Chemomechanical Disinfection

Question 1

What is the etiology of endo disease

Answer 1

bacterial, fungal and viral origins

Question 2

What are the bacterial interactions in the dental biofilm development

Answer 2

Attachment
Colonization
Biofilm development

Question 3

How does the dental biofilm confer resistance

Answer 3

○ 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

Question 4

What are the clinical objectives of endo therapy

Answer 4

• Removing canal contents

Eliminating infection

Question 5

What are the design objectives of chem-mechanical

Answer 5

Create a continuously tapering funnel shape
Maintain apical foramen in original position
Keep apical opening as small as possible

Question 6

What is the point of mechanical preparation

Answer 6

This creates space to allow irrigating solutions and medicaments to more effectively eliminate micro-organisms from the root canal system

Question 7

What are the stages of mechanical preparation

Answer 7

○ Prep of tooth
		○ Access cavity prep
		○ Creating straight line access
		○ Initial negotiation
		○ Coronal flaring
		○ Working length determination
Apical preparation

Question 8

Why do we work on the coronal part first

Answer 8

• The most infected part of the root canal is the coronal part, apically there is less infected material which is why we start of prepping coronally so when we place our irrigant there we can start to disinfect there and as we go deeper into the tooth we are less likely to carry infected material deeper into the tooth

Question 9

How do we determine the size of the apical prep

Answer 9

• Size is determined by the initial size of the root canal apex
• Passive exploration is known as ‘gauging’
• The minimum size should be at least ISO size 25
• Some advocate a size 30 and larger to allow irrigation
  The canal curvature impacts upon what is achievable

Question 10

What are the ideal properties of an irrigant

Answer 10

• Low cost
  
  • Washing action
  • Reduction of friction
  • Improving cutting of dentine by the instruments
  • Temperature control
  • Dissolution of organic and inorganic matter
  • Good penetration within the root canal system
  • Killing of planktonic microbes
  • Killing of biofilm microbes
  • Detachment of biofilm
  • Non-toxic to periapical tissues
  • Non-allergenic
  • Does not react with negative consequences with other dental materials
    Does not weaken dentine

Question 11

Describe the equilibrium seen in sodium hypochlorite

Answer 11

It ionises in water into Na+ and the hypochlorite ion, Ocl-
It establishes equilibrium with hypochlorous acid (HOCl)
Acid/neutral HOCl predominates
pH 9 and above then Ocl- predominates
HOCl is responsible for the antibacterial activity

Question 12

Why do we use sodium hypochlorite

Answer 12

potent antimicrobial activity
dissolves the pulp remnants and collagen
only root canal irritant that dissolves necrotic and vital tissue
helps disrupt the smear layer by acting on the organic component

Question 13

How does sodium hypochlorite have potent AM activity

Answer 13

Can disrupt biofilm as can remove ECM component

Question 14

How does sodium hypochlorite dissolve pulp remnants and collagen

Answer 14

Is it can dissolve organic tissue

Question 15

What factors are important in the function of sodium hypochlorite

Answer 15

concentration
volume
contact
mechanical agitation
exchange

Question 16

How is sodium hypochlorite concentration a factor in its function

Answer 16

There is a variation in the suggested optimum concentration for antibacterial activity
The presence of organic material affects antibacterial activity
Used between 0.5% and 6%

Question 17

How does contact effect the function of sodium hypochlorite

Answer 17

Irrigant penetration
Need it to get apically
Importance of mechanical prep
Front flow needles can force the hypochlorite ahead which increases risk of a hypochlorite accident where it is forced through the constriction causing tissue damage

Question 18

How is mechanical agitation effect the sodium hypochlorite effect its function

Answer 18

Syringe irrigation alone is the least effective
Endoactivators can be used which vibrate and aggitate the solution resulting in debris removal and biofilm disruption
mechanical dynamic irrigation can be used

Question 19

What are problems in sodium hypochlorite

Answer 19

possible effect on dentine properties
inability to remove smear layer by itself
effect on organic materials

Question 20

How does sodium hypochlorite effect dentine properties

Answer 20

It will dissolve organic tissue and so will dissolve/modify the organic content in dentine
The higher the concentration the greater the effect on the modulus of elasticity and flexural strength of dentine

Question 21

What is the smear layer

Answer 21

○ Smear layer is formed during prep
○ Contains organic pulpal material and inorganic dentinal debris
○ Bacterial contamination, substrate and interferes with disinfection
○ Prevents sealer penetration

Question 22

How can the smear layer be removed

Answer 22

17% EDTA
10% citric acid
MTAD
sonic and ultrasonic irrigation

Question 23

What is EDTA

Answer 23

□ EDTA is a chelating agent that is capable when used with NaOCl of removing the smear layer
□ 17% solution is used
□ 1 minute contact time is necessary
□ EDTA and NAOCl should NOT be present in the root canal at the same time if the therapeutic benefits of NaOCl are to be realized
NaOCl used as a final irrigant solution after demineralization agents causes marked erosion of root canal dentine

Question 24

What are the complications of sodium hypochlorite

Answer 24

• Discoloration of fabrics
  
  • Ophthalmic injuries due to eye contact
    ○ Eye protection is ESSENTIAL
    ○ Can cause blindness
  • Apical extrusion leading to tissue necrosis - intracanal use, no more toxic than saline solution
    Allergic reactions

Question 25

What are the advantages of chlorhexidine digluconate

Answer 25

○ Antibacterial activity - studies show conflicting results, may have similar activity to NaOCl
○ Dentine medicated with CHX acquires antimicrobial substantivity
○ Adsorption of CHX prevents microbial colonisation beyond time of application
Biocompatibility considered acceptable

Question 26

What are the disadvantages of chlorhexidine digluconate

Answer 26

○ Less antifungal activity than NaOCl
○ Somewhat active against biofilms but unable to disrupt biofilms
○ CHX sensitivity possible
Risk of anaphylactic reaction

Question 27

What is the irrigant interaction between CHX and hypchlorite

Answer 27

• Interaction with NaOCl forms para-chloroaniline
  
  • It is cytotoxic and carcinogenic
  • Can stain the teeth
  • Has an uncertain bioavailability

Question 28

What is the proposed protocol cleaning and shaping

Answer 28

• One the canal preparation is complete, the canal should be finally irrigated with
  ○ 3% NaOCl throughout instrumentation and at least 30mL after instrumentation is complete with manual dynamic irrigation - at least 10 minutes prior to obturation
  ○ 17% EDTA 1 min penultimate rinse
  ○ 3% NaOCl final rinse
  Dry canal using absorbent paper points between irrigants