What are the three design objectives of root canal preparation?
Create a continuously tapering funnel shape
Maintain apical foramen in original position
Keep apical opening as small as possible
What is the access shape for upper central and lateral incisors?
Triangular, with the point towards the gingival margin
What is the access shape for upper canines?
Oval
What size of taper do all ISO stainless steel K files have?
02 taper or 2% taper
What are the different lengths of ISO instrument files?
21, 25 or 31mm
The handles of ISO instruments are colour coded. Which colours represent which file sizes?
Pink - 06 Grey - 08 Purple - 10 White - 15,45 Yellow - 20,50 Red - 25,55 Blue - 30,60 Green - 35,70 Black - 40,80
What is the length of the cutting flutes on ISO instruments?
16mm
What are the drawbacks of conventional stainless steel preparation techniques?
mishaps (ledges, canal blockage, zipping of foramen)
debris extrusion with filing motion
time consuming
less predictable shapes in curved canals
Nickel-Titanium alloy allows files to have superelasticity. What is this and what are it’s benefits?
Superelasticity means alloy can be strained more than other alloys before permanent deformation occurs.
It allows NiTi files to be placed in curved canals with less lateral forces exerted - less transportation, zipping or ledging; more centrally placed preparation in harmony with the original canal shape
What are the advantages of NiTi vs SS?
- increased flexibility in larger sizes and tapers
- increased cutting efficiency
- better safety in use
- better user friendliness with less instruments and simple sequences
What are the disadvantages of NiTi preparation?
- instrument fracture
- expense
- access can be difficult in posterior teeth
- unsuitable for complex canal anatomy
ProTaper hand files come in sizes Sx, S1-S2 and F1-F4. What are the tip sizes of the Sx, S1 and S2 files?
Sx = 19 S1 = 17 S2 = 20
How is working length calculated?
Working length is measured from a fixed reference point (which will remain unchanged throughout the treatment + is within clinicians field of view)
Determined after coronal flaring
WL should be as close as possible to CDJ - usually the apical constriction (narrowest part of canal)
Can be determined radiographically or by using an electronic apex locator
What is a glide path and how do you create one?
Glide path - space created within root canal where instruments can glide in relatively easy and bind/gauge apically
- confirm straight line access, explore anatomy
- introduce files 10-25 to resistance only (coronal only), coronal flare - S1
- size 10 WW (watch winding) establish apex
- irrigate + repeat using size 15 (WW) and size 20 (BF)
What is recapitulation and patency filing?
patency filing - use a small file eg size 08/10 through the apical constriction to minimise blockage
What is apical gauging?
- decide which file to finish with apically by going 2 file sizes bigger than the first file to bind
- check F files for debris apically when removing - if no debris then file is not engaging
- use K file to check apical binding as K file will not bind coronally or middle 1/3 since taper in canal is larger
When obturating, GP points are coated with resin sealers. What are these and what are their properties?
- epoxy resin, two paste mixing system
- slow setting (8 hours)
- good sealing ability
- good flow
- initial toxicity declining after 24 hours
- water resistant (insoluble)
What are the contents of GP points?
- gutta percha 20%
- zinc oxide 65%
- radiopacifiers 10%
- plasticisers 5%
Describe the cold lateral compaction technique used for obturation.
- Master GP point fits apical collar, tweezers locked at WL
- Master GP point forced to side of canal
- Finger spreader inserted to 2mm from apical stop
- Accessory points used in space created by finger spreader and added until canal is fully obturated
- excess removal of GP done using heated instrument, aim to cut just below ACJ
- use CaOH as a sealer and restore cavity with appropriate material
What are the signs and symptoms of reversible pulpitis?
- discomfort is experienced only lasting a few seconds when a stimulus is applied
- exposed dentine (dentinal sensitivity), caries or deep restorations
- no significant radiographic changes in periapical region
- pain experienced is not spontaneous
What are the signs and symptoms of irreversible pulpitis?
- may include sharp pain upon thermal stimulus, lingering pain (often 30secs or longer after stimulus removed), spontaneity (unprovoked pain), referred pain
- pain may be accentuated by postural changes such as lying down or bending over
- OTC analgesics typically ineffective
- deep caries, extensive restorations, fractures exposing pulpal tissues
- hyperaemic pulp
What are the signs and symptoms of pulp necrosis?
- non-responsive to pulp testing, asymptomatic
- pain to percussion or radiographic evidence of osseous breakdown unless canal is infected
What part of sodium hypochlorite is responsible for antibacterial activity?
- NaOCl ionises in water into Na+ and hypochlorite OCl-
- establishes equilibrium with hypochlorous acid (HOCl)
- HOCl is responsible for antibacterial activity
What are the properties of sodium hypochlorite?
- potent antimicrobial activity
- dissolves pulp remnants and collagen
- only irrigant that dissolves necrotic and vital tissue
- helps disrupt smear layer by acting on organic component
- time essential for effectiveness: should irrigate for 10mins from when you have accessed the root apex with file
