3 - Preparation of the Root Canal System

Question 1

ProTaper Next instrumentation:

sequence of treatment?

Answer 1

1. pre-treatment radiograph
2. access cavity
3. rubber dam
4. initial negotiation then measure working length
5. create glide path
6. shape canal to working length using protaper next XI
7. complete apical preparation

Question 2

what is known as the Tooth Length aka Estimated working length?

Answer 2

the length of the tooth from incisal edge to radiographic apex

Question 3

accessing the root canal: sequence?

Answer 3

1. cut access cavity to appropriate shape and size (remove pulp horns for central incisors)
2. irrigate pulp chamber with NaOCl
3. locate canal orifice using DG16 (endodontic probe)

Question 4

accessing anterior teeth:
what should be removed?
initial external outline form - how deep on the palatal surface?
what to do to penetrate roof of pulp chamber?

Answer 4

• remove all caries, defective restorations, crowns
• 1mm on the palatal surface
• change bur angle from perpendicular to palatal surface to parallel to long axis of root

Question 5

what should be done to confirm straight line access?

Answer 5

remove palatal shoulder, use long shanked round bur

Question 6

refinement and smotthing of restorative margins: rough margins can contribute to?

Answer 6

coronal leakage

Question 7

glide path management: what should be used to flare canal orifice?

Answer 7

SX file

make sure to remove palatal shoulder

Question 8

glide path management: what is used to negotiate the canal? what to do if toot tight?

Answer 8

• use a 10 s/s flexofile to negotiate the canal

- drop down to 08 or 06 if too tight

Question 9

why is the glide path important?

Answer 9

• gives information about canal morphology: open, restricted or calcified canals. root canal anatomy
• creates or confirms a smooth reproducible path of adequate diameter before introducing rotary instruments

Question 10

what is a useful method of measuring length of files?

where ti place dirty, used files?

Answer 10

• endoblock

- endopot, NOT in bracket tray

Question 11

paste lubricants: useful in?

Answer 11

useful in narrow or curved canals

Question 12

anatomy of the root apex: what is the apical constriction and where is it found?
what is the significance of it?

Answer 12

• apical constriction is the narrowest part of the canal
• 0.5 to 1mm coronal to the apical foramen
• apical termination for shaping, cleaning and obturation

Question 13

anatomy of the root apex: where is the cementodentinal junction located? where is it relative to the apical constriction?

Answer 13

• where cementum meets dentine
• where pulp tissue ends and periodontal tissue begins
• located approx 1mm from AC

Question 14

anatomy of the root apex: what is the apical foramen? usually offset from?

Answer 14

the major apical diameter of the root canal

usually offset from anatomical/radiographical apex,

Question 15

measuring working length: preparation should end at?

what is this area known as?

Answer 15

should end at junction of pulpal and periodontal tissue

apical constriction

Question 16

radiographic working length:
is it useful to determine AC?
acceptable range from radiographic apex?
how to create reproducible reference point?

Answer 16

• does not determine position of AC
• 1mm of radiographic apex
• place size 15 Flexofile in canal with rubber stop

Question 17

taking a radiograph for working length: what kind of technique used? what kind of film holder used?

Answer 17

• paralleling technique

- endodontic film holder (with gap in holder to accommodate endodontic file)

Question 18

electronic apex locators:
what does it make use of?
how does it function? (by measuring what?)

Answer 18

• multiple alternating currents of different frequencies
• uses the body the complete an electric circuit
• measures the difference in electrical impedance between the lip and the file in the mouth

Question 19

use of electronic apex locators?

• EAL is connected to?
• relies of the value of impedance between which 2 structures?
• what happens as the file is advanced towards the PDL?
• when does the audio alert sound?

Answer 19

• EAL is connected by a wire to the lower lip, and to a file placed in the root canal
• lip and the PDL
• as the file is advanced down the root canal, the EAL detects the changing impedance values, and indicates the approach to the apex on its screen
• audio alert sounds when pdl is contacted by the file (also visually indicated on screen)

Question 20

what are the steps to take in establishing working length?

Answer 20

• use EAL and size 10 file
• irrigant in canal, but not in pulp chamber
• ask patient to wet lip clip with tongue
• ensure no contact with metal restorations when file in canal
• use glyde to improve conductivity

Question 21

aqueous irrigation:

why should we use irrigant as a lubricant when instrumenting in wet canals with rotary files?

Answer 21

helps to prevent file breakage

avoid accumulation of dentine dust that can potentially block the canal

Question 22

ProGlider

• progressive apical taper brings what advantage?
• used in what kind of motion?

Answer 22

• flexible and resistant to cyclic fatigue
• avoids transportation, ledging and perforation
• good time saver, especially in difficult canals as it reaches full working length quickly
• used in an in/out motion

Question 23

important guidelines for safe use of rotary instruments?

