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DENTAL TRIBUNE Middle East & Africa Edition | January-February 2015 7mCME ofNaOCl,significantlyincreasing production and consumption of available chlorine in comparison toultrasoundactivation.13 A recent study has reported how the use of an Er:YAG laser, equipped with a newly designed radial and stripped tip, in com- bination with 17 percent EDTA solution, using very low pulse duration (50 microseconds) and low energy (20 mJ) resulted in effective debris and smear layer removalwithminimalornother- mal damage to the organic den- tinal structure through a photo- acoustic technique called photon inducedphotoacousticstreaming or “PIPS.”14,15 Also the same pho- toacusticprotocolincombination with 5.25 percent sodium hypo- chlorite solution has been inves- tigated and shown to reduce the bacterial load and its associated biofilm in the root canal system threedimensionally.16 Other similar studies are in prog- ress for publication and the re- sultsarepromisingandsuggesta three-dimensional positive effect of this laseractivated decontami- nation(LAD)method. The purpose of this article is to present briefly the experimen- tal background of this laser tech- niqueandtointroducetheclinical protocol. Scientificbackground The microphotographic record- ing of the LAI studies suggested that the erbium lasers used in ir- rigant-filled root canals generate astreamingoffluidsathighspeed through a cavitation effect.17 The laserthermaleffectgeneratesthe expansionimplosionofthewater moleculesoftheirrigantsolution, generatingasecondarycavitation effect on the intracanal fluids. To accomplish this streaming, it is suggested the fiber be placed in the middle third of the canal, 5 mm from the apex and station- ary.18 Thisconceptgreatlysimpli- fies the laser technique, without the need to reach the apex and to negotiateradicularcurves. Also, the recorded video of the new technique, PIPS, showed a strong agitation of the liquids in- side the canals. It differs from the already cited LAI technique by activatingtheirrigantsolutionsin the endodontic system through a profoundphotoacousticandpho- tomechanical phenomena. The use of low energy (50 microsec- ond pulse, 20 mJ at 15 Hz, 0.3 W averagepower,orless)generates only a minimal thermal effect. The study with thermocouples applied to the radicular apical third revealed only 1.2 degrees C of thermal rise after 20 seconds and1.5degreesCafter40seconds ofcontinuousradiation.14 When the erbium laser energy is delivered at only 50 microsecond pulse duration through a special designed tapered and stripped 400 microns tip (Fotona Light- Walker, Technology4Medicine), it produces a large peak power of 400wattswhencomparedtoalon- gerpulseduration.Eachimpulse, absorbedbythewatermolecules, creates a strong “shock wave” that leads to the formation of an effective streaming of fluids in- side the canal while also limiting the undesirable thermal effects seen with other methodologies. The placement of the tip in the coronalportiononlyofthetreated toothallowsforamoreminimally enlarged canal preparation with lessthermaldamageasseenwith those techniques placed into the canalsystem. The root canal surfaces irrigated with 17 percent EDTA and laser activated for 20 seconds showed exposed collagen matrix, opened tubulesandtheabsenceofsmear layer and debris (Figs. 1-3). The rinsing with 5.25 percent sodium hypochlorite and laser irradia- tion for 20 seconds produced a strong activation of the solution, as reported by Macedo,13 improv- ing the disinfecting action of the sodium hypochlorite.16 The dis- infecting action of PIPS is very effective both on the root surface, thelateralcanalsandthedentinal tubules, as confirmed with SEM andconfocalstudies(Fig.4). The profound and distant effect of PIPS eliminates the need to in- troduce the tip into the root canal system. Unlike traditional laser techniques requiring placement of the tip 1 mm from the apex, or even 5 mm from the apex as proposed for LAI18 , the PIPS tip is placed in the coronal portion of the pulpal chamber only and left stationary, allowing the pho- toacousticeffecttospreadintothe openings of each canal. A new tip designconsistingofa400-micron diameter, 12 mm long, tapered endisusedforthistechnique(Fig. 5). The final 3 mm of