CSAR 33, 34, 35 - Bridges

Question 1

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

Answer 1

Angulation
Vitality
Crown-root ratio

Question 2

When are articulated study models needed before tooth preparations?

Answer 2

Long bridge spans
Multiple extracoronal restorations
Reorganising occlusion

Question 3

Why are bridges used?

Answer 3

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

Question 4

What is the retainer of the bridge?

Answer 4

Restoration that attaches the bridge to the abutment tooth/teeth

Question 5

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

Answer 5

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

Question 6

How are RBB attached to tooth prep?

Answer 6

Resin-based cements for adhesion

Question 7

What are advantages and disadvantages of conventional bridges?

Answer 7

+ 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

Question 8

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

Answer 8

PARALLEL

Question 9

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

Answer 9

Has a stress breaker

Teeth don’t need to be parallel

Question 10

What are the connections on a fixed-moveable bridge?

Answer 10

One side rigid support

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

Question 11

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

Answer 11

Small amount of vertical movement

Resists lateral movement

Question 12

What are advantages and disadvantages of adhesive bridges?

Answer 12

+ 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

Question 13

What is the difference between minor and major bridge retainers?

Answer 13

Major need full occlusal coverage and minor don’t

Question 14

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

Answer 14

• 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

Question 15

When are conventional bridges more suitable than adhesive?

Answer 15

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

Question 16

What is Ante’s law when treatment planning dentures?

Answer 16

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

Question 17

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

Answer 17

The endo must be good, or redo it

Question 18

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

Answer 18

• 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

Question 19

What is the optimum crown-root ratio and why?

Answer 19

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

Question 20

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

Answer 20

Increases load on abutment teeth

Less rigid and increased flexing, resulting in fractures/debonding

Question 21

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

Answer 21

Add pink porcelain

Question 22

Why should a bridge with double abutments be avoided?

Answer 22

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

Question 23

What are advantages and disadvantages of fixed-fixed bridges?

Answer 23

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

• Parallel preps = DIFFICULT
• Destructive
• Cementation is difficult

Question 24

What are advantages and disadvantages of fixed-moveable bridges?

Answer 24

+ 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

Question 25

What are advantages and disadvantages of cantilever bridges?

Answer 25

+ 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

Question 26

Why would a bridge fail?

Answer 26

One abutment loosens Debond and fall out Fracture

Question 27

Why would an abutment fail?

Answer 27

``` Loss of vitality Endo failure Caries Periodontal disease Fracture of natural crown ```

Question 28

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

Answer 28

Sensitivity

Question 29

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

Answer 29

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

Question 30

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

Answer 30

Group function

Question 31

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

Answer 31

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

Question 32

What type of margin is created with a RBB?

Answer 32

Chamfer margin, to help with seating the wing

Question 33

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

Answer 33

``` Sandblast metal with alumina Silicate coating Tin plating Primer added Enamel surface etch ```

Question 34

Why may a cingulum rest help adhesive with a RBB?

Answer 34

Resists sheer stress and acts as a locating device

Question 35

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

Answer 35

Possible crown lengthening using electrocautery

Question 36

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

Answer 36

To stop grey shine through use an opaque cement

Question 37

What is the process when cementing a RBB with panavia?

Answer 37

* 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

Question 38

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

Answer 38

* 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

Question 39

What is the bucket handle effect of anterior bridges?

Answer 39

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