Answer 23

• constant speed of rotation with torque control
• irrigation before engaging file
• light pressure and progress slowly, withdraw when resistance is felt
• do not stop or start instrument in the canal
• clean files regularly during use

Question 24

what are the factors that prevent passive movement of the file?

Answer 24

• insufficient glide path
• buildup of debris within the canal
• buildup of debris on flutes of file
• complicated root canal anatomy

Question 25

what to do if improved radicular access required? | what does this ensure?

Answer 25

- use SX from protaper universal system - introduce into coronal part of canal, remove restricting dentine using back stroke, outwards brushing motion - ensures straight line access to root canal system

Question 26

apical preparation: - carried out for what purposes? - what process is done to achieve this?

Answer 26

- to determine the diameter of the canal at the apical constriction - to finish the canal preparation to this size - apical gauging

Question 27

larger apical sizes: - what must be used to complete apical preparation? - how are they used?

Answer 27

- flexofiles must be used to complete apical preparation - size 55> - used straight with Balanced Force

Question 28

what is referred to by Balanced Force?

Answer 28

60-90 degrees CW, 120-180 degrees CCW with apical pressure

Question 29

larger apical sizes - what happens once canal prep complete?

Answer 29

- canal should be irrigated, either with NaOCl, citric acid | - canal should be dried using paper points matched to size of completed apical preparation + measured to working length

Question 30

inter appointment disinfectant - aims?

Answer 30

- reduce and prevent multiplication of microorganisms that remain after shaping and cleaning - prevent reinfection through coronal or apical leakage - biomechanical preparation removed cultivable bacteria in 50-80% of cases

Question 31

what is essential to reach and disinfect areas that cannot be instrumented in the root canal system?

Answer 31

irrigation with NaOCl

Question 32

if treatment is carried out in two visits, what must be put in the canals in between?

Answer 32

antibacterial dressing

Question 33

what are the requirements of an interappointment disinfectant?

Answer 33

- long lasting disinfectant action - non irritating to periradicular tissues - no systemic effect - not damaging to the tooth surface or restorative material

Question 34

what chemical is commonly used as an interappointment medicament?

Answer 34

CaOH | calcium hydroxide

Question 35

CaOH - dycal? | constituents?

Answer 35

no - interappointment medicament needs to be non-setting | - powder + sterile water

Question 36

odontopaste: based on what chemical? what does it contain? name the substane in each constituent

Answer 36

- zinc oxide - corticosteroid and antibiotic - corticosteroid: triancinolone - antibiotic: clindamycin hydrochloride

Question 37

what does triamcinolone do?

Answer 37

- anti-inflammatory; causes rapid pain relief | - inhibits clastic cells, may be helpful to manage inflammatory root resorption

Question 38

what does clindamycin do?

Answer 38

antimicrobial action (though limited)

Question 39

uses of odontopaste?

Answer 39

- management of symptomatic irreversible pulpitis - pulpotomy agent in the emergency management of irreversible pulpitis - anti-inflammatory action on the remaining pulp tissue - can be mixed 50:50 with calcium hydroxide and used as intracanal medicament

Question 40

odontopaste - uses - how do its anti-inflammatory properties work on the remaining pulp tissue? - why is antibacterial action on intracanal bacteria short lived?

Answer 40

- they diffuse through the apical foramen into the periapical tissues - the odontopaste does not penetrate far into the dentinal tubules

Question 41

odontopaste: why should we prevent the paste from contacting access cavity walls?

Answer 41

this could lead to tooth discoloration

Question 42

odontopaste - contraindications?

Answer 42

- not recommended during pregnancy or breastfeeding (potential teratogenic effects) - if there is any known hypersensitivity to corticoids and clindamycins - purulent pulpitis - endodontic treatment of deciduous teeth

Question 43

iodine in endodontic treatment: - how does it cause cell death? - what properties does it have? - what specific iodine chemicals are used in endo treatment?

Answer 43

- it penetrates into microorganisms, attacking cell molecules e.g. proteins, nucleotides and fatty acids -> resulting in cell death - bactericidal, fungicidal, virucidal, sporicidal - iodine potassium iodide - povidone iodine

Question 44

povidone iodine - what kind of polymer? - how does it induce cell death? - contraindications?

Answer 44

- iodinated polyvinyl polymer - oxidising effects of free iodine cause cell death nonspecifically - iodine hypersensitivity, pregnancy, breastfeeding

Question 45

Enterococci faecalis: - describe - isolated and cultured in which type of cases?

Answer 45

- gram positive cocci, facultative anaerobe | - in retreatment cases

Question 46

temporary dressing - after sealing access cavity: - what is placed over canal orifice? - what is placed in pulp chamber? - what is placed in access cavity?

Answer 46

- small piece of cotton wool - coltosol - glass ionomer