Dentures Flashcards
1
Q
What percentage of the population are denture wearers?
A
15%
2
Q
Where should the upper denture finish?
A
1-2mm before the fovae palatine
3
Q
What sort of landmarks to look for in the upper arch?
A
Midline raphe, Hamular notch, sulcus and fraena, incisive papilla
4
Q
What sort of landmarks to look for in the Lower arch?
A
retromolar pad, external oblique ridge (outer) and mylohyoid ridge (inner), lingual gingival remnant (rare)
5
Q
What is the average distance from the tip of the incisors to the bac of the incisive papilla?
A
12 1/2 mm
6
Q
What issues can arise with the mental nerve and dentures?
A
When teeth is lost, bone shrinks away and the mental foramen with mental nerve gets closer to the surface - can get pressurised by denture above it so patients get numbness/ sharp pains in this region
7
Q
Why do impression materials need to be rigid?
A
impressions have to be sent to the lab and need to retain their shape (alginate prone to shape change due to water changes)
8
Q
What does greenstick allow you to do?
A
It allows you to increase the length of a stock tray to make it more suitable for a patient’s mouth e.g. extending the trays over the retromolar pads or post-dam regions
can also use inside a poorly fitting tray to customise to an extent where a satisfactory primary impression can be made
9
Q
What is the purpose of primary impressions?
A
record anatomy and permit primary models to be cast
To allow construction of special trays to record working impressions
10
Q
What is border moulding?
A
pulling down the lips and cheeks to simulate what happens during chewing/speaking etc whilst taking the impression
11
Q
How long should you disinfect the impression for?
A
10 minutes
12
Q
How can you alter the properties of alginate?
A
more water = more running and vice verse
13
Q
What happens to site and pattern in mandibular resorption?
A
Ridge is pushed further lingual anteriorly (in at the front) and further buccal posteriorly (out at the back)
14
Q
What happens to site and pattern in maxillary resorption?
A
Residual ridge is displaced palatally in all cases
15
Q
What are the influencing factors of bone resorption? (systemic, local, denture induced)
A
Systemic - osteoporosis
Local - retained roots preserve alveolar bone as do biocompatible implants
Denture induced - some evidence that denture wearing contributes to resorption
16
Q
What is the molar crossbite?
A
When the buccal cusps of the upper molars sit inside of the buccal cusps of the lower molars
In edentulous patients this is often due to the buccal resorption of the upper arch and the buccal change of the lower ridge due to the resorptive pattern
17
Q
How does irregular resorption cause pain?
A
Caused as mucosa is sandwiched between sharp bony spicules and denture
18
Q
What is angular cheilitis?
A
inflammation of one or both corners of the mouth. Often the corners are red with skin breakdown and crusting. It can also be itchy or painful. The condition can last for days to years.
19
Q
How are the requirements of ridges with and without undercuts different?
A
Ridge without undercuts (or minimal) - rigid impression material in close fitting special tray
Ridge with large undercuts - elastic impression material in spaced special tray
20
Q
What are the properties of ZnO?
A
- Mucostatic - minimal force going through mucosa, recording mucosa at rest - runny material whereas silicone putty is mucocompressive - forces tissues down
- technique is mucocompressive if used with non spaced non perforated tray (close-fitting tray), mucostatic in areas where it isn’t as close-fitting
- Sometimes used with one spacer - fine, bumpy ridge, zno wants to be thickened up around these areas
- Can be used with two spacers and wide perforations in mild flabby areas – relatively mucostatic at the front of the mouth but mucocompressive at the back of the mouth
Cheap, easy to modify and accurate
21
Q
Why are tissue stops used?
A
All impression materials work at an optimum thickness
- ZnO needs no tissue stop
- Silicone requires a 1.5mm tissue stop
- Alginate requires a 3mm tissue stop
- stops the tray showing through if excessive pressure is placed
22
Q
Where should the tray extend to?
A
Extension of tray should be 1-2mm away from the deepest part of sulcus
23
Q
Why are finger rests made sometimes?
A
To prevent the fingers distorting the periphery
24
Q
How is the impression corrected wherever the tray penetrates?
