Removable Pros Flashcards
(206 cards)
1
Q
List some examples of major connectors
A
Mid Palatal Bar
Anterior Bar
Posterior Bar
Skeletal or ring design
2
Q
What are partial dentures most commonly made for?
A
To facilitate appearance, speech and mastication
3
Q
What are the other reasons that partial dentures may be made?
A
Maxfax defects (due to palatal cancer) or cleft palate
- congenital hole between mouth and nose/air sinus
- needs blocked off to avoid food/drink passage into the nose or lispe
Prevention of:
- tooth wear - spreading load
- unwanted tooth movement - overerupt, drift, tilt
- lateral tongue spread
4
Q
What is the health gain of partial dentures?
A
Appearance
Masticatory function
Speech
Craniofacial function - jaw joint, facial expression
Societal function
Self-esteem
5
Q
What is the Kennedy Classification System 1925?
A
A classification system used to classify edentulous saddles for partial dentures
6
Q
What is a Kennedy Class I?
A
Bilateral free-end saddle
7
Q
What is Kennedy Class II?
A
Unilateral free-end saddle
8
Q
What is a Kennedy Class III?
A
Single-bounded saddle, not crossing the midline
9
Q
What is a Kennedy Class IV?
A
Single bounded saddle, crossing the midline
10
Q
With modifications, which saddle influences the main classification?
A
The most posterior saddle
11
Q
Can Kennedy Class IV have modifications?
A
No
12
Q
What must be dealt with before dentures are made?
A
Caries
Perio disease
Angular chelitis
Denture stomatitis
13
Q
What is the purpose of 1st imps?
A
To establish the denture bearing area
14
Q
What are record blocks used for?
A
Used to record the occlusion/bite when posterior teeth are missing
15
Q
In which cases might an occlusion visit not be necessary?
A
If there are enough index teeth - this can be assessed on the study models.
16
Q
What instrument can be used in the lab to carry out jaw registration?
A
An articulator
17
Q
What are the different types of articulator?
A
- Study models / Simple Hinge
- Plane line
- Average value
- Semi-adjustable
18
Q
What does surveying study casts do?
A
It establishes:
- the path of insertion/removal of denture
- areas of undercuts - may stop the denture from being seated
- areas that are useful for holding/clasping the denture in place.
19
Q
Which type of denture requires a casting to be made?
A
CoCr based dentures
20
Q
What are the checks that you would carry out at the “try in” stage?
A
Extensions
Adaptation
Retention
Occlusion
Appearance
21
Q
How do you test the fit a chrome framework?
A
Must be precision fit - use a probe between the tooth and the casting to check that there isn’t any big spaces
22
Q
In order, what are the clinical/lab stages in the construction of partial dentures?
A
- Assessment (clinic)
- 1st Imps (clinic)
- Pour casts + construct record blocks if req (lab)
- Occlusion if req (clinic)
- Jaw reg + design of partial dentures (lab)
- 2nd imps (clinics)
- Casting + setting of teeth in wax (lab)
- Try in stage + retry if necessary (clinic)
- Processing of dentures (lab)
- Fit (clinic)
- Review/Ease (clinic)
23
Q
What are the primary and secondary support areas of the upper jaw?
A
Primary - basal bone
Secondary - ruggae and tuberosities
24
Q
Which area of the upper jaw does NOT contribute to support?
A
Denture border
25
Which 2 structures in the upper jaw occasionally require denture relief?
Midline suture and incisive papilla
26
What are the primary and secondary support areas of the lower jaw?
Primary - buccal shelf and pear shaped pad
Secondary - ridge crest and genial tubercles
27
Which area of the lower jaw does NOT contribute to support of the denture?
Labial ridge incline
28
Which 2 structures in the lower jaw occasionally require denture relief if prominent?
Prominent genial tubercles
Prominent mental tubercles
29
What might you observe if there is excess FWS?
Pt may be over closed
30
What might you observe if there is inadequate FWS?
Pt may not be able to put their lips together, bite propped open
31
What is denture retention?
