Removable Prosthodontics Flashcards
1
Q
Name the three parts of a surveyor
A
- Surveyor tools
- Movable arm and tool holder
- Adjustable platform
2
Q
What is a dental surveyor?
A
“A paralleling instrument used in the construction of a dental prosthesis to locate and delineate the contours and relative positions of abutment teeth and associated structures”
3
Q
What are the two main aims and objectives of surveying?
A
- Determining the most desirable path of denture placement
- Identifying proximal tooth surfaces that are or need to be parallel, so they cant act as guiding planes during placement and removal
4
Q
Name the four surveying tools
A
- Analysing rod
- Graphite marker
- The undercut gauge
- The chisel
5
Q
what is the function of the analysing rod?
A
Analyses tooth and tissue undercuts and determines the path of insertion for the denture
6
Q
What is the function of the graphite marker?
A
To scribe tooth and tissue undercuts on the model
7
Q
What is the function of the undercut gauge?
A
Measures desired amount of undercut for the clasp material used
8
Q
What is the function of the chisel?
A
Used to trim the blocked out undercut areas on the model
9
Q
What is the purpose of the universal joint?
A
It allows the platform of the surveying table to be moved in any direction
10
Q
What is meant by the “path of displacement”?
A
The path taken when the denture is dislodged in function
11
Q
What is meant by the “path of insertion”?
A
Path of denture to seat it
12
Q
If the model is at zero tilt, what will this mean in regards to the path of insertion and displacement? What is the consequence of this?
A
The path of insertion and displacement will be the same, therefore the denture will drop down
13
Q
If the model is at posterior tilt, what will this mean in regards to the path of insertion and displacement? What is the consequence of this?
A
The path of insertion and displacement will differ, therefore the denture will have more retention
14
Q
why is it unsuitable to have an anterior tilt of the model on the survey table?
A
Due to the space created between the analysing rod and tissue, the finished denture would also be fabricated with this space
15
Q
Define, no space between analysing rod and tooth.
A
Non undercut
16
Q
Define, space between analysing rod and tooth
A
Undercut
17
Q
Once the path of insertion is decided, where are lines drawn on the model and why?
A
Lines drawn on both sides of model and one on the back using the analysing rod. This allows model to be put back on surveyor at the same angle at a later date
18
Q
In regards to the survey line, where is the undercut area found?
A
Below the survey line
19
Q
In regards to the survey line, where is the non-undercut area found?
A
Above the survey line
20
Q
What two pieces of information can be obtained from a survey line?
A
- Where the undercut and non undercut areas are on a tooth
- The type of survey line indicates what retentive component is required to obtain the denture
21
Q
What type of clasp is suitable for a diagonal survey line? (Give two examples of clasp materials)
A
Occlusally approaching clasp (e.g. stainless steel or cobalt chrome)
22
Q
What clasp is suitable for high survey line?
A
Gingivally approaching clasp
23
Q
What clasp is suitable for low survey line?
A
Gingivally approaching clasp
24
Q
What is the benefit of a gingivally approaching clasp compared to occlusally approaching clasp?
A
Gingivally approaching clasp is less visible so better aesthetically
25
A gingivally approaching clasp only contacts tooth surface at its tip. True or false?
True
26
A cobalt chrome clasp can utilise what undercut measurement?
0.25mm
27
A stainless steel clasp can utilise what undercut measurement?
0.5mm
28
A gold clasp can utilise what undercut measurement?
0.75mm
29
What are the 4 components that make up a denture?
1. PMMA acrylic plate
2. Saddle areas
3. Clasps
4. Occlusal rests
30
which part of the denture is a major connector?
The plate (either PMMA acrylic or cobalt chrome)
31
what is the purpose of the saddle areas of a denture?
They consist of the replacement teeth and flange extensions
32
What part of a denture is the retentive component?
Clasps
33
What are the two types of clasps materials you can get?
Stainless steel or cobalt chrome
34
What are the 3 functions of occlusal rests?
1. Provide support for denture
2. Directs occlusal loads down the long axis of the teeth
3. Can provide indirect retention
35
What is the benefit of using a PMMA plate over a cobalt chrome plate?
PMMA is very affordable, whereas cobalt chrome is more expensive
36
What is the benefit of using cobalt chrome plate over a PMMA plate?
Cobalt chrome is thinner so much more comfortable for patient, also it is stronger so doesn’t fracture as easily as PMMA plate
37
Name the part of a lingual bar that resists posterior uplift of the denture
Cummer arms
38
what is the minimum space allowed from sulcus depth to the gingival margin in order to prescribe a lingual bar?
7mm space
39
What are the two implications for use of lingual bar?
- it covers less gingival margins than cobalt chrome plate
- should be used where there is spacing between anterior teeth
40
In what situation can a dental bar not be used?
When there is spacing between anterior teeth
41
What is the minimum total crown height required for a dental bar to be used?
9mm
42
what are the three advantages of a Dental D acetyl resin clasp?
1. Very flexible
2. Can engage deeper undercuts than metal clasps
3. Available in a variety of tooth shades
43
Give two examples of types of gingivally approaching clasps
1. T clasp or roach T
2. I Bar clasp
44
Name the 5 different upper major connectors that can be used in a denture
1. PMMA plate
2. Mid palatal bar (cobalt chrome)
3. Posterior bar (cobalt chrome)
4. Skeletal or ring design (cobalt chrome)
5. Horseshoe design (cobalt chrome)
45
what is the typical width range for a mid palatal, posterior or anterior bar?
Between 7-12mm
46
Why is a reciprocal component required on a denture?
In order to prevent tooth movement
47
Why might you choose an anterior tilt of the casting model when surveying over a posterior?
Because the denture will eventually fit with no anterior spacing, there may be a larger posterior under-cut but this should be relatively easy to clean and won’t be as visible as an anterior undercut would be if a posterior tilt were used.
48
What is a partial denture?
A denture where some natural teeth remain in the jaw
49
What is a complete denture?
A denture where there are no natural teeth in the jaw, so artificial teeth replace them all
50
What are the materials that can be used to make partial dentures?
PMMA or cobalt chromium
51
What are three main reasons that we make partial dentures?
1. Appearance
2. Speech
3. Mastication
52
What is lateral tongue spread?
When there are missing posterior teeth, the tongue can spread into the space where natural teeth previously occupied
53
What is an obturator?
A prosthetic device that is bonded onto denture and closes/blocks opening, such as a Maxillofacial defect in the palate
54
If there’s spacing between teeth, or teeth don’t meet each other properly, what three things could happen?
1. Over-erruption of teeth
2. Drifting of teeth
3. Tilting of teeth
55
What is a shortened dental arch?
Where all the molar teeth are lost
56
What are the 7 negatives of partial dentures?
1. Caries
2. Gingivitis
3. Periodontitis
4. Gingival stripping
5. Plaque accumulation
6. Overloading of natural teeth
7. Oral mucosal problems
57
What is the main negative consequence of partial dentures?
Caries
58
How do dentures cause gum stripping?
