28/08/2018 0 Σχόλια
Q-switched Versus Free-running Er:YAG Laser Efficacy on the Root Canal Walls of Human Teeth
Marouan G. Khabbaz, Mersini I. Makropoulou, Alexandros A. Serafetinides, Dimitris Papadopoulos, and Eirini Papagiakoumou
Twenty-one teeth with one root canal were prepared by the step-back technique, divided into three groups, and split longitudinally. Group A served as a control. In group B, 20 to 150 pulses of 100 μs, 30 to 70 mJ per pulse at 1 to 4 Hz from a free-running Er:YAG laser were applied to the rootcanal dentin. In group C, the Q-switched Er:YAG laser, with the same energy parameters and a 190-ns pulse duration was used. Scanning electron microscopy examination revealed that control specimens had debris and smear layer obscuring the dentinal tubules at all levels in the canals without crack formation. Both groups of laser-treated dentin were clean with opened dentinal tubules except around the lased area in which there was an intact smear layer. Cracks were observed in both laser groups with higher frequency in group C. In group B, craters with different depth levels at the root canal walls were produced and the energy apparently was distributed equally, because craters were well-shaped. In contrast, the ablation efficiency in group C was questionable with the parameters used in this study. Consequently, suitable parameters of the free-running Er:YAG laser must be found before its careful use as an adjunct in endodontic therapy.
It is well established today that cleaning and shaping of the root-canal system are essential for the successful outcome of endodontic treatment. The objectives of the cleaning procedure are to eliminate microorganisms and all tissue remnants as well as inflammatory irritants from the root-canal space. Shaping creates a suitable space that facilitates debridement, irrigation, and canal obturation. Studies have shown that chemomechanical instrumentation with different instruments, methods, and techniques is unable to totally remove the debris from the root-canal walls (1–3).
Laser treatment with Er, Cr:YSGG Er:YAG CO₂, Nd:YAG Argon and other types of irradiation has been investigated on the root-canal walls by several researchers (4–13). Although some of these results are promising, some disadvantages remain evident when lasers are applied to endodontic treatment. For example, the Nd:YAG laser has the difficulty of absorption on the surface of dentin because of its wavelength, and the CO₂ laser cannot be delivered through a suitable fiber-optic system to the root canal. The diffusion of heat into adjacent tissues is a drawback for the both of these lasers (5). Excimer laser can be transmitted via fiber optic without heating damage of dentin, but using this type of laser, especially the KrF at 248 nm, there is the possibility of making a genetic changes because of the proximity to the 260 nm DNA absorption peak (14, 21).
Because water has the strongest absorption peak for electromagnetic radiation at the wavelength of 2.94 μm, the Er:YAG laser emitting at this wavelength is a suitable instrument for ablation of dentin, which consists of 12–13.5% of water. Dentin can be removed by the Er:YAG laser by a continuous vaporization process of its water resulting to high internal pressure, which leads to microexplosions in the irradiated dentin mass. Because only a small amount of water content has to be vaporized, little energy is necessary for this ablation process (15). Experimental studies on the efficacy of the Er:YAG laser irradiation for cleaning the root-canal walls demonstrated that this type of laser is more effective in removing the smear layer than other laser type and endodontic irrigants (9), and the dentinal walls were free of debris with opened dentinal tubules (6, 7). When a root canal model was drilled into a bovine dentin block it was found that the Er:YAG laser technique can have the advantage of decreasing the preparation time (11).
The laser effects depend, among other factors, on the power setting, mode of energy delivery, type and condition of laser, and target tissue (8). Although the temperature increase during the Er:YAG laser irradiation is not significant (16), melting and fusing of the orifice of the dentinal tubules caused by 40 mJ of irradiation has been noted (11). Investigators studying the morphological changes of the root dentinal walls after their irradiation with Nd:YAG, CO₂, and Argon laser found that it was highly dependent on energy level and duration of irradiation (5). During tissue irradiation, the thermal damage may be limited when the laser intensity is high and the interaction time is short (17, 18). In this JOURNAL OF ENDODONTICS Printed in U.S.A. Copyright © 2004 by The American Association of Endodontists VOL. 30, NO. 8, AUGUST 2004 585 case, especially effective is the Q-switched mode of the laser operating with the pulse length below the thermal relaxation time of the irradiated tissue, so less thermal damage is caused to the tissue (19). However, no studies have examined the efficacy of the Q-switched Er:YAG laser on the root canal. This study was designed to evaluate the morphological changes at the root-canal walls produced by the free-running and Q-switched Er:YAG laser. In addition, the efficacy of conventional cleansing procedures and the two types of laser used, in removing debris and smear layer from the root-canal walls was studied.
