Irrigation and Disinfection

Question 1

How do root canal infections start?

Answer 1

Don’t develop w/o bacteria

Primary infections are polymicrobial - dominated by obligate anaerobic bacteria

Question 2

What does irrigation achieve?

Answer 2

Kill and removal of microorganism, necrotic and inflamed tissue, dentine debris and smear layer
Provide lubrication

Question 3

Why does canal anatomy cause problem with disinfection?

Answer 3

Only 61% canals instrumented - 40% remain infection

Irregular and complex system

Question 4

Why does smear layer affect disinfection?

Answer 4

Provides protection for bacteria, inhibit and delay penetration or irrigant into dentine tubules

Question 5

What is smear layer?

Answer 5

Created during cleaning and shaping - cover instrumented canal wall
Inorganic and organic substance, fragment odontoblastic process, microorganism, necrotic debris

Question 6

How does fluid dynamic affect disinfection?

Answer 6

Irrigant penetrate 1-2mm further end of needle - needle needs to be apical region
Absence fluid motion = stagnation plane - no flushing of debris

Question 7

What are the rules of irrigation?

Answer 7

Use side venting needle
Luer-lok syringe 
Size 27/30 gauge 
Keep needle tip moving - prevent wedging
Constant agitation

Question 8

What is biofilm?

Answer 8

Group of microorganism in which cells stick to each other

Adherent cells embedded in self-produced matrix of extracellular polymeric substance

Question 9

What is EPS?

Answer 9

Polymeric conglomeration generally composed of extracellular DNA, proteins and polysaccharides

Question 10

When are bacteria less susceptible to antimicrobials?

Answer 10

In planktonic phase

Question 11

What is the most resistant microbiota?

Answer 11

E. faecalis - prevalence 90%
Can survive as monoculture
Associated failure endo tx
Highly resistant to species of NaOCl

Question 12

Ideal characteristics of irrigant?

Answer 12

Effective antimicrobial, not irritation periapical tissue, stable in solution, low surface tension, not stain, no cell immediate immune response, remove smear layer, non toxic, non carcinogenic, no adverse effect exposed dentine, no adverse affect sealing, easy use, inexpensive

Question 13

Sodium hypochlorite as irrigant?

Answer 13

Dissolves organic matter including biofilm

Antimicrobial, affordable

Question 14

Disadvantage NaOCl?

Answer 14

Diluted therefore need large bol
Minimal removal dentine debris/ smear layer 
Reduce flexural strength dentine
Rare case allergic reaction
Toxic vital tissue
Corrosion metal object

Question 15

What is EDTA?

Answer 15

Synthetic amino acid
Chelating agent - remove smear layer
Relatively non-toxic 
Different solution %
Use penultimate rinse for 1-2min

Question 16

Disadvantage EDTA?

Answer 16

Not bacteriostatic/cidal - eventually kill via starvation

Over use = removal of dentine

Question 17

What is chlorhexidine?

Answer 17

Cationic bibiguanide antiseptic 
Broad spec - resistance less likely
Bactericidal at high conc and static low conc
Less toxic NaOCl
No corrosion

Question 18

Disadvantage chlorhexidine?

Answer 18

No tissue disolving affect
Potential severe allergic reaction
Form parachloroanaline when used NaOCl = brown precipitate - potentially carcinogenic

Question 19

What is iodine potassium iodide?

Answer 19

Oxidising agent - attack key group proteins, nucleotides and fatty acid = cell death
Favoured in re-tx cases
Broad spec inc. against e.faecalis, p. aeruginosa and yeast species

Question 20

Disadvantages iodine potassium iodide?

Answer 20

Allergic reaction to iodine
Can stain dentine
Not stable in presence of organic material
No tissue dissolving properties

Question 21

What is hydrogen peroxide?

Answer 21

Hydroxyl-free radicals destroy proteins and DNA

Active against bacteria, virus and yeast

Question 22

Disadvantages of hydrogen peroxide?

Answer 22

Antimicrobial efficacy is poor and less tissue dissolving than NaOCl
Can release 02 gas - lead air emphysema

Question 23

What is MTAD?

Answer 23

Mixture tetracylcine, acid and detergent
Doxycycline provides broad-spec antibacterial effect
Citric acid removes smear layer

Question 24

Disadvantages MTAD?

Answer 24

Less efficient on biofilm
More toxic than NaOCl
Expensive
Risk of bacterial resistance
Risk tetracycline staining

Question 25

What is photo-activated disinfection?

Answer 25

A dye (toluidine blue) introduced root canal - low power laser is used activate dye
Photosensitive molecules attach to bacteria and following introduction of laser - singlet oxygen is produced which rupture the cell wall

Question 26

Advantages PAD?

Answer 26

Broad-spec activity with little risk resistance

Can destroy bacteria left by other irrigants

Question 27

Disadvantages PAD?

Answer 27

Depend power, length of exposure, absorption of light into tissue
No evidence suggest benefit over other irrigant
Expensive

Question 28

What is electronically activated water?

Answer 28

Electrolysed saline solution
Creates hypochlorus acid and free radicals which can remove biofilm and destroy bacteria
Lack study

Question 29

What are the ideal irrigants to use?

Answer 29

NaOCl - antimicrobial and dissolve organic tissue - fail remove smear layer
Chelating solution - remove smear layer but limited property as antimicrobial

NaOCl throughout endo procedure and finish flush EDTA

Question 30

What is ultrasonic agitation?

Answer 30

Agitation improves efficacy

Cause acoustic micro-steaming - disrupts biofilm - enhance antibacterial efficiency