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**Pediatric Dentistry Boards 2019 > Dental Materials > Flashcards

Flashcards in Dental Materials Deck (15)
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1
Q

Soncini 2007 : RCT of Amalgam vs Resin

- Results?

A

267 children randomized

  • 5 years follow up
  • Differences in longevity not statistically significant
  • Compomer/resin was replaced significanly more frequently due to recurrent caries and required 7x as many repairs
2
Q

Meta analysis of SSCs vs amalgams in primary teeth (Randall)

A

Failure rates of SSC 1.9 to 30%
failure rates of amalgams: 12-90%
1.5 to 2 failed amalgams for each failed SSC
**Cochrane Review no studies met inclusion criteria however, lean toward SSC placement

3
Q

Function of filler

A
  • Reduce polymerization shrinkage
  • decrease coefficient of thermal expansion
  • increase hardness (compressive strength)
  • improve wear
  • control transulcency
  • need about 70% or more filler for the wear you need
4
Q

Polymerization shrinkage:

A

Incremental filling reduces stress

  • Bond strengths of >18 MPa needed to overcome polymerization shrinkage stress
  • Less material, less shrinkage, therefore a base (GIC/RMGIC) reduces shrinkage stress
  • Resins vary in polymerization shrinkage (2-6%) lower filled resins shrinkage more
5
Q

Flowable resin composites

A

Lower filler volumes 45-70% same partical size as hybride, micro, minifilled composites, decreased viscosity/stiffness

  • increased polymerization shrinkage, decreased viscosity, decreased wear resistance, decreased strength
  • bond strength 8-10MPa
  • most contain fluoride; effective release
  • radiopacity is an issue
6
Q

Glass Ionomer cements: advantages

A
  • bond to dentin and enamel through chelation; no bonding agent required
  • leaches F
  • bio compatible w/connective tissue
  • thermal expansion similar to enamel and dentin
  • low setting shrinkage
  • bond strength of .5-4 MPa to carious and on carious dentin
7
Q

GIC disadvantages

A
  • Technique sensitive- moisture imbibition/dessication

- bond sterngth less than that of composite/dentin bonding

8
Q

Smear Layer

A
  • about 1-5 microns thick; dentin chips, debris, partially denatured collagen
  • partly porous, but dramatically reduces fluid flow from tubules
  • weak attachment to dentin (6MPa)
  • extends several microns into tubules
  • permeability increased by primers
9
Q

Dentinal tubule structure and its effects on bond strength

A
  • Tubule diameter increases w/depth toward the pulp
  • superficial dentin: relatively few tubules per surface area, less area for lateral diffusion of bonding agent
  • bond strength decreases with progressive depth from DEJ because water in dentinal fluid competes with collagen for hydrophilic monomers; also, fluid dilutes concentration of monomer
10
Q

Dentin sclerosis and effect on bond strength

A
  • Sclerotic, caries affected dentin is denser in mineral content
  • Reduced penetration of bonding agent
  • Caries -affected dentin: additional/extended acid etching can increase tensile bond strength
11
Q

Primer : what does it do? effect on dentin/collagen?

A
  • Provides micro-mechanical retention to modified smear layer and dentin
  • Primer wets/penetrates collagen meshwork, raises it to nearly original level, creates “hybrid layer” increases wetability of dentin
12
Q

Adhesive :

A

Unfilled resin adhesive bonds w/primer and composite restorative material placed over it

13
Q

What is the gold standard of etch to adhesive?

A

Two bottle etch and rinse system : etch-rinse-prime-bond is the gold standard for bonding agents.

  • any simplification in procedure results in loss of bonding effectiveness
  • Self etch products modify but do not remove the smear layer
14
Q

Bonding in primary teeth

A
  • Smear layer is removed more easily
  • 25-30% thicker hybrid layer compared to permanent teeth
  • Greater reactivity of primary dentin to acid conditioning; deeper demineralized zone may preclude complete penetration of primer and adhesive
  • less time required for acid conditioning of primary teeth
  • Microtensile bond strength of adhesive systems similar in permanent and primary dentin
15
Q

Where are implants ‘best’ placed in a growing child?

A

Anterior mandible