A
Use of handpiece and bur to trim away where tray shows through
25
How is an impression of a flabby ridge taken?
- upper anterior region mainly
- natural teeth oppose an edentulous ridge
-
26
What does the alma gauge measure?
The vertical and horizontal height relative to position of anterior central incisors
27
What are the average vertical and horizontal heights?
22mm upper
| 18mm lower
28
What is resting face height?
Height from nose to chin when all muscles in face relaxed, jaw slightly open but lips put together
29
What is occlusal face height?
Height from nose to chin when teeth are brought together, lips still closed
30
What is the freeway space?
The difference between RFH AND OFH
31
How are OFH and FWS related?
Increasing OFH reduces FWS - INVERSLEY PROPORTIONAL
32
What is the ideal freeway space?
2-4mm
33
What is the intercuspal position/ centric occlusion
occlusal position of the mandible in which the cusps of the teeth of both arches fully interpose themselves with the cusps of the teeth of the opposing arch
teeth fully meet
34
What is central relation/ retruded position?
retruded contact position - first contact within the rotational movement of the condyle sliding down the fossa when the mouth opens
the mandibular jaw position in which the head of the condyle is situated as far posteriorly and superiorly as it possibly can within the mandibular fossa/glenoid fossa
35
What is retruded contact position?
The first teeth/tooth that meets when the head of the condyle first makes rotational movement?
36
Why do denture patients need RCP as a reference point?
Only reliable starting point for occlusion due to being edentulous
37
What are foxes plane guide?
See whether dentures are parallel in 2 planes - intrapupillary plane and alatragal plane
38
What do the dividers do?
measure distance between nose and chin
39
What are the 3 key measurements at the registration rims stage?
The OFH with old dentures in
The RFH with the patients most comfortable denture in
Then determine what you want the OFH to be when the new dentures are made
40
Why is the OFH of the old set of dentures important?
OFH of old dentures is much easier to measure than RFH as patient has something to bite against that is reproducible
Patients struggle to adapt to large changes in OFH
41
How to relax the patient to find RFH?
Ask patient to touch their lips together very gently whilst staring at a distant object
1,2,3, - lips touch on 3
Gentle imperceptible blowng
Say mmm
Look away and wait until patient relaxed
- measure with the patient wearing only one denture
42
Where do you mark the incisal plane of the registration rim?
Parallel to the interpupillary line and approx level of upper lip
Mark posterior occlusal plane parallel to alar of nose/tragus of ear
43
What can be added to improve lip support to the wax blocks?
Extra wax
44
How to adjust the lower block?
Guide patient to RCP
tongue to back of mouth
Trim lower block until meeting evenly in retruded position at the predetermined OFH
45
Why do we use finger rests on registration block?
Secure hold of the mandible and prevent the registration block from moving during the process
46
Why do we use occlusal notches on both blocks?
They allow silicone to seal the blocks together in a unique position and allow the technicians to reattach the blocks in the correct position if they come apart
47
What should you check at the try in phase?
```
Aesthetics
The OVD/OFH
Occlusion in relation to ICP and RCP - ICP = RCP
The border extensions
The border thickness
Neutral zone issues
Tongue space
Mark post dam and lower border extensions
```
48
What is a class 2 div 2 occlusion?
Anterior incisors slightly retroclined
| Lateral incicsors slightly proclined
49
How can you get more teeth to contact in occlusion?
Take tip off canine
50
What is a post dam?
Raised part at the back of the dentures - need to map this for retention of denture
Bigger the patient = deeper the post dam
- compressibility different indifferent areas - edges of hard palate are more compressible
51
How to mark the post dam?
Get patient to say aah
See where the vibrating line is - mark visually
Palpate anteriorly to this with a ball/pear burnished to see which tissues are compressed
Consider 2 post dams - retching
Ask lab to make it as thin as possible
52
What sort of faults can arise with dentures?
Patient related
Laboratory related
Clinical related
53
What sort of patient related faults with dentures can arise?
Systemic disease - Parkinson’s, dyskinesia, hormonal
| Local pathology - atrophy, fibrous replacement, undercuts, anomalies
54
What is a torus palatinus?
Solid lump of bone in the palate
55
What lab related faults can arise?
