Irrigation and Medicaments

Rationale for irrigation

Classic In vivo studies have shown reductions in bacterial counts after mechanical preparation with hand filing and saline irrigation. However culturable bacteria were still present afterward.

(Siquera et al., Bystrom and Sundqvist, Orstavik and Dalton)

Mechanical preparation alone cannot predictably eliminate/reduce the bacterial load within the canals

Why?

• Insignificant antibacterial activity of saline• Bacterial penetration of dentinal tubules (Love 1996)• Biofilm • Accessory canals, lateral canals, canal ramifications (De Deus 1975)

Every root canal system has spaces that can not be cleaned mechanically .

The only way to clean webs, fins and anastomoses is through effective use of irrigation solution.

“of all the phases of anatomic study in the human system, one of the most complete is that of the pulp cavity morphology” - Barret 1925

MAIN AIM OF MECHANICAL PREPARATION IS TO FACILITATE IRRIGANT PENTETRATION TO THE FULL EXTENT OF THE CANAL

SYSTEM

Objectives of irrigation:

Mechanical Biologic

Flushing Antimicrobial activity

Lubricating

Dissolution of organic materials

Smear Layer Removal

• Flushing action and debris removal

• Dissolve inorganic tissue (dentin)

• Low surface tension (penetration of dentinal tubules)

• Dissolve organic matter (dentin collagen, pulp tissue, biofilm)

• Effective antimicrobial – bacteria, virus, yeast, fungi

•No irritation or damage periapical tissues

•Does not weaken tooth structure

•Stable in solution

•Prolonged antibacterial action

•Inexpensive/Easy to use

Ideal properties of irrigants

Sodium Hypochlorite (NaOCl)

Effective antimicrobial

Excellent organic tissue solvent

Lubricant

Fast acting

Why do we like it?

Caustic agent – very toxic to periapical tissues

Not substantive

Labile

Taste/smell

No effect on inorganic components (eg smear layer)

Why do we not like it?

NaOCl + H2O ↔ NaOH + HOCl ↔ Na+ + OH- + H+ + Ocl-

Three modes of action:

1. Chloramination

Hypoclorous acid (OCL-) causes Irreversible oxidation of cellular enymes and components of cell membrane

2. Saponification

Dissolution of Organic Material

Phospholipid degradation – breakdown of fatty acids and lipids within organic materials

NaOCL + fatty acids soap + glycerol

3. High pH (>11)

cell membrane integrity, inhibits enzymatic activity and disrupts cell metabolism

Used in varying concentrations ranging 0.5% - 5%

E.g. Dakins Solution – 0.5% Miltons 1% Parcan 3%

Domestic Bleach is usually sold as 3-5%

Does it matter what concentration of bleach we use?

Any concentration above 0.5% eliminated bacterial suspensions within 30secs - 30minutes (Bystrom et al. 1970)

Higher concentrations:

+ improved and quicker tissue dissolving capacity (Berber et al.)

+ quicker elimination of bacteria - 30sec for 5.25% versus 30mins for 0.5% (Vianna et al.)

- greater cytotoxic and caustic effect on periapical tisses with 5.25% versus 1.0% (Pashley et al.)

- thicker solution with higher surface tension and therefore lower wettability of the canal wall.

NaOCl effect on dentin

Degradation of the organic component of dentine – reduced elasticity and strength (Grigoratus et al.)

Concentration dependant effect on mechanical properties – erosion of dentinal tubules etc

Allergic Reaction to NaOCl

Unlikely

Contact dermatitis reported with skin contact (minimised with rubber dam usage)

Greater cytotoxic and caustic effect on periapial tisses with 5.25% versus 1.0% (Pashley et al.)

NaOCl effect on dentine bonding

NaOCl compromises bond strength1. Effecting the organic components of enamel/dentine necessary for hybrid layer formation2. Residual free radicals from oxidation reaction inhibits composite polymerisation reaction

10% sodium ascorbate (antioxidant/reducing agent) scrub prior to bonding

Improving Efficacy of NaOCl

1. Increase temperature of NaOCl

Bactericidal rates doubled for each 5°C rise in the range of 5 to 60°C

1% NaOCl at 45°C similar dissolution capacity to 5.25% solution at 20°C(Sirtes et al 2005)

2. Replenish NaOCl as often a possible (after every file)

NaOCl is a very labile compound - free chlorine is readily depleted Important to continually refresh the irrigant - especially apically (Moorer and Wesselink)

3. Inter appointment medication with CaOH

Synergistic tissue dissolution properties (Hassellgren 1984)

4. Ultrasonic ActivationAcoustic streaming (agitation) results in greater penetration of the irrigantUS energy also increases the temperature of the irrigant (see above)

Why are in vitro findings not reflected in in vivo studies/our day to day practice?

