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12 I I special _ laser exploits the photoacoustic and photomechanical phenomena exclusively, which result from the use of subablativeenergyof20mJat15Hz,withimpulsesof only50µs.Withanaveragepowerofonly0.3W,each impulse interacts with the water molecules at a peak power of 400W, creating expansion and successive “shock waves” and leading to the formation of a powerful stream of fluids inside the canal, without generatingtheundesirablethermaleffectsseenwith other methodologies. The study with thermocouples applied to the radicular apical third revealed only a 1.2°C thermal rise after 20 seconds and 1.5°C after 40 seconds of continuous radiation. Another considerable advan- tage is derived from the insertion of the tip into the pulp chamber at the entrance to the root canal only, without the problematic insertion of the tip into the canal or 1mm from the apex required by the other techniques (LAI and CI). Newly designed tips (12mm in length, 300 to 400µm in diameter and with “radial and stripped” terminals) are used. The final 3mm are withoutcoatingtoallowagreaterlateralemissionof energy compared with the frontal tip. This mode of energy emission makes better use of the laser energy when, at subablative levels, delivery with very high peakpowerforeachsinglepulseof50µs(400W)pro- ducespowerful“shockwaves”intheirrigants,leading to a demonstrable and significant mechanical effect on the dentinal wall (Figs. 18–20). Thestudiesshowtheremovalofthesmearlayerto besuperiortothecontrolgroupswithonlyEDTAordis- tilled water. The samples treated with laser and EDTA for20and40secondsshowacompleteremovalofthe smearlayerwithopendentinaltubules(scoreof1,ac- cording to Hulsmann) and the absence of undesirable thermal phenomena, which is characteristic in the dentinal walls treated with traditional laser tech- niques. With high magnification, the collagen struc- ture remains intact, suggesting the hypothesis of a minimallyinvasiveendodontictreatment(Figs.21–23). The Medical Dental Advanced Technologies Group, in collaboration with the Arizona School of Dentistry and Oral Health (A. T. Still University), the Arthur A. DugoniSchoolofDentistry(UniversityofthePacific), the University of Genoa and the University of Loma Linda’s School of Dentistry, is currently investigating the effects of this root-canal decontamination tech- nique and the removal of bacterial biofilm in the radicular canal. The results, which are forthcoming, are very promising (Figs. 24–29). _Discussion and conclusion Laser technology used in endodontics in the last 20 years has undergone an important development. Theimprovedtechnologyhasintroducedendodontic fibres and tips of a calibre and flexibility that permit insertionupto1mmfromtheapex.Researchinrecent years has been directed towards producing technolo- gies (impulses of reduced length, “radial firing and stripped” tips) and techniques (LAI and PIPS) that are abletosimplifytheuseoflaserinendodonticsandmin- imise the undesirable thermal effects on the dentinal walls, using lower power in the presence of chemical irrigants.EDTAhasprovedtobethebestsolutionforthe LAItechniquethatactivatestheliquidandincrements its chelating capacity and cleaning of the smear layer. The use of NaClO increases its decontamination activ- ity. Finally, the PIPS technique reduces the thermal effects and exerts a potent cleaning and bactericidal actionthankstoitsstreamingoffluidsinitiatedbythe photonicenergyofthelaser.Furtherstudiesareneces- sary to validate these techniques (LAI and PIPS) as innovativetechnologiesformodernendodontics._ Editorial note: Part I of this series was published in roots 1/11. A PDF of the article and a complete list of references are available from the publisher. Figs.28a–d_Confocalmicroscope imagesofthedentineoflateraltubules coveredinbiofilm(a).Viewin fluorescentlightofbacterialbiofilm (ingreen;b).Dentineautofluorescence (inred;c).3-Dviewsuperimposed(d). Figs.29a–d_Confocalmicroscope imageofdentine(a).Autofluorescence withnosignofbacteria(b&c). 3-Dviewsuperimposed(d). roots2_2011 Prof Giovanni Olivi University of Genoa DI.S.TI.B.MO Department of Restorative Dentistry Genoa,Italy Private Practice Piazza F. Cucchi,3 00152 Rome Italy olivi.g@tiscali.it _contact roots Fig. 29a Fig. 29b Fig. 29c Fig. 29d Fig. 28a Fig. 28b Fig. 28c Fig. 28d