MATERIALS AND METHODS Twenty-one, human permanent straight and single-rooted, freshly extracted teeth were used in this study. After extraction, the teeth were stored in phosphate-buffered saline until use. All teeth were radiographed to confirm root canal patency, the absence of complicated root-canal anatomy, and the presence of one root canal only. The crowns of the teeth were resected at the CEJ, and the working length of each root canal was established 1 mm shorter of the apical foramen. Root canals were then prepared by the step-back technique using Flexo-files (Maillefer, Switzerland) with filing motion. Apical preparation was accomplished after a file #50 had enlarged the root canal at the working length. The coronal third of the canal was prepared with Gates Glidden burs #2 and #3. The root canals were irrigated with 2 ml of 3% sodium hypochlorite solution after each file and 10 ml of the same solution at the end of the preparation. The irrigant solution was delivered with a 25-gauge needle as apically as possible without binding. The root canals were then dried with paper points, and teeth were randomly divided into three groups (A, B, and C) of seven teeth each.
Afterward the roots were grooved longitudinally with a diamond bur without penetration into the root canal and split into two halves. In group A, which served as the control, the root canal dentin was not lased. In group B, the free-running Er:YAG laser, developed in the National Technical University of Athens (NTUA), with a wavelength of 2.94 DISCUSSION
Laser irradiation on the root-canal walls for the evaluation of cleaning ability has been investigated by many researchers. Khan et al. (5) reported that the CO₂, Nd:YAG, and Argon laser produced more carbonization (thermal damage) and greater shape changes of the root canals as energy and duration of the laser treatment were increased. On the contrary, Q-switched laser application with less pulse duration than the normal spiking mode produced less thermal damage to the irradiated tissues (19). Arrastia-Jitosho et al. (13) applied the Nd:YAG Q-switched nanosecond pulsed laser on dentin and predicated that this laser cannot replace the conventional method of hand instrumentation in root canals, but it was shown that it was capable of complete removal of smear layer. Rohanizadeh et al. (20) studied the effects of the Q-switched Nd:YAG laser on dentin, enamel, bone, and cementum at different frequencies and irradiation times. They demonstrated that this type of laser can produce craters with frequency-related depths without carbonization or high-melting zones but with cracks and fractures in the irradiated tissues.
In our study, it was shown that cracks were found in the majority of surfaces that were lased with the Q-switched Er:YAG. Only the use of decreased energy, frequency, and pulse repetition rate produced acceptable shape changes of irradiated dentin. Therefore, our results taken together with those of the other previously mentioned authors (13, 20) enunciate that much work is needed to improve the parameters used with the Q-switched type of laser on dentinal root canal walls because of the creation of cracks on them. Cracks are not desirable because they can reduce the integrity of the tooth structure and the success rate of the endodontic treatment. It is believed that the crack formation as well as the reduced ablation ability of the hard dental tissue produced by the Qswitched Er:YAG laser are caused by the formation of plasma in the surface of dentin. The application of a relevant and appropriate water spray in conjunction with suitable parameters of the laser beam will prevent these problems (22).
