Clinical


An endosonic file in its adaptor Fig 4


Continued »


by at least one study to be the most dominant factor in irri- gant penetration 20


. The preparation taper has


also been found to affect irri- gant exchange, with apical preparations of greater taper producing greater flow of irri- gant than narrow tapers 2ı


. Irrigant activation may be


enabled either by manual or machine-assisted means. Manual techniques include agitation with the delivery needle, use of endodontic brushes or by manual dynamic irrigation. In this technique, a well-fitting gutta percha cone is placed into the irrigated canal and moved rapidly in and out with a 2-3mm stroke. This action is thought to create a hydrodynamic effect increasing the penetration and exchange of the reagent 20


. A


drawback of manual pumping is that it is laborious (Figure 2). Machine-assisted agitation


systems have come about to facilitate better penetra- tion. Rotary brushes such as Canalbrush can be used in a handpiece but, again, only where the brush can penetrate. Quantec-E provides contin-


uous irrigation during rotary instrumentation. This concept should provide for greater irrigant exchange than needle irrigation alone and this has been shown to be true in the coronal third of canals,


however; this has not resulted in cleaner canal walls in the middle and apical thirds of canals studied 22


. Sonic agitation devices,


such as the Endoactivator from Dentsply, work at lower frequencies than ultrasonic devices and demonstrate higher amplitudes of displace- ment. Endoactivator utilises a smooth-sided polymer tip that has been demonstrated to be resistant to fracture and passive towards the dentinal walls of the canal (Figure 3). Passive ultrasonic irrigation


(PUI) has been demonstrated to be highly effective in increasing both the penetration and cleaning efficiency of irrigant solutions. Although PUI can be used with intermittent irriga- tion it has been demonstrated to be most effective when applied to the completed canal preparation 9


. The prepared


canal is flooded with irrigant such as sodium hypochlorite. A file is then introduced to the maximum length at which it does not bind with the canal walls and activated with an ultrasonic unit. With the file tip free, a node of vibration is established, generating a wave of energy that streams irrigant coronally. Endosonore files are highly effective for this tech- nique (Figure 4). While passive irrigation with sodium hypochlorite does not remove the smear layer, when a 3 per cent solution of sodium


Fig 5


Two teeth with accessory anatomy that has been cleaned by the reagent regime, not filing


hypochlorite is used with PUI several studies have found complete removal of the smear layer 23, 24


. These findings were


not reproduced when the irri- gant was replaced with saline. The precise mode of action


of PUI is unclear but acoustic streaming is thought to be the primary factor in debris removal. Cavitation has also been postulated as an effect. Cavitation occurs with the generation and collapse of microbubbles within the irri- gant solution as the pressure drops momentarily below the liquid’s vapour point. This has been shown to generate high temperatures in the micro- environment and may explain the synergistic effect of PUI and sodium hypochlorite 25


.


Pressure alternating devices Devices have been introduced that create alternating nega- tive pressure and positive irrigation within the canal. Examples include EndoVac and RinsEndo. A study of one of these systems (RinsEndo) found that it outperformed passive irrigation in the removal of a layer of stained collagen from the canal walls but was inferior to manual dynamic irrigation 26


.


Summary Despite attempts to create alter- native solutions and methods, the evidence supports a regime that involves:


• A solution of sodium hypochlorite with a concen- tration in the range ı per cent to 3 per cent


• The use of a decalcifying agent to remove the smear layer


• Ultrasonic activation of the irrigant


• Adequate apical prepara- tion and taper of the canal to permit placement of the irrigant within ımm of the apex and enable sufficient irrigant flow. Figure 5 shows two completed


cases demonstrating accessory anatomy that is not accessible to files but which has been cleaned by irrigant penetration.


®


A full list of references for this article is available on request or by visiting www.irelandsdentalmag.ie where the references will be reproduced in full.


ABOUT THE AUTHOR


Adrian graduated from Queen’s University Belfast in 1992. He holds an MSc in Clinical Dentistry (Restorative Dentistry) from Leeds University and the Post Graduate Diploma in Endodontic Practice from the Eastman Institute, UCL. Adrian works in practice limited to endodontics at The Dental Specialist Clinic, Shore Road, Holywood and South Down Dental Clinic, Newry.


Ireland’s Dental magazine 33


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