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Endodontics > Instrumentation of RCS > Flashcards

Instrumentation of RCS Flashcards

1
Q

Why instrumentation?

A
  • remove infected soft and hard tissues
  • give disinfecting irrigants access to apical canal space
  • create space for delivery of medicaments and subsequent obturation
  • retain integrity of radicular structures
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2
Q

Who invented Chemomechanical disinfection?

A

Dr Herbert Schilder

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3
Q

Design objective

A
  • create a continuously tapering funnel shape
  • maintain apical foramen at original position
  • keep apical opening as small as possible
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4
Q

What is Chemomechanical prep?

A

Chemo
- irrigate to kill microorganism
- remove smear layer

Mechanical
- prepare shape
- flush out

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5
Q

Mechanical aim

A
  • shape canal
  • allow delivery of irrigant, ie: NaOCl to WL
  • creates shape to obturate
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6
Q

Vertucci classification

A
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7
Q

Estimated WL

A
  1. Estimated WL
    - estimated length at which instrumentation should be limited
    - obtained by measuring pre-op radiograph to determine distance between coronal reference point and radiographic apex then subtract by 1mm
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8
Q

Corrected WL

A
  • length at which instrumentation and subsequent obturation should be limited
  • obtained by thr use of electronic apex locator/ WL radiograph
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9
Q

Master apical file

A
  • largest diameter file taken to WL and therefore represents the final prepared size of apical portion of canal at WL
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10
Q

Type of motion

A
  • filing
  • reaming
  • watch-winding
  • balanced force motion
  • envelope of motion
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11
Q

How is watch- winding method?

A
  • back and forward oscillation 30-60 degrees
  • light apical pressure
  • effective with K files
  • useful for passing small files through canals
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12
Q

Balanced force

A
  • insert file and engage CW into dentine 1/4 turn
  • with continued pressure, go CC 1/2 turn to strip dentine away
  • do this 1-3 times before removing file to remove debris and check file
  • remove
  • clean
  • reintroduce
  • working to WL
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13
Q

Modified Double Flare

A
  • incorporating balanced force and step back technique
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14
Q

Reciproc

A
  • modified reciprocation
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15
Q

Irrigation protocol after shaping complete

A
  • 17% EDTA for 1 min
  • 3% NaOCl, 30ml for 10 mins
  • use index finger, do not use thumb
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16
Q

Barbed Broach

A
  • used for extirpating, not enlarging
  • formed from tapered round shaft by lifting up portions of metal of shaft almost at right angle to shaft
  • must not engage canal walls
  • will break easily if misused
  • engage the pulp tissue and remove it from canal
17
Q

ISO colour code

A

size 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 70, 80

18
Q

ISO SS sized instruments

A
  • all have 16mm cutting flutes
  • named according to diameter
19
Q

Instrument design

A
20
Q

Hedstrom files

A
  • machined steel blank
  • used in filing motion, cuts on withdrawal
  • good cutting efficiency but can cause iatrogenic damage
  • no longer used for canal prep
  • removing GP/ fractured instruments in cases of re-tx
21
Q

Reamer

A
  • tapered triangular shaft
  • cutting edge nearly parallel to long axis
  • rotate 1/4 to 1/2 turn clockwise to cut as advanced to length
  • in contact with the walls of canal in order to be effective
22
Q

NiTi

A
  • superelasticity
  • can be strained more than other alloys before permanent deformation
  • allows NiTi to be placed in curved canals with less lateral forces exerted
  • ## less transportation, zipping and ledging
23
Q

Components of Endodontic Rotary

A
24
Q

Advantages of NiTi vs SS

A
  • increased flexibility in larger sizes and tapers
  • increased cutting efficiency
  • more user friendly
  • ie: ProTaper rotary
25
Q

Disadvantages of NiTi prep

A
  • instrument fracture
  • expense
  • access can be difficult in posterior teeth
  • unsuitable for complex canal anatomy
26
Q

What is true reciprocation?

A
  • mimics manual movement
  • reduces risks associated with continuous rotating a file through canal curvatures
  • decreased cutting efficiency
  • requires increased inward pressure
  • limited capacity to auger debris out of canal
27
Q

Why do instrument separation happen?

A

Torsional stress
- extensive instrument surface encounters excessive friction on canal walls
- instrument tip is larger than canal section to be shaped

Flexural stress
- repeated cyclic metal fatigue

28
Q

What is cyclic fatigue?

A
  • freely rotating in curvature
  • generation of tension/ compression cycles
  • cyclic fatigue
  • failure
29
Q

Torsional fatigue

A
30
Q

Modified Double flare

A
  • Gates Glidden and K files
  • ensure orifices are filled with irrigants before using K files to check for smooth movement into canal
  • doesnt need to be to WL with size 10 and 15, ensure clear passage into the canal
  • use GG size 4 at coronal portion to flare coronal portion
  • 2/3 of the estimated WL
  • with light apical pressure to create smooth flare prep
  • after gates 4, use K files 10 to remove excess debris and irrigate
  • move on to GG 3, drop the flaring more apically

Apical prep
- light apical pressure with watch winding using size 10
- attach apex locator
- measure length of file that has reached the red band on apex locator
- CWL should be 0.5-1mm short than what is on apex locator
- advance with size 15 to CWL with watch winding motion
- use size 20 until CWL
- irrigation
- using patency file size 10 to ensure no debris accumulation at apical region
- use balanced force for size 25
- size 25 is master apical file (15mm)
- size 30 use 1mm short of WL (14mm)
- size 35, 13mm
- size 40, 12 mm- balanced force technique
- use master apical file, filing motion to smooth the steps at canal

31
Q

Reciproc file system

A
  • introduce irrigant into orifice and pulp chamber
  • size 10 file to 2/3 of WL
  • size 15 to 2/3 of WL, watch winding
  • irrigate
  • start coronal prep with reciproc R25, 2/3 of EWL
  • introduce in a pecking motion, 3 pecks and remove debris from the flute
  • recapitulate using size 10
  • once reach 2/3 of EWL, recapitulate, irrigate and then check CWL
  • use size 10 file to EWL, use apex locator
  • measure the file and substract 0.5-1mm for CWL
  • prep glide path using size 15 set to CWL
  • recapitulate with size10 and use as patency file to touch PDL
  • R25 to CWL and follow through 3 pecks and irrigate
  • patency file to prevent likelihood of blockage and lost of WL
  • brush away from furcation if multirooted teeth
  • use K file 25 similar to reciproc 25
  • attach apex locator and check if it remain in green, check tuck back sensation
  • irrigate with activation using manual dynamic irrigation; GP cone towards CWL inwards and outwards
  • go through 3% NaOCl for 10 mins
  • 17% EDTA 10 mins
  • final rince of NaOCl
  • try master cone and feel tuck back
32
Q

Obturation

A
  • dry with paper point until dry
  • coating with sealer into canal CWL
  • use B spreader to check if accessory cones are needed
  • SuperEndo- alpha to separate the GP
  • endo plugger and plug to coronal aspect
  • ensure well condense, just below level of orifice
  • place Vitrebond before perm restoration

Endodontics (13 decks)

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