Bridgework 2

Question 1

What are the different types of conventional bridges?

Answer 1

Fixed-Fixed
Fixed Cantilever
Fixed Moveable
Hybrid- fixed retainer And adhesive retainer
Spring cantilever

Question 2

What is a fixed-fixed bridge?

Answer 2

This type of bridge has a retainer at each end with a pontic in the middle joined by rigid connectors- can be all ceramic or metal/ceramic
E.g. (Retainer)-(pontic)-(Retainer)

Question 3

What are the advantages of a conventional fixed-fixed bridge design?

Answer 3

Robust design- larger connectors to withstand occlusal forces

Maximum retention (chemical and mechanical) and strength

Abutment teeth splinted together -Perio cases with mobile teeth

Can be used in longer spans

Laboratory construction straightforward

Question 4

Why are longer spans more achievable in patients with Class II or AOB?

Answer 4

Low levels of occlusal force on bridge due to minimal if any contact

-> Biting on pontics makes bridge more likely to fail

Question 5

What are the disadvantages of conventional fixed-fixed design?

Answer 5

Preparation difficult- parallel tooth preparations needed to create single POI

Preparation must be minimally tapered (5-7 degrees is ideal)

Common path of insertion for abutments

Removal of tooth tissue (danger to pulp)

Question 6

What is a cantilever bridge?

Answer 6

Bridge that provide support for Pontic at one end only
-> there is no retainer on other side of Pontic

Question 7

What are the types of cantilever bridge

Answer 7

Conventional/crown retainer OR
Adhesive/resin retained – metal wing

Question 8

What are the advantages of Cantilevers?

Answer 8

Conservative design- Compared to fixed-fixed conventional design

Laboratory construction straightforward

No need to ensure multiple tooth preparations are parallel

Question 9

What are the disadvantages of Cantilevers?

Answer 9

Short span only

Rigid to avoid distortion- fracture risk

Mesial cantilever preferred- pontic tooth is more anterior

Question 10

When may a distal cantilever be used?

Answer 10

Missing teeth

SDA

Question 11

When would a fixed moveable bridge be used?

Answer 11

If abutment teeth aren’t parallel (different POIs)

Question 12

How does a fixed-moveable bridge work?

Answer 12

A slot is made on the crown of distal marginal ridge of anterior tooth (female component), the pontic that is attached to the posterior crown has a male component which slots into the female component

Question 13

What are the features of fixed-moveable bridges?

Answer 13

This type of bridge has a rigid connector usually at the distal end of the pontic and a moveable connector mesially

-> Allows some vertical movement at the mesial abutment tooth

Question 14

What are the advantages of fixed-moveable bridges?

Answer 14

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

Question 15

What are the disadvantages of FM bridges?

Answer 15

Length of span limited- only used to replace one tooth

Laboratory construction more complicated

Possible difficulty in cleaning beneath moveable joint

Can’t construct provisional bridge- would need to accept space or provide denture/essix retainer

Question 16

What is a hybrid bridge?

Answer 16

One retainer = “Conventional” preparation

Other retainer = minimal preparation
(Adhesive /Resin retained/Resin bonded)

Question 17

Why are hybrid bridges considered obsolete?

Answer 17

metal adhesive wing is more likely to debond resulting in undetected leakage and caries

Question 18

What is a spring cantilever?

Answer 18

One pontic attached to the end of a metal arm that runs across the palate to a rigid connector on a posterior retainer

-> adhesive preferred now

Question 19

What are the advantages of SC?

Answer 19

Useful if spacing present between upper incisors

Where adjacent teeth are unrestored

Where a posterior tooth would provide a suitable abutment (i.e. already has a crown/large direct restoration)

Question 20

What are the disadvantages of SC?

Answer 20

Can only be used to replace upper incisor teeth

Difficult to clean beneath palatal connector

May irritate the palatal mucosa- mucositis

Difficult to control movement of pontic, due to springiness of metal arm and displacement of palatal soft tissues

Question 21

What are the requirements for abutment teeth?

Answer 21

Must be able to withstand the forces previously directed to the missing teeth

Supporting tissues should be healthy and free of inflammation
i.e. periapical disease and periodontal disease

Crown to root ratio- length of tooth coronal to alveolar crest compared to length of root embedded in bone (Optimum ratio 2:3, but Minimum ratio 1:1)