The resistance to displacement of the denture away from the ridge at rest
32
What is denture stability?
The ability of a denture to resist displacement at functional stresses
33
What is denture support?
The resistance of vertical movement of a denture towards the ridge
34
What is denture adaptation?
The degree of fit between a prosthesis and supporting structures
35
If the mandibular posterior teeth on a denture are positioned too lingual, what can happen?
The tongue can displace the denture
36
Primary 1st imps are used to construct study models.
What are these study models used for in the construction of partial dentures?
Treatment planning
Examination of occlusion
Determination of path of insertion and denture design - surveying
Construction of special trays
37
Primary 1st imps are used to construct study models.
What are these study models used for in the construction of complete dentures?
Treatment planning
Construction of special trays
38
When recording 1st imps, how much space should there be between the tray flange and teeth/denture bearing area?
Ideally should be ~4mm between the tray flange and teeth/denture bearing area
39
If the stock tray is underextended, what can you use to modify the tray?
High-viscosity materials such as:
Greenstick/wax
- to increase length of impression/sulcus depth
Putty in edentulous saddle areas
- to maintain a more successful impression of the denture bearing area
- trim putty to allow ~3mm clearance from remaining teeth
Thermoplastic red composition in edentulous (saddle areas)
40
What material do you use for taking denture impressions?
Commonly alginate
41
For partial dentures, when do you take 2nd imps?
After denture design and any necessary tooth prep
42
When prescribing to the lab for a special tray, what must you request?
3mm spacer to create space for the alginate to flow into
43
When is a 3mm spacer not required for a special tray?
If the pt has a resorbed ridge.
However, the impression must be taken with a bulkier impression material such as zinc oxide eugenol as alginate does not work well in thin section.
44
What material would you used to form your custom made special tray that would be used to take 2nd imps?
Light-cured acrylic resin - blank sheets
45
With replica complete dentures, what would you use to take your 2nd imps?
You would use a replica of the previous denture as the tray
46
Before taking 2nd imps what must you check?
The extensions of the tray - should be ~2mm short of the sulcus depth to allow for border moulding
47
What do mould stops help with?
Help to position the tray, maintain spacing for the impression material and allow consistent positioning of the tray
48
What can mould stops be made of?
Greenstick
49
How would you disinfect your impressions?
Rinse in running water to remove saliva, blood, debris
Disinfect for 2 minutes in 10,000ppm (1%) sodium hypochlorite or sodium dichloroidocyanurate (Actichlor) solution
Note the time that the impression is to be removed from the solution and rinsed
Rinse thoroughly after 2 mins (having put clean gloves on)
Cover alginate impression in damp napkin
Label and place in a plastic laboratory bag
On lab prescription indicate that impressions have been disinfected - signed by supervising clinician
Take to lab ASAP for casting
50
What concentration of sodium hypochlorite would you use for disinfecting?
(1%) - 10,000ppm
51
How many actichlor tablets would you use in 1 litre for disinfection?
10 tablets per litre
52
Why must you keep the alginate impression in a damp napkin?
To prevent SYNERESIS (loss of fluid - drying out of the alginate)
Don't submerge in water - can cause IMBIBITION (uptake of fluid - swelling of alginate)
53
What is a critical abutment tooth?
If the tooth is lost then it convert the saddle from a 'bounded saddle' to a 'free end saddle'
54
What are the 3 different flange designs?
Full flange
Part flange
Flangeless
55
What might impact your decision on flange design?
Ridge shape
Undercuts into sulcus area
56
What is a major connector?
A plate/bar that:
- Unites partial denture saddles
- Provides bracing - resistance to lateral movements
- Provides indirect retention
- Acts as a splint
57
List 6 different types of major connectors for the lower jaw?
PMMA lingual plate
CoCr lingual plate
Lingual bar
Dental bar
Sub-lingual bar
Swinglock denture
58
List 8 different types of major connectors that can be used for the upper jaw?
PMMA plate
Horseshoe plate
Anterior palatal bar (CoCr)
Mid palatal bar (CoCr)
Posterior palatal bar (CoCr)
Ring design
Spoon denture
T denture
59
What is an advantage of a dental bar?
