Resin Based Composite vs Amalgam Flashcards
Aim initial restoration?
Eliminate problem w/ no further tx being required
Arrested lesion and total disease control
Problems see with restorations?
Structural degradation
Fatigue effects
Change in physical properties
Secondary dsiease
What is restorative cycle?
Restoration failure = replacement = further loss of tooth
Cause of structural degradation?
Due function and parafunction
Occlusal laoding
Stress-induced parafunction
Loss proprioception
Why is the mouth an unfavourable environment?
Environment full bacteria
Temperature changes - cyclic
Variable pH
Bacterial biofilm
What want do avoid cyclic changes due variable temperature?
Want coefficient of thermal expansion of material to be similar to tooth
Issue w occlusal loads on restored cusps?
Axial load can be translated into lateral force = cusp fracture
What are the evidence levels?
Systematic review and meta-analysis RCT Cohort studies Case controlled study Case series Case report Opinion - expert
Annual failure rate of posterior stress-bearing restorations? Diff amalgam and composite?
Amalgam = 3% Composite = 2.2%
Principle reason of failure of posterior restoration?
Secondary caries Fracture Marginal deficiency Wear Post-op sesitivity
Most common reason for failed amalgam restoration?
Tooth fracture > secondary caries > loss restoration > restoration fracture
Most common reason for failed composite?
Restoration fracture > secondary caries > restoration loss > tooth fracture
In study of longevity of amalgam vs composite what are results?
No difference survival at 12 years
Amalgam slightly higher failure rate
Adv of composite > amalgam in early carious lesions?
Smaller cavities required for composite
What factors affect polymerisation shrinkage strain?
Speed and intensity of activation
Ratio of free to bonded surface area
Congifuration factor and volume of composite
Elastic modulus of resin composite
What is C-factor?
More enclosed the material is - the greater the stain on interface walls
C= constraining walls/ free surface
C factor of class II restoration?
Bonded 4 walls and amount of unbonded surface is 2 = C factor = 4/2 = 2
What does number of C factor mean ?
Higher C factor = increased stress
What restorations have highest C factor?
Class V
How overcome polymerisation shrinkage?
Increased filled load
Modify clinical placement
Flowable - lower filled but elastomeric
Adv of composite > amalgam when preparing tooth?
Reduced need for prep
Tooth strong when composite used
Future of amalgam?
Phase out use and eventually eliminate use of mercury therefore amalgam
What convention related to phased out use amalgam?
Minemata
Measures taken at minemata convention on mercury?
Improve caries prevention
Minimise use of amalgam
Promote cost effective alternative/ mercury free alternative
Encourage promotion mercury free material
Discourage program/ insurance policies favouring amalgam
