Partial Dentures Flashcards
1
Q
What are some unwanted extra-oral effects of losing teeth?
A
Obtuse naso-labial angle
Loss of facial height
TMJ problems
Alveolar compensation
Loss of lip support
Difficulty in function- speech and mastication
2
Q
What are some unwanted intra-oral effects of losing teeth?
A
Alveolar resorption
Tooth movement- tilting and drifting
Over-eruption of teeth
Toothwear
3
Q
What is the definition of support?
A
Resistance of the denture to occlusal directed load.
4
Q
Outline the Craddock Classification.
A
Class 1- tooth borne
Class 2- mucosa borne
Class 3- tooth and mucosa borne
5
Q
What is the advantage of a Craddock class 1 denture?
A
Load of the denture is transferred down the PDL.
Makes the denture base feel more like the natural dentition.
More comfortable.
6
Q
What teeth are best for providing support?
A
The teeth with the longest root area depending on the health of the PDL
- Molars, then canines, then upper centrals, upper laterals and lastly lower incisors.
7
Q
What denture component provides support?
A
Rests
- occlusal, cingulum or incisal.
8
Q
What is the disadvantage of having a Craddock Class 2 denture?
A
More movement in the denture because it rests on soft tissue.
Denture will need to be bigger for retention.
9
Q
What is a Kennedy class I?
A
Bilateral free end saddle.
10
Q
What is a Kennedy class II?
A
Unilateral free end saddle.
11
Q
What is a Kennedy class III?
A
Bounded saddle.
12
Q
What is a Kennedy class IV?
A
Bounded saddle that crosses the midline.
13
Q
What is the definition of retention?
A
Resistance of the denture to vertical displacement.
14
Q
What components of the denture are used for retention?
A
Clasps
- occlusal approaching or gingival approaching.
Guide planes.
Shape of the denture
Coverage of the mucosa
Soft tissue undercuts
Adhesion from saliva
Path of insertion
Precision attachments
15
Q
What is a disadvantage of having to cut a rest seat?
A
Potential exposed dentine.
Loss of occlusal stop when denture is not worn.
Destruction of tooth surface.
16
Q
For a free end saddle, where is the rest placed?
A
Mesial on the abutment tooth.
17
Q
Where should you not place a rest?
A
On an occlusal centric stop.
18
Q
For a bounded saddle, where should the rest be placed?
A
Closest to the saddle area- distal.
19
Q
What is the purpose of a rest?
A
Prevents movement of the RPD towards the mucosa.
Assists in distribution of occlusal load.
Prevent over-eruption of unopposed teeth.
Retention and indirect retention.
20
Q
What is a major connector?
A
Portion of the RPD that connects all the components together.
21
Q
What is a minor connector?
A
Connects the major connector to other components.
22
Q
What is the use of impression compound in primary impressions?
A
Used in free end saddles to stabilise the tray and supports the alginate material.
- more accurate impression.
23
Q
What is the purpose of a primary impression?
A
To produce a special tray to take master impressions.
To make a study cast which is used to survey.
24
Q
Why do you need to place the alginate impressions in a bag with a damp cloth?
A
Syneresis of the alginate occurs- releases water in dry situations.
This can cause the material to distort.
25
Why must you already have the design before you take master impressions?
Need to know whether you need to cut rest seats, determine guide planes, make undercuts and do this before you take the masters.
26
What type of dental stone is used to cast primary impressions for cobalt chrome?
100% dental stone.
27
What is the purpose of a master impression?
To make record blocks
28
What measurements do you take at the jaw registration stage?
Jaw reg
Shade
Mould
29
What is the purpose of surveying primary casts?
Identify and mark the maximum contours of the tooth and tissue surfaces to fabricate an RPD.
Establish a suitable path of insertion.
30
How long does a stainless steel occlusal approaching circumferential clasp need to be to engage a 0.25mm undercut?
15mm.
31
How much of the clasp engages an undercut?
terminal 1/3.
32
What are the seven aspects of denture design?
1. Saddle(s)
2. Support
3. Retention
4. Indirect retention
5. Bracing/reciprocation
6. Connectors
7. Review and simplify
33
What is indirect retention?
Resistance to rotational displacement.
34
What type of clasp should be placed on a canine or premolar?
Gingival approaching clasp
35
What type of clasp should be placed on a molar tooth?
Occlusally approaching.
36
What is reciprocation?
Each clasp will have an opposing element to prevent the clasp from putting pressure on the tooth and acting as an orthodontic appliance.
37
What is the ideal pattern of retention?
Triangular pattern of retention.
38
What is the purpose of indirect retention?
Adding a support leg that will make the denture more effective in retaining the denture and stopping displacement.
Extend the denture and move the pivot point further away from the clasps.