Technical errors - investment *tooth movement, processing - flash of acrylic, post dam*
- damage to the model
56
What clinician related faults can arise with dentures?
Impression defects
| Registration errors
57
What is the placement technique for correcting clinican related faults for dentures?
```
Inspect fitting surface
Insert - correct faults
Check occlusion - correct faults
Fitting surface - remove pressure spots
Security - correct faults
```
58
What is the fitting surface? I
Anything in direct contact with the tissues
59
What is the polished surface?
The outer labial part of the denture
60
What rule is used to adjust the lateral excursions with a bur?
BULL rule - for articulation - adjust buccal uppers and lingual lowers only
61
What is the main reason for getting denture stomatitis?
Keeping dentures in at night
62
What are the important points about the denture try in stage?
get patient to sign in the notes that aesthetics are acceptable
- get opinion of significant other person
- mark borders and extensions of periphery
63
What are the two compensation curves introduced for occlusal balance?
The antero-posterior curve - curve of spee
a lateral curve - curve of monson
64
What is balanced occlusion?
This relates to the first point of contact when the patient occludes in centric relation – view as a static position
As many teeth as possible should contact evenly in this position
ICP must equal RCP
65
What is the antero-posterior curve called?
curve of Spee
66
What does the antero-posterior curve maintain?
Mesio-distal contact between teeth
67
What is the lateral curve called?
Curve of Monson
68
How much should the teeth of the denture be showing when at rest?
1/2 or 2/3 of incisors but be careful of patients opinion of old dentures
69
How would you fix an error in vertical jaw relations?
If small, can make changes at articulator pin and request re-try
70
How would you correct an error in antero-posterior alignment of the top and bottom dentures?
Remove teeth where not aligned and place wax block to re-register the bite, then replace teeth in correct position
71
How would you guide the patient's lower jaw into ICP?
Take firm control of lower jaw - index fingers buccal to the lower 456 region and thumbs under the chin
72
How would you check for overextensions of the denture?
Check cheek traction and see if denture is coming up when cheeks and lips are moved around it, trim away where extended
73
What is a common problem with the lower anterior tooth position?
Lower anteriors are often too far forward and have to be moved back
74
What is a common problem with the lower posterior teeth?
May be too far lingually so not enough space for tongue
75
Why are 7's usually not placed in dentures?
Need good space for buccal fat pads (cheeks), dentures can often be misaligned and misplaced with 7's present
76
What is the post dam?
back part of denture (where hard palate and soft palate)has shrinkage - no air seal to hard palate so suction reduced
post dam is the raised bit on the back
Back of denture needs to be pressed on hard palate
77
Why do we need to mark the post dam?
Technician has no idea as to the compressibility of the mouth
every patient is different - bigger the patient- deeper the post dam
compressibility is different in different areas
inadequate post dam leads to poor posterior seal
78
How do we mark the post dam?
Get the patient to say aaaaaaaahhhhhh
see where the vibrating line is (where midline raphe is tethered into)
palpate anteriorly to this with a ball or pear burnisher to see which tissues are compressible
consider marking more than one post dam if retching or poor tolerance is expected.
Ask the lab to keep the acrylic between the two post dams as thin as possible
79
Where should the distal margin of the maxillary denture finish?
1-2mm anterior to foveae palatini
need to see 2 little dots when denture has tried in - cut forward
80
Where is the palate always more compressible?
Lateral sides of palate
81
What would you use to cut the post dam?
Ash 3- 693
scribe to the required depth with ash knife or large bur in a straight handpiece
82
What other markings are useful for the lab technician?
Retromolar extensions
width of frenal relief
Buccal extensions around the external oblique regions (mark where the lower denture should finish - 1/2 to 2/3 back onto the retromolar pad)
83
What problems can be encountered at review stage? (SPAINC)
```
Speech
Pain
Appearance
Insecurity
Nausea
Chewing
```
84
Where can pain mostly be experienced?