More hygienic - free's up lingual mucosa and gingival margins
60
What crown height is required for a dental bar?
9mm crown height
- 5mm for bar
- 2mm above and below to keep clear of the gingival margin and incisal edge
61
What depth of lingual sulcus is required for a sub-lingual bar?
5mm
62
What are the dimensions of a sublingual bar?
2mm height
4mm width
63
When are sublingual bars used?
Kennedy Class IV cases
64
What depth of lingual sulcus is required for a lingual bar?
7mm
- 3.5mm for bar
- 3.5mm for gingival margins for hygiene and comfort
65
What is the advantage of a split lingual plate?
Avoids metal shine through
66
When is a swinglock denture used?
Only when labial undercuts are present
67
What are the properties of CoCr in comparison to acrylic?
Thinner, stronger, and heavier than acrylic
68
What must the width be of a mid-palatal bar?
~7-12mm
69
What are minor connectors?
A connecting component between the major connector or the base of a partial denture and other units such as clasps and rests.
70
What is the purpose of a striking plate?
Minimises the risk of a denture fracturing
71
What is denture retention dependent on?
Film of saliva between the denture and tissues (quality and amount)
Adaptation of the denture
Good border seal - created by physical forces from saliva between denture base and mucous membrane, and the muscle activity of the lips, cheeks and tongue
72
How can you improve denture retention?
Add direct retainers (clasps engaging undercuts of teeth)
Precision attachments - lock and key
73
Should clasps be passive or active?
Must be passive in order to flex to enter and be removed from an undercut.
74
Where is the point of action of a clasp?
Point of action is the tip of the clasp
75
Where must the terminal 1/3 of the clasp engage?
Below the survey line
76
What should denture clasps always be opposed by to prevent tooth movement?
A reciprocal component - ie. an extension of the base plate or an opposing clasp arm
77
What are the 2 different styles of clasp?
Occlusally approaching clasp
Gingivally approaching clasp
78
How does an occlusally approaching clasp compare to a gingivally approaching clasp?
An occlusally approaching clasp is:
- More rigid
- More efficient bracing component preventing lateral movements
- May be less aesthetic
Whereas, a gingivally approaching clasp is:
- More retentive
- More efficient due to push type 'trip action'
- Less visible, more aesthetic
- More hygienic as covers less tooth structure
79
Why is adequate space required for an occlusally approaching clasp?
So that there is no occlusal interference
80
What are the different styles of ring clasps?
Ring clasps - used for critical abutment teeth
3 arm clasps
81
What are the 3 different styles of gingivally approaching clasp?
T roach clasp - canines and premolars (used more anteriorly)
I bars
L bars
82
List the different materials that can be used for clasps
Cast CoCr
Wrought Stainless Steel
Gold
Thermoplastic copolymer (e.g. Dental D)
83
What undercut depth do Cast CoCr clasps engage?
0.25mm
84
What undercut depth do wrought SS clasps engage?
0.5mm
85
What undercut depth do gold clasps engage?
0.75mm
86
What is the RPI system?
A system used for free-end saddles to reduce stress on the abutment tooth and more evenly spread the load
It involves a:
- Mesial rest
- Distal guiding plane
- I-shaped retentive clasp (ie. I bar)
87
When would you opt for using a replica technique?
When there is a history of successful denture wear with no major pathological changes and no major design changes required
88
How would you take replica 1st imps?
Using self-supporting putty in a disposable impression tray
89
In what cases may you need to modify the denture prior to 1st replica imps?
If under extended - adjust with greenstick
If chrome palate - must thicken up the chrome part of the palate with wax before replicating it
90
What must you do if you are replicating a denture that is overextended?
Replicate as normal and prescribe on lab card for shellac to be shorter than normal in that specific area
This can be easily adjusted chairside prior to taking 2nd imps
91
How might you fix minor faults, air blows, or wrinkles in the replica impression?
By use of light bodied material (perfecting paste)
92
In complete denture making, why do we record 2nd imps before occlusion?
