Endodontics
Course Review
Enoch Ng, DDS 2014
Obturation preparation
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Smear layer – cutting debris of mineralized collagen, odontoblastic process remnants, pulp tissue, and bacteria
that is burnished over dentin surface
o
1-2um thick
o
Can penetrate up to 40um into dentin tubules
o
Can block penetration of sealer into tubules
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Smear layer removal – irrigation
o
Irrigation with 17% EDTA (chelator) – removes inorganic part of smear layer
o
Irrigation with 3% NaOCl – removes organic part of smear layer
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Drying the canal
o
Aspiration after irrigation
o
Paper points
Comes in Fine, Medium, Coarse or Tapered to fit final preparation
Let paper point sit in canal for a few seconds to wick moisture
Measure paper points to not induce bleeding or apical inflammation
Obturation materials
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Ideal requirements
o
Easily introduced, easily removed
o
Liquid/semisolid and becomes solid, seals laterally and apically, does not shrink
o
Impervious to moisture, bacteriostatic, sterile/sterilizable
o
Does not stain tooth, doesn’t irritate apical tissues, radiopaque
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Historical materials
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Silver points
Non-adaptable to canal
Can corrode – releases toxic byproducts into apical tissues
Difficult to remove – post space or retreatment
o
Pastes
Quick to use
Lacks length control – difficult to avoid overfill
Unpredictable/inconsistent seal
Shrinkage of material
Some have paraformaldehyde and arsenic
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Gutta Percha – trans-isomer of polyisoprene (rubber is cis-isomer)
o
Contains
Zinc oxide (59-75%)
Gutta percha (19-22%)
Waxes, antioxidants, coloring agents, metallic salts
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Advantages
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Plasticity, ease of manipulation and removal
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Minimal toxicity
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Radiopaque
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Disadvantages
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Lack of adhesion to dentin
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Significant shrinkage on cooling
2 distinct crystalline states – alpha and beta
Heating of beta phase (37
o
C) causes structural change to alpha state (42-44
o
C) and then to
amorphous state (56-64
o
C), with significant shrinkage when returning to beta state
Compaction on cooling is necessary