Periphery of denture bearing tissues
Centrally on denture bearing tissues - bulky prominences on ridge
Cheek/lip biting - too far buccal or too far lingual
Numbness
85
What are common ulcer sites from dentures? (M, H, P, F, G)
```
Mylohyoid region
Hamular notch
Post dam - junction of hard and soft palate
Around frenal attachments
Genial tubercles - atrophic mandible
```
86
How would you adjust a denture at review stage?
```
Pick up technique
Dry surfaces
Mark with ZnO2 or Dycal paste
Transfer to denture
Adjust denture accordingly
```
87
How to adjust an area causing an ulcer?
Apply cream to the ulcer (ZnO2, Dycal paste)
Insert denture
Ulcer area picks up on the denture when removed
Adjust with bur
88
How would you stop the denture impacting the mental nerve region in a severely resorped mandible?
Cut hollows in the areas of the denture that would impact the mental nerve region
89
How would you stop the tongue being trapped by the dentures?
Cut the posterior tooth in half to make more space for the tongue
90
How would you correct freeway space at the review stage?
Have to start again and remake dentures
91
What can cause insecurity when speaking?
Muscle interference at periphery
| Muscle interference of polished surfaces
92
What causes insecurity when eating?
Occlusal interference
| Poor ridge form
93
How would you fix underextensions of the denture?
Self curing acrylic
| Apply to specific areas and insert in patient’s mouth to get exact shape of area
94
How would you solve an occlusal fault?
Pre-centric check record - insert dentures with wax on the periphery to register the bite, dentures then re-articulated
- makes sure retruded and intercuspal positions match again (ICP = RCP)
95
What can affect speech with a denture in?
Tooth position
Shape of base
Lack of FWS
96
How can speech be improved?
Ridge of acrylic on upper anterior lingual surface adjusted - with ridge removed, speech is improved
Palatal cusps of 4’s can be too bulky compared to the old set
Tongue cramping
97
What can cause nausea from a denture?
```
Insecurity - post dam deficient
Thick posterior margin
Intolerance
Dropping on to posterior tongue
general intolerance of the denture
```
98
How can you manage nausea patients?
Use a training denture
99
What can cause TMJ or facial muscle pain?
```
Nearly always FWS or occlusal problem
Patient might sleep with dentures in
Check for general redness on the ridges (FWS problem - remake dentures)
Palpate ridges for general redness
Often no discernible ulcers
```
100
Where can pain mostly be experienced?
Periphery of denture bearing tissues
Centrally on denture bearing tissues - bulky prominences on ridge
Cheek/lip biting - too far buccal or too far lingual
Numbness
101
What are common ulcer sites from dentures?
```
Mylohyoid region
Hamular notch
Post dam - junction of hard and soft palate
Around frenal attachments
Genial tubercles - atrophic mandible
```
102
How would you adjust a denture at review stage?
```
Pick up technique
Dry surfaces
Mark with ZnO2 or Dycal paste
Transfer to denture
Adjust denture accordingly
```
103
How to adjust an area causing an ulcer?
Apply cream to the ulcer
Insert denture
Ulcer area picks up on the denture when removed
Adjust with bur
104
How would you stop the denture impacting the mental nerve region in a severely resorped mandible?
Cut hollows in the areas of the denture that would impact the mental nerve region
105
How would you stop the tongue being trapped by the dentures?
Cut the posterior tooth in half to make more space for the tongue
106
How would you correct freeway space at the review stage?
Have to start again and remake dentures
107
What can cause insecurity when speaking?
Muscle interference at periphery
| Muscle interference of polished surfaces
108
What causes insecurity when eating?
Occlusal interference
| Poor ridge form
109
How would you fix underextensions of the denture?
Self curing acrylic
| Apply to specific areas and insert in patient’s mouth to get exact shape of area
110
How would you solve an occlusal fault?
Pre-centric check record - insert dentures with wax on the periphery to register the bite
111
What can affect speech with a denture in?
Tooth position
Shape of base
Lack of FWS
112
How can speech be improved?
Ridge of upper anterior lingual surface adjusted
Palatal cusps of 4’s can be too bulky compared to the old set
Tongue cramping
113
What can cause nausea from a denture?
Insecurity - post dam deficient
Thick posterior margin
Intolerance
Dropping on to posterior tongue
114
How can you manage nausea patients?
