Chemomechanical Disinfection

Question 1

What are the design objectives of canal preparation?

Answer 1

• create a continuously tapering funnel
• maintain apical foramen in original position
• keep apical opening as small as possible

Question 2

What does mechanical preparation facilitate?

Answer 2

• irrigation of solutions and medicaments to more effectively eliminate micro-organisms from the root canal system

Question 3

What are the stages in mechanical preparation?

Answer 3

• preparation of tooth
• access cavity preparation
• creation of straight line access
• initial negotiation
• coronal flaring
• determination of working length
• apical preparation

Question 4

What is the minimum size of apical preparation?

Answer 4

• ISO 25

Question 5

What is used for the chemical disinfection of canals?

Answer 5

• sodium hypochlorite (NaOCl)
  
  • potent antimicrobial
  • dissolves pulp remnants and collagen
  • disrupts smear layer by acting on organic compound

Question 6

What concentration of sodium hypochlorite should be used for chemical disinfection of canals?

Answer 6

• between 0.5-6%

Question 7

What are the problems with sodium hypochlorite as a chemical disinfectant?

Answer 7

• possible effects on dentine properties
• inability to remove smear layer itself
  
  • combined with EDTA
• effect on organic material
  
  • discolouration of fabrics
  • ophthalmic injuries on eye contact
  • apical extrusion leading to tissue necrosis
  • allergic reactions

Question 8

What can be used to remove the smear layer?

Answer 8

• 17% EDTA
  
  • EthyleneDiamineTetracetic Acid
  • 1 minute contact time
• 10% citric acid
• MTAD
  
  • Mixture of a Tetracycline isomer, Acid and Detergent
• sonic and ultrasonic irrigation
• apical control is vital

Question 9

What is chlorhexidine digluconate?

Answer 9

• liquid with antibacterial activity
  
  • some antifincal activity
  • somewhat active against biofilm but unable to disrupt
• adsorption prevents microbial colonisation
• sensitivity and anaphylaxis possible
• interacts with sodium hypochlorite
  
  • forms para-chloroaniline
  • cytotoxic and carcinogenic
  • uncertain bioavailability

Question 10

What is the proposed protocol for cleaning and shaping?

Answer 10

• completed canal preparation
• irrigation
  
  • 3% NaOCl
    - throughout instrumentation
    - 30ml after instrumentation
    - completed with MDI 10 mins prior to obturation
  • 17% EDTA
    - 1 minute penultimate rinse
  • 3% NaOCl
    - final rinse
• dry canal using absorbent paper points between irritants