CSA endo labs week 2 Flashcards
What is working length ?
Length from apical limit of obturation (usually apical constriction) to a recordable reproducible reference point on the clinical crown
What is apical constriction ?
narrowest point of canal before reaching apex,
- 0.5-2mm away from apex
How to determine working length ?
after coronally flaring & removing interim dressing
- Insert a small file
- Feel for a stop near estimated working length (pre-op radiograph to determine)
- Slide rubber stopper to reference point
- Expose working length radiograph to x rays
- Leave file in place until radiograph checked
What file to use for working length determination ?
a. Size 15 shows up well on radiograph
b. In narrow canal may need to use size 8 & 10 first before 15
Where to slide rubber stopper to reference point ?
incisal edge for the incisor
What do electronic apex locators do ?
- save time & repeat radiographs
* be used routinely
Problems when determining working length
- Fractionally too short:
* Much too long/short
What happens when fractionally too short working length ?
o Check file length
o Add/Subtract accordingly
o Record working length
What happens when Much too long/short working length ?
o Check file length
o Reposition
o Take new radiograph
How do we create APICAL stop ?
• shape apical portion of the canal at working length
What do we do from apical stop ?
use step back technique to increase taper (2% to 5%) & make it flush with coronal portion
What are filing techniques ?
- Watch winding technique
- Twist & pull technique
- Circumferential
- Balance force technique
What is watch winding technique ?
• Repeated 60degrees to 120 anticlockwise rotations with light apical pressure
What is twist and pull technique ?
- Rotate 60Degrees clockwise turn
- Fell flutes engage & pull straight out again
- Lessen turning movement if resistance is too much
- useful to advance file if slight resistance
What is Circumferential filing?
- No rotation of file
- Move file with in & out motion – filing on outstroke only
- methodically around and against canal circumference
What is circumferential filing useful for ?
o Very wide canals
o Smooth junction between apical & coronal preparations
What is balanced force technique ?
for apical shaping
• file tip must remain same length throughout movement
• rotate clockwise 60Degr to engage flutes
• rotate 360O anticlockwise to cut
•only use K files
How to apical shape at working length with Balanced force technique ?
- Start at working length with file number 15
- balanced force technique to prepare apical area
- Increase file size until it is 2 sizes bigger than original file size
- This creates an apical stop >Stop gutta percha going through apex
What is Master apical file size ?
file size is 2 sizes bigger than original file size
- number 15 Now number 25
What does step back technique involve ?
using a larger file size every 1mm we move away from working length
What are steps of the step back technique ?
- Step back from the working length 1mm and increase file size by 5
- Irrigate after each file
- Before stepping up and moving back we must recapitulate:
- Check master apical file at working length – should fit
What technique used in step back ?
balanced force technique at each point – creates greater taper
What does recapitulate do ?
a. Insert small file 8/10 to full working length & irrigate
b. Frees up dentine debris at apical constriction/apex and ensure the MAF can still go way down
When does stepping back stop ?
when file no longer binds when you move 1mm back
When is there a flush margin between coronal and apical section /
when file no longer binds when you move 1mm back
What is master point that gets exposed?
•Select a0.02 taper GP point
•Place in moist canal and fit snugly with slight tug back
o tip close to apical constriction
What are problems with master apical file radiograph ?
•Master point is too short / extends too long
What is Obturation ( cold lateral condensation )
- Dry canal using paper points
- Use master point to coat canal with sealer
- Re insert master point to working length
- Select finger spreader
- Insert firmly twist & withdraw
- Insert matching accessory GP point tip coated lightly in sealer
- Repeat – must work quick
- Continue until no more accessory points can fit in
- Expose obturation to radiograph
What are finger spreaders?
(Size: A, B, C, D)
- Use larger finger spreaders when smaller ones no longer fit
What happens if canal is curved?
insert finger spreader on outside edge of curve
• inside of curve perforate canal & pierce GP points creating voids
How to assess the obturation radiograph?
- Length
a. Should extend 0.5 to 2mm from radiographic apex
b. No change in working length - Taper
a. Smooth uniform taper maintaining course of smooth canal - Density
a. Even fill with GP
b. No voids seen, especially at apex
Problems of obturation ?
- Under/over-extended – pull out GP, try again and re expose
- Large voids
- Poor taper
What if there are large voids?
- if coronal 1/3> place more GP
- If middle/ apical 1/3 >pull out GP & try again
What is coronal seal ?
- cut back GP & neatly cut canal orifice
- Vertically condense GP
- Clean access cavity
- Place definitive restoration if circumstances permit
- Otherwise place a temporary filling – chemfil rock
How to vertically condense GP?
o Use a heated instrument
How to place definitive restoration ?
o Place GIC liner over GP
o Place resin composite/amalgam on top of that
