Bridges Flashcards
1
Q
What are the function of bridges
A
restore aesthetics, function, speech and maintain dental health
2
Q
How do bridges maintain dental health
A
by preventing overeruption/tilting of opposing/adjacent teeth
3
Q
What is the benefit of a denture over a bridge
A
o Denture has the benefit that it replaces the lost soft tissue as well as the missing tooth, something which bridges can’t replace
4
Q
What are general indications for a bridge
A
- Function and stability
- Appearance
- Speech
- Physiological reasons
- Systemic disease
- Cooperative patient
5
Q
What systemic disease can be a strong indication for bridges over dentures
A
epileptics
risk of inhalation during seizures
6
Q
Why must a patient be cooperative to be suitable for a bridge
A
Bridges require a lot of oral hygiene maintenance to ensure longevity
7
Q
What are local indications for bridges
A
- Big teeth
- Heavily restored teeth (conventional)
- Favourable abutment angulations
- Favourable occlusion
8
Q
What is meant by favourable occlusion in reference to indications for bridges
A
Don’t want a heavy occlusion
9
Q
What are general contraindications for bridges
A
- uncooperative patient
- MH contraindications
- poor OH
- high caries rate
- periodontal disease
- large pulps
10
Q
What sort of medical history could contra indicate a bridge
A
allergies to certain metals used in bridgework fabrication
11
Q
Why can periodontal disease be a contraindication for bridgework
A
bone loss can impact abutment support
12
Q
Why are large pulps a contraindication of conventional bridges
A
- Young patients have larger pulps so with conventional bridges there is a higher likelihood of pulp exposure resulting in a non vital tooth
13
Q
What are local contraindications of bridgework
A
- High possibility of further tooth loss within arch
- Prognosis of abutment poor
- Length of span too great
- Ridge form and tissue loss
- Tilting and rotation of teeth
- Degree of restoration
- Periapical status
- Periodontal status (bone loss)
14
Q
Why are long spans a contraindication for bridges
A
- Long bridges flex more when bitten on which increases likelihood of fracture
15
Q
When taking the history for bridges, what sort of info are we looking for
A
establish any habits such as bruxism
16
Q
What are we looking for in a clinical examination when planning bridges
A
- Want to look at occlusion
- Get radiographs & look at ABC (apices, bone levels, caries)
17
Q
How do we want our study models articulated
A
- Want them mounted on a semi-adjustable articulator with a facebow registration
18
Q
What are the patients options for provisional restorations for brdiges
A
- Consider an RPD
- If prep is in enamel, may not need a provisional
- If prep is into dentine and tooth becomes sensitive then cover with layer of DBA
19
Q
Why do we want to fit the bridge asap after prepping/impressions
A
to prevent unwanted tooth movement
20
Q
What are the two main types of retainer designs
A
- fixed fixed
- cantilever
- some other types that sit inbetween
21
Q
What is a fixed-fixed bridge
A
- Retainer at each end with pontic in the middle held together by a rigid connector
22
Q
Where are fixed-fixed bridges mainly used?
