Composite vs Amalgam

Question 1

Why is replacing a restoration such an issue? (4)

Answer 1

Restoration can lead to structural degradation and multiple hits decrease longevity:
Increased stress fields due to
-placement of adjacent restorations
-other destructive lesions
-change in physical properties
-fatigue effects
Restoration failure
Restoration replacement
Further loss of tooth structure
Worsened due to occlusal loading, reduced oclcusal support and stress-induced parafunction

Question 2

Environmental challenges in the oral cavity (5)

Answer 2

Constantly wet
T changes
Variable pH
Bacterial biofilm
Tooth-materials interactions

Question 3

How compromised is a restored tooth (Stat)? (1)

Answer 3

MOD cavity and/ or ‘passive restoration’ (non-adhesive e.g. amalgam) reduces cuspal stiffness by 63%

Question 4

Factors that determine restoration survival (4)

Answer 4

Build quality
Product handling
Environment
Maintenance

Question 5

Variables when it comes to posterior composites with no RCTs (6)

Answer 5

Tooth status
Occlusal forces
Materials
Variable expertise
Technique
Maintenace

Question 6

Mean annual failure rate in posterior stress-bearing restorations: amalgam vs direct composite (2)

Answer 6

Amalgam 3% +/- 1.9
Direct composite 2.2% +/- 2.0
*is this right???

Question 7

Principal reasons for failure in posterior stress-bearing restorations (5)

Answer 7

2. caries
Fracture
-tooth fracture more in amalgams
-restoration fracture more in composites
Marginal deficiencies
Wear
Post-op sensitivity

Question 8

High risk vs low risk failure rate (3)

Answer 8

Substantially higher in high-risk group
Caries found in high risk patients - more in composites
Fracture and cracked tooth syndrome predominantly with amalgam
Otherwise no difference between materials

Question 9

Advantages of adhesive restoration (2)

Answer 9

Smaller cavities for early carious lesions

-5% of occlusal surface vs 25% for amalgam

Question 10

Polymerisation: you need to (3)

Answer 10

Achieve an adequate degree of cure (conversion)
Achieve and adequate depth of cure (at all levels of the material)
Overcome the effects of shrinkage with photoinitiatiors, effectiveness of light-curing and clinical technique

Question 11

Polymerisation: what affects shrinkage strain (5)

Answer 11

Volumetric polymerisation shrinkage
Speed and intensity of activation
Ratio of free to bonded surface area
Configuration factor and volume of composite
Elastic modulus of resin composite

Question 12

Consequences of polymerisation shrinkage and shrinkage stress (6)

Answer 12

Marginal staining
Debonding
Microleakage
Secondary caries
Enamel micro-cracks
Post-op sensitivity

Question 13

C factor - what does it stand for and how is it worked out? (2)

Answer 13

Configuration factor

Constraining walls / free surfaces

Question 14

Strategies for reducing polymerisation shrinkage (3)

Answer 14

Modifying and increasing filler load
Modified clinical placement technique
-use of flowables?

Question 15

Microfilled hybrid composite resins particle size (2)

Answer 15

Glass particle size 1-10 microns
or
Glass particle size ~1micron and dispersed nanoparticles

Question 16

Drivers for amalgam replacement (2)

Answer 16

Approx 50% elemental mercury by weight

-Minemata 2013 phase down and eventually eliminate

Question 17

Measures at 2013 Minemata convention (6)

Answer 17

Improve caries prevention
National objectives to minimise use
Promote cost effective alternatives
Promote research into mercury free alternatives
Encourage profession and schools to promote best use of mercury free materials
Discourage insurance policies and programmes favouring amalgam