Materials used in restorative dentistry Flashcards
(34 cards)
Advantages of amalgam
- lower cost compared to composite
- durable and strong
- high wear resistance
- ease of placement
- less technique sensitive
- self-sealing (due to expansion)
Disadvanatages of amalgam
- poor esthetics
- conductive (temperature and galvanic reaction)
- less conservative preps needed
- preparations are more difficult
- “mercury exposure” complaints
Amalgam indications
- posterior restorations
- selected anterior restorations
- heavy occlusal loads
- high caries risk patients
- working field compromised
contraindications of amalgam. Why?
patients with renal disease/immunocompromised.
some studies have shown that these patients are unable to remove amalgam from their system
bonded amalgam was developed to increase ___ form
resistance
How is bonded amalgam different from conventional amalgam?
- adhesive is added prior to addition of amalgam
- dual cured - it can be light cured or cures over time
- Observed less microleakage and staining
- increased strength of coronal structure
Amalgam reaction
Hg + Ag3Sn –> Ag3Sn + Ag2Hg3 + Sn7Hg8
What is the weakest phase of the amalgam reaction and how can this be reduced?
Weakest phase is gamma-2 (Sn7Hg8). It is more corrosion prone. This can be reduced with the addition of Copper
Overall reaction for high copper amalgam
Hg + Ag3Sn +AgCu –> Ag3Sn + Ag2Hg3 + Cu6Sn5
Contamination with moisture in an amalgam restoration leads to what disadvantages?
- decreased strength
- increased corrosion
- increased creep
What is creep?
deformation under occlusal load. Ideally, you want less creep
How much copper required to be considered high copper amalgam?
> 12% Cu
Why is zinc added to Ag?
To enhance mechanical properties, reduce marginal fracture, and increase longevity
How much condensation and carving time in extended carving Ag?
5 min cond. time. 7 min carving time
BisGMA stands for
bis-glycidyl methacrylate
4 major components of composite resins
- Organic polymer matrix (resin -BisGMA)
- inorganic filler particles
- silane coupling agent
- initiators
Curing occurs through a ____ reaction
polymerization
3 uses of composite resins
- replacement of carious or fractured tooth structure
2. restoring erosion and abrasive defects in cervical areas
3. esthetically re-creating teeth with developmental anomalies
To place composite, the entire cavosurface margin must be on ____
enamel. Bonding to dentin is unreliable
What effect does hgher filler loading have on the composite material?
- increases ease of handling material (less sticky and more packable)
- increases the strength of the material (fracture resistance)
- decreases polymerization shrinkage
- increases color stability
filler loading for:
- Macrofills
- Microfills
- Hybrids
- Nanofills
- Flowable
- Macrofills - high
- Microfills - low
- Hybrids - high
- Nanofills - high
- Flowable - low
Advantages of composite resins
- aesthetic
- bonded total seal with enamel
- conservation of tooth
- manipulative control with LC material
- Non conductive
- tooth reinforcement
- no metal/Hg
Disadvaantages of composite resins
- technique sensitive
- difficult to recreate interproximal contact
- poor wear in areas of high masticatory forces
- staining
- polymerization shrinkage
- higher rates post-op sensitivity
- recurrent decay
- people say it contains BPA”
Cimposite resins indications
- anterior restos
- selected posterior restos where masticatory forces are limited
- preparation cavosurface margins are all on enamel and do not end on occlusal static contact
