bridgework design and materials

Question 1

What is the success rate of a resin bonded cantilever bridge?

Answer 1

80% over 5 years

Question 2

What is the success rate of a fixed-fixed resin bonded bridge?

Answer 2

90% over 5 years

Question 3

What occlusal information is needed before a bridge is placed?

Answer 3

Find incisal class
Whether canine guidance or group function
Are teeth overerupted
Will bridge interfere with current occlusion
Are there signs of parafunction

Question 4

What needs to be thought about when designing and planning for a bridge?

Answer 4

Will the bridge require prep - none, minimal or conventional
What material to use
Evaluate abutments
Cleansability
Appearance

Question 5

Name 4 parts about abutment teeth that should be evaluated?

Answer 5

Any from :
- root configuration
- angulation or rotation of tooth
- periodontal status
- surface area for bonding
- quality of enamel
- risk of pulpal damage
- remaining tooth structure present
- quality of any endodontic treatment

Question 6

What are the stages of bridge design?

Answer 6

1. Select abutment teeth
2. Select retainer
3. Select pontic and connector
4. Plan the occlusion
5. Prescribe the material

Question 7

What are the different types of pontic?

Answer 7

1. Wash-through pontic
2. Dome pontic (bullet shaped or torpedo shaped)
3. Modified ridge-lap pontic
4. Ridge lap pontic (full saddle pontic)
5. Ovate pontic

Question 8

What are the functions of a pontic?

Answer 8

Restore appearance of missing tooth
Stabilise the occlusion
Improve masticatory function

Question 9

What should be considered when designing a pontic?

Answer 9

Cleansability - should always be smooth, surface should not harbour join of metal and porcelain
Appearance - as tooth like as possible
Strength - the longer the span, the greater the thickness required to withstand the occlusal forces

Question 10

Describe a wash-through pontic

Answer 10

Makes no contact with soft tissues
Functional rather than appearance
Considered in lower molar area

Question 11

Describe a dome-shaped (torpedo or bulled-shaped) pontic

Answer 11

Useful in lower incisor, premolar or upper molar area
Upper 2/3 looks like a real tooth
Poor aesthetics if lower 1/3 is visible
Lower 1/3 allows for better cleaning

Question 12

Describe a modified ridge-lap pontic

Answer 12

Buccal surface looks as tooth like as possible
Lingual surface cut away (tooth looks good from facial perspective)
Line contact with buccal or ridge
Problems with food packing on lingual ridge

Question 13

Describe a ridge lap/saddle pontic

Answer 13

Greatest contact with soft tissue
If designed well, can be cleaned
Less food packing than ridge lap
Care taken not to displace soft tissue or cause blanching of tissue

Question 14

Describe an ovate pontic

Answer 14

Good for patients with good oral hygiene
Presses down on gingivae causing gingivae to mould into a divot, moulding the gingivae
Used in tandem with an Essix retainer to mould the gingivae giving a good aesthetic appearance

Question 15

What material types are used for conventional bridges

Answer 15

All metal - gold, NiCoCr or SS
Metal ceramic
All ceramic - zirconia or lithium disilicate (Emax)
Ceromeric - porcelain combined with composite eg - BelleGlass

Question 16

Where are gold and metal ceramic bridges often used?

Answer 16

Gold - lower posterior area
Metal ceramic - anywhere, majority of bridges in UK

Question 17

Describe the clinical procedure for conventional bridgework before preparing the teeth

Answer 17

Mounted study models
Consider diagnostic wax up
Request lab to construct a vacuum formed stent
Select shade
Impression for provisional bridge

Question 18

Describe the clinical procedure for conventional bridgework while prepping the teeth

Answer 18

Occlusal or incisal reduction
Separation of teeth
Aim for parallelism
Consider retentive features such as slots or grooves

Question 19

Describe the clinical procedure for conventional bridgework after prepping the teeth

Answer 19

Construct provisional bridge
Make impression and occlusal registration
Temporarily cement provisional bridge
Demonstrate cleaning with superfloss
Write/draw prescription for technician (pontic, abutments, shades, materials)

Question 20

Why is parallelism used in tooth prep for bridges

Answer 20

So bridge only has a single path of insertion, making better retention
Be careful not to make an undercut

Question 21

What cement is used for an all metal conventional bridge?

Answer 21

Aquacem (GI luting cement) or
RelyXLuting (RMGI luting cement)

Question 22

What cement is used for a metal ceramic bridge?

Answer 22

Aquacem (GI luting cement) or
RelyXLuting (RMGI luting cement)

Question 23

What cement is used for an adhesive/resin bonded/resin retained bridge?

Answer 23

Panavia 21 (dual cure resin cement with 10-MDP)

Question 24

What cement is used for an all ceramic bridge?

Answer 24

NEXUS kit (dual cure resin cement)

Question 25

What is the purpose of 10-MDP?

Answer 25

Helps tooth stick to medal

Question 26

Why should distal cantilevers be avoided?

Answer 26

Occlusal forces on pontic will produce leverage forces on the abutment causing it to tilt

Question 27

When is a distal cantilever considered?

Answer 27

From premolar abutment if unopposed or opposed by a denture to give the patient second premolars (shortened dental arch)