Because a denture will not sit absolutely firmly in the mouth, there will always be some sort of movement. Over time, the bone shrinks back under the denture causing it to “rock”. This causes gum recession.
59
Why does denture stomatitis occur?
When a patient wears their denture all the time, including at night. Poor denture hygiene.
60
What fungi causes denture stomatitis?
Candida albicans
61
In partial dentures, where is the most common place to find plaque accumulation?
Around clasps
62
what is an edentulous saddle?
A saddle with no teeth or where there are missing teeth
63
What is a free end saddle?
A saddle where the back teeth are all missing
64
What is a bounded saddle?
Where there is a natural tooth on either side of a gap
65
how many Kennedy classifications are there?
4
66
What Kennedy class is this:
Bilateral free end saddle
Class I
67
What Kennedy class is this:
Single bounded saddle crossing the midline
Class IV
68
What Kennedy class is this:
Unilateral free end saddle
Class II
69
What Kennedy class is this:
Single bounded saddle not crossing the midline
Class III
70
What Kennedy class is essentially missing front teeth?
Class IV
71
When are modifications used to refine the basic Kennedy classifications?
If more than 1 edentulous saddle is present
72
Which Kennedy class cannot have modifications?
Class IV
73
What should you use to define the main Kennedy classification when there are modifications?
The most posterior saddle
74
How many clinical visits are there to creating a partial denture?
7
75
How many lab stages are there to creating a partial denture?
4
76
when planning to make partial dentures, what occurs in the first clinical visit?
History and examination, and treatment planning
77
When examining the occlusion in order to make a partial denture, what are you looking for initially?
Index teeth
78
what are index teeth?
A natural tooth in one jaw has a contacting facet or cusp which meets the opposing tooth in the other jaw
79
when planning to make partial dentures, what occurs in the 2nd clinical visit?
Recording of primary impressions
80
when planning to make partial dentures, what occurs in the 1st lab stage?
- Production of primary casts in plaster
- production of record blocks
81
What are record blocks?
Constructed out of wax, these are used to record the occlusion
82
In what situation would record blocks not be required to make a partial denture?
If there is sufficient index teeth
83
When planning to make partial dentures, what occurs in the 3rd clinical visit? (This stage is not always required)
Recording of the occlusion
84
when planning to make partial dentures, what occurs in the 2nd lab stage?
Surveying of articulated casts, design of partial denture, and construction of special tray
85
What is the purpose of surveying?
Gives information on:
- the path of insertion of a denture
- areas around teeth that may stop denture from seating
- areas around the teeth that are useful for holding (or clasping) the denture in place
86
when planning to make partial dentures, what occurs in the 4th clinical visit?
- Discussion of denture design with patient
- tooth modifications if necessary
- secondary impressions taken in special tray
- select artificial teeth, shape shade and mould
87
What materials can be used to take a secondary impression?
Alginate or silicone
88
when planning to make partial dentures, what occurs in the3rd lab stage?
- preparation of secondary working casts
- construction of casting
- setting of artificial teeth in wax
89
How is a cobalt chrome denture cast constructed?
Initially it is made in wax, then by a technique called the lost wax technique, it is cast in cobalt chromium.
90
when planning to make partial dentures, what occurs in the 5th clinical visit?
Trial insertion of dentures
91
At the try in stage, what do you need to assess?
- extensions
- adaptation
- retention
- occlusion
- appearance
92
at try in stage, what is important to let the patient know about their dentures?
That they will feel looser at this stage than when they are finished
93
when planning to make partial dentures, what occurs in the 4th lab stage?
Processing of the denture:
- conversion of wax parts to PMMA.
- artificial teeth secured into denture
94
How is wax converted to PMMA?
Wax trial denture placed in a flask, the wax would be boiled out and the acrylic would be injection moulded into the flask
95
when planning to make partial dentures, what occurs in the 6th clinical visit?
Insertion of final denture
96
when planning to make partial dentures, what occurs in the 7th clinical visit?
Review patient after a year
97
what is a complete denture?
A removable dental prosthesis that replaces the entire dentition and associated structures of the maxillae and/or mandible
98
What material are complete dentures usually made of?
- PMMA (mostly)
- Nylon (if patient allergic to PMMA)
99
What are the two types of complete dentures that can be made?
1. Replica dentures
2. Conventional dentures
100
What are replica dentures?
“Copy dentures”- they are based on existing dentures
101
what are conventional dentures?
Dentures made from scratch
102
How is a replica denture made?
1. Take mould of existing denture in putty
2. Produce a copy of the denture in wax and shellac
103
What is the health gain for the patient from use of complete dentures?
- Appearance
- masticatory function
- speech
- cranial-facial function
- societal function
- self esteem
104
Which denture is more likely to have issues with retention and stability? The upper or lower denture? And why?
The lower, because it sits on the residual ridge so the tongue moves around beside it and can tend to lift it
105
what are the two most common oral mucosal problems due to dentures?
1. Denture stomatitis
2. Denture hyperplasia
106
What is denture stomatitis?
When the denture bearing area is red and has sloughing, largely due to the denture being worn overnight and not cleaned properly
107
What fungi tends to cause denture stomatitis?
Candida albicans
108
What is denture hyperplasia?
Where the tissues become chronically inflamed causing overgrowth of fibrous tissue. Usually caused by flange on denture digging in.
109
If a patient uses denture fixative what does this suggest?
That dentures are inadequate
110
When might you choose to use a closer fitting impression tray?
In a situation where the patient is edentulous and they have a resorbed ridge
111
what materials could be used for a close fitted tray?
Silicone or zinc oxide euganol
112
when placing artificial teeth on the mount casts, what teeth should be placed first?
Anterior teeth
113
What is the benefit of replica dentures over conventional dentures?
One less clinical and lab stage as the master impressions and occlusion stage happens at the same visit
114
What material do you use to record the occlusion of a replica denture?
Silicone paste
115
What are the 7 main questions to ask a patient in a denture history?
1. What age are the dentures?
2. Are the dentures a matched set?
3. What are the most recent set of dentures you have worn?
4. When did you get your 1st dentures?
5. How many sets of dentures do you own?
6. Are they acrylic or Co/Cr?
7. Are they a success or failure?
116
What are the 5 main medical conditions to look out for in a medical history in regards to making dentures and why?
1. Neuromuscular problems, such as MND. (Patient cannot control jaw)
2. Tremor, such as Parkinson’s disease. (Can be very difficult to do a jaw registration)
3. Stroke (affects face and tongue muscles)
4. Dementia (affect patients understanding of treatment)
5. Sjögren’s syndrome (causes xerostomia)
117
What information is needed from a social history in order to make dentures?
- mobility of teeth
- does the patient have barriers to treatment
- alcohol/smoking
118
In an extra-oral examination for a denture case, what are you looking for?
- signs of TMJ dysfunction
- facial pathology
- facial contours
- overall appearance of dentures
119
What combination of bacteria causes angular chelitis?
1. Candida albicans
2. Beta-haemolytic streptococci
3. Staph aureus
120
When may angular chelitis present in a denture case?
