S2 - Endo sim content Flashcards
What is the importance of accurate detection of foramen
helps determine how far instruments should advance within canal and at what point preparation and filling should stop (WL) -> at the apical constriction (narrowest diameter of canal)
Where does WL terminate
apical constriction (usually 0.5-1mm before apical foramen)
What is patency?
where the apical portion of the canal is maintained free of debris by recapitulation with a small file through the apical foramen
What are the measurements shown
- radiographic length
- patency length
- WL
Name some irrigants in RCT
- NaOCl
- CHX
- EDTA
Why is NAOCl the most common irrigant. What is a caution
antibacterial capacity
+ ability to dissolve necrotic tissue, vital pulp tissue and organic components of dentine and biofilms in fast manner
if used w/o caution, very destructive to IO soft tissues, the periradicular vasculature and cancellous bone where it can elicit severe inflammatory responses and degradation of organic components
Pro and con of CHX. Which strength is best? A caution
- antibacterial efficacy is concentration dependent (2% > 0.12%)
- lacks dissolution capacity of organic matters like NaOCl
- combination of NaOCl and CHX produces change of colour and toxic insoluble precipitate, formation of 4-chloroaniline, that may interfere w the seal of the root obturation
When is EDTA used and why? At which concentration and for how long?
once cleaning and shaping is complete, to chelate and remove mineralised portion of smear layer
17% for 3min in direct contact w RC wall
What is the taper of ISO files
0.02mm
ISO colours
8 - grey
10 - purple
15 - white
20 - yellow
25 - red
30 - blue
35 - green
40 - black
45 - white
Summarise the crown down technique (6)
Using K files
Scout the canal to RL using 15 or 10
- Coronal to middle 2/3: File RL-5mm using increasing files 5 sizes up from the first one that binds + Use Gates Glidden burs to open entrances/orifices for better access, do not force down or go further than RL-5mm
- Patency length: get a small file (6-15) down to PL.
- WL: 0.5-1mm less than PL, and enlarge canal to file size 2x larger than PL (first to bind)
- Step back: WL -1, -2 then -3mm w 3 increasing large files from the last step
- Recapitulate: to patency and irrigate w size 15 or 10 between steps
- Finish: using size 20 K and H files to WL
rmb: coronal and middle 1/3, PL, WL + 2, step back, recapitluate, finish
What is apical stop
apical end of RC preparation that prevents further advancement or progression of both endodontic instruments and obturation materials
What is radiographic length
tip or end of root determined radiographically, location can vary from anatomic apex due to root morphology and distortion of radiographic image
What is the crown down prep?
WHAT IS THE MAIN POINT?**
technique of canal prep involvig early flaring w instruments followed by incremental removal of canal debris and dentin from orifice to apical foramen, involves files w no apical pressure once binding occurs
emphasises cleanign and shaping of coronal portion of canal prior to apical portion (avoid transferring bacteria)
What is recapitulation
reintroduction of small files during canal preparation to keep apical area clean and patent
Reasons for/aims of obturation
- minimise coronal leakage from oral environment
- obturation must seal apex from PA tissue fluids and entombs remaining bacteria in the canal
- 3D obturation essential for long-term healing outcome (should be sealed apically, coronally, laterally)
*Which factors influence the appropriate time to obturate (4)
- signs and symptoms
- status of pulp and periradicular tissues
- degree of difficulty
- patient management
What is the most widely used semi-solid material in endo and why?
Gutta-percha
optimally adapts to canal walls because of compactibility, once heated, can be compacted against canals walls in such a wall to eliminate and collapse any voids
+
once set, it is stable in size
*Composition of commercial GP (4)
(greatest to least %)
- Zinc Oxide - filler (60-75%)
- GP - matrix (~20%)
- waxes or resins - plasticity
- metal sulphates - radioopacity (barium or strontium)
Non-standard GP cone sizes
How long must you decontaminate GP for?
depends on NaOCl conc
1% - 20min
Purpose of sealers (2)
Properties of sealers (2)
purpose:
- seal space between dentinal wall and GP interface
- fills voids and irregularities in RCS, lateral and accessory canals, spaces between multiple GP points in lateral compaction
properties:
- should be biocompatible and well tolerated by periradicular tissues
- all exhibit toxicity when freshly mixed but greatly reduced on setting
What material can sealers be made of?
**resin-based expoxy resin (best e.g. AH Plus)
Zinc oxide - eugenol (ZOE)
Ca(OH)2
GIC
How to select master cone
- select cone w tip and taper consistent w prepared canal diameter
- master cone measured and grasped to correct length, can make reference point by pinching
- try cone in, if right size it will be resistant to ‘tug back’ if loose, adapt by removing small increments from tip. if too big, choose smaller cone. if cone goes further than WL, get larger or shorten existing until tug back at WL
- confirm placement with radiograph
Briefly explain lateral compaction technique
- Fit master cone (check tug back, take radiograph to confirm) & disinfect it
- Irrigate and dry canal w paper points
- Cover cone w sealer, insert to WL
- Use spreader
- Add accessory cones, repeat until no space left
- Heat tip to cut off, use plugger (needs to be 2mm below CEJ)
Why do you need to do compaction along with heating for GP
once introduced into RC and heated, GP expands, this helps to ensure a tighter seal
however, GP shrinks during cooling phase, thus to compensate for thermal shrinkage, any technique that requires heating must also require compaction