To ensure occlusal blocks are as stable and firm as possible before recording occlusion
93
In partial denture making, why do we record occlusion before taking 2nd imps?
To enable us to design the denture considering interocclusal space and to plan for any tooth modification needed to be undertaken prior to taking 2nd imps
94
What impression material can you use to record replica 2nd imps for a complete denture if the ridge is atrophic?
Wash impression using a light bodied silicone material - Rapid liner or Aquasil
95
If the ridge is atrophic, what impression technique can you use and why?
The closed mouth technique
To avoid occlusal errors such as open bite
96
What is mucosal support gained from?
Saddles and connectors
97
What are the disadvantages of mucosal support?
Degree of compressibility to mucosa so when loaded the pt may feel denture movement
98
What is tooth support gained through?
Use of PDL
Force transmitted through tooth to PDL and ultimately underlying bone
99
What additional components can provide tooth support?
Occlusal/cingulum rests
Onlays
Overdenture abutments
Connectors
100
What must you do to an overdenture abutment prior to providing an overdenture?
Dome/restore it to provide a smooth rounded surface - must sit 1mm above gingival margin
101
What is the purpose of indirect retention?
Prevents displacement of saddle away from ridge by extension of the denture
102
How can indirect retention be achieved with a removable prosthesis?
By placing:
The clasp axis as close as possible to the saddle
The indirect retainers as far as possible from the saddle
103
List some different indirect retainers
Cummer arms - provides bracing
Lingual plate connector - bracing
Continuous clasp with lingual bar
Occlusal rests
Anterior palatal arm and bar
Posterior palatal bar
Extension of palatal coverage
Dental bar
Embrasure hooks
104
List the 4 denture components and their functions:
Saddle:
- Retention
- Support
- Bracing
Connector:
- Support
- Indirect Retention
- Bracing
Clasp:
- Retention
- Support
- Bracing
Rests:
- Support
- Indirect Retention
105
What materials can be used to make denture teeth?
Acrylic-based (majority use)
Porcelain based
Composite resin based
Combinations
106
What are the 3 different types of acrylic based teeth?
Types:
Senator
Vivodent
Orthotype
107
What are the features of vivodent acrylic based teeth?
More expensive
Harder
Longer lasting
Light reflects better
Don't bond well to acrylic base
108
What shade guide is most commonly used in DDH?
The Vita standard shade guide
109
What 2 classifications can be used to help choose mould of the teeth?
Leon Williams Classification
- square
- tapered
- oval
Frush and Fisher Classification
- men: square/angular teeth
- women: curved and rounded teeth
110
How can denture teeth be arranged? (4)
NN - necks normal
SS - slightly spaced
CC - crossed centrals
TT - twisted tips
111
What biometric guides can you use to assist with tooth positioning?
Use incisive papilla - remains static with bone resorption when teeth are lost
On average tips of incisors are 5.5mm anterior to incisive papilla
Horizontal = ~5.5mm
Vertical height = ~7mm
112
What tool can be used to check tooth position?
Alma Gauge
113
Which factors will determine the amount of incisal overjet/overbite?
Skeletal class
Smile line
114
Which tool is used to measure the occlusal plane?
Foxs Guide Plane
115
When might you opt for cuspless teeth?
When its difficult to get a reproducible jaw relationship
116
Where should you position the lower denture teeth?
On the crest of the ridge to ensure stability
117
Where should you position the upper denture teeth?
Slightly buccally to the ridge without compromising the border seal
118
What would you aim for your occlusal plane to be?
Parallel to the ala-tragus line
119
How might you achieve balanced occlusion and balanced articulation?
By setting up the teeth on an articulator, using compensating curves:
- Curve of Spee
- Bilateral Curve of Wilson
120
What is the ICP?
Intercuspal position:
The maximum contact point of contact between opposing teeth.
Dictated by tooth relationships - vary throughout life
121
What is the RCP?
Retruded contact position:
Guided occlusal relationship when the condyles are at their most retruded position in the joint cavities
Dictated by the condyles - reproducible position
122
In what partial denture cases must you record occlusion?
