Determination of working length and inter-visit medication

Question 1

Master apical file

Answer 1

> prep of apex at working length up to size 25 at minimum OR

>/ 2 file sizes above file size which first fitted snugly at working length

Question 2

Step-back

Answer 2

Prepares apical 1/3 by creating series of steps
Achieved by shortening length of file and reducing length
Continue until you have met up with the prep of coronal 2/3

Question 3

File size 25 prep length

Answer 3

20mm

Question 4

File size 30 prep length

Answer 4

19mm

Question 5

File size 35 prep length

Answer 5

18mm

Question 6

Apical gauging

Answer 6

Finish prep of RC - MAF size 25
Insert MAF - should meet some light resistance and feel snug in last 2mm - shows there is contact between file and RC wall
Insert size 25 file to working length and ensure it is at your reference point
Apply apical pressure to file with fingers
If file moves apically at all a larger file size is needed
Move up 1 file size and repeat ‘apical gauging’ procedure
If you > size of MAF, refine your step-back prep

Question 7

Chemical prep

Answer 7

Irrigants

Inter-visit medication

Question 8

Ideal irrigants

Answer 8

Antimicrobial
Cheap
Able to dissolve pulp tissue
Able to remove smear layer
Easy to use
Long shelf-life
Compatible with dentine
Tissue-friendly
Substantive (remain in RC for sustained period)
Non-corrosive for dental instruments
Non-toxic

Question 9

Smear layer

Answer 9

1-2 microns
Amorphous film or organic and inorganic material generated from instruments contacting RC walls
‘Plugs’ dentinal tubules
Delays penetration and effects of antimicrobials

Question 10

Action of irrigants

Answer 10

Removal of debris
Lubrication of instruments
Antisepsis
Decomposition and removal of blood and tissues

Question 11

Irrigants

Answer 11

Medical-grade sodium hyperchlorite (NaOCl, 1% - kill time: 90 minutes// 5.25% kill time 90 seconds)
Ethylendiaminetetraacetic acid (EDTA 17%)
Chlorhexedinegluconate (2%)
Iodine compounds (allergic reaction)

Question 12

Sodium hyperchorite

Answer 12

Conc 0.5-5.25%
Highly effective antibacterial agent
Dissolve residual pulp tissue & organic matter
Much more effective warmed
Must be frequently replenished for effective cleaning and disinfection
Does not remove smear layer

Question 13

Hyperchlorite accident

Answer 13

Inadvertent extrusion of hypochlorite into periapical tissue

Percentage, volume and pressure is important

Question 14

EDTA

Answer 14

Chelating agent
Solution and paste
Minimum 2 minutes
Remove smear layer
Aid negotiation of calcified RCs
Unable to dissolve organic matter
Used in conjunction with NaOCl

Question 15

How to remove smear layer

Answer 15

Use sodium hyperchlorite throughout access into pulp chamber and complete canal prep
Use EDTA to remove smear layer and open tubules for soaking
The more infected the case, the more disinfection required

Question 16

Benefits of smear layer removal

Answer 16

Harbours bacteria and may also act as nutriment for microbes
May act as barrier to irrigant and medicament penetration
May influence quality of bond obtainable with RC sealers
If disintegrates after completion of RCT, will affect seal of RC filling material

Question 17

Chlorhexidine

Answer 17

Anti-bacterial
Unable to dissolve organic or inorganic tissue
Not as effective as NaOCl but suitable alternative
Suggested conc 2%
Should not be used in combination with NaOCl due to formation of cytotoxic PCA

Question 18

Inter-visit medication

Answer 18

Visible bacteria can still be isolated from approx 60% of RCs following disinfection
Type of material: non-setting calcium hydroxide, odontopaste

Question 19

Calcium hydroxide

Answer 19

Ca(OH)2 has high initial pH (approx pH12)
Few bacteria can flourish in its presence
21 days for hydroxyl ions to diffuse through dentine to reach maximum pH 9
Optimally, calcium hydroxide should be left in root canal between 2 and 4 weeks but not more
(non-setting, needs to be in contact with bacteria to kill them)

