Endodontics
Course Review
Enoch Ng, DDS 2014
Step Back Preparation
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Hand instruments – enlarge canal 3 file sizes larger than first file that bound at corrected working length
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Each step back is 0.5mm shorter, but 1 file size larger
o
Irrigate, recapitulate, irrigate, work with next step back file
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Recapitulation is always MAF size set to corrected working length
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Access
instrumentation
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ID canal orifices, scout coronal 2/3
rd
of canal with #10 file
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Scout with Gates Gliddens and flare orifice – straight line access allows for file entry without deflection
#2 GG 6mm into orifice
#3 GG 3mm into orifice
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Minimal file for estimated working length should be a #20
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For >1mm difference between EWL and CWL, take a new radiograph
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Enlarge to MAF (usually at least #35) at CWL
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Step back preparation, 0.5mm steps
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Irrigate and recapitulate between each step
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Place MAF at corrected working length for MAF radiograph
Pre-Obturation Evaluation
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Glassy smooth walls
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Canal clean of dentin and irrigant
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Spreader penetrates to 1mm from CWL
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Canal shape reflects natural root shape
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Accurate ID of apical foramen
Common Errors
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Ledge formation
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Caused from uncurved file short of CWL gouging dentin, creating ledge blocking file from getting to CWL
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Corrected by bending file tip 45
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to tease it past the ledge
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Transportation of apical canal
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Non-precurved file can straighten a curved canal, possibly causing an apical perforation
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Strip perforation
Cervical portion of file straightens canal in multirooted teeth
Communication on furcal side of root
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Prevented by good straight line access
Avoid furcation region of canal when filing
Use smaller file sizes in very curved canals
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Separated instruments
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Prevented via discarding worn instruments
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Avoid binding instruments in canal
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Always instrument wet/irrigate
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Canal blockage
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Prevented via copious irrigation/recapitulation, not instrumenting on dry canal, don’t force files down,
removing materials that may fall in and block canal (amalgam, IRM, etc), using files sequentially
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Cleaned with a small file at CWL
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Overinstrumentation (beyond apex)
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Prevented via an accurate CWL before instrumentation with larger files