No posterior teeth
Worn-down index teeth
Premature contact on closure - false index
Limited space for prosthesis placement
123
What do free-end saddle partial dentures require?
Indirect retention - to prevent the denture from lifting/moving in function and subsequent trauma to soft tissues
124
What can reduced mandibular support result in?
Trauma to the denture bearing area
Instability of denture
Bone resorption of the ridge
125
How can optimum mucosal support be achieved in a free-end saddle situation?
Reduce load of denture bearing area by reducing the number of denture teeth - remove 7s or premolar
Cover the maximum area with the denture saddles to spread the load
Extend onto areas that are best able to take the load - e.g. primary stress bearing areas like the buccal shelf of the mandibular ridge
Use natural teeth for support where possible
- occlusal rest
- cingulum rest
126
What problems can occur with tooth/mucosal-supported dentures?
And how might these problems be resolved?
Instability on occlusal loading and torque on abutment teeth - can jeopardise the health of the tooth
Can use special impression techniques for free end saddles to reduce the likelihood of these problems occurring
- Altered cast technique
- Stress breaker technique
127
What is the altered cast technique?
A functional impression that involves recording the saddle areas under load
Using this technique will:
- Increase stability
- Reduce stress on abutment tooth/teeth
- More predictable occlusion
128
What is the stress breaker technique?
Where part of the denture is cut away to allow the saddles to seat further down to tissues without adding additional strain
This technique is not used frequently
129
When deciding on the path of insertion for free-end saddles, which direction will you likely have to tilt the cast?
Forward
130
Which is normally the clasp of choice in a free-end saddle situation?
A gingivally approaching clasp on a premolar tooth - less trip action and less likely to cause wrenching action on abutment tooth
131
When checking the occlusal plane what are your 2 reference lines?
Ala-tragus line
Intra-pupillary line
132
What is the purpose of the post dam?
To aid retention - by creating atmospheric pressure under the denture
133
What depth should you prescribe the post dam to be?
0.5mm
134
What are the 3 different types of post dam?
Heat cured
Cold cured
High impact
135
Where should your post dam sit?
At the junction of the hard and soft palate
136
Where are the most common sites of plaque/calculus build up and why?
Buccal aspect of U6s
Lingual aspect of lower anteriors
As this is where the major salivary glands exit
137
How does plaque/calculus form on the denture?
Pellicle layer is formed by salivary proteins and bacterial products
Oral debris (mucin, food, desquamated epithelial cells) and microorganisms (bacteria and fungi) can adhere to the pellicle layer
Then the plaque flora matures - if left can turn to calculus.
138
What is the bacterial flora present in denture plaque build up?
S.aureus, e.coli, alpha strep, spirochetes and more
Fusobacterial sulphur products - leads to halitosis
139
Why do dentures favour candida (fungal) activity?
Acidic environment under the denture
Fit surface of denture not exposed to cleansing effect of saliva
Acrylic is porous and rough - collates debris/fungi more easily
140
What are ideal properties of denture cleaners?
Cheap
Easy to use
Effective removal of deposits
Bactericidal and Fungicidal
Harmless to denture materials
Non-toxic
141
What is the best way to clean dentures?
Mechanical clean:
- plain soap and soft brush
- do not use toothpaste - too abrasive
Chemical clean:
- Alkaline peroxides (Steradent)
- Alkaline Hypochlorites (Milton or Dentural)
- Use cold water with chemical cleaners
142
What might record blocks be reinforced with?
Shellac or cured/heat-cured acrylic base plates
143
Where can support be achieved through?
Teeth
Mucoperiosteum
144
What is the disadvantage to mucosal support?
There is a degree of compressibility to mucosa
When loaded the pt. may feel movement of the denture
145
Where is tooth support gained through/from?
Gained through the PDL.
Gained from:
- occlusal/cingulum rests
- onlays
- overdenture abutments
- connectors
146
How can you gain indirect retention?