Supporting component on either side of the clasp.
39
What type of major connectors are present for upper dentures?
Palatal plate
Palatal strap
Horseshoes
Ring design
40
What type of major connectors are present for lower dentures?
Lingual plate
Lingual bar
Sublingual bar
Dental bar
41
How much space is required between the gingival margin and the floor of the mouth for a lingual bar?
7-8mm.
42
When would you use the RPI system?
In a free end saddle to prevent stress on the last abutment tooth in the mandibular arch.
43
What components form the RPI system?
Mesial rest
Proximal guide plate
GIngivally approaching clasp.
44
Why does any fixed prosthodontics need to be done after denture design but not denture construction?
Must know the denture design before the crown is constructed, so that the technician knows exactly what is in the mouth to construct the denture
Also need to make some of the crowns to fit the denture- i.e. rest seats.
45
When should tooth preparation be done?
After denture design fabrication but before master impressions.
46
What types of tooth preparation can be done?
Cut rest seats.
Create favourable guide planes
Modify unfavourable survey lines
Create retentive areas
47
What are guide planes?
two or more parallel axial surfaces on abutment teeth, which limit the path of insertion of a denture.
tooth surfaces are prepared to be parallel to each other and the path of insertion.
48
How much of the tooth should be removed for a guide plane?
0.5mm of enamel and extend vertically 3mm.
49
How much tray space should be allocated for alginate?
3mm spacer.
50
Why do you need to record the occlusion?
Need to know the occlusion to keep it the same and facilitate denture design.
To allow the technician to set up the teeth.
To allow the survey casts to be mounted.
51
What is the OVD and RVD?
OVD- jaw relationship when the teeth are in the inter-cuspal position
RVD- jaw relationship when the mandible is relaxed and the lips are touching.
52
What is freeway space?
2-4mm, RVD-OVD.
53
What reference lines are used during jaw reg?
Dento-facial midline.
Interpupillary line
Incisal plane
Ala-tragus line.
Curvature of the lower lip
Smile line
Gingival margins of existing anterior teeth
54
What is a foxes occlusal guide plane used for?
Should be co-incident with the ala-tragus line.
55
What checks do you have to perform at the framework trial stage?
Check the framework seats correctly- no rests standing proud
Check clasp adaptation and undercut engagement
Check for anything sharp or jaggy
Path of insertion
Assess stability when in situ
Not interfering with the occlusion or guidance.
56
What checks do you need to perform at the framework with tooth trial in wax stage?
Check fit of the framework
Check shade and mould of teeth
Extension of anterior denture flange
Check occlusion with articulating paper
Check no framework interference
Even occlusal contacts on denture teeth
57
What technique is used to make the metal framework?
Lost wax technique.
58
What type of cast is used during the lost wax technique?
Refractory cast, made of phosphate bonded investment material.
59
What are some advantages of using acrylic teeth in dentures?
Chemically bonded to the acrylic base.
Natural appearance
Silent during function
Early trimmed and polished
60
What are some disadvantages of using acrylic teeth in dentures?
Low abrasion resistance
Cold flow under pressure
Insoluble in mouth fluids- some dimensional change
61
What are some advantages of using porcelain teeth in dentures?
Natural appearance
High resistance to abrasion
Inert in mouth fluids
High heat distortion
62
What are some disadvantages of using porcelain teeth in dentures?
Noisy in function
Mechanical attachment with the denture
Brittle
Grinding removes surface glaze
63
What can you use to check if there are any areas of pressure when inserting the denture?
Pressure indicating paste.
64
What aspects should you check at delivery?
Aesthetics- Patient happy with shade and mould of teeth
Fit- comfortable, seats full with no rest seats standing proud
Retention- are the clasps engaging the undercuts?
Stability- does It rick?
Occlusion- identify any premature contacts,
Speech
65
What instructions should be given to the patient on delivery of the denture?
Increased saliva
Speech may be altered
Sore when eating
Remove the dentures at night and leave them soaking in water over night
Clean the denture with a toothbrush and soap, over a full sink of water
Make sure to use cold water- hot water will melt the denture.
Clean the dentures morning and night
Clean other teeth as normal
66
Name some potential areas of pain following insertion of a denture?
Encroachment on renal attachments
Rough area on the fitting surface
Overextended in upper post dam region- impinging on the hauler notch
Overextension lingually into he mylohyoid ridge
Abutment morbidity
67
What is an articulator?
An instrument where the upper and lower casts can be attached to, reproduce recorded relationships of the mandible and maxilla.
68
What types of articulators are there?
Average value- ARCON or NON-ARCON
Semi-adjustable- ARCON or NON-ARCON
69
When assessing primary impressions, what should you be asking yourself?
Do I have good extension of the denture bearing area?