In patients wearing very worn/old dentures which make the mouth over-close, or if a patient has dry mouth
121
What can cause denture stomatitis?
- poor denture hygiene
- anaemia
122
why does denture hyperplasia occur?
Usually because the denture is digging in somewhere causing blanching and trauma to the area
123
How would you manage denture hyperplasia?
Take an acrylic bur and trim the denture so to clear the area of trauma
124
What are the three issues you are scanning for when assessing occlusion, before denture construction?
1. Over-eruption
2. Drifting
3. Tilting
125
What does peri-oral opening mean?
How big your oral orifice is
126
In an edentulous patient, what is the primary support of the upper jaw?
Hard palate
127
In an edentulous patient, what is the secondary support of the upper jaw?
Ridge crest
128
In an edentulous patient, what are the primary supports of the lower jaw?
Buccal shelf and retro-molar pad
129
In an edentulous patient, what are the secondary supports of the lower jaw?
Ridge crest and genial tubercles
130
Define, the resistance to displacement of a denture away from the ridge.
Retention
131
define, the ability of a denture to resist displacement by functional stresses.
Stability
132
Define, the resistance of vertical movement of a denture towards the ridge.
Support
133
Define, the degree of fit between a prosthesis and supporting structures.
Adaptation
134
what happens to adaptation of a denture after it is worn for a long time?
Decreases
135
What is a diagnostic wax up?
A special test where you make a wax up model which you can articulate and show the patient
136
Give two examples of pre-prosthetic treatment?
1. Improving OH to get the underlying tissues back to heath
2. Restoring a natural tooth
137
In what case what you refer a denture patient to oral medicine?
If they have persistent oral mucosal problems (e.g. ulcer)
138
Why are impressions necessary in dentistry?
1. For construction of appliances ( dentures, crowns, bridges etc.)
2. Pre & post treatment monitoring
3. Show progression of tooth wear (bruxists)
4. Record keeping
5. Medico-legally/regulations
139
What should the ideal primary impressions record?
“The clinical relevant landmarks without excessive tissue distortion”
140
what are the clinically relevant landmarks to record on a primary impression prior to making a partial denture?
Natural teeth and denture bearings areas
141
what are the clinically relevant landmarks to record on a primary impression prior to making a complete denture?
Denture bearing area
142
What is the denture bearing area?
The edentulous ridge and surrounding sulci
143
In partial denture construction, what are primary impressions used for?
1. Treatment planning
2. Used to construct models
3. Examination of occlusion on articulator
4. Surveying and determination of path of insertion and denture design
5. Construction of special trays
144
In complete denture construction, what are primary impressions used for?
1. Treatment planning
2. To construct models
3. To construct special tray
145
what materials can impression stock trays be made out of?
Metal or plastic
146
when would dentate stock trays be used to take an impression? What is the disadvantage of dentate trays and how can this be resolved?
For individuals with partial or entire dentition. They do not seat well over edentulous areas (this can be improved using putty of edentulous areas before taking impression)
147
what material is used to make denture impressions?
Alginate
148
when are master impressions taken for partial denture construction?
After denture design, tooth preparation, record of occlusion, and special tray construction
149
when are master impressions taken for complete denture construction?
Prior to record of occlusion, to record denture bearing area, functional depth and width of sulci
150
In what situation would custom special trays not be used to take master impressions?
When making replica complete dentures which use a replica of the previous patient dentures as the tray
151
What is the objective of recording master impressions for partial dentures?
To record the tissues of the denture-bearings areas, the teeth and in addition the functional width and depth of sulci
152
What is the objective for recording master impressions for complete dentures?
To record the tissues of the denture-bearings areas and the functional width and depth of sulci
153
what are the important anatomical structures in the upper denture bearing area?
- labial frenum
- palatine rugae
- buccal sulcus
- Hamilcar notch
- palatine foveae
- vibrating line
- tuberosity
- palatine raphe
- buccal frenum
- incisive papilla
- labial sulcus
154
what are the important anatomical structures in the lower denture bearing area?
- labial frenum
- buccal frenum
- lingual sulcus
- buccal shelf
- retromolar pad
- buccal sulcus
- lingual frenum
- labial sulcus
155
What is the palatine foveae?
Two tiny dimples at the back of the palate, just behind where the hard and soft palate meet.
156
What is the vibrating line?
Junction of the hard and soft palate. It is called vibrating line because of you say “ahhh” you can see where the soft palate vibrates.
157
Denture should never extend over palatine foveae and vibrating line. True or false?
True
158
What anatomical feature of the lingual sulcus can be quite prominent and sometimes give discomfort under a lower denture?
Mylohyoid ridge
159
What three materials can special trays be made from?
1. Visibly light-cured resin PMMA (acrylic)
2. Shellac
3. Self-cure PMMA (acrylic)
160
What are the advantages of using a visibly light-cured resin material for special trays?
- pre-rolled sheets
- easy to mould
161
What are the disadvantages of using a visibly light-cured resin material for special trays?
Very rigid, problems removing from model
162
What are the advantages of using a shellac material for special trays?
Good for deep undercuts, softens with heat and can be removed easily from model
163
What are the disadvantages of using a shellac material for special trays?
Brittle and fractures easily
164
What are the disadvantages of using a self-cure PMMA material for special trays?
Problems rolling an even layer
165
How are special trays usually made?
By placing a thickness of wax over a primary cast
166
What does the thickness of wax depend on when making special trays?
Depends on the properties of the impression material to be used
167
What should the thickness of wax (spacing) on the special tray be in order to use alginate for a secondary impression?
3mm
168
What are the advantages for using special trays for secondary impressions?
- accurate peripheral extension
- uniform thickness of material
- reduced amount of material to be used so less discomfort for patient
- record dentures bearing areas more accurately than primary impression
169
Ideally, what should the spacing be between the tray flange and the teeth/denture bearing areas in the patients mouth?
4mm
170
If a tray is not moulding to certain areas of the mouth, what three materials could be used to modify the tray?
1. Greenstick/wax
2. Putty in edentulous areas
3. Thermoplastic red composition in edentulous areas
171
What are the 5 main steps to taking a primary impression?
1. Apply thin layer of adhesive to tray
2. Load tray with alginate
3. Seat tray in mouth (never leave unsupported)
4. Border mould
5. Remove with sudden sharp movement
172
What specific border moulding has to be done for lower impression that isn’t done for upper impressions?
Ask patient to stick tongue out so that you can border mould the lower anterior lingual sulcus
173
What is the advantage of using greenstick ( also known as mould stops?)
1. Helps with positioning of tray
2. Maintains space for material to flow into tray
3. Allows consistent placing of tray
174
What do you NEED to use alongside use of greenstick on special tray and why?
Need to use Vaseline separator because greenstick is heated with bounsen burner so would be too hot on its own and potentially burn patients mouth
175
what does the extension of the special tray for master impressions have to measure in comparison to the sulcus depth in order to allow for border moulding?
Approx 2mm
176
which type of impression requires use of less alginate. Primary to master?
Master impressions
177
how would you handle alginate impressions?
