of PMMA to form denture base
184
what programmes can we use for denture miling
CAD and CAM
185
when would we use a flexible denture base
high undercut
| presence of Tori
186
how do we reline dentures
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
when are soft liners given
at point of production to put at base of denture to resolve pain e.g. above mental foramen, genial tubercle
188
what types of soft liners are there
PMMA
| silicone
189
when is relining done to a denture
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
compare a model and a die
model shows a whole ridge
| a Die is part of a model that shows only part of a ridge
191
what are some dental modelling material properties
```
cheap
heat resistant up to 100 degrees
hard and robust
don't react with impression materials, wax, PMMA
resistant to wear
```
192
for secondary impressions what do we use for no undercut
Zinc Oxide Eugenol with Close fitting tray
193
for secondary impressions what do we use for undercuts
alginate with a spaced tray of 2-3mm perforated
194
POI for try in week of complete denture
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
if a pt has a dry mouth with dentures, what do we reccomend
biotene
196
if a patient has large undercuts, what impression do we use for secondary impressions
mucocompressive, flexible, 2mm spaced perforated tray with alginate
spaced + alginate for undercut
perforated for retention of alginate
197
if a patient has no undercuts, what do we do for a secondary impression
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
what material do you use for flabby ridges or soft tissue excess
ZnOE mucostatic so the flabby ridges are not compressed or distorted
199
why do we add spacers to some denture impression bases
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
what is the cause of a midline fracture
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
what is a short term and long term treatment of pt with broken denture
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
if a pt has a broken denture what checks do we make and why
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
how do we clean dentures
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
What determines the Kennedy classification of a edentolous area and why does class 4 not have any modifications
```
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
What is the ideal overjet to overbite ratio
1:2
Overbite is vertical
Overjet is horizontal
206
what type of tray do we use for a ZnOE impression
rigid mucocompressive material
| close fitting custom tray
207
what two ways can we prepare alginate for impressions
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
