L1 Crown intro and core construction

Question 1

What materials can a crown be made of?

Answer 1

• Metal (gold or non-precious alloy)
• All ceramic
• Metal ceramic
• Composite

Question 2

What are the indications for crowns?

Answer 2

• Protect remaining tooth structure where an internal restoration is not possible
• Aesthetics
• Maintenance of stable occlusion e.g. excessive tooth wear

Question 3

How many crowned teeth lose vitality after 5 years?

Answer 3

1-15%

Question 4

What is a core?

Answer 4

A restoration placed inside of a tooth prior to the placement of a crown.
For extensively damaged teeth.

Question 5

What materials are used for crown core buildup?

Answer 5

• Amalgam
• Composite (including Paracore and EverX)
• Glass ionomer
• Resin modified GIC

Question 6

What are the advantages of an amalgam core?

Answer 6

• Good bulk strength
• Not technique sensitive
• Can be bonded in place (Panavia)
• Well known, good long term track record

Question 7

What are the disadvantages of an amalgam core build up?

Answer 7

• Non-adhesive in itself
• Need to wait 24 hours before prep
• Weak in thin sections (not suitable for anterior teeth)
• Minimata treaty, commitment to reduce amalgam use

Question 8

What are the advantages of composite for core build up?

Answer 8

• Strong
• Can be used in thin sections
• Can be prepared immediately

Question 9

What are the disadvantages of composite for core build up?

Answer 9

• Technique sensitive, moisture control
• Requires dentine bonding agents
• Polymerisation shrinkage
• Increased placement time
• Can be difficult to distinguish between core material and tooth when preparing finshing line due to colour similarities (choose an obviously different colour)

Question 10

What is ParaCore?

Answer 10

A composite-based, dual cured, radiopaque core build up material which comes in automix syringes.
Available in 3 shades:
- Dentin
- White
- Translucent

Can be light cured to increase rate of setting.

Question 11

When are GIC and RMGIC used in core build ups?

Answer 11

• Useful fillers (placed between RCT and composite)

Question 12

Describe the features of GIC and RMGIC in crown core build ups.

Answer 12

• Naturally adhesive
• Release fluoride
• Insufficient strength for large cavities under occlusal loading
• Brittle
• Need at least 1-2mm of sound tooth tissue beneath the crown

Question 13

What is EverX?

Answer 13

• Known as ‘hairy composite’
• Modified with varying lengths of reinforcing fibres which create a meshwork
• Reduces risk of crack propagation
• Can’t be left exposed as the fibres cause tissue irritation to the gums

Question 14

How can core retention be improved?

Answer 14

• Cavity modifications (slots and grooves)
• Adhesive bondings
• Auxiliary pins (no longer used)

Question 15

What type of core is used with amalgam?

Answer 15

Nayyar core
- Core into the canals

Question 16

How can adhesive bonding be used to improve core retention?

Answer 16

• Panavia can be used to bond amalgam
• Conventional bond for composite
• Technique sensitive, follow manufacturers instructions

Question 17

Describe auxiliary (dentine) pins.

Answer 17

• Traditional (old fashioned)
• Effective
  High risk for:
• Pulpal and periodontal trauma/injury
• Fractured/crazed dentine
• Can become loose

Auxiliary pins are no longer used, but other pin types are

Question 18

What considerations should be made regarding pin placement?

Answer 18

• Only use 1 pin per cusp
• Must position at least 1mm away from the ADJ
• Place away from the pulp
• Use a slow speed drill in an in/out motion to clear debris
• Place pin using slow speed

Question 19

What type of pins are used in practice?

Answer 19

• Self shearing pins (drill hole and insert pin) aka Unity pins
• Cemented pins (seldom used)