- must be kept moist and cast asap
178
what are the necessary steps to disinfection of impressions before being sent to lab?
1. Rinse in running water
2. Disinfect for 2 mins in actichlor solution or sodium hypochlorite
3. Rinse impression throughly
4. Cover impression wit damp paper towels
5. Label and place in laboratory bag
6. Indicate impressions have been disinfected on lab prescription and get signed of by clinician
179
what is the concentration of actichlor used to disinfect impressions?
10,000ppm (1%)
180
What type of denture material would be used where the dentures life expectancy is short, additions to the denture may be likely and where few natural teeth remain in the mouth?
Acrylic (PMMA)
181
What are abutment teeth?
The teeth that support a partial denture
182
What is a bounded saddle?
Where there are abutment teeth at either end of the saddle
183
What is a free end saddle?
Where there is a single abutment tooth at the mesial end of the saddle
184
what is a critical abutment tooth?
A tooth which the loss of will convert a bounded saddle into a free end saddle
185
What are the 4 main roles of the major connector (plate or bar)?
1. Unites partial denture saddles
2. Provides bracing
3. Provides indirect retention
4. Acts as splint (holds everything in place)
186
What is meant by ‘bracing’?
Resistance to lateral movement of the denture (stops the denture moving sideways)
187
What crown height is required for a dental bar to placed? How is this measurement divided to ensure proper fit of denture?
9mm.
- 5mm for height of bar
- 2mm above and below the bar for gingival clearance
188
What space is required for a lingual bar to placed? How is this measurement divided to ensure proper fit of denture?
7mm.
- 3.5mm for bar
- 3.5mm clearance from gingival margin
189
what is a split lingual plate?
Where there are areas cut out in the denture design, especially for anterior teeth, so that the metal does not show through spacing in teeth.
190
what is a swing lock removable partial denture?
A design which has a labial/buccal retaining bar, hinged at one end and locked with a latch on the other end. It also has a reciprocal lingual plate.
191
when would swing lock dentures be considered?
Where retention of normal lower denture is an issue, due to minimal undercuts.
192
When creating a denture design, what areas should ideally not be covered for hygiene reasons?
Gingival margins
193
What are the two available designs for temporary upper dentures when the patient has only lost one anterior tooth?
1. Spoon denture
2. T-denture
194
How is a t-denture more retentive than a spoon denture?
Spoon denture does not have any clasps. Whereas t-denture has clasps and extends onto the palatal aspect of molar teeth
195
what is the typical width of a mid palatal bar?
7-12mm
196
what are minor connectors?
The connecting component between the major connector or base of partial denture and other units such as clasps and rests
197
In a situation where a lower natural tooth is occluding onto the upper ridge of a denture, so much so that it may fracture, what modification could be made to the denture to prevent this?
Use of a striking plate. They are made out of cobalt chromium and have little tags which attach to the acrylic of the denture. The lower teeth can occlude against this without risk of fracturing the denture.
198
What are the 4 most important factors that denture retention is dependant upon?
1. Adequate film of saliva between denture and soft tissues
2. Quality and amount of saliva present
3. Good base adaptation
4. Good border seal
199
How are dentures retained?
- physical forces created by a film of saliva between the denture base and mucous membrane
- muscle activity of lips, cheek and tongue
200
Why occlusally approaching clasps more rigid than gingivally approaching clasps?
Because they are shorter
201
Which type of stainless steel clasp design has a more efficient bracing component. Occlusally approaching claps or gingivally approaching clasps?
Occlusally approaching clasps
202
what clasp is most suitable for a critical abutment tooth, especially when there is an undercut on the lingual aspect?
Ring clasp
203
what are the three types of gingivally approaching clasps?
- T-roach clasp
- I-bar clasp
- L clasp
204
What are the 5 main “musts” for clasps?
Must…
1. Be passive when seated, no force on the tooth
2. Flex to enter and be removed from undercut
3. Have point of action at tip
4. Have terminal 1/3 below the survey line
5. Be opposed by reciprocal component
205
what are the two most common reciprocal components used in dentures?
1. Base plate extension
2. Reciprocal clasp
206
Name two unusual variations of occlusally approaching clasps
- reverse action clasp
- ball ended clasp
207
what is the purpose of a reverse action clasp?
It engages undercut on same side that clasp originates. (E.g. clasp originates mesially so engages undercut mesially)
208
what is the purpose of a ball ended clasp?
Engages undercut in interproximal area (usually for teeth that have very minimal to no undercuts)
209
What clasp material is able to engage undercuts at a depth of 0.25mm?
Cobalt chromium
210
What clasp material is able to engage undercuts at a depth of 0.5mm?
stainless steel
211
What clasp material is able to engage undercuts at a depth of 0.75mm?
Gold
212
Stainless steel clasps can be added directly to co/cr denture. True or false?
False. Stainless steel cannot be soldered, therefore must be attached mechanically to PMMA, not co/cr.
213
What tooth-coloured clasp material could be used for very deep undercuts?
Thermoplastic copolymer e.g. dental d
214
Should the force required to flex the clasps over the maximum bulbosity of the teeth be greater or lesser than the force that’s attempting to dislodge the denture?
Greater
215
Which clasp has a better retentive ability, gingivally or occlusally approaching clasps?
Gingivally approaching clasps
216
The forces required to displace a clasp vary with what 4 factors?
1. Depth of undercut engaged
2. Length/cross section of clasp
3. Flexibility of arm depending on what material is used
4. Angle of approach of clasp (gingival or occlusal)
217
When would you choose to add composite to a tooth to help a clasp engage better?
When there is no undercut on buccal aspect of a tooth and you cant clasp lingually. Adding composite will create an undercut for clasp to engage.
218
when would you choose to selectively grind a tooth in preparation for a denture?
To create a depression in enamel for ball ended claps to engage
219
What are guide planes used for? And how?
To improve stability of a denture. They make surfaces of teeth parallel to each other at either end of saddle area, this then restricts path of insertion to the direct path that follows the guide plane.
220
What are the 4 main benefits of guide planes?
1. Increase stability
2. Reciprocation
3. Prevention of clasp deformation
4. Improved appearance due to reduction of stagnation are at gingival margin of teeth
221
What is the RPI system used for?
To prevent distal movement/tipping of abutment tooth to a free end saddle. It reduces stress put on abutment tooth when denture is loaded.
222
what does RPI stand for?
R= mesial rest
P= distal guiding plate
I= I-shaped retentive clasp
223
What is a precision attachment?
A pre-made device that joins an abutment and the partial denture and supports it
224
When we say we want a denture to be ‘dimensionally accurate’, what is meant by this?
So that it won’t warp or contour between lab stages
225
What material is used for the impression stage of replica dentures?
Putty
226
How many scoops of putty is required for a replica denture impression?
4-5
227
How much activator in cm is required per scoop of putty? (Depends on manufacturer)
3cm per scoop
228
What separating medium should be used to ensure that the upper and lower replica dentures do not stick to one another?
Vaseline
229
What material should be used to fix a fault in replica putty impressions?
