Bridges Flashcards

1
Q

Benefits of Resin Bonded Bridges (4)

A

Minimally invasive
Good survival rate
Cheap and fast
Ideal for hypodontia cases

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2
Q

What must you consider when designing adhesive bridges (8)

A

Perio support
Occlusal loading (which way force will go)
Conservative design
Cleansability
Aesthetics
Rigidity
Abutment (quant and qual)
Choice of adhesive luting (cement)

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3
Q

Why are single unit, cantilevers the best (3)

A

Pontic moves with abutment

Reduced shear forces on pontic

Lower risk of debond and caries

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4
Q

min thickness of retainer in adhesive bridges

A

0.7mm

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5
Q

how much prep for adhesive bridges?

A

kept to an absolute minimum
- Anterior teeth may not even be prepped at all

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6
Q

pros (3) and cons (2) of no prep adhesive bridges

A

Pros:
- Conservative, leaves enamel for bonding
- no sensitivity
- if not in occ, no need for cingulum rest

Cons:
- a lot of load on cement if teeth are in occlusion
- may be difficult to locate the wing during cementation (is it in the right place?)

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7
Q

2 types of preparation for adhesive bridges + reasoning

A
  1. axial tooth prep
    - increases SA for bonding, resistance and retention form
  2. Grooves
    - resists lateral displacment
    - increase rigidity
    - increases resistance to debonding forces
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8
Q

Should you place a cingulum rest when doing prep for an adhesive bridge? why or why not?

A

Only if tooth is already restored and you are drilling into comp- helps resist axial forces. helps locating position as well.

IF tooth is unrestored, better to preserve enamel

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9
Q

What is the point of occlusal rest seats in adhesive bridges

A

Transmits occlusal forces along long axis of tooth
- should be kept minimal and within enamel
- Can also help locate the wing

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10
Q

Canines vs centrals as abutments for adhesive bridges

A

Canine:
- Bulbosity may cause connector to be too thin/fragile
- Impede aesthetics
- Use guide plane to overcome this

Centrals
- Metal can shine through due to translucent enamel
- Use opaque cement to overcome this

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11
Q

What teeth make for poor abutments (5)

A
  1. Laterals
  2. Tilted incisors (unfavourable pulp chambers)
  3. Root-filled
  4. Heavily restored
  5. Perio compromised
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12
Q

Mechanism of failure with fixed-fixed adhesive bridges

A
  • Stress due to differential tooth movements between the abutments during tooth contact
  • These forces tend to push one of the abutments away from the pontic
  • Increased tensile stress on cement
  • Debonding of abutment and caries under the retainer

same concept applies to double abutments (34+35 to replace 33)

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13
Q

pros and cons of prepped adhesive bridges

A

Pros:
- Conservative prep compared to conventional bridge
- fixed resto w/o compromising abutment
- Less endo complications resulting from extensive prep
- Faster and cheaper

Cons:
- technique sensitive
- aesthetic issues due to metal wing
- debonding issues
- lack of studies

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14
Q

synonym for adhesive bridge

A

RBB

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15
Q

Main challenge of anterior RBB and how to avoid (2)

A

Metal connector shine through
- Most common reason for patient dissatisfaction with RBB

Avoid by:
- Using opaque cement
- Design retainer to avoid extension of metal within 2mm of incisal edge

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16
Q

What is a locating tag used for in adhesive bridges / RBB

A
  1. helps you position the retainer in the correct orientation
  2. resists displacment during cementation
  • if you didnt prep, can be difficult to position the pros exactly right
  • Locating tag hangs over incisal edge
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17
Q

what to do if grey shines through the abutment from RBB and opaquer doesnt help? (2)

A

Consider changing the abutment tooth (ex. canine rather than central)

composite veneer

18
Q

Why can fixed-fixed RBBs work anteriorly when using canines for abutments?

A
  1. Less occlusal loading than posterior
  2. Canines are good abutments bc:
    - High SA
    - Crown to root ratio
    - Similar mvmt characteristics of abutment teeth
    - Greying can be masked
19
Q

Rules for occlusion in RBB

A
  1. Must do pre-op assessment of ICP, dynamic excursions to ensure room
  2. Should be in LIGHT contact, otherwise opposing tooth will overerupt
  3. pontic should NOT be involved in guidance, where possible
  4. ICP contact should be kept away from margin of retainer
  5. If space is limited, metal framework can be cemented high
20
Q

pros (4) and cons (5) of fixed fixed bridges

A

pros
- predictable, aesthetic
- good for cases where implant not poss
- even force distribution
- can be used ant/post, long spans, perio spinting

cons
- invasive
- requires meticulous planning of occlusion
- pulpal death in abutments, will need to be remade after RCT
- $$$
- requires excellent OH