The cleaning effect of different instrumentation techniques and irrigation solutions on the smear layer produced after the preparation of the root canal walls has been investigated by several researchers. Siqueira et al. (3) used five instrumentation techniques with copious irrigation with 5% sodium hypochlorite to evaluate their cleaning ability on the apical third of curved root canals. They found that none of the technique used totally debrided the entire root-canal system, especially when variations in the internal anatomy were present. Takeda et al. (9) used 3 ml of 5.25% sodium hypochlorite and 3% H₂O₂ alternately between each file size and final irrigation with 17% EDTA, 6% phosphoric acid, and 6% citric acid, in different teeth groups, to remove the smear layer from the prepared root canal. They demonstrated that none of the irrigation solutions used had effectively cleaned all the smear layer from the root-canal system. Mayer et al. (1) reported that ultrasonically activated irrigants (5.25% NaOCl and 17% EDTA) did not reduce debris and smear layer from rotary prepared root canal with ProFile .04 and lightspeed. Our results are similar because after the root canal preparation, using the sodium hypochlorite as irrigating solution, the root canal walls were covered with debris and smear layer. Consequently, it seems that it is very difficult to obtain clean dentinal walls in the root canal by instrumentation and irrigation only.
On the contrary, it seems that laser irradiation with different laser types (Er:YAG, Nd:YAG, Ar, and CO₂) is effective in removing debris and smear layer from the root canal walls (4–9, 12, 13). We agree with these researchers because our results indicated that it was possible to vaporize debris and smear layer from the irradiated area of the prepared root canals with the parameters used in this investigation. However, we noticed that around the irradiated area, smear layer was still existing. This SEM observation indicates that temperature increase caused by the laser beams does not diffuse from the irradiated to the nearest area, or if it does, it was not able to vaporize debris and smear layer located there. Another verification of this observation was, as the findings of Takeda et al. (7) indicated, that in specimens in which the irradiation beam did not touch the root canal walls, laser was not effective in removing debris and smear layer. Furthermore, it was demonstrated that the angle of the laser beam in relation to the target surface can be a deciding factor of how much energy will be absorbed by the dentin (4).
In this investigation, the root canals of freshly extracted teeth were prepared to a file size #50, split, and irradiated in air because an optical fiber was not used. Our results cannot be directly equated to an intact tooth or an in situ interaction; they are the nearest ones to the optimum situation when one considers the low availability of clinical endodontic fibers. Future improvements to laser fiber tips will result in suitable medium for the clinical use of the laser Er:YAG irradiation to vaporize debris and smear layer from the prepared root canal.
Supported by a grant from the secretariat of the Research Committee of the National and Kapodistrian University of Athens.
1. Mayer BE, Peters OA, Barbakow F. Effects of rotary instruments and ultrasonic irrigation on debris and smear layer scores: a scanning electron microscopic study. Int Endod J 2002;35:582–9.
2. Hulsmann M, Schade M, Schafers F. A comparative study of root canal preparation with HERO 642 and Quantec SC rotary Ni-Ti instruments. Int Endod J 2001;34:538–46.
3. Siqueira JF, Araujo MC, Garcia PF, Fraga RC, Saboia Dantas CJ. Histological evaluation of the effectiveness of five instrumentation techniques for cleaning the apical third of root canal. J Endodon 1997;23:499–502.
4. Anic I, Segovic S, Katanek D, Prskalo K, Najzar-Fleger D. Scanning electron microscopic study of dentin lased with Argon, CO₂ and Nd:YAG laser. J Endodon 1989;24:77–81.
5. Khan MA, Khan MFR, Khan MW, Wakabayashi H, Matsumoto K. Effect of laser treatment on the root canal of human teeth. Endod Dent Traumatol 1997;13:134–45.
6. Takeda FH, Harashima T, Eto JN, Kimura Y, Matsumoto K. Effect of Er:YAG laser treatment on the root canal walls of human teeth: an SEM study. Endod Dent Traumatol 1998;14:270–3.
7. Takeda FH, Harashima T, Kimura Y, Matsumoto K. Efficacy of Er:YAG laser irradiation in removing debris and smear layer on root canal walls. J Endodon 1998;24:548–51.
8. Harashima T, Takeda FH, Zhang C, Kimura Y, Matsumoto K. Effect of argon laser irradiation on instrumented root canal walls. Endod Dent Traumatol 1998;14:26–30.
9. Takeda FH, Harashima T, Kimura Y, Matsumoto K. A comparative study of the removal of smear layer by three endodontic irrigants and two types of laser. Int Endod J 1999;32:32–9.