Do I have enough detail of the teeth and other sift tissue structures?
Do I have rolled borders with no drags?
Are there any voids, air blows or drags of material on the impression?
Is there any encroachment of the impression material on the tongue space?
Do I have the appropriate impression of muscle attachments and frenal attachments?
70
After taking primary impressions, what would you ask the lab for?
Please pour casts using the impressions given in 100% dental stone.
Please construct master trays.
71
Why might you want to add red ribbon wax to the primary impression tray?
If patients are in between sizes if trays to allow adequate extension of the tray.
72
Why might you want to do a two stage impression technique for primaries?
Initially do a wash impression with impression compound on the free end saddle areas.
Then wash with alginate and take the full impression.
Stabilises the alginate in the tray on the free end saddle areas.
More precise impression of the saddle areas.
Reduces movement of the tray in the free end saddle area
73
When trying in the master tray, what should you look for?
Adequate extension of the tray flanges- ensure it does not overextend.
Frenal attachments should be relieved and leave 2mm space at the sulcus depth to allow for a rolled border.
74
How can you do border moulding?
Add greenstick to areas that you want greater detail- i.e. retromolar pad and lingual pouch regions.
Ensure to get the patient to lift their tongue up and go from side to side.
Massage the face in areas of where the impression material is to allow accurate impression of these areas during function.
75
What would you do if the master impression tray was over or under extended?
Under extended- add green stick
Over-extended- trim back with acrylic bur
76
What options do you have for impression materials?
Alginate- irreversible hydrocolloid
Impression compounds- green stick, red ribbon wax
- non-elastic
Polyvinylsiloxane- light, medium or heavy bodied.
- Medium bodied is most commonly used.
Polyether- Impregum
77
What are the advantages and disadvantages of alginate?
Advantages
- Easy to use
- Cheap
- Hydrophillic- less sensitive to water
- powder to water ratio can be altered to the operators preferences.
- Flexes over undercuts easily.
Disadvantages-
- Poor dimensional stability- syneresis occurs and imbibition of water.
- Low tear resistance.
78
What are the advantages and disadvantages of PVS?
Addition reaction silicone elastomer.
Advantages
- Good surface detail production
- Good tear strength
- Low setting shrinkage
- Good elasticity
- Good dimensional stability
- Automated mixing machines available- reduces risk of air blows.
Disadvantages-
- Expensive
- Hydrophobic- so moisture contamination can influence the accuracy of impression.
79
What are the advantages and disadvantages of Polyether?
Non-aqueous elastomer.
Advantages
- Good surface detail
- Good elasticity
- Low setting shrinkage
- Good dimensional stability
Disadvantages-
- Difficult to get off soft tissues and beards
- Cannot be used in deep undercuts- sets very rigidly
- May cause breakage of the cast when pouring up.
80
What equipment is required or a jaw reg?
Record blocks
Wax knife
Pallet knife
Pros kit- electron carver, price, mirror
Bunsen burner or hot air burner
Registration medium- Registration paste (PVS) or pink wax, modified wax wafer (Almanax).
Willis bite gauge or dividers
81
How can you measure the OVD and RVD?
Willis Bite gauge
Dividers
82
Describe the contents of a jaw reg appointment.
Inspect the blocks on the casts.
Remove any obvious areas of over extension.
Measure OVD, RVD and freeway space- should be 2-4mm.
- this is of the existing denture.
Check the blocks in the mouth- retention, support, extension.
- do upper block first.
Remove any overextension using a hot wax knife.
Adjust labial/buccal thickness- aim for 90-100 degree nasa-labial angle.
Adjust the blocks according to the reference lines- use foxes occlusal plane guide for this.
- Ala-tragus line
- Inter-pupillary line
- Incisal plane
- Dento-facial midline
Ensure roughly 2mm of wax is on show when the patient smiles- this indicates the level of tooth on show.
Adjust lower blocks in the same way.
Measure OVD, RVD and freeway space of the blocks.
- ensure this stays the same when the record blocks are removed.
Cut notches into the blocks
Apply registration paste or wax and get patient to close into ICP.
83
If there is an anterior saddle area, what must you also add to the record blocks?
Centre line
Canine line
High smile line
84
Apart from the jaw reg itself, what else should be done at this appointment?
Take a shade and mould.
85
If major adjustments are required at the framework stage with teeth in wax, what would you do?
Reset the teeth chair side or remove all the teeth and do a jaw reg again.
86
What should you assess about an existing denture?
Take a denture history from the patient- what do they not like about it?
Check OVD, RVD and freeway space
Check how much of the incisors are on show
Check dental centre line, inter pupillary line, alatragus line
Check the lip line, lip support, oral incompetence
Speech
Facial structure- face height, asymmetry