21
Q

Advantages of canitlever bridges (5)

A
  1. Good aesthetics
  2. more conservative, less complications
  3. less chance of caries development
  4. non-catastrophic failure
  5. good option for single tooth replacement
22
Q

Disadvantages of cantilever bridges (3)

A
  1. Risk of debonding, esp on RCT teeth
  2. Metal shine through
  3. Not ideal for load bearing cases
23
Q

Advantages of fixed-movable bridges (4)

A
  1. since bridge can flex, less load on the retainer
  2. Allows for partial coverage- less prep
  3. Compensates for abutment misalignment
  4. Allows for individual mvmt of sections
24
Q

Disadvantages of fixed-movable bridges (5)

A
  1. Destructive- think of dovetail prep on abutment
  2. Metal of joint may show
  3. Wear and mechanical failure of joint can happen
  4. Try in and cementation difficult
  5. Difficult for technician to make
25
Q

3 types of stress that occur in a fixed bridge

A

tensile

compressive

shear stress

26
Q

what type of stress is dental porcelain susceptible to?

A

Shearing
- when the resto is twisted
- thats why you see failure of PFM in the proximals, rather than occlusal

27
Q

ideal measurement (thickness) of the metal connector in a bridge

A

at least 2.5mm occluso-gingivally and bucco-lingually

*will need to write this measurement of your desired thickness on lab forms for pfm

28
Q

PFM vs Layered zirconia
(6)

A

PFM
- Stronger
- Better for posteriors
- Good for bruxists
- Can incorporate movable joint
- Potentially less invasive (metal backing w/o porcelain)
- Good long-term evidence

Layered zirconia
- Problems with chipping/breaking
- Aesthetic, better for anteriors
- Not ideal for bruxirs
- Cannot incorporate joints
- Lacks long-term evidence

29
Q

Are pier abutments good?

A

No
Abutments will move differently -> leakage
- Do two single units instead
- Only time pier is good is in perio compromised teeth with some degree of mobility (splinting), but if abutments are healthy: “No no”

30
Q

Solutions to malpositioned abutments (mesially drifted) (4)

A
  1. Recontour
  2. Telescopic crowns
  3. 3/4 crown prep w/ fixed/movable design (most conservative)
  4. ortho
31
Q

3 considerations when choosing a pontic

A
  1. Cleansibility
  2. Abutment height
  3. Aesthetics
32
Q

ID + pros (2) and cons (5)

A

Saddle Ridgelap
- Very aesthetic
- good pt adaptability bc it feels like real tooth

Cons:
- difficult to remove excess from under pontic
- poor cleaning ->
- food trap ->
- inflammation of soft tissues ->
- gingival recession

33
Q

Pontic design consideration in relation to soft tissues

A

Pressure-free / passive contact btw pontic and soft tissues

Passive contact only on the attached gingiva, if contact on free gingiva, will ulcerate

34
Q

ID + pros (4) and cons (2)

A

Modified ridge lap
Pros:
- good aesthetics
- easy to remove xs cement
- easier to clean
- can replace any tooth

Cons:
- requires pt adaptation (doesnt feel like real tooth)
- May cause air/saliva percolating through embrasures, esp in anterior during speaking

35
Q

ID + pros (2) /cons (3)

A

Sanitary / Hygienic pontic
Pros:
1. Ideal cleansibility
2. Easy to remove excess cement from pontic

Cons:
1. Requires pt adaptation (doesnt feel like real tooth)
2. lacks aesthetics (posterior only)
3. pts need to accustom to design during provisionalisation before it can be made definitively

36
Q

ID + pros (3) / cons (2)

A

Ovate pontic
Pros:
- most aesthetic
- ideal for anteriors, esp high lip lines
- OH can be maintained

Cons:
- requires more effort to mould soft tissue (ex. surgery to remove bone or soft tissues)
- requires multiple appts

37
Q

What pontic to use for mx anterior + alt

A

Ovate

alt- mod ridge lap

38
Q

What pontic to use for mx posterior

A

mod ridge lap

39
Q

What pontic to use for md anterior + alt

A

ovate

alt- mod ridge lap

40
Q

What pontic to use for md posterior + alt

A

Sanitary

alt- mod ridge lap

41
Q

Most common fixed bridge complications in descending order
(8)

A
  1. Caries
  2. Need for RCT
  3. Lost retention
  4. Aesthetics
  5. Perio
  6. Tooth fracture
  7. Pros failure
  8. Porcelain fracture