1. Higher volume of solution in vitro

2. Anatomical considerations- fins/lateral canals/anastamoses etc

3. Planktonic bacteria/dentine blocks are very different to biofilm

4. Presence of obstructions/other materials such as GP, necrotic tissue, inflammatory exudate etc

5. Buffering capacity of dentine (resulting in lowering the pH)

In vitro studies demonstrate killing of practically all microorganisms in a few seconds/minutes - when concentrated solutions are used.

Whereas the in vivo effectiveness of NaOCl in the root canal against the infecting microflora is somewhat disappointing.

Chlorhexidine Gluconate (CHX)Mode of Action:

Permeates the cell wall or outer membrane and breaks down the bacterial cytoplasmic membrane

Bacteriostatic at low concentrations (0.2%) Bacteriocidal at higher concentrations (2%)

Chlorhexidine (CHX)

Less effective than NaOCl on biofilm

Organic matter reduces its antibacterial efficacy

No tissue dissolving capacity

Why do we like it? Why do we not like it?

Low toxicity to healthy periapical tissues

Substantive for up to 4 weeks

Wide antimicrobial spectrum

Improves dentine bonding

Cytotoxicity of CHX:

Normally used at concentrations 0.12% - 2.0%

Low level of cytotoxicity both locally and systemically

CHX effect on dentine bonding:

Inhibition of matrix metallo proteinase (MMPs) which degrade the hybrid layer in dentine bonding

Application of CHX improves dentine bond stability

Effect on biofilm:

CHX is ineffective in disrupting or removing the protective

Interaction with NaOCl + CHX :

Insoluble brown precipitate (parachloroanaline) forms when used in conjunction with NaOCl – carcinogenic and occludes tubules Important to carry out a saline rinse as an intermediary flush

Substantivity:

CHX is adsorbed onto the dentine – positive charged CHX binds electrostatically to hydroxyapatite

Inhibiting recolonization of the dentine walls

Continual antibacterial effect for up to 30 days (Rosenthal et al. 2004)

When would you use CHX:

1. Retreatment cases: Adjunct/addition to the “usual” irrigating regime

2. Resistant bacteria – E.feacalis E. faecalis contains a proton pump which enables it to survive in high pH environments

3. Suspected perforation – iatrogenic/resorption

IodineMode of action:

Potent broad spectrum antibacterial solution

10% iodine potassium iodide

Advantages

Rapid action even at low concentrations

Broad spectrum

Disadvantages

No tissue dissolving capacity

Allergic reaction common (shellfish)

Discolouration of dentine

Indications:

5-10min iodine soak (Kvist et al. 2004)

Persistent disease cases that are not responding to NaOCl/CaOH treatment

Hydrogen Peroxide (H202)Mode of action:

H202 H20 + O2

Effervescence (bubbling) of O2 has a flushing/physically agitation effect

Release free radicals (OH-) which oxidises bacterial cell walls and proteins

Advantages

Low tissue toxicity

Bleaching effect - breaks down ferrous haemolytic pupal breakdown products

Oxygen is toxic to anaerobic bacteria

Debris removal due to flushing activity

Disadvantages

Weak antibacterial effect

Weak tissue dissolving capacity

Possible pain/emphysema due to O2 release

Smear LayerChemo-mechanical preparation leaves a layer of debris on the root canal wall which occludes dentinal tubules

Comprised of dentin particles, remnants of vital or necrotic pulp tissue, bacterial components and retained irrigants

Surface thickness:

Extension in tubules:

1 to 5 μm

40 μm to 100um

Smear Layer - Should it stay or should it go…..??

Advantages1. Occludes dentinal tubules – creating “plugs” which limit bacterial, nutrient and toxin penetration

2. Entombing any surviving bacteria from surrounding canal system

(Safavi et al. 1990, Pashley et al. 1985)

Disadvantages1. Harbour bacteria and bacterial toxins which can act as a source of reinfection(Meryon & Brook 1990)

2. Act as a substrate nutrients for surviving bacteria(George et al. 2005)

3. Prevents penetration of irrigants and medicaments into tubules (Haapasalo & Ørstavik 1987)

4. Prevents penetration of sealer into tubules and therefore affecting obturation seal.(Saunders and Saunders 1992)

Evidence is unequivocal…….