Perfecting paste
230
What will the technician cut in the polished surface of the replica impression in order for wax to be poured into the mould to make replica block?
Sprue holes
231
How do you make perfecting paste ready to use?
It’s is a two part product, mixed in equal parts with a catalyst which forms a fairly runny but sticky paste that can be used to correct faults
232
If a denture base is under extended, what material can be used to temporarily correct this before replication?
Green stick
233
How would you modify a denture with a palatal metal chrome plate to allow for a good quality impression to be taken?
Metal chrome plate is thin. Use wax over chrome to thicken up area, this will accommodate shellac and wax of the replica block
234
How would you manage an overextended denture base?
- replicate denture as normal
- prescribe on lab card for shellac to be shorter than normal in that specific area OR remove overextension from replica chairside
235
In replica denture construction, what material is used to form the special tray part of the replica block?
Shellac (with wire placed in it to prevent fracture)
236
Why in complete denture construction, are secondary impressions taken before recording the occlusion?
This is to ensure we have occlusal blocks as stable and firm as possible before recording the occlusion. Recording the occlusion in edentate patient is challenging so a firm base to work from helps.
237
in partial denture construction, why is the occlusion recorded before taking secondary impressions?
This is to enable a design to be made for the denture, which considers inter-occlusal space and plans for any tooth modifications that need to be made.
238
What materials could be used for replica denture master (wash) impressions?
light bodied silicones:
1. rapid liner
2. Aquasil
239
which light bodied silicone is most commonly used for master (wash) impressions?
Rapid liner
240
What light bodied silicone can be used for impressions of a particularly atrophic ridge?
Aquasil (it has more body than rapid liner)
241
When would a closed-mouth technique be used for taking secondary impressions?
- if there was no major occlusal discrepancies between blocks
- most useful when there is an atrophic ridge
242
How do you take a closed-mouth impression?
1. Seat upper replica block and then lower block with impression material applied to it
2. Get patient to bite together
3. Patient should maintain even pressure whilst you support mandible and perform border moulding
243
when constructing replica dentures, what two processes are completed in the one single clincial visit?
- master impressions
- recording of occlusion
244
During the occlusion stage, what is being recorded?
The vertical and horizontal jaw relations
245
During the occlusion stage of replica dentures, what two things do you need to prescribe for?
- tooth position
- arch form
246
When assessing vertical jaw relationship, what are we looking for?
Presence of freeway space
247
When assessing horizontal jaw relationship, what are we looking for?
Reproducible path of closure
248
Define, the space between occlusal surfaces when mandible is in rest position.
Freeway space
249
What is the average measurement of freeway space?
2-4cm
250
what is another term for rest position?
Postural position
251
Define, the position that the mandible passively assumes when the mandibular musculature is relaxed and patient is upright.
Rest/postural position
252
define, the resting face height (the vertical dimension with the mandible in the rest position)
Rest vertical dimension (RVD)
253
What equation should be used to work out hw ‘tall’ dentures should be? (OVD)
OVD= RVD-FWS
254
What are the two parallel lines that need to be considered when assessing occlusal and incisal planes when recording occlusion?
1. Alar-tragal line (occlusal plane)
2. Inter-pupillary line (Incisal plane)
255
At rest, what level should incisors sit below lip level?
1mm below lip level
256
what is always the last modification that should be made to replica block at this stage, if required?
Correcting the centre line
257
If the teeth are positioned on the record block too far forward, what are the consequences?
The lip will bash the denture when it ,over and contracts
258
If the teeth are positioned on the record block too far lingually, what are the consequences?
There is insufficient space for tongue, this will cause denture instability
259
How would you assess labial fullness?
Look at the patient from side on, assess upper lip and nasal Philtrum
260
If the philtrum appears too flattened, what may this suggest?
That the prosthesis is too bulky
261
Define, when the mandible is raised from the rest position by balanced muscle activity and tooth contact is made.
Muscular position
262
Define, the Jaw relationship in which maximum occlusal contact occurs.
Intercuspal position (ICP)
263
In a denture wearer which mandibular positions should coincide?
Muscular position and ICP
264
If a patients muscular position does not seem to be retrainable and when their occlusion is different every time they close/ not reproducible, what position can the mandible be manipulated into which will give a reproducible occlusion and is safe for the patient to function in?
Retruded contact position (RCP)
265
What is another commonly used term for RCP?
Ligamentous position
266
What are the 4 key things you MUST prescribe for before the try in stage of replica denture construction?
1. Shade of tooth
2. Mould of teeth (anterior and posterior)
3. Tooth arrangement (straight or twisted?)
4. Type of articulator to be used
267
What type of articulator is most commonly used for complete dentures?
Average value articulator
268
What are the three ways in which support can be achieved for a removable prosthesis?
1. Teeth (toot-borne support)
2. Mucoperiosteum (mucosa-borne support)
3. Both (tooth/mucosa borne support)
269
what is the most favourable form of support for a removable prosthesis?
Tooth-borne support
270
In a partially edentate patient, what is the most common form of support used in a removable prosthesis?
Tooth/mucosa borne support
271
What parts of a denture is mucosal support gained from?
- saddles and connectors
272
what is the main downside of mucosal support for removable dentures?
There is a degree of compressibility to the mucosa, so when the denture is loaded it may move around.
273
What part of a natural tooth supports a removable denture?
use of the periodontal ligament.
- The force is transmitted through the tooth from the denture to the PDL and ultimately the underlying bone.
274
where will an occlusal rest sit on the tooth?
On the occlusal surface where the marginal ridge is
275
How deep and wide should rest seats be?
1mm deep
1-2mm wide
276
How do we design a cingulum rest so that the force on the tooth is vertical?
By cutting a small seat on the palatal or lingual aspect of the tooth, in the enamel layer, this means the rest can sit on the tooth rather than leaning on it
277
What are the 4 ways that tooth support is gained for a removable prosthesis?
1. Occlusal/cingulum rests
2. Onlays
3. Overdenture abutments
4. Connectors
278
what are onlays?
These work in a similar way to occlusal rests but cover a larger area of the occlusal surface, these are useful when there is significant wear on a tooth.
279
What is an overdenture abutment?
“A removable prosthesis that covers and rests on one or more remaining natural teeth, the roots of natural teeth, and/or dental implants”
280
what is the purpose of an overdenture abutment tooth?
It will provide support, retaining a tooth like this will preserve alveolar bone and help with denture retention
281
What Kennedy classification allows for an ideal tooth-borne support for a removable denture? And why?
Kennedy class III, because it will have a bounded saddle.
282
What does indirect retention prevent?
The displacement of entire saddle away from ridge
283
Give an example of a “fixed point” on a denture?
Clasps
284
How will cummer arms help improve indirect retention?
They have a bracing action, so will help prevent rotation of denture
285
What design would be a better option over a lingual bar and cummer arms, so to gain better indirect retention and why?
Lingual plate, as it covers a larger area so will have better bracing power.
286
What is the downside to a lingual plate?
- It covers more gingival margins, which may have a detrimental effect on periodontal health.
