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RO0211

06 I I special _ laser _After explaining the basic physics of the laser anditseffectsonbothbacteriaanddentinalsurfaces, thesecondpartofthisarticleserieswillanalysesome of the most important research in the international literaturetodayandthenewguidelinesfortheuseof laser as a source of activation of chemical irrigants. _Laser-assisted endodontics Preparationoftheaccesscavity The preparation of the access cavity can be per- formed directly with Erbium lasers, which can ablate enamelanddentine.Inthiscase,theuseofashorttip is recommended (from 4 to 6mm), with diameters between600and800µm,madeofquartztoallowthe use of higher energy and power. The importance of this technique should not be underestimated. Owing to its affinity to tissues richest in water (pulp and carious tissue), the laser allows for a minimally invasive access (because it is selective) into the pulp chamberand,atthesametime,allowsforthedecon- tamination and removal of bacterial debris and pulp tissue. Access to the canal orifices can be accom- plished effectively after the number of bacteria has been minimised, thereby avoiding the transposition of bacteria, toxins and debris in the apical direction during the procedure. Chen et al. demonstrated that bacteria are killed during cavity preparation up to a depth of 300 to 400µm below the radiated surface.20 Moreover, Erbium lasers are useful in the removal of pulp stones and in the search for calcified canals. Preparationandshapingofcanals The preparation of the canals with NiTi instru- ments is still the gold standard in endodontics today. In fact, despite the recognised ablative effect of Erbium lasers (2,780 and 2,940nm) on hard tissue, their effectiveness in the preparation of root canals appears to be limited at the moment and does not correspondtotheendodonticstandardsreachedwith NiTitechnology.21–23 However,theErbium,Chromium: YSGG (Er,Cr:YSGG) and the Erbium:YAG (Er:YAG) Fig. 5_Localisation to 1mm from the apex of the near infrared laser fibre and different penetration of the dentinal wall with Nd:YAG laser and diode 810nm (on the right). Fig. 6_Radial firing tips for Er,Cr:YSGG laser. Fig. 7_Undesirable thermal effects: during the retraction movement of the fibre of an Nd:YAG laser in a dry canal, contact with the dentinal wall can cause burns. Fig. 8_Undesirable thermal effects: during the retracting movement of an Er,Cr:YSGG laser tip used according to a traditional method, the tip contacting the dry dentinal wall causes burns, ledging and transportation of canals. roots2_2011 Laser in endodontics (Part II) Authors_ Prof Giovanni Olivi, Prof Rolando Crippa, Prof Giuseppe Iaria, Prof Vasilios Kaitsas, Dr Enrico DiVito & Prof Stefano Benedicenti, Italy & USA Fig. 6 Fig. 8Fig. 7 Fig. 5