+ increased irrigant penetration and enhanced disinfection following smear layer removal

- contradictory evidence for obturation seal and effect on bacterial proliferation

Only one study looked at the effect of smear layer removal on outcome/healing which found no significant difference between smear and no smear layer (Byström and Sundqvist 1985)

Evidence for smear layer removal…..?

How do we get rid of it?

17% Ethylene Diamine Tetra Acetic Acid (EDTA)

Mode of action:

Chelating agent - binds to calcium ions (from smear layer or dentine) to form soluble calcium chelates

Demineralises and softens root canal wall dentine to depths of 20–50 μm in approximately 5 mins.

Mild antibacterial properties – weakens bacterial cell membranes

Interactions with NaOCl:

EDTA neutralises the tissue dissolving capacity of NaOCl (Grawehr et al.)

Saline rinse important between irrigants

Interactions with CHX:

White foggy precipitate caused by the degradation of CHX (Rasimck et al.)

Effect on dentine:

Reduction in flexural strength and modulus of elasticity (proportional to length of exposure)

Prolonged exposure can result in erosion of peritubular and intertubular dentine

Alternatives to EDTA

Organic Acids

Citric Acid, Tannic Acid and Polyacrylic Acid used in 10-40% concentrations

Similar demineralising capacity as EDTA in removing smear layer (Yamada et al. 1983)

HEBP – Etidronic Acid

No effect on proteolytic capacity of NaOCl

Weaker than EDTA/Organic acids – needs to be used in conjuction with NaOCL to effectively remove smear layer

Combination Irrigants

QMix

Ingredients:17% EDTA CHX Detergent

Detergent reduces surface tension and improve wettability (Grossman)

No tissue dissolving and weak antimicrobial properties

Premixed solution does not from the white precipitate that occurs with using them individually

Qmix removes smear layer as effectively as EDTA (Stojicic et al)

Combination Irrigants

MTAD

3 % Doxycycline

4.25% Citric Acid

Tween 80 (detergent)

Tetraclean

Doxycycline

Citric Acid

Propylene glycol

Tetracyclines:

Wide spectrum antibiotics – inhibiting protein synthesis

Substantive - binds to dentine therefore bacteriostatic

No tissue dissolution and relatively weak antimicrobial properties

Why use the fancy combo irrigants?

Safer - Low cytotoxicity compared to NaOCl (Zhang et al.)

Lower surface tension due to wetting agents

Better smear removal compared to EDTA – especially in apical third (Torabinajad et al.)

NaOCl causes cell lysis - releasing antigenic molecules (eg endotoxins)

Why not?

Cost

Weak antibacterial effect

No tissue dissolution

RECOMMENDATION: MUST BE USED IN CONJUNCTION WITH NaOCl

Application of Irrigants

Syringe IrrigationSide venting:

- minimises apical extrusion - flushes debris “upwards” out of canal

Use smallest gauge possible and place as close to apex as possible

Finger pressure only

Passive fit in canal

Luer lock design

a) Bevelledb) Open ended c) Safe ended

Prebend irrigation neede to 90 degrees to a predetermined length from pre op radiographs

Finger pressure only to minimise risk of extrusion

Considerations:

1. Irrigant stays mainly in canal lumen

2. Irrigant delivered only 1mm deeper than tip

3. Increasing volume of irrigant does not improve flushing action or debris removal

4. Vapour lock – important to recapitulate with a small file after every irrigant application

Irrigation Complications - Hypochlorite Extrusion

Symptoms:

Immediate severe pain

Immediate oedema of the soft tissue

Oedema spreads to neighbouring structures – orbits, lip or cheeks

Profuse interstitial bleeding result in profuse ecchymosis

24 hrs post op - ulceration and sloughing of mucosa

3 weeks post op - osteonecrosis

Pooling of bleach during treatment – chemical burn of soft palate

Management:

1. Critical to recognise what is happening

2. Calm the patient – can be difficult as they may be writhing in the chair

3. Immediate irrigation with saline or local anaesthetic solution

4. Leave the access cavity open to encourage drainage and escape for inflammatory exudate/blood

Optional but probably necessary - 5. Change your underpants……

Evidence on prescribing antibiotics and steroids is unequivocal

ANY RISK TO AIRWAYS NEEDS EMERGENCY TRANSFER TO A+E

24 hrs post op: ice pack and NSAIDS/painkillers

24 - 48hrs post op: heat pack and NSAIDS/painkillers

Daily review of the patient – assess healing and reassurance

Avoiding extrusion of irrigant:

1. Rubber Dam Isolation and relevant PPI

2. Side venting irrigation needle

3. Place irrigant 2mm short of working length (even shorter in open apex cases)

4. Avoid excessive pressure when applying irrigant – finger rather than thumb pressure

5. Avoid locking need in the canal

Manual Dynamic Agitation

Well fitting GP cone pumped up and down in 2-3mm strokes

GP cone displaces irrigant into anatomy away from the main canal lumen.

