chemomechanical disinfection

Question 1

aetiology of endodontic disease

Question 2

biofilm resistance

Answer 2

provides protection against antimicrobials

Antimicrobials may fail to penetrate beyond the surface layers of the biofilm
Antimicrobials may be trapped and destroyed by enzymes
Antimicrobials may not be active against non-growing microorganisms
Expression of biofilm-specific resistance genes (e.g., efflux pumps)
Stress response to hostile environmental conditions (e.g., leading to an overexpression of antimicrobial agent-destroying enzymes).

Question 3

clinical objectives of endo

Answer 3

remove canal contents
eliminate the infection

Question 4

design objectives in endo

Answer 4

create a continuously tapering funnel shape

maintain apical foramen in orginal position - as small as possible

Question 5

mechanical preparation creates space to allow

Answer 5

to allows irrigating solutions and medicaments to more effectively eliminate micro-organisms from the root canal system

Question 6

why stages in preparation go coronal towards apices

Answer 6

to reduce bacterial load and not take it back

Question 7

sizing of the canal determined by

Answer 7

Size determined by initial size of root canal apex
Passive exploration known as “gauging”
Apical preparation size controversial
Usually at least ISO size 25
Some advocate 30 and larger to allow irrigation
Canal curvature impacts upon what is achievable safely

Question 8

ideal properties of disinfectant

Answer 8

low cost
washing action
reduces friction
killing of planktonic and biofilm microbes
detachment of biofilm
non-toxic and non-allergenic
doesn’t weaken dentine

Question 9

Sodium Hypochlorite (NaOCl)

Answer 9

NaOCl ionises in water into Na+ and the hypochlorite ion, OCl-

Establishes equilibrium with hypochlorous acid (HOCl)
Acid/Neutral HOCl predominates
pH 9 and above OCl- predominates
HOCl is responsible for antibacterial activity

Question 10

why NaOCl

Answer 10

potent antimicrobial activity
dissolves pulp remnants and collagen

ONLY root canal irrigant that dissolves necrotic and vital tissue
disrupts smear layer by acting on organic component

Question 11

factors important for NaOCl function

Answer 11

concentration
volume
contact
mechanical agitation
exchange

Question 12

concentration of sodium hypochlorite

Answer 12

presence of organic material affects antibacterial activity
used between 0.5% and 6%

we use 3% in GDH - Parcan

Question 13

contact for NaOCl

Answer 13

coronal flaring is key to prepare the entrance

we use syringe - as recommended by fluid dynamics model

endoactivator allows vibration for smooth irrigation = mechanical agitation

Question 14

manual dynamic irrigation

Answer 14

moving GP point in and out of canal

Question 15

problems with NaOCl

Answer 15

has effect on dentine - edits its organic content = 3 % protects dentine

doesn’t have an ability to remove smear layer by itself

effect on organic material = not just the dentine, but discolouration of fabrics, opharlmic injuries and allergic reactions

can cause tissue necrosis

Question 16

preparation of the canal for obturation

Answer 16

smear layer is formed during prep

organic pulpal material and inorganic dentinal debris
superficial 1-5µm with packing into tubules
bacterial contamination, substrate and interferes with disinfection

prevents sealer penetration !!

Question 17

smear layer is removed

Answer 17

EDTA is a chelating agent that is capable, when used with NaOCl, of removing smear layer

17% solution used
1 minute contact time necessary

dry after NaOCl, aspirate and then go again

Question 18

chlorhexidine digluconate

Answer 18

Antibacterial activity – studies show conflicting results, may have similar activity to NaOCl.
Less antifungal activity that NaOCl
Somewhat active against biofilms, but unable to disrupt biofilms

e.g. corsodyl

Adsorbtion of CHX prevents microbial colonisation for time beyond time of application
Varying times, upto 12 weeks

Question 19

GDH proposed protocol cleaning and shaping

Answer 19

Once canal preparation is complete the canal should be finally irrigated with:

3% NaOCl throughout instrumentation and at least 30mL after instrumentation complete with MDI – at least 10 minutes prior to obturation
17% EDTA 1min penultimate rinse
3% NaOCl final rinse

Dry canal using absorbent paper points between irrigants

Question 20

common symptoms of NAOCl extrusion

Answer 20

pain
swelling
ecchymosis - BRUISING
hemorrhage
neurological complications
airway obstruction

Question 21

classic NaOCl accident

Answer 21

bruising along the course of superficial venous vasculature
very rare

Question 22

risk factors

Answer 22

excessive pressure during irrigation

needle being locked within the canal

loss of control pf working length = use burr stopper !!

larger apical diameters/constriction (root resorption, immature teeth and developmental anomalies)

anatomical factors / proximity to sinus - check anatomy - UR 6,7

watch out for nigher NaOCl concencration

Question 23

pressure is the problem

Answer 23

patent apical foramen
facilitied by ANATOMY

need POSITIVE-PRESSURE IRRIGATION
pressure at the periapex EXCEED the venous pressure in the superficial veins of the neck

flow rate is 1 mL/15 sec

Question 24

management of NaOCl extrusion

Answer 24

all treatment should stop
keep calm
advise what happened
pain present = LA
allow bleeding until HAPOIG

give steroid paste (e.g. odontopaste) into a root canal, ensure no pressure

do not obturate, just seal

priority pain relief

review in 24h

refer if severe

Question 25

guidelines for the use of NaOCl

Answer 25

use oraseal for the dam
test the dam by irrigating chlorhexidine
ensure syringes are labelled

make supervisor check ur dam

use side-vented needle

don’t fill syringe full - 3/4s

use silicone stopper and set 2 mm short of the working length

depress with index finger not thumb

report to senior member