A
posterior
23
Q
What is a cantilever bridge
A
- Retainer at one side of pontic only
24
Q
Where are cantilever bridges generally used
A
anteriorly
25
Why are cantilever bridges generally used anteriorly
* Due to divergent guidance paths
* means that occlusal forces will be going in different directions resulting in the bridge being moved around, increasing the likelihood of it coming off
26
What is an abutment
* A tooth which serves as an attachment for a bridge
27
What is a pontic
* The artificial tooth which is suspended from the abutment teeth/tooth
28
What is a retainer
* The extracoronal or intracoronal restorations that are connected to the pontic and cemented to the prepared abutment teeth
29
What is a connector
* Component which connects the pontic to the retainer
30
What is the edentulous span
* Space between natural teeth that is to be filled by a bridge or partial denture
31
What is the saddle
* Area of the edentulous ridge over which the pontic will lie
32
What is a pier
* An abutment tooth which stands between and is supporting two pontics, each pontic being attached to a further abutment tooth
33
What is meant by unit
* Either a retainer or a pontic (total number)
34
What is resin bonded bridgework aka
* Same as resin retained bridgework/adhesive bridgework (has other names too but these are most common)
35
What is the most common bridge design
Resin bonded bridgeowrk
retainer made of metal (CoCr) with porcelain pontic
36
What are advantages of resin bonded bridgework
* Minimal preparation
* No LA needed
* Less costly
* Less surgery
* Can be used as provisional restoration
* If it fails then there hasn’t been much destruction to the tooth so not much has been lost
37
How do you get away with minimal prep for RBB's in regards to the occlusion
dahl effect
bridge holds bite open
teeth come into contact
38
What are disadvantages of RBBs
* Rigorous clinical technique required
* Metal can shine through due to incisal translucency
* Chipping porcelain
* Can debond
* Occlusal interferences
* No trial period possible
39
Why does RBB requires such a rigorous technique
* use of composite cement (moisture control)
40
What is the problem with RBB debonding
* First bond is the best bond, so one can recement again but there is a high chance of it debonding again
41
When can occlusal interferences be an issue (after bridge fitted)
* If it is a static occlusal interference, this is not a huge issue due to the ‘dahl effect’ and should only be temporary
* If it is a dynamic occlusal interference, it will knock off the bridge with lateral forces
42
What are the indications for RBB
* Young teeth
* Good enamel quality
* Large abutment tooth surface area
* Minimal occlusal load
* Good for single tooth replacement e.g hypodontia
* Simplify partial denture design
43
What are contraindications for RBBs
* Insufficient or poor quality enamel
* Long spans
* Excess soft or hard tissue loss
* Heavy occlusal force e.g bruxism
* Poorly aligned, tilted or spaced teeth
* contact sports
44
Why can poorly aligned/tilted/spaced teeth be a contraindication
* Can be hard to get the bridge in and receive an aesthetic result
45
What should px who play contact sports be told
* must be well informed and wear their mouthguard
46
When are direct (chairsside) RBBs used
* trauma, emergency, immediate extraction
47
What can be used as the pontic for direct RBBs
* Can use patients own tooth ideally, if not then can get acrylic tooth, polycarbonate crown or cellulose matrix filled with composite
48
What are the types of indirect RBBs
* No preparation
* Minimal preparation
* Heavy preparation
49
Why is heavy prep undesirable for RBB
goes into dentine and dentine doesn’t provide as good a bond to resin
50
What is required abutment wise for indirect RBBs
* Need good palatal/lingual coverage - the greater the surface area the greater the bond
* Need good enamel quality for bonding
* Keep margins supragingival (ideally 0.5mm away) to ensure cleanability
* Take care with coverage near incisal edge due to translucency
51
How do we minimally prep for anterior RBB (can also do no-prep if suitable)
* Occlusal contact reduction
* Cingulum undercut removal only
* Chamfer margin (0.5mm supra gingival)
52
How do we do a heavier prep for anterior cantilever RBB
* 0.5mm palatal reduction (metal retainer is 0.7mm thick)
* Cingulum rest
* +/- proximal groove
* Chamfer margin (0.5mm supra gingival)
53
What is the preparation for posterior RBB if required
* Occlusal rests
* 180 wrap around with chamfer finish line (0.5mm supragingival)
* +/- proximal grooves
* Can be cantilever or fixed-fixed design
54
Describe the fitting process for RBB
* Retainer usually cobalt chrome or nickel chromium alloy (surface should be sandblasted for retention)
* Clean retainer (through ultrasonic bath or ethanol)
* Treat tooth
* Apply composite luting cement and fit
* Remove excess cement
* Oxygen inhibitor placed around cement margins for 3 minutes (wash off)
* Check occlusion + demonstrate OHI with superfloss and interdental brushes
55
How do we treat a tooth for RBB cementation
* Etch
* Primer for 30 seconds, dry for 2 seconds, no curing required
56
What are different types of bridges that have a conventional component
* classic conventional preparation
* fixed moveable
* hybrid
* spring cantilever
57
What are advantages of conventional fixed-fixed bridge
* robust design
* max retention and strength
* abutment teeth splinted together
* can be used in longer spans
* lab construction straight forward
58
Why is conventional f/f bridge more robust
