Please activate JavaScript!
Please install Adobe Flash Player, click here for download
ePaper created 2016-07-29, 16:53:04 | version 1.38.0
| industry 22 laser 2 2016 tem.30 Furthermore, you can improve the effective- ness by a longer reaction time.31 Ethylene diamine tetra-acetate (EDTA) serves to remove the smear layer mentioned above. Irrigation withapprox.5 mlofEDTAinaconcentrationof17per centleadstothecompleteremovalofthesmearlayer within one minute.32 The reason why this effect is so important is that antimicrobial agents like e.g. NaClO canreactdeeplyinthedentinaltubulesonlyafterthe smear layer was removed. We should also mention that the effectiveness of EDTA against fungi like e.g. Candidaalbicanshasbeenproven(Fig.4).33 Theanti- microbial effect of EDTA is of rather minor impor- tance.34 Thecombinationofthetwodescribedirriga- tionsolutionsisstillthegoldstandard.Pleasereferto the related technical literature for more detailed in- formation. Laser in endodontics In the past decades, lasers were established in endodontics.35 Laser is the abbreviation of light am- plification by stimulated emission of radiation. They are electromagnetic waves with a high-energy den- sity. In endodontics, lasers of different wavelengths areused.Byphotothermalandpartlyphotomechan- icaleffects,laserradiationcanunfolditsbactericidal effect, depending on the wavelength and the asso- ciatedabsorptionintheirradiatedtissue.Mostlybe- cause of heating and the subsequent change of the osmotic gradient within the bacterial cell wall, the celldies.36 Lasersusedinendodonticssofardifferin their wavelengths, which again have critical influ- ence on the interaction with the irradiated tissue.37 Nd:YAGlasersfunctionatawavelengthof1,064 nm, diode lasers within a range between 810 nm and 980 nm, and erbium lasers at 2,780 nm (Er,Cr:YSGG) and 2,940 nm (Er:YAG). FirstreportsontheapplicationofNd:YAGlasersin the root canal were published in 1984 already.38 In thisprocedure,specialendodonticopticalfiberswere usedwhichcouldemitthelaserlightonlylinearly.For this reason, the optical fiber had to be moved in spi- rals in the canal to reach as many canal sections as possible.At15Hzand100 mJ,theantibacterialeffect may then reach up to 1,000 µm39 and enter deeply into the dentinal tubules. Compared to that, the reduction of bacteria using NaClO was proven to a depth of only 100 µm.40 How- ever, the linear emission and the high energy density in connection with the work in the dry canal had det- rimental effects. The antibacterial effect is lower in curved canals because of the linear emission of laser radiation.41 In addition, heat of up to 38°C developed in the canal, which may cause the dental hard tissue to burn (Fig. 5).42 Matusomo et al. explain that, due to the linear emission of the laser beam, on the one hand consis- tent wall contact was impossible and on the other hand, because of the heat formation, emission over the apex had to be avoided, making the work in the apical third considerably harder.43 When comparing the disinfecting effect of Nd:YAG lasers with “tradi- tional” disinfection using NaClO and ultrasound, DeMoore et al. arrived at the conclusion that the Nd:YAG laser has no advantage in this respect.44 The effects described for the Nd:YAG laser apply to the diode laser as well. Two different wavelengths are differentiated for erbium lasers: 2,780 nm for Er,Cr:YSGG and 2,940 nm for Er:YAG lasers. These wavelengths have their maximum absorption in water and hydroxy apatite.45 Whenerbiumlaserradiationhitsthedental hardtissuedirectly,thewatercontainedinthetissue evaporatesimmediatelyanddentalhardtissueisab- lated “gently” with only minimal thermal effects.46 With regard to endodontics, experimental studies with erbium lasers proved the removal of the smear layer to be more effective than by other types of la- sers and endodontic irri gation solutions.47 Further- more,thecanalwallswerefreefromdebrisandsmear layer and had mostly open dentinal tubules.48 Be- cause of the linear emission of the laser beam by the optical fiber and due to the cumbersome handling, the canal walls were cleaned imperfectly.49 To resolve these limitations, special endodontic so-called “side-firing” tips were developed, which areintendedtoemitirradiationlaterallyandapically sealed:50 Unfortunately, a construction-related re- Fig. 6 Fig. 6: PIPS® tip. 22016