Use a training denture
115
What can cause TMJ or facial muscle pain?
```
Nearly always FWS or occlusal problem
Patient might sleep with dentures in
Check for general redness on the ridges (FWS problem - remake dentures)
Palpate ridges for general redness
Often no discernible ulcers
```
116
What is a summary of the first 4 stages in making a denture?
Record the shape of the ridges
Record the inter-ridge relationships
Make a wax template
Convert the template to a denture
117
What are the 7 stages of denture making?
```
Construction
Primary Impressions
Secondary or Definitive Impressions
Registration
Wax Try in
```
Provision
Denture Fit
Post-fit Review
6-12 months post-fit Review
118
What are the 2 categories of relevant anatomical structures to dentures?
Those making the denture periphery - the maxilla and the mandible
Those marking the site of the teeth - the maxilla
119
What does the hamular notch mark?
The distal edge of the maxillary denture where tendon of tensor palatine expands into soft palate
120
What do the sulcus and fraena mark?
Marks functional extent of the denture
121
What does the retromolar pad mark?
Distal extent of mandibular denture
122
What does the mylohyoid ridge and and external oblique ridge mark?
Medial and lateral limits of bony support
123
What does the lingual gingival remnant and incisive papilla indicate?
Indicates the lingual margin of posterior teeth and labial surfaces of anterior teeth
124
What 2 muscle insertions are important landmarks for dentures?
Insertion of mentalis
| Insertion of genioglossus
125
List some points of information you would give to gain the full and valid consent of dentures?
Diagnosis – what the current problem is
Prognosis – chance of success of the new dentures
Can the patients desires and wishes be realistically achieved?
The number of visits needed and what treatment will be carried out
Proposed changes, benefits and risks
Ask the patient if they understand, and ask if they have any questions
Clearly document in the clinical notes that this has been carried out
126
What should you tell or ask the patient on subsequent denture visits?
Diagnosis – what the current problem is
Prognosis – chance of success of the new dentures
Can the patients desires and wishes be realistically achieved?
The number of visits needed and what treatment will be carried out
Proposed changes, benefits and risks
Ask the patient if they understand, and ask if they have any questions
Clearly document in the clinical notes that this has been carried out
127
What are the 4 requirements of a denture impression material?
Accuracy
Resolution
Dimensional Stability
Rigid or elastic
128
What are the ideal properties of a denture impression material? and what are the practical problems?
Simple technique, cheap to use, bonds to tray
Viscous during placement
Elastic when set
Viscoelastic when set
Unstable with time
129
Why is a bonding agent applied to the tray?
Mechanical retention via perforations insufficient by itself.
130
Why is the impression material made in a stiff mix?
Stiff, viscous mix serves to displace soft tissues from denture-bearing area
131
Where do you stand in relation to the patient when taking impressions?
For upper impression – stand behind the patients right shoulder and their maxilla should be at your elbow height
For lower impression – stand in front of the patient and the mandible should be at your elbow height
132
What is the angle of the chair for an upper impression?
60 degrees
133
Where do you first put the maxillary tray when inserting?
Hover the tray , pull back the upper lip then place the tray in the labial sulcus first – the midline labial frenum is your key landmark.
Then tip the tray upwards posteriorly until alginate can be seen just beyond the distal aspect of the tray
134
How can you adjust the primary impression?
Remove overextensions
Remove obstacles to peripheral flow
Relieve fraena
135
Where do you mark the periphery of the primary impression for the lab?
Mark periphery 2mm inside the maximum depth of the impression
This will confirm the extent of the special tray
-indelible pencil
136
Where does the ridge resorb in the maxilla?
Residual ridge is displaced palatally in all cases
137
What is the most common material and tray used for the working/definitive impressions?
Close fitting tray with zinc oxide eugenol (rigid material) - CCDH
138
What do you do if you have a ridge with some undercuts for the working impression?
Change the spacing around the undercuts rather than changing to a complete elastic impression material - silicone can't define the borders as well as zinc oxide
139
What is an undercut?
the contour of a cross-section of a residual ridge of dental arch that would prevent the placement of a denture or other prosthesis
140
Which materials require a spacer if used for the working impression?
