CSAR 33, 34, 35 - Bridges Flashcards

1
Q

What do you need to know about abutment teeth before any prep?

A

Angulation
Vitality
Crown-root ratio

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2
Q

When are articulated study models needed before tooth preparations?

A

Long bridge spans
Multiple extracoronal restorations
Reorganising occlusion

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3
Q

Why are bridges used?

A
Aid chewing and speech 
Distribute forces
Prevent drift 
Aesthetic 
Maintain face shape
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4
Q

What is the retainer of the bridge?

A

Restoration that attaches the bridge to the abutment tooth/teeth

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5
Q

What do conventional bridges rely on when placed? And what 3 types are there?

A

Rely on crown principles for retention
Cantilever
Fixed-fixed
Fixed-moveable

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6
Q

How are RBB attached to tooth prep?

A

Resin-based cements for adhesion

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7
Q

What are advantages and disadvantages of conventional bridges?

A

+ Abutments may already be heavily restored
+ Can alter shape and colour of teeth
+ Retention better if crown principles applied correctly
+ Last longer than adhesive bridges

  • Use crowns as retainers is very destructive
  • Impression-taking more difficult = silicone used which is hydrophobic
  • Longer preparation time
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8
Q

What shape are the tooth preparations of fixed-fixed bridges?

A

PARALLEL

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9
Q

What is the advantage of using a fixed-moveable bridge over a fixed-fixed bridge?

A

Has a stress breaker

Teeth don’t need to be parallel

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10
Q

What are the connections on a fixed-moveable bridge?

A

One side rigid support

Other side intra/extra-coronal attachments and small degree of movement

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11
Q

What movements are allowed and resisted by a fixed-moveable bridge?

A

Small amount of vertical movement

Resists lateral movement

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12
Q

What are advantages and disadvantages of adhesive bridges?

A

+ Preservation of sound tooth tissue
+ Little preparation
+ Impression taking very much easier

  • Don’t last as long
  • Cannot change shape of abutment teeth
  • Can discolour abutments if they are thin
  • Heavily restored abutments not ideal – need ENAMEL!
  • Shine through of wing
  • Hard to try-in
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13
Q

What is the difference between minor and major bridge retainers?

A

Major need full occlusal coverage and minor don’t

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14
Q

When planning for a bridge, what do you want to know about the edentulous ridge?

A
  • Ridge shape (pontic selection)
  • Alveolar bone loss (disguise or augment)
  • Retained roots
  • Unerupted teeth = need to let patient know that they are there and document it
  • Lip line
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15
Q

When are conventional bridges more suitable than adhesive?

A

Heavily restored teeth when can not be bonded to enamel
Long spans
Repeated failure of adhesive bridges
Implants not possible

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16
Q

What is Ante’s law when treatment planning dentures?

A

THE TOTAL PERIODONTAL MEMBRANE AREA OF THE ABUTMENT TEETH MUST EQUAL OR EXCEED THAT OF THE TEETH TO BE REPLACED

17
Q

When using an abutment tooth that has had endo, what should be known of the tooth?

A

The endo must be good, or redo it

18
Q

What abutment teeth are preferred due to their root shape and angulation?

A
  • Molars with divergent roots offer more support than those with straight conical roots
  • Single rooted teeth with elliptic cross sections offer more support than those with a circular cross section
19
Q

What is the optimum crown-root ratio and why?

A

Optimum crown-root ratio 2:3
Large root – coronal part may break
Small root – root may break
Official minimum is 1:1 = IF OPPOSED BY DENTURE

20
Q

What happens to forces on a bridge with a longer span?

A

Increases load on abutment teeth

Less rigid and increased flexing, resulting in fractures/debonding

21
Q

If there are small defects in the alveolar ridge due to bone loss when placing a bridge, what can be done to correct this?

A

Add pink porcelain

22
Q

Why should a bridge with double abutments be avoided?

A

Central abutment acts as a fulcrum causing debonding of the peripheral retainer

23
Q

What are advantages and disadvantages of fixed-fixed bridges?

A

+ Robust with maximum retention and resistance
+ Recommended for larger bridges

  • Parallel preps = DIFFICULT
  • Destructive
  • Cementation is difficult
24
Q

What are advantages and disadvantages of fixed-moveable bridges?

A

+ Preps do not need to be parallel
+ More conservative as prep for minor retainer less than major
+ Allows minor movements of teeth
+ Parts can be cemented separately

  • Length of span limited
  • Complex laboratory process
  • Temporisation is difficult
  • More expensive
25
Q

What are advantages and disadvantages of cantilever bridges?

A

+ Most conservative easier prep
+ Anterior region where occlusion is favourable

  • Limited to one pontic
  • Rigid construction
  • Occlusal forces can encourage tilting posteriorly if the pontic is distally positioned
  • Occlusal forces can encourage rotation of abutment anteriorly if care not taken with occlusion
26
Q

Why would a bridge fail?

A

One abutment loosens
Debond and fall out
Fracture

27
Q

Why would an abutment fail?

A
Loss of vitality
Endo failure 
Caries 
Periodontal disease
Fracture of natural crown
28
Q

After prepping a tooth for a RBB and not putting a temporary over it, what might the patient complain of?

A

Sensitivity

29
Q

After prepping a tooth for a RBB why mustn’t fluoride varnish be placed on after?

A

Fluoride ion integrates with hydroxyapatite and changes the surface, affecting bonding

30
Q

If can not get Pontic tooth out of guidance, what type of guidance is referred?

A

Group function

31
Q

When doing a preparation for a RBB what should you do to ensure bonding success?

A

Have 180 degrees wraparound
Occlusal coverage posteriorly to increase surface area for bonding and reduce sheer stress
Minimum thickness of 0.7mm to reduce flexing

32
Q

What type of margin is created with a RBB?

A

Chamfer margin, to help with seating the wing

33
Q

Before bonding of RBB, what steps can aid success of bonding

A
Sandblast metal with alumina 
Silicate coating 
Tin plating 
Primer added 
Enamel surface etch
34
Q

Why may a cingulum rest help adhesive with a RBB?

A

Resists sheer stress and acts as a locating device

35
Q

How may you ensure you have adequate crown height for a bridge preparation?

A

Possible crown lengthening using electrocautery

36
Q

When using a metal wing on a RBB, what cement would be best?

A

To stop grey shine through use an opaque cement

37
Q

What is the process when cementing a RBB with panavia?

A
  • Clean abutment
  • Etch for 10s, rinse and dry
  • Apply ED Primer II to entire abutment surface, leave for 30s, then dry
  • Apply the mixed panavia paste to the wing
  • Firmly seat the retainer and maintain finger pressure for 60s
  • While maintaining finger pressure remove all excess with a microbrush/probe
  • Light cure for 20s or Oxyguard and leave for 3 min then rinse off Oxyguard
  • Remove any excess
38
Q

Why would bond failure occur in a bridge? and how is this overcome?

A
  • Inadequate moisture control
  • Inadequate seating resulting in uneven cement layer
  • Inadequate surface treatment of fit surface
  • Cement out of date/ instructions not followed

What to do if it is a bond failure
• Remove all existing cement
• Sand blast
• Rebond

39
Q

What is the bucket handle effect of anterior bridges?

A

Curve involved when placing Pontic teeth in their natural position, not straight line
Tilting forces on abutment teeth are greater