10. Yamazaki R, Goya C, Yu D, Kimura Y, Matsumoto K. Effects of Erbium, Chromium:YSGG laser irradiation on root canal walls: a scanning electron microscopic and thermographic study. J Endodon 2001;27:9–12.
11. Shoji S, Hariu H, Horiuchi H. Canal enlargement by Er:YAG laser using a cone-shaped irradiation tip. J Endodon 2000;26:454–8.
12. Levy G. Cleaning and shaping the root canal with a Nd:YAG laser beam: a comparative study. J Endodon 1992;18:123–27.
13. Arrastia-Jitosho AM, Liaw LH, Lee W, Wilder-Smith P. Effects of a 532 nm Q-switched nanosecond pulsed laser on dentin. J Endodon 1998;24:427– 31.
14. Pini R, Salimbeni R, Vannini M, Barone R, Clauser C. Laser dentistry: a new application of Excimer laser in root canal therapy. Lasers Surg Med 1989;9:352–7.
15. Hibst R, Keller U. Experimental studies of the application of the Er:YAG laser on dental hard substances: I. Measurement of the ablation rate. Lasers Surg Med 1989;9:338–44.
16. Kimura Y, Yonaga K, Yokoyama K, Kinoshita J, Ogata Y, Matsumoto K. Root surface temperature increase during Er:YAG laser irradiation of root canals. J Endodon 2002;28:76–8.
17. Anastasopoulou N, Ziolek C, Serafetinides A, Lubatschowski H. Qswitched Er:YAG radiation transmission through fluoride glass fibers and dielectric-coated metallic hollow waveguides. Optics Commun 2000;186:167–71.
18. Serafetinides AA, Khabbaz MG, Makropoulou MI, Kar AK. Picosecond laser ablation of dentin in endodontics. Lasers Med Sci 1999;14:168–74.
19. Walsh JT, Flotte TJ, Deutsch TF. Er:YAG laser ablation of tissue: effect of pulse duration and tissue type on thermal damage. Lasers Surg Med 1989;9:314–26.
20. Rohanizadeh R, Jean A, Daculsi G. Effects of Q-switched Nd:YAG laser on calcified tissues. Lasers Med Sci 1999;14:221–7.
21. Neev J. Analysis of excimer laser interactions with hard tissue. In: Miserendino L, Pick R, eds. Lasers in dentistry. Chicago: Quintessence Pub, 1995:261–82.
22. Wigdor H, Walsh J, Featherstone J, Visuri S, Fried D, Waldvogel J. Lasers in dentistry. Lasers Surg Med 1995;16:103–33.
Laser_efficacy_on_root_canal_walls.pdf
Twenty-one teeth with one root canal were prepared by the step-back technique, divided into three groups, and split longitudinally. Group A served as a control. In group B, 20 to 150 pulses of 100 μs, 30 to 70 mJ per pulse at 1 to 4 Hz from a free-running Er:YAG laser were applied to the rootcanal dentin. In group C, the Q-switched Er:YAG laser, with the same energy parameters and a 190-ns pulse duration was used. Scanning electron microscopy examination revealed that control specimens had debris and smear layer obscuring the dentinal tubules at all levels in the canals without crack formation. Both groups of laser-treated dentin were clean with opened dentinal tubules except around the lased area in which there was an intact smear layer. Cracks were observed in both laser groups with higher frequency in group C. In group B, craters with different depth levels at the root canal walls were produced and the energy apparently was distributed equally, because craters were well-shaped. In contrast, the ablation efficiency in group C was questionable with the parameters used in this study. Consequently, suitable parameters of the free-running Er:YAG laser must be found before its careful use as an adjunct in endodontic therapy.
It is well established today that cleaning and shaping of the root-canal system are essential for the successful outcome of endodontic treatment. The objectives of the cleaning procedure are to eliminate microorganisms and all tissue remnants as well as inflammatory irritants from the root-canal space. Shaping creates a suitable space that facilitates debridement, irrigation, and canal obturation. Studies have shown that chemomechanical instrumentation with different instruments, methods, and techniques is unable to totally remove the debris from the root-canal walls (1–3).
