Restoration of cavities with different materials

Question 1

What percentage of fractured teeth had been previously restored?

Answer 1

92% of fractured teeth been previously restored

Question 2

Describe the events leading to a fracture of a restored tooth (5)

Answer 2

• Deflection of cusp weakened by restoration
• Open interface between
  restoration and tooth
• Microleakage
• Recurrent caries
• Fracture

Question 3

Comment on the fracture resistance of a restored tooth

Answer 3

The fracture resistance of the restored tooth is lower than of the unrestored regardless of the cavity shape and restoration material

Question 4

What can high stress at the tooth restoration interface cause?

Answer 4

Cause crack propagation and fatigue failure on mastication

Question 5

What is photoelasticity?

How does it work?

How is stress seen in this?

Answer 5

• Stress analysis technique using 2 indexes
• Ray of light passing through a birefringent material experiences two refractive indices
• Stress is seen as fringes

Question 6

What is finite element analysis?

Answer 6

Computer modelling technique of stress distribution

Question 7

Where will cracks occur in bonded restorations?

Answer 7

Within the enamel in contact to the opposing tooth

Question 8

Where will cracks occur in non-bonded restorations?

Answer 8

Internal line angles and EDJ

Question 9

What considerations should be taken when applying a restoration?

Stress?
Shape?

Answer 9

• Stress should be uniform and minimised along the interface
• No sharp edges and corners
• Bigger curvature radius of the base