coating is stripped from the end to allow for greaterlateralemissionofenergy comparedtothefrontaltip. This mode of energy emission allows for improved lateral dif- fusion with low energy and en- hancedphotoacousticeffect. Discussion Laser irradiation is a common technique used in endodontics to improve the cleaning, the de- briding and disinfection of the root canal system. Many wave- lengths and protocols are used. Near infrared lasers are used for the three-dimensional decon- tamination of the endodontic system. Nd:YAG and diode lasers use thermal energy to destroy bacteria. Observations reveal a certain grade of thermal injury to the root canal surface and cre- ate a typical morphological dam- age. Moreover, they are not able to thoroughly remove the smear layer. On the contrary, erbium lasers are used for their effective smear layer removal while their bac- tericidal activity is limited to the root surface. The placing of the tip close to the apex and its back movement during the activation processisrelatedtotheriskofapi- cal perforation, ledging and sur- face thermal damage, because of the ablation ability of this wave- length. Also a combination of the near and medium infrared lasers has been proposed. A technique, calledtwinlightendodontictreat- ment(TET),usestheerbiumlaser energyfirst,tocleantherootcanal surface and remove the smear layer, and the Neodimium:YAG laser second, used in dry mode as the final disinfecting step. All these techniques utilize tradi- tional tips and fibers placed into the canal, close to the apex (1 mm) with all the corresponding thermal disadvantages observed inlong,narrowandcurvecanals. The erbium lasers are also used asamediumofactivationofcom- monlyusedirrigants(LAI),avoid- ing the risk of thermal damage, whileincreasingthecleaningand disinfecting activity of the fluids. PIPS, in particular, reduces all these risks and disadvantages, thanks to the position of the tip in thecoronalorificeonlyandtothe use of minimally ablative energy levelsof20mJorless. The findings of our studies dem- onstrated that PIPS technique resultedinasafeandeffectivede- briding and decontaminating of therootcanalsystem.Ourclinical trialsshowedthatPIPStechnique greatly simplifies root canal ther- apy while facilitating the search fortheapicalterminus,debriding andmaintainingpatency. As a result of the efficacy of PIPS, the final size required for canal shaping can be significantly re- duced,oftentoasize25/04,allow- ingforamoreminimallyinvasive and biomimetic preparation that can then be obturated three di- mensionally. Conclusion Lasersareanextremelyversatile additiontothedentalpracticeand can be used in many instances insteadoftheconventionalmeth- odsemployedbythevastmajority of dentists. Incorporating a laser in the dental practice should be viewed as an investment rather than a cost. When used with a good knowledge of laser physics, trainingandsafety,lasersprovide our patients a new standard of dentalcare. References 1. Weichman JA, Johnson FM. Laser use in endodontics. A preliminary investigation. Oral Surg Oral Med Oral Pathol. 1971 Mar;31(3):416–20. 2. Pini R, Salimbeni R, Vannini M, Barone R, Clauser C. Laser dentistry:anewapplicationofex- cimerlaserinrootcanaltherapy. Lasers Surg Med. 1989;9(4):352– 357. Full list of references is available from the publisher. < Page 6 Fig. 3. Representative sample image of root canal dentinal walls irrigated with 17 percent EDTA and PIPS for 20 seconds Fig. 4. SEM image of clean lateral canal Fig. 5. New tapered tip design for this technique Lawrence Kotlow, DDS, has been in private dental practice in Al- bany, N.Y., since 1974. He is board certified in pediatric dentistry. He is a recognized standard pro- ficiency course provider for the Academy of Laser Dentistry. En- rico DiVito, DDS, is an adjunct professor at the Arizona School of Dentistry and Oral Health. He is in private practice at the Ari- zona Center for Laser Dentistry in Scottsdale, Ariz., in conjunc- tion with MDATG research group. Giovanni Olivi, MD, DDS, is a pro- fessor of endodontics at the Uni- versity of Genoa School of Den- tistry, where he is director for the Laser in Dentistry Master Course with Prof. S. Benedicenti. He is in private practice in Rome, Italy. 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