Continuous clasp with lingual bar
Occlusal rests
Cummer arms
Anterior palatal arm + bar
Posterior palatal bar
Extension of palatal coverage
Dental bar
Lingual plate connector
Embrasure hooks
147
What is a clasp axis?
An axis formed through 2 clasps on opposing sides of the arch - it is formed through the active part of the clasp (terminal 1/3 of clasp)
Where there is more than one clasp on one side of the arch:
- the major clasp axis (where the main pivot point is) = the closest to the free-end saddle
- the remaining clasp axis is known as the minor clasp axis
The part of the denture distal to the major clasp axis will resist rotation by the use of an indirect retainer
148
What FWS should you aim for?
2-4mm
149
How do you calculate the FWS?
RVD - OVD = FWS
150
How far should the lower denture extend into the retromolar pad area?
1/3 into the retromolar pad area
151
When selecting a stock tray for impressions, how much space should you ideally have between the denture bearing area and the tray to allow space for the impression material?
2mm
152
What does pre-packing the palate avoid?
Air blows
153
Tissue stops can sometimes be used with special (spaced) trays.
What is the purpose of tissue stops?
Ensure thickness of impression material
Help localise the tray during imp taking
154
What is the purpose of finger rests on special trays?
To ensure the tray is fully seated posteriorly
To ensure more even distribution of pressure to the tissues
To help stabilise the tray in the mouth
155
Which areas of the mucosa will experience more movement under loading and pressure?
Thick areas of mucosa will experience more movement under loading and pressure than thinner areas of mucosa
156
What impression techniques can be used to facilitate discrepancies in mucosal thickness causing denture movement/rocking?
Mucocompressive and Mucostatic impression techniques
Both techniques can be used in conjunction with one another to facilitate different areas
157
Which impression technique would you use to facilitate a better denture fit in function?
Mucocompressive impression technique
158
Which impression technique would you use to facilitate a better denture fit at rest
Mucostatic impression technique
159
How might you avoid compression of fibrous tissue during impression recording?
2 stage technique:
- mucostatic impression for the anterior part
- mucocompressive impression for the posterior part
or
Single stage technique with a perforated tray and low viscosity material
- can use if fibrous ridge isn't too severe
- exert as little pressure as possible
160
List 4 displacive forces on the denture
Gravity
Muscle activity
Sticky foods
Function
161
List 2 interfacial forces on the denture
1. Interfacial surface tension
2. Interfacial viscous tension
162
What is interfacial surface tension?
The tension generated when a thin layer of fluid is present between 2 parallel planes of rigid material
Happens as a result of an air seal being formed at the edge of a rigid material.
Relies on wetting of the denture
163
What is interfacial viscous tension?
The force holding 2 parallel planes together that is due to the viscosity of the interposed liquid (e.g. saliva)
Relies on good quality plentiful saliva
164
What is adhesion?
The physical attraction of unlike molecules for each other
Saliva - mucous membrane
Saliva - denture base
The larger area covered, the greater the adhesion.
165
What is cohesion?
The physical attraction between similar molecules - eg. salivary film
166
What is the neutral zone?
An existing zone where the outward forces of the tongue are balanced by the inward forces of the cheeks
167
Why is the neutral zone important?
As placing teeth in this zone will increase stability, retention and comfort
168
What other aids are available to facilitate denture retention/stability?
Denture fixative seal (Seabond)
Adhesives (Fixadent or Polygrip)
Valves
Implant anchors
169
What is a reline?
New fit surface for an existing denture/part of an existing denture
Can be done chairside
170
What are the 3 types of reline?
Temporary (coe-comfort)
Soft - provides cushioning
Permanent - resilient
171
What are temporary liners used for?
Tissue conditioning - grossly ill-fitting dentures
Post immediate dentures
After implant surgery
172
When are soft liners used?
Useful for those with:
- Parafunctional habits
- Very atrophic ridges
- Cancer/cleft lift pts (obturators)
173
What are the disadvantages of soft liners?
Plasticiser leaches
Deteriorates with time
Harbours microorganisms
174
What are the different soft lining materials that are available?