* This is due to the presence of more retainers which means the bridge can withstand better occlusal forces in the long term
59
Why do conventional f/f bridges have better retention/strength
* This is because it is not just reliant on adhesive, has a degree of mechanical retention
* Keep in mind, chemical bond is not as great as the adhesive bridge
60
When may we use the conventional f/f as a splint aid
* reduce mobility for perio cases
61
What are the disadvantages of conventional fixed-fixed bridge
* Preparation is difficult
* Preparation must be minimally tapered
* Common path of insertion for abutments
* Removal of tooth tissue
62
Why is conventional bridge prep for fixed fixed difficult
ideally want the abutment teeth parallel (either natural or after prepping) to allow for a common path of insertion to increase retention (this is because it means that the crown can only come off in one direction) but this can be difficult to achieve and there is a risk of over tapering which ends up reducing the retention as It creates multiple paths of insertion
63
What are advantages of conventional cantilever bridge
* Conservative design
* Laboratory construction straight forward
* No need to ensure multiple tooth preparations are parallel
64
What are disadvantages of conventional cantilever bridge
* Short span only
* Rigid to avoid distortion
* Mesial cantilever preferred
65
What is the disadvantage of the conventional cantilever bridge being more rigid
more prone to fracture
66
Why are mesial cantilevers preferred
* This is because when one occludes, more likely to bite on the posterior teeth first
* Don’t want the pontic tooth posterior otherwise will result in pressure on the pontic → creates a see-saw effect as the pontic gets pushed down, lifting the retainer
67
When can distal cantilever be used
* Can use a distal cantilever occasionally, useful for creating a shortened dental arch as will be occluding against false teeth
68
What is the procedure for creating a conventional bridge
* Mount study models
* Consider diagnostic wax up and custom impression tray
* Request lab to construct vacuum formed stent
* Select shade
* Lab made stent or make pre-operative putty impression for provisional bridge
* Occlusal or incisal reduction
* Separation of teeth
* Aim for parallelism of tapered surface of each preparation, then confirm
* Consider retentive features if short clinical crown height or overtapered e.g slots and grooves
* Construct provisional bridge
* Make impression and occlusal registration
* Temporarily cement provisional bridge
* Demonstrate cleaning with superfloss
* Write prescription
* Cement definitive restoration
69
What is the function of the lab vacuum formed stent
* Allows construction of provisional
* Allows for tooth prep evaluation
70
What is a fixed moveable bridge
* It comes in two components and it allows for different paths of insertion of the retainers
* There is a ‘female’ and male’ component
* The female component goes on the distal of the anterior abutment and the male portion on the mesial of the pontic
71
What is the main indication for a fixed moveable bridge
* Main indication is when there is different axial inclinations and tooth reduction to have the preparations align would result in a lot of tooth prep + risk of pulp exposure
* It allows for some vertical movement at the mesial abutment tooth
72
What are the advantages of fixed-moveable bridge
* Preparations don’t require a common path of insertion
* Each preparation designed to be retentive independent of others
* More conservative of tooth tissue
* Allows minor tooth movement
* May be cemented in two parts
73
What is the disadvantages of fixed moveable bridge
* Length of span is limited
* Laboratory construction is more complex
* Possible difficulty in cleaning beneath moveable joint (small gap can collect plaque)
* Cant construct provisional bridge – will have to be provide two provisional crowns with no pontic or can provide essix retainer to replace pontic
74
What is a hybrid bridge
* One of the abutments is prepared as a conventional preparation meaning one retainer is a crown
* The other abutment has had minimal preparation and so the other retainer is a metal wing similar to that seen on the RBB
75
Why is a hybrid bridge not desirable
* Not a favourable design as the adhesive wing is likely to debond but will stay put due to the conventional preparation remaining in its place, this allows for the wing to collect plaque
76
What is a spring cantilever bridge
* One pontic is attached to the end of a metal arm that runs across the palate to a rigid connector on the palatal side of the retainer
77
What was the intention behind the spring cantilever design
* It was initially constructed as a conservative preparation to preserve tooth tissue as if there was an anterior tooth missing but there was already a crown on the posterior tooth then that crown was replaced with this type of bridge, sparing the anterior teeth from prep
78
What are advantages of conventional spring cantilever bridge
* Useful if spacing present between upper incisors
* Where adjacent teeth are unrestored
* Where a posterior tooth would provide a suitable abutment i.e already heavily restored
79
What are disadvantages of conventional spring cantilever
* Can only be used to replace upper incisor teeth
* Difficult to clean beneath palatal connector
* May irritate palatal mucosa
* Difficult to control movement of pontic, due to springiness of metal arm and displacement of palatal soft tissues
80
What should we look at when evaluating abutment teeth
* can they withstand force
* are they healthy - no perio/periapical disease
* root surface area?