- it may also not be suitable for aesthetic reasons if there is spacing between teeth
287
what are the two principles we work with when designing a denture, considering how to best achieve indirect retention?
1. By placing the clasp axis as close as possible to the free end saddle
2. By placing the indirect retainers as far as possible from the free end saddle
288
how is a clasp axis formed?
Through the active part of two clasps on opposing sides of the arch (one is clasp axis major and the other clasp axis minor)
289
when there is more than one clasp on the side of an arch, which is determined as the major clasp?
The clasp axis which is closest to the free end saddle
290
What part of the clasp is the active part?
Terminal 3rd
291
What is an alternative design to a lingual plate connector which would free up the gingival margins, however unlikely to be used if there’s spacing between the teeth?
Lingual bar with continuous clasps
292
What are the 8 components that can be utilised when indirect retention is required on a denture?
- continuous clasps with lingual bar
- occlusal rests
- cummer arms
- anterior palatal arm and bar
- posterior palatal bar
- extension if palatal coverage
- dental bar
- embrasure hooks
293
What is an embrasure hook?
An extension into the embrasure above the contact area
294
What functions does the saddle of a denture perform?
1. Retention
2. Support
3. Bracing
295
What functions does the connector of a denture perform?
1. Support
2. Indirect retention
3. Bracing
296
What functions does the clasp of a denture perform?
1. Retention
2. Support
3. Bracing
297
What functions does the rests of a denture perform?
1. Support
2. Indirect retention
298
When would an putty primary impression be used over an alginate primary impression?
If the alginate impression is poor fit, or if the patient has a very resorbed ridge
299
What are the limitations of the perforated primary impression stock trays?
1. They rarely fit the mouth accurately
2. Often require modification with putty wax or green stick
3. May be difficult to obtain necessary border seal
300
Where should the operator be stood when taking an upper impression?
Stand behind patient
301
Where should the operator stand when taking lower impressions?
Stand in front of patient
302
When is it particularly useful to prepack the palate with impression material?
For some edentulous patients, especially when the palate is very high, it helps avoid air blows in this area.
303
Where should an upper impression extend to in the oral cavity?
To the post-dam area
304
Where should a lower impression extend to in the oral cavity?
Onto the retro molar pad
305
When evaluating your impression, what are the 5 aspects you’re looking to assess?
1. general adaptation (e.g. blow holes)
2. Appropriate Sulcus depth and shape
3. Tray placed correctly (ridge in centre of tray)
4. All appropriate landmarks are included
5. Impression is fixed to the tray
306
What 3 materials can be used for special trays?
1. Light cured acrylic resin
2. Heat/cold cured acrylic resin
3. Shellac
307
What is the most commonly used material for special tray in DDS?
Light cured acrylic resin
308
What are the advantages of special tray use?
1. Require less impression material than primary impression
2. Ensures even thickness of impression material (minimises tissue displacement + maximises dimensional stability of impression material)
3. Less bulky than primary imp. so more comfortable for patient
309
What are the two reasons a spaced tray would be used?
1. To ensure the thickness of impression material is uniform
2. Help to localise the tray during impression taking
310
What patient may require a lower tray with a finger rest on it?
Edentulous patients
311
Where are finger rests placed on lower edentulous trays?
Placed in region of 2nd premolar/1st molar
312
What is the purpose of a finger rest on a lower edentulous tray?
1. Allows finger to be placed on either side of the tray to ensure it is fully seated posteriorly and ensure more even distribution of pressure to the tissues
2. Helps stabilise tray in mouth
313
Why is shellac not routinely used as the material to construct a special tray?
As it is a brittle material and the handle tends to fracture off
314
What are the two techniques used for impression taking?
1. Mucocompression
2. Mucostasis
315
What is meant by taking a mucocompressive impression?
Pressure is applied to the mucosa so that the shape of the tissues under load is recorded, this results in a denture that fits better during function.
316
What is meant by taking a mucostasis impression?
Where minimum pressure is applied to the tissues to record their shape at rest, this results in a denture that fits better at rest.
317
What type of special tray would be used if undercuts were present and spacing was 3mm?
Spaced tray
318
What type of special tray would be used if spacing was 1mm and light viscosity materials for wash impressions were to be used?
Closed tray
319
How often does a fibrous (flabby) ridge occur in denture patients?
25% of the time
320
What are two ways that you can avoid compressing fibrous (flabby) tissue during impression recording?
1. Using a two stage technique
2. Using a single stage with perforated tray and low viscosity material
321
Describe the two stage techniques for impression taking when there is a fibrous (flabby) ridge present
1. Take a mucostatic impression of the anterior part- where fibrous ridge is (no pressure)
2. Take a mucocompressive loaded impression of the finer posterior ridge (more stable denture base)
322
How many stages are there to the clinical procedure of recording jaw relationship?
Three stages
323
what is stage 1 of recording jaw relationship? What needs to be assessed?
- record upper block on its own
- assess occlusal plane orientation and labial fullness, including anterior tooth position
324
What two planes are assessed when recording occlusal plane orientation?
- lateral plane
- anterior/posterior plane
325
what is stage 2 of recording jaw relationship?
- Trim the lower block to meet the upper block (at the correct OVD)
326
what is stage 3 of recording jaw relationship?
Look at tooth position and ensure teeth are in neutral zone
327
Define, the position where there is a maximum contact of the upper and lower teeth, independent of the condyle position.
Intercuspal position
328
Can intercuspal position change throughout life?
Yes, depends on the tooth relationships, teeth can move, drift to are lost throughout life.
329
Define, the position of closure produced by balanced muscle activity raising the mandible from rest to initial tooth contact.
Muscular position
330
What is another term used for retruded contact position?
Ligamentous position
331
If an edentulous patient does not have a reproducible muscular position, what position will be used to define horizontal jaw relationship?
Retruded contact position
332
Define, the guided occlusal relationship when the condyles are at their most retruded position in the joint cavities.
Retruded contact position
333
What ligaments in the TMJ limit RCP?
Lateral ligaments
334
Define, the distance between a set point on the maxilla and a set point on the mandible when the teeth are in maximum intercuspation.
Occlusal vertical dimension (OVD)
335
Define, the position of the mandible when patient is upright, at rest.
Rest vertical dimension
336
What is another term for rest position?
Postural position
337
how would you record the rest vertical dimension for an edentulous patient?
Always remove one of their dentures (usually the lower one) and ask the patient to lick their lips and let their mouth relax with their lips lightly touching
338
What is the equation used to work out freeway space?
RVD-OVD=FWS
339
What are the 3 main consequences of an excessive FWS?
- reduced masticatory efficiency
- “overclosed” facial appearance and cheek biting
- TMJ symptoms
340
What are the 2 main consequences of a reduced FWS?
- excessive load on denture bearing area
- continuous muscular activity resulting in pain
341
what are the three instruments that can be used to measure freeway space?
1. Willis gauge
2. Dividers (make a mark on nose and chin)
3. Mirror handle
342
What are the 4 steps in clinically recording occlusion?
