JVD 2020 #1 Endodontic Disinfection for Orthograde Root Canal Treatment in Veterinary Dentistry; Sasser Flashcards Preview

JVD 2019-2021 > JVD 2020 #1 Endodontic Disinfection for Orthograde Root Canal Treatment in Veterinary Dentistry; Sasser > Flashcards

Flashcards in JVD 2020 #1 Endodontic Disinfection for Orthograde Root Canal Treatment in Veterinary Dentistry; Sasser Deck (18)
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Define biofilm


Sessile multicellular microbial community that is attached to a surface and enmeshed in a self-produced matrix of extracellular polymeric substance


How much more resistant are bacteria within biofilms to antimicrobials?


100 to 1000-fold more resistant to antimicrobial agents


Define smear layer


ultrafine layer of inorganic and organic substances, dentin particles, remnants of vital or necrotic pulp tissue, microorganisms and retained irrigants formed by shaping and irrigating the root canal


What are the possible problems/sequela of the smear layer?


harbors microorg., reduces dentin permeability, compromises adequate disinfection by limiting disinfectant diffusion inside the dentinal tubules and is potential channel for microleakage


What are the mechanical and chemical objectives of Irrigation in Endodontics?


flush out debris
lubricate the canal
dissolve organic & inorganic tissue
prevent formation of smear layer


What are the biological objectives of Irrigation in Endodontics?


Highly effective against anaerobic and facultative microorg.
Inactivates toxins
Is nontoxic to vital tissue
Disinfects areas inaccessible to endo instruments


Properties of an IDEAL irrigant for RCT?

  1. Nonirritating to periapical tissues
  2. Remains stable in solution
  3. Prolonged, broad-spec antimicrobial effect
  4. Active in presence of blood, serum and protein derivatives
  5. Low surface tension
  6. Does not stain
  7. Does not induce cell-med immune response
  8. Able to dissolve necrotic pulp and biofilm
  9. Prevents or dissolves smear layer
  10. Able to disinfect dentin/tubules
  11. Non toxic/carcinogenic and doesn’t interfere with healing
  12. No adverse effect on physical properties of exposed dentin
  13. No adverse effects on sealing ability of filling materials

Key points of Sodium Hypochlorite (NaOCl)

  • Most commonly used irrigation solution b/c of ability to destroy variety of microbes and dissolve necrotic pulp and organic debris of smear layer
  • Conc 0.5-6%
  • in water, produces hypochlorous acid and chlorite ions–> dissolve organic tissues
  • removes exposed collagen fibrils, which decreases adherence for E. faecalis
  • Efficacy can be improved by incr temp of solution, volume, contact time (5-20m) and using agitation/activation methods
    • heating 0.5% NaOCl to 113F dissolved pulp as well as 5.25% root temp; Elevating temp to 140F resulted in complete pulp dissolution (diff study)
  • Loses dissolving/antibact capacity within 2 mins–> replenish!

What are the limitations/disadvantages of Sodium Hypochloriate (NaOCl) irrigating solution?

  • It will not dissolve/remove the entire smear layer
  • May negatively affect periapical tissues, if admin forcefully
  • Implicated in hypersensitivity reactions due to phago. of neuts in periapical region
  • Because it removes collagen fibrils when used as final irrigant- could interact and decrease bonding strength of resin-based canal sealer??
  • 5.25% solution compared to 0.5% solution decreases the elastic modulus and flexural strength of dentin due to proteolytic action on collagen matrix (pot weaken tooth)

Key Points Chlorhexidine (2% chlorhexidine gluconate) irrigant

  • Strongly basic molecule with cationic charges capable of binding to negatively charged surfaces of bacteria– damaging cell wall
  • Bactericidal at high conc and bacteriostatic at low conc
  • Shown activity against Gram + & - bacteria and yeasts
  • Sustantive antimicrobial activity by being readily adsorbed into the hydroxyapatite crystals of dentin and released back (tx residual bacteria)
  • Differs from NaOCl as it does not remove collagen fibrils- may improve resin-dentin bond
  • lower grade of toxicity locally & systemically compared to NaOCl– less likely tissue rxn with extrusion