Heat cured acrylics
Self cured acrylics - coe-soft
Heat cured silicones - Molloplast B
Self cured silicones
175
What is a denture rebase?
Replacing the entire base material of an existing denture
Mostly done in the lab
176
Before taking impressions for a rebase, what must you do to the current denture?
Remove all undercuts from the denture using an acrylic bur
177
What does a dental implant consist of?
Implant
Abutment
Abutment screw
Restoration screw
178
What medical conditions may contraindicate implant placement?
Chemoradiotherapy - osteoradionecrosis
Polypharmacy - dry mucosa = implant failure
Immunosuppression - failure of healing between bone and implants
Alendronic acid/bisphosphonates - risk of MRONJ
Cardiac issues - surgical risks, bleeds
Mental health issues - unable to cope, consent/capacity issues
Diabetes - increased failure rate
Thyroxine - increased failure rate
179
What DH aspects may contraindicate implant placement?
- Poor OH
- Perio disease - poor prognosis
- Uncontrolled caries - poor prognosis
- Status of other teeth
- Dental anxiety - long/complex tx
- Status of pre-existing implants
- Bruxism - increased failure rate
180
Under what conditions are pts offered implants on the NHS?
H&N cancer
Severe hypodontia
Significant trauma
Cleft palate
181
What are the different types of implants?
System, tapered, platform, co-axis
Narrow, regular, or wide
Angle of emergence
182
When should have osseointegration occurred following implant placement?
~3 months following implant placement
183
What are the 4 different types of implant overdenture abutments?
1. Locator (TM) abutments
2. Ball abutments
3. Gold bar
4. CAD-CAM Titanium bar
184
What are the 4 different types of implant overdenture abutments?
1. Locator (TM) abutments
2. Ball abutments
3. Gold bar
4. CAD-CAM Titanium bar
185
List 4 post-implant treatment complications
1. Peri implant mucostitis
2. Peri-implantitis
3. Loose/fractured components
4. Late implant failure
186
How does peri-implantitis differ from peri-implant mucostitis?
Peri-implantitis involves crestal bone loss whereas peri-implant mucostitis doesn't.
187
Which flange design would you choose in the case of a surgical extraction?
Full flanged to maximise seal and retention of the denture
188
How long should IR dentures be kept in after extraction?
24 hrs
189
Why is a facebow used?
To record the relationship of the maxilla to the TMJ
190
What can happen to alginate impression if left in the sterilising solution for over a long period of time?
Imbibition
191
What can happen to an alginate impression if f not kept in a sealed bag with wet napkins?
Synerisis
192
How is injection moulding carried out?
The flask and injector in place
The clamp handle is turned and the piston pushes the resin into the mould
Resin escaping the mould at the bottom indicates that the mould is full.
193
How is dough packing carried out?
The acrylic dough is placed in the mould
The mould is closed and squeezed together in a clamp
The excess that comes out the side of the flask is known as flash
194
What are the advantages of injection moulding over dough packing?
No flash minimising open bite when fitting the denture
No trial pack
Less handling of the material
Less pressure when injecting material
195
What are the disadvantages of injection moulding over dough packing?
Need to add a sprue
Extra training
Expense of equipment
Difficult to de-flask
Technique sensitive
196
What causes contraction porosity?
A lack of pressure on the acrylic resin
- not enough resin to fill the mould
- or failure to apply enough pressure when clamping the flasks
197
What does contraction porosity look like?
Small holes through the denture
198
What is gaseous porosity caused by?
Wrong curing cycle
- too much heating when processing the denture
199
Where will the porosity be observed in the denture?
Within the thickest part of the denture
200
What do you use to measure the OVD?
Willis bite gauge
201
Why would you want to avoid having a really thick soft lining?
As it will weaken the denture as there is less acrylic
202
What scientific term is used to describe the change in length of a specimen?
Strain
203
What scientific term is used to describe the force to flatten a cylinder?
Compression
204
What scientific term is used to describe the elongation of a specimen?
Tensile
205
What is the term used to describe the hardness of a material?
Surface hardness
206
What is the force applied to the mid beam to fracture it?
Flexural force