1. Create and form the outline of the upper denture
2. Create and form the outline of the lower denture
3. Record intermaxillary relations
4. Select teeth
343
What material is used for wax jaw registration blocks?
Heat cured acrylic bases
344
What are the two materials that can be used to create conventional record blocks?
1. Shellac
2. heat cured acrylic bases
345
what is the disadvantage of using heat cured acrylic to create record blocks?
They destroy the master cast
346
what is the advantage of using heat cured acrylic to create record blocks?
It is rigid, accurate and stable
347
how would you instruct a patient into RCP?
Ask patient to curl tongue to the back of their mouth and close
348
If a patient is not able to reproduce muscular position and often protrudes with dentures, how would this effect choice of posterior tooth selection?
They would have cuspless posterior teeth as thus will allow them to slide around more between positions
349
in what situation would second molar teeth be left off dentures?
If patient has a resorbed ridge as this reduced load on the ridge
350
What 4 factors does selection of posterior teeth dependant on?
1. Condition of ridge
2. Ability to reproduce muscular position
3. Present denture
4. Patients age
351
What dentist factors may influence the choice of artificial teeth (& gums)?
- previous dentures
- age of patient
- size of facial skeleton
- racial pigmentation
- dentist perceptions
352
What patient factors may influence the choice of artificial teeth (& gums)?
- influence of others around them
- lifestyle/relationships & goals
- psychological factors- tooth loss
- perceptions of ageing
- smilorexia
- coercion
353
What is meant by smilorexia?
A disorder where someone has an irrational desire for the perfect smile
354
What are the 4 materials that can be used for artificial teeth?
- acrylic
- porcelain
- composite resin
- combinations
355
By in large, what material is used to make artificial teeth in DDS?
Acrylic
356
in what situation would porcelain be selected as the material of choice for artificial teeth?
When nylon dentures are to be used as patient has an acrylic allergy
357
what are the 7 factors that can result in wrong shade selection for artificial teeth?
- metamerism
- colour washout
- observer errors
- technical errors
- patient photographs
- family members
- patient preference
358
What is meant by “metamerism”
“ a phenomenon that occurs when two colours appear to match under one lighting condition, but not when the light changes”
359
What is meant by colour washout?
When you look so long that you can’t tell the differences between colours
360
What is the Leon Williams classifications for the shape of artificial teeth?
Classified faces into square, tapering or oval.
Inverted shape of the face corresponded to the shape of the maxillary central incisor.
361
What is the frush and fisher classification for the shape of artificial teeth?
Men should have square and angular teeth, women should have curved and rounded teeth.
362
What anatomical feature is used to determine placement/ central line of maxillary incisors?
Incisive papilla
363
where should the incisal edge of the maxillary incisors be in relation to the incisive papilla?
Approx 5.5mm in-front
364
What instrument should be used to measure distance from incisive papilla to the incisal edge of denture teeth?
Alma gauge
365
what are the two main changes to the facial appearance as we age, in regards to denture wear?
- attrition of the natural teeth
- loss of muscular tone in the lips and face
366
Why are denture posterior teeth narrower than natural posterior teeth?
1. Easier to masticate with
2. To leave sufficient room for the tongue
367
What line is a guide for the orientation of the incisal plane?
Inter-pupillary line
368
What line is a guide for the orientation of the occlusal plane?
The ala-tragal line
369
What is dynamic- balanced articulation?
When there is even occlusal contact on both excursive and protrusive movements
370
Define, “the static relationship between the incising or masticating surfaces of the maxillary or mandibular teeth or tooth analogues”
Occlusion
371
Define the position where there is maximum contact between opposing teeth
Intercuspal position
372
What are the two explanations for lower posterior teeth occluding onto an upper edentulous ridge?
1. Patient over closes
2. Over-eruption of the lower posterior teeth
373
What are the treatment options for a patient whose lower posterior teeth occlude onto an upper edentulous ridge?
1. Extract the lower posterior teeth
2. Use a striking plate in the upper posterior denture to allow teeth to close onto this instead of the ridge
374
What anatomical structure limits RCP?
Lateral ligaments of the TMJ
375
What are the three most common factors that can cause issues when articulating casts?
1. Air bubbles
2. Distorted impressions
3. Heel interference
376
What are occlusal (heel) interferences?
Undesirable occlusal contacts that prevent smooth movements of the mandible
377
Give the design sequence for a partial denture (in 7 steps)
1. Decide teeth being replaced
2. Design saddle areas
3. Select connector
4. Provide support
5. Provide retention
6. Include bracing elements
7. Select materials for clasps
378
What is the simplest Kennedy class to design and why?
Kennedy class III, because it has bounded saddles so better options for support (tooth support)
379
What are the three functions of an abutment tooth in relation to dentures?
1. Retention
2. Support
3. Bracing
380
What are 2 alternative prosthesis that can be utilised instead of a removable partial denture ?
1. Fixed bridgework
2. Implant retained restorations
381
What are the 4 main advantages to fixed bridgework?
- well tolerated
- hygienic
- no clasps
- good aesthetics
382
What are the disadvantages of a fixed bridgework?
- requires extensive prep of abutment teeth
- cannot be altered once finished
- requires high level of operator skill
- not good for long span of time
383
Why is it not ideal to use a fixed bridge when a patient has resorption of their alveolar ridge?
Because you don’t want to provide a bridge that has a gap underneath it and the ridge area.
384
What is usually the best denture design for a Kennedy class 3 situation?
Mid-palatal bar
385
What Kennedy class of denture is also known as a “shortened dental arch”?
Class I
386
How many teeth are considered a “shortened dental arch?
10 teeth
387
Why do free end saddle dentures have issues with support?
They only have an abutment tooth mesially so there is no tooth support posteriorly, which makes the denture more liable to move because its only getting support from soft tissues
388
Why do free end saddle dentures have issues with retention?
You can only clasp anterior teeth
389
When is support of a denture most important?
When patient is functioning/masticating with denture
390
In a maxillary free end saddle situation, where does most of the support come from?
Mucosal coverage
391
What are the three consequences of reduced mandibular support due to a free end saddle situation?
- trauma to denture bearing tissues
- instability of denture
- bone resorption
392
How might you try to achieve optimum mucosal support and reduce load to the denture bearing area in a free end saddle denture?
Reduce the number of denture teeth. E.g. miss the 7’s off the denture
393
How can tooth/mucosal support of a partial denture have negative consequences for abutment teeth?
When a denture is loaded the saddle will sink and tend to rotate around the abutment tooth. This can cause torque/wrenching on the abutment tooth which can jeopardise its health
394
What are the 4 factors that support from a residual ridge depends upon?
- quality and shape of residual ridge
- tissue coverage by a saddle
- accuracy of the impression and fit of denture
- denture design
395
What special impression technique can be used for class I and II Kennedy dentures?
Altered cast technique
396
What are the two main benefits of an altered cast technique?
1. Increases stability
2. Reduces stress on the abutment tooth/teeth
397
What happens in the altered cast technique?