Silcione/alginate (elastic materials) - alginate should also have perforations in the tray
Zno doesn't
141
What is the width of the spacer for alginate?
3mm
| too little or too much - alginate will distort
142
How many tissue stops are used for the working impression usually?
3 different points on the tray
| - stops tray showing through if excessive pressure placed
143
Where is the most common place for underextensions on the working impression?
disto-lingual of the lower
144
Why does a flabby ridge cause instability of the denture?
Due to lack of underlying bone
145
Why are the finger rests placed in the premolar region?
Most stable place
146
What does the horizontal and vertical height of an alma gauge tell you?
horizontal - how many mm the tip of the incisors are forward from the incisive papilla
vertical - the length from the tip of the incisors to the incisive papilla
147
What do you record the jaw relationship for dentures?
retruded position + (RFH - 3mm)
148
Why might it be useful for the patient to wear one denture when measuring RFH?
If they are very overclosed without them in, will help to have one in and measure natural height
149
What does notching of the registration rims allow?
Accurate mutual location of the rims together for the technicians - seal in unique position
150
How do dentures achieve balanced articulation?
They have multiple contacts on both sides of the denture in lateral and protrusive movements which stops the dentures from tipping - opposite to dentate patients
151
Which curve maintains mesio-distal contact?
antero-posterior curve - curve of spee
152
Which is the balancing curve between the working and translating condyles?
Curve of Monson
153
What other markings other than the post dam need to be scribed for the technician?
Retromolar extensions
Width of frenal relief
Buccal extensions around the external oblique regions
Mark where the lower denture should finish – ½ to 2/3 back onto the retromolar pad
154
What are the main approx 10 things to check for when the patient comes in for the try in phase?
check upper for:
intra pupillary plane
ala-tragal plane
colour, shade, appearance, lip support
lower:
lower tooth position correct
anterior teeth position
upper meet lower denture at predetermined height
does icp=rcp
155
What paste can be used to remove pressure spots on the fitting surface?
PSI paste?
156
What could be a causing a loss of security anteriorly?
insufficient fraenal relief
157
What is denture stomatitis?
a common condition where mild inflammation and redness of the oral mucous membrane occurs beneath a denture. In about 90% of cases, Candida species are involved, which are normally a harmless component of the oral microbiota in many people. Denture-related stomatitis is the most common form of oral candidiasis (a yeast infection of the mouth).
158
What is central pain often due to?
Bony ridges
159
What is cheek biting often due to?
Lack of space for buccal fat pads between upper and lower denture
160
What is tongue biting often due to?
Lack of FWS
| or lower dentures too far in lingually
161
What can cause an insecure upper denture?
Lack of peripheral seal usually at the distal margin
162
What type of error is chewing usually?
Occlusal error
Locked occlusion
corrected by pre-centric check record
163
What are the ideal properties for a denture base material?
```
Biocompatible
Aesthetic
Hygienic (Resistant to bacterial contamination)
Dimensionally stable
High Strength, stiffness, hardness and toughness
High thermal conductivity
Low density
Cost
```
Ease of:
Processing
Repair/adjust
Reproduction of surface detail
Radiopacity
164
what materials are used in denture base materials (6)?
```
Polymethyl methacrylate (PMMA)
Polyetheretherketone (PEEK)
Nylon: flexible dentures (Valplast)
Polyamide (Bredent)
Cobalt Chrome alloy
Titanium
```
165
What is PMMA?
Poly (methyl methacrylate)
Plastic
Organic polymer : Long chain molecule of repeated units of methyl methacrylate
Thermoplastic Tg ranges from 85 -165C
166
What initiator is used to start the process of free radical polymerisation of PMMA?
Benzyl peroxide
This molecule readily splits into two, each fragment having one unpaired electron.
These fragments attack the C=C bond starting the polymerisation.
167
What cross linking agent is used between PMMA polymer chains to increase its mechanical and physical properties?
Diethylene glycol dimethacrylate
168
What sort of processing problems can occur with dentures bases?
Porosity - Volatisation of monomer during curing if the temperature is raised too quickly.
