Irrigation in Endodontics Flashcards
What do periapical and pulpal infections need to develop?
Bacteria
What are primary root canal infections?
Polymicrobial
- Dominated by obligate anaerobic bacteria
Aims of irrigation?
Killing and removal of microorganisms
Removal of necrotic/inflamed tissue
Removal of dentine debris and smear layer
Provides lubrication and reduces friction for instrumentation
Obstacles in root canal disinfection?
Anatomical complexities
Smear layer
Fluid dynamics
Biofilm and resistant microbiota
Anatomical complexities of RCT?
Only 61% of canal walls are instrumentated
40% of canal walls remain infected after instrumentation
Irregular and complex systems:
- Webs
- Loops
- Cul de sac
- Fins
- Lateral canals
- Apical delta
= Irrigation disinfects majority of the RC system
Smear layer - what is it and what does it consist of?
Created during cleaning and shaping process Covers the instrumented canal walls Consists of: - Inorganic and organic substances - Fragments of odontoblastic processes - Microorganisms - Necrotic debris
Problems the smear layer can cause?
Provides protection for bacteria
Inhibits/delays penetration of irrigant into dentinal tubules
Why is fluid dynamics a problem?
Fluid motion:
- Irrigant only penetrates 1-2mm further than end of needle
- Needle tip needs to be close to apical region
Absence of fluid motion:
- Stagnation plane
- No flushing of debris/penetration of irrigant into the apical region
Rules for irrigation?
Use a side-venting needle Use a Luer-lok syringe Keep needle tip moving to prevent it wedging and forcing irrigant through the apex Use gentle pressure If the needle binds - stop Constant agitation to improve fluid flow Size 27/30 gauge needle
How to help fluid dynamics?
Consider using a GP point to improve irrigant exchange in the apical region
What is a biofilm?
What is a biofilm extracellular polymeric substance (EPS)?
Any group of microorganisms in which cells stick to each other on a surface
- Adherent cells are frequently embedded in a self produced matrix of extracellular polymeric substance (EPS)
Biofilm EPS = A polymeric conglomeration composed of extracellular DNA, proteins and polysaccharides
Microbial cells growing in a biofilm are physiologically distinct from planktonic cells of the same organism = single cells that may float or swim in a single medium
Difficult to remove as can penetrate into the dentinal tubules
In biofilm, bac are less susceptible to antimicrobial killing than in planktonic phase
What bacterium exhibits a high level of resistance to antimicrobial agents?
E.faecalis
- Can survive monoculture in root canals
- Cultures of root canals irrigated with NaOCl always yielded positive cultures with E.faecalis
- Most frequent species in root canal treated teeth - 90% of cases
- High resistance to NaOCl = failure of endodontic tx
Ideal characteristics of an endodontic irrigant?
Effective antimicrobial action Non irritating to the periapical tissue Stable in soln Prolonged antimicrobial effect Active in presence of blood, serum and protein derivatives of tissue Low surface tension Not stain tooth Non-toxic Cheap Easy to use
When to prepare the canal?
When canal is flooded with irrigant
Types of irrigants?
NaOCl EDTA Clorhexidine Iodine potassium iodide MDTA Hydrogen peroxide Photo-activated disinfection (PAD)
NaOCl advantages?
Dissolves organic matter - including biofilm
Antimicrobial - effective against all endodontic bacteria
Cheap
How to maintain the desired antimicrobial effect of NaOCl when diluted?
Larger vols of irrigant Increase time for action required Increase temp e.g. 0.5% NaOCl - 30 min contact time 5.25% NaOCl < 30 sec
Outcomes of increasing the temperature of NaOCl?
Improves tissue dissolution
Can dissolve tissue but destroy osteoblast and corrose metal instrument
Increase antimicrobial effect (double for each 5 degree C rise)
Disadvantages of NaOCl?
Minimally removes dentin debris or smear layers
Affect mechanical dentin properties (reduce flexural strength)
Rare case of allergic rxns = dermatitis
Toxic to vital tissue (hemolysis, epithelial ulceration, necrosis)
Corrosion to metal object
EDTA features?
Synthetic AA
Chelating agent = removes smear layer -forms ring shaped internal complexes with metallic ions
Not bactericidal/static but eventually kills bac by starvation as metallic ions needed for growth are chelated
Relatively non-toxic
Why avoid overusing EDTA?
Excessive removal of dentine
So do 1-2 minute flush
Types of EDTA?
Soln 15-17%
Rinse for 1-2 mins
Gel to aid canal lubrication
Name an irrigant that is a chelating agent but less than EDTA?
Citric acid
Chlorhexidine features?
Broad spectrum, attacks multiple sites at cellular level making resistance less likely
Bactericidal at high concs and static at low concs
Persistent activity following removal
Concs 0.2-2%
Less toxic than NaOCl
No harmful effects to dentine or corrosion of instruments
Chlorhexidine problems?
Forms ppt when used with NaOCl called para chloroanaline = brown ppt, stains tooth and potentially carcinogenic So if used with NaOCl use with saline No tissue dissolving effects Cannot remove smear layer Potential for severe allergic rxns
Iodine potassium iodide advantages?
Broad spectrum
Substantive effects
Low toxicity relative to NaOCl
Disadvantages of Iodine potassium iodide?
Allergic rxn to iodine Can stain dentine Not stable in presence of organic material No tissue dissolving property Unable to remove smear layer
When is Iodine potassium iodide favoured?
In re-tx and heavily infected cases but not used in isolation
Hydrogen peroxide features?
OH free radicals destroys proteins and DNA
Active against bac, viruses and yeast
No longer used
Hydrogen peroxide negatives?
Antimicrobial efficacy is poorer than NaOCl
Less tissue dissolving capacity than NaOCl
Can release O2 gas - bubbles
Potential danger to tissues = air emphysema
What does MTAD stand for?
Mixture of tetracycline, acid and detergent
Advantages of MTAD?
Doxycycline = broad spectrum antibac
Citric acid removes smear layer
No adverse effect on physical property of tooth
Disadvantages of MTAD?
Less efficient on biofilm More toxic than NaOCl Expensive Risk of bacterial resistance (tetracycline) Risk for tetracycline staining
Photo-activated disinfection (PAD) - how does it work?
Dye introduced into root canal
Laser activates die
Photosensitizer molecules attach to bacteria and kill it
Photo-activated disinfection (PAD) advantages?
Broad spectrum
May destroy some bac left by some other irrigants
No risk of toxicity
Photo-activated disinfection (PAD) disadvantages?
Efficacy depends on power, length of exposure, absorption of light into tissues and distance from tip to target
No evidence to suggest any benefit over other irrigants
Expensive
Features of electronically activated water?
Electrolyses saline solution Disinfects dental piping and tubing Creates hypochlorous acid and free radicals = remove biofilm and destroy bac Lack studies showing efficacy and safety Not as effective as 3% NaOCl
What irrigant to use?
NaOCl alone produces superficially clean canal but does not remove smear layer
EDTA removes smear layer but leaves superficial debris
= NaOCl throughout the endo procedure followed by flush of EDTA
Iodine may be useful as additional irrigant in retreatment cases where bacteria may be more resistant
Ultrasonic agitation of irrigants?
Can improve efficacy
Causes acoustic microstreaming
Enhances antibac efficiency of the irrigants
Disrupts the biofilm
Can eliminate more bac from the root canal than hand instruments alone
Can be perforated with a standard file connected to an ultrasonic device or with endodontic tips