Facilitating exchange of the apical irrigant with fresh coronal solutions.

Eliminates Vapour Lock

*CARE TO NOT PUMP THE CONE TO APEX ESPECIALLY IN CASES DUE TO RISK OF ETRUDINT IRIGANT INTO THE APEX *

Brushes

Adjunct for debridement of the canals and to agitate the irrigants

Physical disruption of biofilms on wall of main canal lumen

Manual brushes: Navitips, Endo brush

Rotary brushes:

Canal Brush – 600 rpm flexible polypropylene bristles

Brushes - Any Good ?

- ? Ability to reach apex without excess enlargement

- ? Bristles left in canal irregularities

- ? Amount of penetration into tubules and irregularities

- ? Compaction of debris at apex

Reports of improved coronal cleanliness but NO difference in middle and apical third cleanliness (AL Hadlaq SM et al. 2006)

*Paeds: use of small interdental brushes in immature necrotic incisors*

Sonic Agitation – Endo Activator

Tip oscillates at 1 – 6 KHz

High amplitude movement (back-forth action) compared to ultrasonic

Strong and flexible polymer tips

Smooth and non cutting

Minimal apical extrusion (Townsend et al. 2009)

Sonic Agitation – Vibringe

Traditional syringe delivery of irrigant

Battery driven vibrations to stir up/agitate the irrigant as it is delivered

9000 oscillations per mins

Similar issues to syringe agitation:1. Vapour lock2. Placing needle tip close to apex3. Risk of extrusion

Sonic Agitation – Ripisonic

Aggressive sonic file

Stainless steel with barbed edges – may damage the prepared canal walls

Attaches to slow handpiece airline

Ultrasonic AgitationPassive movement of a file within the canal system which transmits energy to the irrigant solution.

Frequency: 20-30,000 Khz

Two modes of action: Acoustic streaming and Cavitation

Acoustic Streaming -

Vortex like fluid movement around the vibrating file

Agitated irrigant - shear forces on biofilm and bacteria walls - penetration into ramifications

Dampening effect of contact with canal walls- precurved files to match canal curvatures- apply tip to start of curvature

Cavitation -

Rapid movement of file creates air bubbles which expand/contract

Implosion/expansion releases energy as shockwaves and heat

Requires unimpeded movement of the file - ? possible within confines of a canal or curved canals

(many researchers concluded that cavitation does not occur in vivo)

Clinical Advantages of PUI:

More effective then syringe irrigation in removing organic debris (Gutarts et al. 2005)

Improves tissue dissolving capacity of NaOCl – increasing temperature (Cunningham 1980)

Effective in removing smear layer (Turkun and Cengez 1997)

Improved cleaning and disinfection isthmi and ramifications (Gutarts et al. 2005)

Does it make a difference to outcome?!

Negative Pressure Pressure Irrigation – Endo Vac

Negative Pressure Irrigation – Endo Vac

Advantages:

Promising canal cleanliness and SEM studies

Safely carries irrigant to within 1mm of apex

Minimal risk of apical extrusion (lower post op pain etc) and eliminates vapour lock

Continuous replenishment of irrigant

Endo activator resulted in the cleanest canals when compared to manual agitation, PUI, EndoActivator and Syringe Irrigation. EA achieved 99% disinfection of canal isthmi and ramifications. (Klyn et al. 2010)

Disadvantages:

Cost - £70 / case

Positive + Negative Pressure Irrigation – Rinse Endo

Disadvantages:

Risk of apical extrusion

Technical difficulties attaining suction seal above tooth

Advantages:

Frequent irrigant replenishment

Lasers in Disinfection

Laser emitting diode flexible optical fibre heat and energy into canal system

Pros:

Potential microbial efficacy

Effective at smear layer removal

Cons:

Excess energy can melt/burn dentinal tubules

Energy channelled through tip off fibre – risk of frying periapex through large foramen

Currently developing a spiral optical fibre to enable lateral irradiation of tubules

Photo Activated Disinfection

Photosensitive solution placed in canals - Methylene blue and toluidine blue

Activated with light of a specific wavelength

Releasing antimicrobial oxygen free radicals

Inter appointment Medications

When?

