Instrumentation Flashcards
What does instrumentation provide?
- Remove infected soft and hard tissue
- Give disinfecting irrigants access to apical canal space
- Create space for the delivery of medicaments and subsequent obturation
- Retain the integrity of radicular structures
What are the design objectives of instrumentation?
- Create a continuously tapering funnel shape
- Maintain apical foramen in original position
- Keep apical opening as small as possible
What does chemo mechanical prep cause?
Chemo
* Irrigate to kill microrganisms
* Remove smear layer
Mechanical
* Prepare shape
* Flush out
What is the classification of the root shapes called?
vertucci (4)
What is the estimated working length?
at which instrumentation should be limited.
obtained by measuring pre-operative radiograph to determine distance between coronal reference point and radiographic apex then subtracting 1mm.
What is the corrected working length?
length at which instrumentation and subsequent obturation should be limited. Obtained by the use of an electronic apex locator and/or working length radiograph.
What is the master apical file?
The largest diameter file taken to working length and therefore represents the final prepared size of the apical portion of the canal at the working length.
What are the types of instrument motion
5
- Filing
- Reaming ( warning)
- Watch-winding
- Balanced Forced Motion
What is watch winding and when is it useful?
- Back and Forward Oscillation of 30-60 degrees
- Light apical pressure
- Effective with K files
- Useful for passing small files through canals
What are the types of techniques that incorporate the motions?
- modified double flare
- hand protaper
- reciproc
- reciproc blue
When you have finished shaping, what happens next?
initiate irrigation protocol
What is the irrigation protocol?
- EDTA 17% for 1 minute
- Sodium hypochlorite 3%, 30 ml for 10 minutes.
- Slow injection
What is a barbed broach used for and what should it not be used for?
Used for extirpating, NOT enlarging
* Must not engage the canal walls
* Extremely fragile instrument, and will break easily if misused.
What do all files have?
16mm cutting flutes
What are hedstrom files used for?
- Used in a filing motion, cuts on withdrawal
- Good cutting efficiency but can cause iatrogenic damage
- No longer used for canal preparation
- Useful for removing gutta-percha or fractured instruments in cases of retreatment
How is a reamer manufactured and what are it’s qualities?
- Manufactured by twisting a tapered triangular shaft
- Cutting edges nearly parallel to long axis
- Rotated 1/4 to 1/2 turn clockwise to cut as advanced to length
- Must be in contact with the walls of the canalin order to be effective, must not bind or it may break
How is k-file manufactured and what are it’s qualities?
- Manufactured by twisting or grinding a square tapered shaft
- Cutting edges almost perpendicular to the long axis of the instrument
- Can be used in a filing motion - advanced to the full working length rotated 1/4 to 1/2 turn clockwise, and withdrawn while apply lateral pressure. Repeated circumferentially until canal enlarged.
- Do not use larger instrument too quickly
Why is nickel-titanium alloy (NiTi) good for files?
- Shape memory effect after heat treatment (return to original shape
- Superelasticity
What are components of an endodontic rotary instrument?
what do they each do?
- Taper – diameter change along working surface
- Flute – groove to collect dentine and soft tissue
- Leading/Cutting edge – forms and deflects dentine chips
- Land – surface extending between flutes
- Relief – reduction in surface of land
- Helix angle – angle cutting axis forms with long axis of file
What are the advantages of NiTi V stainless steel?
- Increased flexibility in larger sizes and tapers
- Increased cutting efficiency
- If used appropriately good safety in use
- Can be more user friendly with less instruments and simple sequences
What are disadvantages of NiTi?
- Instrument fracture
- Expense
- Access can be difficult in posterior teeth
- Unsuitable for complex canal anatomy
What is true reciprocation in engine driven systems?
- Mimics manual movement
- Reduces risks associated with continuously rotating a file through canal curvatures
- Decreased cutting efficiency
- Requires increased inward pressure
- Limited capacity to auger debris out of a canal
How is a rotary instrument used?
*Confirm straight-line access *Explore anatomy
*Always introduce files 10-25 to resistance only (coronal only) *Coronal flare
*Size 10 with watch winding establish apex
*Irrigate and repeat using sizes 15 (WW) and 20 (BF)
What is torsional stress?
– Extensive instrument surface encounters excessive friction on canal walls
– Instrument tip is larger than canal section to be shaped
What is flexural stress?
Repeated cyclic metal fatigue
* Cannot be influenced by clinician
How does cyclic fatigue happen?
- Freely rotating in a curvature
- Generation of tension/compression cycles
