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Yr 3 Restorative - Endodontics > Crown down technique (canal filing) > Flashcards

Crown down technique (canal filing) Flashcards

1
Q

What is the purpose of instrumentation of the canal?

A
  • Remove pulp and most microbes
  • Facilitate irrigation
  • Enable medicament placement
  • Enable placement fo root filling
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2
Q

What is the crown down technique?

A
  • Coronal and mid parts of the canal are opened first with high taper instruments (engage only small area of canal wall)
  • More apical parts are shaped last using the tips of these tapered instruments
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3
Q

Where is the apical stop placed for the crown down technique?

A

1mm short of the radiographic apex

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4
Q

What does the crown down instrumentation technique achieve?

A
  • Removes infected material from coronal pulp chamber
  • Improves irrigation
  • Reduces the effective curvature of the canal
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5
Q

When can ProTaper Files be used?

A
  • Suitable for small canals
  • To prodice excelent shaping with minimal number of instrument changes
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6
Q

What material are ProTaper Files made frm?

A

Flexible Nickel titanium

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7
Q

When does care need to be taken with ProTaper canals?

A

In very curved canals

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8
Q

What are the different ProTaper files?

A

3 shaper files and 3 finisher files

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9
Q

Tell me about the SX file?

A
  • 19 mm long
  • Taper varies along legt
  • Tip is at or just below ISO 20 (tip diameter = 0.19)
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10
Q

Tell me about S1 file?

A
  • Tip diameter 0.185
  • Varying taper (D1 = 2%, D14 = 11.5%)
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11
Q

What does D1 or D14 mean?

A

The diameter 1 or 14 mm away from the tip

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12
Q

Tell me about the S2 file?

A
  • Tip Diameter 0.20
  • Varying taper (4% D1 and 11.5% D14
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13
Q

Tell me about F1 file?

A
  • Tip diameter 0.2mm
  • Varying taper (7% at D1 and 5.5.% at D14)
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14
Q

**** Tell me about F2 file?

A

Tip diameter…

Varying taper = 8% at D1 and 5.5% D14

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15
Q

Tell me about the F3 file?

A
  • Tip diameter is 0.30
  • Varying tapers (9% at D1 and 5% at D14)
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16
Q

What is the max flute diameter for ProTaper Hand Files?

A

1.2mm

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17
Q

What is the cutting length of ProTaper Hand Files?

A

14mm

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18
Q

What different lengths are ProTaper hand files availiable in?

A

21, 25 or 31 mm

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19
Q

What does the advanced flute design of ProTaper hand files allow?

A

The flecibility and efficientcy to achieve consistent successful cleaning and shaping of the canal

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20
Q

What are the advantages of ProTaper instruments?

A
  • Patented progressive taper design improves flexibility and cutting efficiency especially in tighter or more curved canals
  • Fewer files are needed to achieve a fully tapered canal (especially in tighter or more curved canals)
  • Engage smaller area of dentine reducing torsional loads, file fatigue and the potential for separation
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21
Q

What is pitch?

A

Distance between sucessive turns

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22
Q

What is the pitch of ProTaper instruments?

A

Variable

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23
Q

Whats the benefit of having a variable pitch?

A

Rotations can only go so far - self limiting

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24
Q

What is a helical angle?

A

The angle from the cutting edge to the long axis of the instrument

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25
Q

What shape is the cross section of a ProTaper file?

A

Convex triangle

26
Q

What is the benefit of the ProTaper instruments having a convex triangle cross section?

A

Reduces the contact area between the file and dentine = greater cutting efficiency (balancing pitch and helical angles)

27
Q

What properties does the Nickel Titanium give to the ProTaper hand files?

A
  • Super elasticity (3-5 times the flexibility of stainless steel)
  • Shape memory

(= decreased ledging and transportation)

28
Q

Which two forms does Nickel titanium change between?

A
  • Austenite (decreased stress)
  • Martensite (increased stress)
29
Q

What are the properties of the new ‘M Wire’ Nickel Titanium?

A

Even more elastic with better shape memory

30
Q

What are the benefits of the varying taper?

A

Touches dentine at only 2 small points = force concentrated (high force) = more readily cuts and shapes

31
Q

How do we enlarge the orifice in the crown down?

A

Use the SX file

  1. Engage dentine by gentle clockwise rotation until file just snug
  2. Disengage by rotating anticlockwise 45-90degrees applying apical pressure to ensure file does not wind out of canal
  3. Rotate handle clockwise whilst simultanously withdrawing file to ensure removal of debris
32
Q

What does orifice enlargement with SX ProTaper file achieve?

A
  • Removes heavily infected material
  • Improves access to apical third of canal
  • Improves irrigation
  • Reduces effective curvature of canal
33
Q

Following orifice enlargement what needs to be done?

A

Restablish patency of the canal #10 K file with watch winding movement

34
Q

How do we create the apical stop with the crown down?

A
  • Watch winding #15 file
  • Balanced force #20
35
Q

Following the production of the Apical stop what do we do in the Crown Down?

A
  1. Use s1 file to instrument full length of canal (modified balanced force = rotating handle clockwise whilst simultanrously withdrawing at the end)
  2. Use S2 file to instrument full length of canal
  3. # 20 K file to check patency
  4. Use F1 file to instrument full length of canal and reinstrument with #20 (if snug the preparation is finished) if not…
  5. Use F2 file to instrument full length of canal and reinstrument with #25 (if snug preparation is finished) if not…
  6. Use F3 file to instrument full length of canal (Tip size ISO 30)
36
Q

What is the tip size of the F1?