Laser treatment with Er, Cr:YSGG Er:YAG CO₂, Nd:YAG Argon and other types of irradiation has been investigated on the root-canal walls by several researchers (4–13). Although some of these results are promising, some disadvantages remain evident when lasers are applied to endodontic treatment. For example, the Nd:YAG laser has the difficulty of absorption on the surface of dentin because of its wavelength, and the CO₂ laser cannot be delivered through a suitable fiber-optic system to the root canal. The diffusion of heat into adjacent tissues is a drawback for the both of these lasers (5). Excimer laser can be transmitted via fiber optic without heating damage of dentin, but using this type of laser, especially the KrF at 248 nm, there is the possibility of making a genetic changes because of the proximity to the 260 nm DNA absorption peak (14, 21).
Because water has the strongest absorption peak for electromagnetic radiation at the wavelength of 2.94 μm, the Er:YAG laser emitting at this wavelength is a suitable instrument for ablation of dentin, which consists of 12–13.5% of water. Dentin can be removed by the Er:YAG laser by a continuous vaporization process of its water resulting to high internal pressure, which leads to microexplosions in the irradiated dentin mass. Because only a small amount of water content has to be vaporized, little energy is necessary for this ablation process (15). Experimental studies on the efficacy of the Er:YAG laser irradiation for cleaning the root-canal walls demonstrated that this type of laser is more effective in removing the smear layer than other laser type and endodontic irrigants (9), and the dentinal walls were free of debris with opened dentinal tubules (6, 7). When a root canal model was drilled into a bovine dentin block it was found that the Er:YAG laser technique can have the advantage of decreasing the preparation time (11).
The laser effects depend, among other factors, on the power setting, mode of energy delivery, type and condition of laser, and target tissue (8). Although the temperature increase during the Er:YAG laser irradiation is not significant (16), melting and fusing of the orifice of the dentinal tubules caused by 40 mJ of irradiation has been noted (11). Investigators studying the morphological changes of the root dentinal walls after their irradiation with Nd:YAG, CO₂, and Argon laser found that it was highly dependent on energy level and duration of irradiation (5). During tissue irradiation, the thermal damage may be limited when the laser intensity is high and the interaction time is short (17, 18). In this JOURNAL OF ENDODONTICS Printed in U.S.A. Copyright © 2004 by The American Association of Endodontists VOL. 30, NO. 8, AUGUST 2004 585 case, especially effective is the Q-switched mode of the laser operating with the pulse length below the thermal relaxation time of the irradiated tissue, so less thermal damage is caused to the tissue (19). However, no studies have examined the efficacy of the Q-switched Er:YAG laser on the root canal. This study was designed to evaluate the morphological changes at the root-canal walls produced by the free-running and Q-switched Er:YAG laser. In addition, the efficacy of conventional cleansing procedures and the two types of laser used, in removing debris and smear layer from the root-canal walls was studied.
MATERIALS AND METHODS Twenty-one, human permanent straight and single-rooted, freshly extracted teeth were used in this study. After extraction, the teeth were stored in phosphate-buffered saline until use. All teeth were radiographed to confirm root canal patency, the absence of complicated root-canal anatomy, and the presence of one root canal only. The crowns of the teeth were resected at the CEJ, and the working length of each root canal was established 1 mm shorter of the apical foramen. Root canals were then prepared by the step-back technique using Flexo-files (Maillefer, Switzerland) with filing motion. Apical preparation was accomplished after a file #50 had enlarged the root canal at the working length. The coronal third of the canal was prepared with Gates Glidden burs #2 and #3. The root canals were irrigated with 2 ml of 3% sodium hypochlorite solution after each file and 10 ml of the same solution at the end of the preparation. The irrigant solution was delivered with a 25-gauge needle as apically as possible without binding. The root canals were then dried with paper points, and teeth were randomly divided into three groups (A, B, and C) of seven teeth each.