* root:crown ratio
* angulation/rotation
* surface area of crown
* tooth structure remaining
81
What is the minimum crown:root ratio
of 1:1 crown root ratio i.e the abutment’s roots should at least be the same size & length as the pontic you are going to be placing
82
How do we plan bridge design
1. select abutment
2. select retainer
3. select pontic and connector
4. plan occlusion
5. prescribe material
83
What are the different pontic designs
* sanitary/wash through
* dome/bullet/torpedo
* modified ridge lap
* total ridge lap
* ovate pontic
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84
What is the function of a pontic
* Restore appearance
* Stabilise occlusion
* Improve masticatory function
85
What are design considerations for a pontic
* cleansability
* appearance
* strength
86
How do we ensure a pontic is cleanable
* Should be smooth and polished so plaque doesn’t adhere well
* Surface shouldn’t harbour any joint of porcelain and metal as it will get battered
* Embrasure surface should be smooth and cleansable
87
Why do we need to consider the span when designing the pontic
* Greater the span, greater the thickness of the pontic
88
How should the occlusal surface of the pontic look
* Want it to resemble replacement tootoh
* Narrower if possible to enable cleaning
* Should have sufficient occlusal contact
89
What are considerations we need to think about in regards to the approximal surface of the pontic
* connector - should be strong (2x2mm)
* embrasure space - keep it if aesthetics arent important. helps keep clean
90
What is a wash through ridge surface
* Also known a hygienic or sanitary
* Makes no contact with soft tissue
* It is functional rather than for appearance
* Because of space it is easy to clean and get stuff through
91
Where should wash through pontic be considered
Consider it in lower molar area
92
What is dome shaped ride surface pontic
* Also known as torpedo or bullet shape
* Acceptable if occlusal 2/3 of buccal surface is visible
* The occlusal 2/3 of the pontic is tooth like but the lower 1/3 is narrowed in a bit so it helps with cleansability
93
Where can dome shaped pontics be useful
Useful in lower incisors, premolars or upper molars
94
What is modified ridge lap pontic
* Buccal surface looks as much like tooth as possible
* Lingual surface is cut away
* This leaves some space in the lingual/palate side to clean better but there have been issues with food packing on the lingual surface of the ridge because of the space
* It is in line contact with the buccal of the ridge
95
What is ridge lap/saddle
* Has greatest contact with soft tissue
* If designed carefully it can be cleansed
* Less food packing than ridge lap
* Care should be taken not to displace soft tissue or cause blanching of the tissue
96
What is ovate pontic
* Where you mould the gingiva
* Add composite to create a shape in the gingiva and keep moulding until you can prescribe an ovate pontic for the final bridge
* Only ok for patients with good OH
97
What are the 4 categories for bridge materials
* all metal
* metal ceramic
* all ceramic
* ceromeric
98
What are the different types of metals used for bridges
* gold
* nickel/CoCr
* stainless steel
99
How should all metal bridges be cemented
* *All metal conventional bridgework should be cemented with either GI luting cement (aquacem) or RMGI luting cement (relyX luting)*
100
What is the most common material for bridges (conventional)
metal ceramic
101
How are metal ceramics cemented in
* *Cemented with same material as all metal*
* *GI luting cement (aquacem) or RMGI luting cement (relyX luting)*
102
What are the different all ceramic materials
* zirconia
* lithium disilicate
103
Why is zirconia becoming more popular
* Very strong
* Good aesthetics
* Similar reduction to MCC
* Preparations on casts are scanned and it is milled and sometimes a layer of porcelain is added on top for aesthetics
104
How is all ceramic bridges cemented on
* *Bonded with dual cure resin cement (NESUX kit)*
105
Wha are RBB cemented on with
*anaerobic dual cure resin cement with 10MDP which helps the tooth stick to the metal work. The brand name is Panavia 21*