A

ISO 20

37
Q

What is the tip size of the F2?

A

ISO 25

38
Q

What is the tip size of the F3?

A

ISO 30

39
Q

What is the issue with the ProTaper files?

A

6 X more expensive!

40
Q

When may ProTaper files be ineffective?

A

Large, more oval/irregular canals

= should use modified step back with K files instead and circumfrential longitudinal filing with K files to smooth irregular walls

41
Q

What is the key issue with circufrential longitudinal filing?

A

Debris is packed apically (can be overcome by frequent recapitulation)

42
Q

How do we select the correct GP point?

A

If instrument to #25 the start with ISO 25 GP

  • Ensure it has tug back
  • Must be marked at the reference point
  • n.b. if loose try GP one size larger than still fits CWL (if #30 doesnt go to CWL then cut 1mm of the end of #25 = #27 if still too lose then cut another 1mm off the end = #29)
43
Q

Becuase endodontics is often carried out over a number of appointments what do we have to do between appointments?

A

Dress the tooth with a medicament and seal with a temporary restoration to prevent re-infection

44
Q

What is a Medicament?

A

The primary se of a medicament is to prevent canal infection where none is present originally (i.e. acutely inflammed vital tooth)

AND/OR

to eliminate bacteria already infecting the canal system (i.e. necrotic tooth)

45
Q

Which Canal medicaments have been used in the past?

A
  • Chemical antiseptics
  • Antibiotics/steroids
  • Calcoim hydroxide paste
46
Q

Which chemical antiseptics were used? And why are they not often used now?

A
  • Beechwoods creosote
  • Para mono chloro phenol

Not used now = highly irritant to periapical tissues (if large amounts used can seem out through apical foramen = intense inflammation = pain

47
Q

Give two examples of antibiotic/steroid paste?

A
  • Ledermix
  • Odontopaste
48
Q

What does Ledermix contain?

A
  • Dimethylchlortetracycline (bacteriostatic antibiotic)
  • Triamicinalone acetonide (potent steroid)
49
Q

What does Odontopaste contain?

A
  • Clindamycin (bacteriostatic antibiotic)
  • Triamcinalone acetonide (potent steroid)
50
Q

Why do we combine steroids with antibiotics?

A

To damp down any inflammatory reaction = dont get chemotaxis (though polymorphs and macrophages are sometimes needed to clear things up)

51
Q

What 2 uses are antibiotic/steroid pastes restricted to?

A
  • Acutely inflammed vital pulp where analgesia for extirpation cannot be obtained (either due to overactive c-fibres or inflammation increasing the pH of tissue stopping dissociastion of LA)
  • Insufficient time to embark on RCT following pulpal exposure (apply paste then dress it)
52
Q

What are the avaliable preparations of Calcium Hydroxide (NON SETTING)?

A
  • Powder (with 1:8 barium sulphate)
  • Proprietry pastes (Hypocal and Reogan)
  • Life (Catalyst paste only)
53
Q

What chemical is usually the medicament of choice?

A

Calcium hydroxide

54
Q

Which 6 medicament actions does the OH ion in calcium hydroxide have?

A
  • pH 12.5
  • Bacteriacidal to wide group of organisms
  • Effective solvent of organic debris (seeps into surrounding tissue influencing their pH)
  • Promotes connective tissue repiar
  • Promotes hard tissue genesis
  • Neutralises acids in areas of resorption (stops chemotaxis of odontoclasts etc = stops resorption)
55
Q

Which medicament action do calcium ions from calciu hydroxide have?

A

Activate calcium dependent ATP reaction for hard tissue formation (although studies show tissue fluid contains sufficient Ca for this anyway and new hard tissue formed contains Ca from tissue fluid rather than the paste)

56
Q

How is Calcium Hydroxide placed as a medicament?

A
  • Spiral root filler = onto sterile paper pad = drag hand file through it and anticlockwise action wipes it off onto the canal walls
  • Injection syringe system (less control and can inject through tooth into periapical tissues)
57
Q

What are the 6 different uses of Calcium Hydroxide?

A
  • INTER-VISIT MEDICAMENT
  • Pulp capping/pulpotomy
  • Treatment of large periapical lesions
  • Apexification
  • Root resorption
  • Root fractures and perforations
58
Q

Which chlorhexidine solution can be used in root canals?

A

20%

59
Q

What action does medicament with chlorhexidne solution have?

A
  • Wide spectrum of antibacterial action
  • Effective against anaerobic bacteria (Str. Faecalis & Candidal species (C. Albicans)
  • Substantivity (binds to surface of dentine in root canals and stays there)
  • Non-irritant
60
Q

When is Chlorhexidine solution used as a medicament?

A

Not used routinely but is used for teeth that do not settle (tends to indicate presence of Str. Faecialis and candial species)

61
Q

Which temporary restorations are placed for a good seal over the medicament?

A
  • Cotton wool dressing (fill chamber)
  • Common temporary restorations (GIC cement & Zinc Oxide Eugenol)
62
Q

Why is it really important that the walls of the acess cavity are slightly tapered?

A

We fill the cavity with cotton wool = no solid base = biting pshes GIC into the cotton wool = recolonisation so have to repeat the process

Yr 3 Restorative - Endodontics (5 decks)

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