This is because the reaction is exothermic and the monomer has a relatively low boiling point
Polymerisation shrinkage - Can result in the denture not contacting the hard palate or porosity
- polymer heated too quickly
Processing strains
These may arise due to dissimilar materials being used (e.g.ceramic teeth or CoCr components)
Also if the polymer is cooled too quickly
169
How can porosity of a denture base be avoided?
Use a slow heating cycle when curing and keep under pressure
170
How can polymerisation shrinkage of the denture base be minimised?
Use polymer beads to reduce the necessary polymerisation to a minimum
Keep denture under pressure and use a slow cool when curing
Incorporate a post dam on to the denture to compensate
171
What alternative processing routes are there to make a denture base?
‘Injection molding’ of acrylic dough
Injection molding of acrylic above Tg
Milling from block
172
What is injection moulding?
Heat material to above to above Tg
Squeeze into mould using high pressure
works for PMMA, Polyamide, PEEK
173
What is the composition of PMMA?
```
Powder
Polymethyl methacrylate granules
Initiator
Pigments, Dyes & Opacifiers
Plasticisers
Synthetic fibres (nylon)
```
Liquid
Methyl methacrylate monomer
Inhibitor (hydroquinone)
Cross linking agent
174
What is cold cure/auto cure used for?
Mainly used for repairs or attaching teeth to a CoCr RPD
175
Why does cold cure have more porosity?
Has a lower molecular weight so more porosity which is less dense, soft, weaker and is prone to discolouration.
176
What does high impact PMMA contain a co-polymer of?
butadiene and styrene
Results in a dispersion of rubber inclusions.
177
What materials can denture teeth be made out of?
Acrylic
Highly crossed linked acrylic
Composite
Ceramic
178
Why may denture wearers get irritant contact dermatitis?
usually associated with the release of residual monomer
Delayed hypersensitivity (Type IV)
179
Why do dentures need relining?
Carried out when denture becomes ill-fitting due to bone resorbtion.
180
What do you usally reline a denture with?
conventional PMMA.
Cold cure resin may be used if this is to be a temporary measure or the procedure is being carried out on an RPD
181
How is a denture relined?
Remove undercuts & periphery chairside
Take an impression (ZOE or Silicone)
Send to lab, Model is cast
Vertical dimension recorded (articulator or reline jig)
Impression material replaced with wax
Usual processing to replace wax with acrylic
182
What are the issues with Tokuso chairside reline material?
Remove too soon – distortion
Remove too late – exothermic reaction
Residual monomer
Colour retention
183
Why may soft liners be used?
It absorbs shock between the hard base of your denture and your gums. Soft liners can be used when creating new dentures or retrofitted into existing dentures. Processed soft liners provide comfort and relief for individuals with receded and flattened gum tissues that don't respond well to the stress of dentures.
184
What are the requirements of a soft liner?
```
Low elastic modulus
Retain low elastic modulus
High resilience
Good adhesion to denture base
High tear strength
Biocompatible
Antibacterial
Dimensionally stable
Good surface wettability
```
185
What materials can be used for a soft liner?
Plasticised Heat cured acrylic
e.g Coe Super Soft
Silicone rubber
Cold Cured - e.g Flexibase, TSR
Heat cured - e.g. Molloplast-B
Silicone/Acrylic co-polymer
e.g. Flexor
186
What are the differences between silicone based and acrylate based soft liners?
Silicone based:
```
Highly resilient
Retain softness
Weak bond to acrylic
Susceptible to growth of candida
Poor tear strength
No permanent deformation
Poor wettability
Needs regular replacement
```
Acrylate based:
```
Not as resilient as silicones
Go hard with time
Resistant to bacterial growth
Excellent bond to acrylic
Acceptable tear strength
Susceptible to creep
Good wettability
needs regular replacement
```
187
What are tissue conditioners?
These are temporary linings that allow traumatised tissue to recover before carrying out definitive treatments
Tissue conditioning is an effort to restore the health of the tissues of the denture foundation area before master impressions are made by relining the dentures with temporary denture reliners.
188
What is the composition of tissue conditioners (visco gel)?
Polyethylmethacrylate (low Tg)
Butyl phthalyl glycolate (plasticiser)
Ethyl alcohol (solvent)