The residual ridge is recorded in a functional form (under load)
398
What are the three means of achieving retention?
- mechanical (clasps, path of insertion)
- muscle control of polished surface shape of denture
- use of inherent forces from tissue coverage
399
For a bilateral free end saddle (Kennedy class 1) what is the preferred tilt used when surveying casts in order to achieve optimum retention (path of insertion)?
Anterior tilt
400
What system is used in the management of clasping Kennedy class I or II dentures, where an abutment tooth is adjacent to a free end saddle?
RPI system
401
What is the RPI system?
It’s a specific design used for abutment teeth adjacent to free end saddles.
Mesial Rest
Distal Plate
I-Bar
402
When under load, explain the movements that occur in each aspect of the RPI system.
Mesial rest = saddle rotates around this
Distal plate = moves down and away from tooth
I-bar = moves down and away from tooth
403
Indirect retention isn’t required for free end saddle partial denture design. True or false?
False, it ESSENTIAL, otherwise the denture will lift and move during function
404
Define, the resistance of a denture to displacement by functional forces.
Stability
405
For an upper Kennedy class I denture, what is the most appropriate major connector?
A plate (either Co/Cr or PMMA)
406
What three major connector designs should be considered for a Kennedy class II denture?
- horseshoe/ring
- mid-palatal bar
- posterior palatal bar
407
What is a post-dam?
“ a groove cut along the posterior palatal margin of a denture cast which produces a ridge on the finished denture and forms a more effective posterior seal to aid retention.”
408
What is the spacing usually required for alginate impressions?
3mm
409
What type of special tray is usually required in DDH?
Light cured
410
What denture material requires an extra week between visits?
Cobalt chromium
411
How will the wax denture at the try in stage feel different to the patient in comparison to the finished denture?
- it will feel more bulky
- clasps will not be engaged
- colour of wax will be much more vibrant pink than the finished product
412
What are the 10 try in checks that need to be made?
1. Lip support
2. Incisal level
3. Occlusal planes (anterior/posterior)
4. Retention and stability
5. Position of teeth compared with the ridge
6. Base extensions
7. Vertical dimension
8. Even contact on occlusion when in RCP
9. Speech
10. Aesthetics
413
What must you prescribe for at the end of the try in appointment?
Prescribe for a post dam (depth and location) and any changes required before finishing
414
How would you check retention of a finished denture?
Gently rock on denture or apply little force to move denture away from tissues
415
After finished denture appointment, when should the review appointment be made?
1 week later
416
If a patient attends a review denture appointment complaining of pain in muscles, what is the likely cause?
The FWS is too small
417
What are the 5 main consequences of poor denture hygiene?
- caries
- denture stomatitis
- halitosis
- pain
- exacerbates periodontal condition
418
What bacteria causes denture stomatitis?
Candida
419
What makes up the “pellicle layer”?
Salivary proteins and bacterial products
420
What bacteria is the main cause of halitosis?
Fusobacterial sulphur products
421
What fungi has an affinity for adherence to PMMA?
Candida
422
Why is the so much debris build up with dentures?
1. The fit surface of a denture is not exposed to cleansing effects of saliva
2. Denture surface is not smooth, acrylic can be porous and rough and fungi can actually be retained within the acrylic.
423
What is the best way to mechanically clean a denture at home?
Soap and a soft denture brush
424
Give 5 examples of denture cleaners that could be used for further cleaning after effective mechanical cleaning?
1. Alkaline peroxides
2. Alkaline hypochlorites
3. Acids
4. Enzymes
5. Abrasive cleaners
425
Give an example of a well known alkaline peroxide denture cleaner.
Steradent
426
What denture cleaner should never be used when dentures have a soft lining?
Steradent
427
What is a disadvantage of alkaline peroxides as denture cleaners?
They do not effectively deal with calculus or darker stain
428
What is a disadvantage of alkaline hypochlorites as denture cleaners?
May corrode metal (isn’t suitable for clasps or co/cr plates)
429
What is a commonly used alkaline hypochlorite denture cleaner?
Milton
430
How should you advise a patient to use a denture alkaline hypochlorite cleaner?
Mix alkaline hypochlorite with cold water and immerse denture in it for 15 minutes and then rinse
431
Why should cold water always be used to dilute chemical denture cleaners and not hot water?
Because hot water will help strip the colour from the acrylic and weaken it
432
What type of denture cleaner is good at dissolving calculus/stains, however has been discontinued?
Acids (e.g. denclen)
433
What is the major patient-related issue with enzyme denture cleaners such as polident?
They are expensive
434
Give an example of an abrasive denture cleaner, and what is its disadvantage?
Dentu-creme, this scratches the acrylic, promoting more debris
435
What are the 6 things you should tell patients about their dentures?
1. Rinse mouth/denture after every meal
2. Remove denture at night
3. Brush softly with soap and water (DON’T use toothpaste)
4. Any chemical cleaner should be used with cold water
5. After using chemical cleaner, store in cold water overnight
6. Stress cleaning of remaining natural teeth
436
Why is it very important to store dentures in cold water overnight and not leave them out dry?
Acrylic will become more brittle and likely to fracture if left out dry overnight
437
Would the incisal guidance pin be touching the incisal guidance table when the denture is fitted to the master model for a dough packed case. If not, explain what may have caused this to happen?
No, the incisal guidance pin was not touching the table. This is because the PMMA (flash) increases the thickness of the mould.
438
If the incisal guidance pin does not touch the incisal guidance table, what actions would need to be undertaken on clinic when fitting the denture to ensure a comfortably footing and functioning denture?
Use articulating paper to check occlusion, then modify teeth by spot-grinding.
439
Would the Incisal guidance pin touch the incisal guidance table when the denture is fitted back to master model by injection moulding? If so, explain why?
Yes, the incisal pin would be touching. This is because the PMMA is injected into the mould to the correct size.
440
If the incisal pin is not touching the Incisal table, what could have caused this?
Tooth movement
441
Explain how contraction porosity is caused?
The mould isn’t under pressure so air bubbles were produced
442
Explain how gaseous porosity is caused?
The mould is placed in water of rapidly increasing heat (100 degrees), so the monomer boils (thickest part if denture)
443
What other dimensional change takes place due to processing heat cure PMMA?
Contraction of acrylic
444
What problem is someone most likely to experience with acrylic denture processing?
Occurrence of porosity during the processing stage
445
What is the single most appropriate description for RCP?
The initial tooth contact whilst closing a round the terminal hinge axis
446
What is the single main reason for taking secondary impressions for a new denture after primary impressions?
To record and define the full functional limits of the denture bearing area
447
Which surfaces if a denture can be changed easily using the replica technique?
Fitting and occlusal surfaces
448
What is the single most appropriate clasp length and undercut required for a Co/Cr clasp?
Length = 15mm
Undercut =0.25mm
449
What is the minimum clasp length required?
14mm
450
What act protects the practice of dentistry for GDC-registered dentists?
Dentists act 1984
451
What are guiding planes?
Two or more vertically parallel surfaces of abutment teeth shaped to direct a prosthesis during placement and removal