Question 20

Mode of action of calcium hydroxide - Ca(OH)2

Answer 20

pH ~12
Damages bacterial cytoplasmic membranes
Denatures proteins
Damages DNA
Inactivates bacterial enzymes
Bacterial replication associated with loss of genes and lethal mutations
Hydroxyl ions to induce lipid peroxidation
This results in the destruction of phospholipids and breakdown of lipopolysaccharides

Question 21

Odontopaste

Answer 21

New, effective therapeutic endodontic dressing (used as a paste instead of calcium hydroxide to help calm a very acute situation)
Antibiotic (5% Clindamycin) - kills bacteria
Corticosteroid (1% Triamclinone) - reduces inflammation
Calcium hydroxide in a zinc oxide paste
Shouldn’t be left for a long time

Question 22

Delivery of inter-visit medication

Answer 22

Master K-file
Large paper point
Lentulo spiral fillers

Question 23

Above inter-visit medication

Answer 23

Make sure access cavity is completely clean and dry from ACJ upwards
Temporise tooth:
-CaO2
-Endosponge
-Cavit or coltosol (ZOE)
Coronal seal: GIC/ IRM/ Kalzinol (ZOE)
-optimally, CaOH should be left in root canal between 2 or 4 weeks

Question 24

Cotton wool

Answer 24

Traditionally used underneath temporary
Has no anti-microbial properties
Does not prevent ingress of microbes from oral environment
Catches bur when it cuts through temporary filling and enters pulp chamber - loud screeching noise
Binds on bur and ruins it
Damages bacterial cytoplasmic membranes
Fibres trapped in cavity margin will wick bacteria and contaminants from oral environment (saliva and nutrients for dormant bacteria)

Question 25

Removal of inter visit medication

Answer 25

At next apt all hard material in access cavity removed before removing endo sponge
Flush out CaOH with irrigation syringe and sodium hyperchlorite and break it up with K file OR use ultrasonic scaler (or air scaler) with water ‘on

Question 26

Inflammation

Answer 26

Expect discomfort from either residual pulpal or periapical inflammation (acute local inflammatory process)
2-3 days common
Inflammation peaks at 5-7 days and lasts 10-12
Analgesics e.g. Paracetamol before numbness wears off
Anti-inflammatory drugs NSAID’s e.g. ibuprofen
Advise against codeine
Against occlusion

Question 27

Following disinfection

Answer 27

Viable bacteria can still be isolated from approx 50% of root canals

Question 28

Size 10 file

Answer 28

For initial negotiation and path-finding

Apical patency: making sure the orifice of the root canal remains open at this size

Question 29

Hypo-Cal

Answer 29

98% Calcium hydroxide, 2.5ml screw-fed syringe - Ellman International Inc.

Question 30

Roeko

Answer 30

Calcium hydroxide points, impregnated, doesn’t work that well

Question 31

UltraCal XS

Answer 31

Ultradent
35% calcium hydroxide
Disposable system
Plastic flexible tip
Gently inject paste into coronal aspect

Question 32

Squirt sodium hypochloride through apex of mandibular 2nd premolar

Answer 32

May damage mental nerve which lies very close to apex

Question 33

GIC

Answer 33

Used as restoration that provides outermost seak
Aim: effective seal that is durable, will not affect tooth structure detrimentally and easy to remove
Use chemically-set GIC in preference to RMGIC
Chemically-set GIC (e.g. Fuji IX) provides reliable and predictable bond to enamel and dentine
RMGIC (e.g. Fuji II) is not as predictable
GIC does not provide strong bond (~6MPa compared to 20-30MPa with resin based composite) - but if pleased well will provide effective and predictable seal
Ensure that cavity margins clean of all debris and water

Question 34

Is GIC brittle or tough

Answer 34

Brittle
Can snap/ crack under occlusal load
On molar try to put Cavit below GIC not just sponge, otherwise might crack

Question 35

What’s special about Endo-Z bur?

Answer 35

Non-cutting tip

Tungsten carbide bur

Question 36

What causes pain in endodontic cases

Answer 36

Build up in pressure

Can make if difficult to administer LA without first giving course of antibiotic to reduce inflammation

Question 37

Post-op instructions

Answer 37

Beware inflammation and infection