Limitations/Disadvantages of Chlorhexidine gluconate 2% irrigant

  • Inability to dissolve organic debris compared to NaOCl
  • Cannot destroy resistant biofilm structure
  • Creates parachloroaniline insoluble precipitate when used with NaOCl
    • Parachloroaniline can cause cyanosis, carcinogenic, penetrates tubules and interferes with sealer

Key points Ethylenediaminetetraacetic acid (EDTA) irrigant

  • Demineralizing- used to remove the inorganic mineralized components of smear layer
  • highly biocompatible
  • normally conc 15-17% disodium EDTA liquid or paste
  • Detergents frequently added to solution to aid in wetting of the root canal wall and increase penetration into the dentin
  • Lubrication of hand or rotary files
  • Most commonly used with or alternately with NaOCl to enhance cleaning/antimicro
  • EDTA retains Ca-binding abilities when combined with NaOCl but NaOCl will lose some tissue-dissolving capacity

Limitations/Disadvantages of EDTA irrigant

  • Little to no antimicrobial effects
  • When used by itself, incapable of removing entire smear layer and disinfection
  • EDTA as a final irrigant demineralizes dentin, exposing collagen, and potentially creates ideal envir for residual E. faecalis to adhere

Key points MTAD - “mixture of tetracycline, acid and detergent” irrigant

  • Combination irrigant as alternative to EDTA as final rinse
  • supplied as powder and liquid when mixed creates aqueous sol 3% doxycycline, 4.25% citric acid as a demineralizing agent and 0.5% polysorbate as a detergent
  • Synergistic effects on disruption of bacterial cell walls and membranes, effectiveness against E. faecalis
  • Increasing effectiveness of MTAD in eliminating smear layer by first irrigating canal with 1.3% sol of NaOCl
  • has not demonstrated effects on flexural strength or elastic modulus of dentin- beneficial if using resin-based sealer
  • Failed to demonstrate dentin disinfection against E. faecalis compared to 5.25% NaOCl

Delivery of Endo Irrigants

  • Critical component of chemical debridement and disinfection
  • Irrigation dynamics depend on ability of irrigant sol to be dispersed to apical portion
    • penetration depth of needle, diameter and length of root canal, diameter of needle, irrigation pressure and velocity, type and angle of needle bevel
  • needle–> flexible and has one side opening to prevent excess pressure/velocity apically
  • Standard 25- or 31-mm endo needles shorter than many veterinary species canal lengths thus disinfection of most apical portion impossible

Negative- pressure irrigation

  • Irrigant delivered to the coronal access site and aspirated down the canal to the apical terminus of needle then drawn into the microcannula needle through a series of holes in terminal aspect.
  • Microcanula needle has sequence of 12 laser drilled microscopic holes; manufactured in 32 and 50mm lengths making adaptation to the longer canals possible.
  • Less risk of periapical exgtrusion of irrigant

Manual canal irrigation

  • Frequent replenishment of solutions, flusing debris from the root canal space with placement of irrigant in area of microorganisms
  • Actual exchange of fluids occurs within 1.0 to 1.5mm apical to needle tip
  • Wider needle enables more active flushing but risks wedging in canal limiting necessary backflow of irrigant and potential apical extrusion

Key points of Intracanal Medicaments

  • Use when standard disinfection and tissue disolution does not resovle pulpal bleeding during standard RCT
  • Use as root canal dressing between 2 endo appointments
  • Impede bacterial regrowth, supply continued disinfection and create a physical barrier in the root canal system
  • Calcium hydroxide most commonly used as slurry with water or NaOCl
    • high pH provides sustained broad-spec antimicrobial, capacity to dissolve necrotic tissue remants, bacteria and by-products
    • Needs complete removal at 2nd appointment to reduce effect on sealer
    • may have limited action on biofilm and E. faecalis

Decks in JVD 2019-2021 Class (44):