1. Unable to complete treatment in on visit – time/complications

2. Suppuration or exudate within the canal that cannot be stopped

3. Presence of a swelling/sinus

4. Retreatment/Persistent disease cases

5. Immature Apicies – apexification/apexogenesis

Definition:antimicrobial agent that is placed inside the root canal between treatment appointments in an attempt to destroy remaining microorganisms and prevent reinfection

Ideal properties of medicament:

Antimicrobial Effect

Non toxic to periradicular tissues

Ease of removal and application

Low surface tension and easily diffuse into canal system

Physical barrier to reinfection

Substantive antimicrobial effect

Calcium Hydroxide (CaOH2)Disassociation of CAOH2–> CA2+ + OH- Strong alkali with pH of 11.5

Two Modes of Action:

Antibacterial:

1. Damage to bacterial cytoplasmic membrane- lipid peroxidation of the phospholipids in the membrane- highly reactive free radicals (Coltran et al 1999)

2. Protein denaturation- Increase pH results in breakdown of ionic bonds in protein tertiary structures - disrupting enzyme activity and cell metabolism (Voet and Voet 1995)

3. Damage to bacterial DNA- hydroxyl ions disrupts DNA structure and induces mutation

Tissue Dissolving:

Similar to that of NaOCl but to a lesser degree – saponification reaction – (negated by extended application time)

pH gradient over time in monkey teeth after application of CaOH - Nerwich et al. 1993

<- Canal lumen - coronal

<- Canal lumen – apical

<- Root outer wall – coronal

<- Root outer wall – apical

Calcium hydroxide is effective as long as a high pH is maintained

Canal lumen pH 11 root surface ph 9Buffering action of root dentine (proton doors within the hydroxyapatite)

(Tronstad et al. 1981)

10 -14 days for pH to rise in periphery of root (Nerwich et al. 1993)

What is the optimal length of application?

Unequivocal evidence….

Sjogren (1991) reported 100% disinfection after one weekOrstavik (1991) and Barbosa et al. (1997) reported approx 75% disinfection at 1 weekCvek (1976) and Bystrom et al. (1985) reported over 90% disinfection after 4 weeks of application

Prolonged application of CaOH is probably necessary….longer the better…… gradual diffusion of hydroxyl ions though dentine

Considerations with CaOH

Resistant Bacteria – E.Faecalis

E.Faecalis is a bacteria commonly cultured in persistent disease/retreatment cases.

1. Bacterial coagulation/adherence to collagen within dentine (Love et al.)

2. Deep penetration into tubules (Haapasolo et al.)

3. Intracellular proton pump (Evans et al.)

Strategies - Alternative medicaments such as CHX or Iodine

Bacterial Lipopolysaccaride (LPS)

Potent antigens released during bacterial cell lysis

LPS release potent inflammatory mediators and prostaglandins periapical bone resorption

CaOH disrupts protein structure of LPS reduce periapical bone loss and encourage healing (Safavi and Nicholls 1993)

Modes of Delivery:

Water soluble:

Saline, methylcellulose solution

Highest disassociation of hydroxyl ions

Readily washed away by periradicular fluids

Viscous vehicles :

Glycerine, polyethylene glycol (PEG)

Oily vehicles:

Eugenol, Camphoricated parachlorophenol (CMCP)

Thicker consistency

Useful in suppurating/exudative canals

Lowest disassociation of hydroxyl ions

Difficult to remove - leaves residue

Effect on Dentine:

Degradation of organic component of dentine leads to reduction in strength and flexural modulus (Grigoratus et al.)

30-50% reduction in fracture strength and modulus of elasticity with long term application - greater than 6 monthse.g. apexification of immature teeth. (Andreasson et al.)

CaOH Toxicity:

Well tolerated by bone and pulp tissues. Resorbed if extruded into periapex

Interaction with NaOCl:

CaOH makes necrotic tissue more susceptible to the solubilising action of NaOCl (Hasselgren et al. 1984)

Method of Removal:

Instrumentation with 17% EDTA followed by NaOCl

Patency filing + circumferential filling of master apical file and ultrasonic activation

CaOH remnants may occludes dentinal tubules and affect obturation seal (similar to smear layer) (Kim and Kim)

Corticosteroid – Antibiotic Combination

Mode of action:

Corticosteroid - Triamcinolone

Bacteriostatic Antibiotic - Tetracycline

Poor inter appointment medication - weak antimicrobial properties

30% corticosteroid released within 24hours

Indications:

Inflamed/Hyperaemic pulps

Traumatised teeth – prevent/arrest/inhibit external inflammatory resorption arising on the root surface

? Efficacy in minimising post op discomfort when canals over instrumented

Questions?

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