Clinical


Fig 2


A well-fitting GP cone can be used in a rapid pumping motion for manual dynamic irrigation


and ozone gas filtration of the root canal system. Studies comparing the antimicrobial efficacy these approaches to irrigation with a 3 per cent sodium hypochlorite solu- tion found all to be inferior to varying degrees ıı-ı3


.


Decalcifying agents Although sodium hypochlo- rite has the ability to dissolve organic tissue, it cannot dissolve the inorganic compo- nent of dentine. Decalcifying agents such as EDTA and citric acid are recommended for dissolution of dentinal debris and removal of the smear layer from canal walls. In addi- tion, inorganic obstructions to negotiation of the root canal during preparation may be overcome with the aid of chela- tion agents 9


. It is not recommended that


EDTA be used as an alter- nating rinse with sodium hypochlorite due to the deacti- vation of sodium hypochlorite by EDTAı4


. It is recommended


that EDTA be used as a penul- timate rinse. The canal is dried of sodium hypochlorite and the EDTA is introduced and left in the canal for one minute. This is then rinsed out and the canal dried again before the final rinse with sodium hypochlorite. In this way, the smear layer is removed, opening the dentinal tubules and any lateral canals to pene- tration with hypochlorite.


There is clinical folklore that


mixing sodium hypochlorite in the canal with EDTA and creating an acid-base reaction, the so-called “Champagne Effect” aids with coronal trans- portation of debris. No evidence exists to support this claim 9 Factors that influence the


.


effectiveness of irrigation • Concentration of the irrigant.


• Temperature of the irrigant. • Level of corono-apical penetration of the irrigant.


• Volume of irrigant exchange.


Concentration The antimicrobial and tissue dissolution capacity of sodium hypochlorite are both a func- tion of its concentration, but so is its toxicity. Spangberg found that a 0.5 per cent solution of sodium hypochlorite was sufficient to kill most micro- organisms with the exception of Staphylococcus aureus and retained the ability to dissolve necrotic tissue though not vital tissue. One per cent solution killed Staphylococcus aureusı5 and 5.25 per cent sodium hypochlorite has been found to reduce the elastic modulus and flexural strength of human dentine while 0.5 per cent solu- tion does not ı6


. The risk of apical extru-


sion of sodium hypochlorite also militates against the use of unnecessarily high concentrations although a


The Endo Activator from Dentsply Fig 3


concentration of 0.0ı per cent has been demonstrated to be lethal to fibroblasts and a case of skin injury with exposure to 2.5 per cent following rubber dam leakage is recorded ı7


. Rapid dissolution of vital and


necrotic tissue remnants within the pulp canal is an essential facet of the use of sodium hypochlorite irrigant. No other irrigant has been shown to dissolve pulpal remnants in the same manner. It is, therefore, necessary to balance the needs for a higher concentration of hypochlorite with the caveat that higher concentrations are more likely to result in tissue damage if accidentally extruded through the apex or exposed to the mucosa. A concentration of 2.5 per cent is commonly used. An alterna- tive to increased concentration has been experimented with ex-vivo as described below.


Temperature Heating the hypochlorite solu- tion has been shown to increase both its bactericidal and tissue dissolving effects. The capacity of a ı per cent solution of sodium hypochlorite at 45ºC to dissolve human pulp tissue was found to be equal to that of a solution of 5.25 per cent at 20ºC ı8


. No clinical studies


have been carried out to deter- mine the applicability of this technique in-vivo, however; the benefit of using heated, weaker solutions of hypochlorite is


Corono-apical penetration Root canal irrigants are conventionally delivered using a side-vented needle, fitting loosely in the canal. Side venting and loose fit are impor- tant to reduce the risk of apical extrusion of irrigant and to increase the flushing effect on debris. Vapour lock (a body of gas trapped in the apical portion of the root canal) means that penetration of the irrigant under such passive irrigation circumstances has been shown to be no more than ımm beyond the tip of the needle ı9


. In order to increase


the efficacy of the irrigation it is vital to: ı. Maximize the extent to which the needle can penetrate.


2. Activate the irrigant in order to increase the penetration of the root canal. The needle penetration is


a function of both the size of the needle and the size of the apical preparation of the canal. Apical preparations in the order of ISO size 25-30 and the use of currently available 27-30 gauge needles will enable penetration to approximately ımm from working length. (Figure ı) This has been found


Continued » Ireland’s Dental magazine 31


that a temperature equilibrium is quickly reached within the root and extrusion or mucosal exposure is less likely to cause serious injury.


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