Afterward the roots were grooved longitudinally with a diamond bur without penetration into the root canal and split into two halves. In group A, which served as the control, the root canal dentin was not lased. In group B, the free-running Er:YAG laser, developed in the National Technical University of Athens (NTUA), with a wavelength of 2.94 DISCUSSION
Laser irradiation on the root-canal walls for the evaluation of cleaning ability has been investigated by many researchers. Khan et al. (5) reported that the CO₂, Nd:YAG, and Argon laser produced more carbonization (thermal damage) and greater shape changes of the root canals as energy and duration of the laser treatment were increased. On the contrary, Q-switched laser application with less pulse duration than the normal spiking mode produced less thermal damage to the irradiated tissues (19). Arrastia-Jitosho et al. (13) applied the Nd:YAG Q-switched nanosecond pulsed laser on dentin and predicated that this laser cannot replace the conventional method of hand instrumentation in root canals, but it was shown that it was capable of complete removal of smear layer. Rohanizadeh et al. (20) studied the effects of the Q-switched Nd:YAG laser on dentin, enamel, bone, and cementum at different frequencies and irradiation times. They demonstrated that this type of laser can produce craters with frequency-related depths without carbonization or high-melting zones but with cracks and fractures in the irradiated tissues.
In our study, it was shown that cracks were found in the majority of surfaces that were lased with the Q-switched Er:YAG. Only the use of decreased energy, frequency, and pulse repetition rate produced acceptable shape changes of irradiated dentin. Therefore, our results taken together with those of the other previously mentioned authors (13, 20) enunciate that much work is needed to improve the parameters used with the Q-switched type of laser on dentinal root canal walls because of the creation of cracks on them. Cracks are not desirable because they can reduce the integrity of the tooth structure and the success rate of the endodontic treatment. It is believed that the crack formation as well as the reduced ablation ability of the hard dental tissue produced by the Qswitched Er:YAG laser are caused by the formation of plasma in the surface of dentin. The application of a relevant and appropriate water spray in conjunction with suitable parameters of the laser beam will prevent these problems (22).
The cleaning effect of different instrumentation techniques and irrigation solutions on the smear layer produced after the preparation of the root canal walls has been investigated by several researchers. Siqueira et al. (3) used five instrumentation techniques with copious irrigation with 5% sodium hypochlorite to evaluate their cleaning ability on the apical third of curved root canals. They found that none of the technique used totally debrided the entire root-canal system, especially when variations in the internal anatomy were present. Takeda et al. (9) used 3 ml of 5.25% sodium hypochlorite and 3% H₂O₂ alternately between each file size and final irrigation with 17% EDTA, 6% phosphoric acid, and 6% citric acid, in different teeth groups, to remove the smear layer from the prepared root canal. They demonstrated that none of the irrigation solutions used had effectively cleaned all the smear layer from the root-canal system. Mayer et al. (1) reported that ultrasonically activated irrigants (5.25% NaOCl and 17% EDTA) did not reduce debris and smear layer from rotary prepared root canal with ProFile .04 and lightspeed. Our results are similar because after the root canal preparation, using the sodium hypochlorite as irrigating solution, the root canal walls were covered with debris and smear layer. Consequently, it seems that it is very difficult to obtain clean dentinal walls in the root canal by instrumentation and irrigation only.
On the contrary, it seems that laser irradiation with different laser types (Er:YAG, Nd:YAG, Ar, and CO₂) is effective in removing debris and smear layer from the root canal walls (4–9, 12, 13). We agree with these researchers because our results indicated that it was possible to vaporize debris and smear layer from the irradiated area of the prepared root canals with the parameters used in this investigation. However, we noticed that around the irradiated area, smear layer was still existing. This SEM observation indicates that temperature increase caused by the laser beams does not diffuse from the irradiated to the nearest area, or if it does, it was not able to vaporize debris and smear layer located there. Another verification of this observation was, as the findings of Takeda et al. (7) indicated, that in specimens in which the irradiation beam did not touch the root canal walls, laser was not effective in removing debris and smear layer. Furthermore, it was demonstrated that the angle of the laser beam in relation to the target surface can be a deciding factor of how much energy will be absorbed by the dentin (4).
In this investigation, the root canals of freshly extracted teeth were prepared to a file size #50, split, and irradiated in air because an optical fiber was not used. Our results cannot be directly equated to an intact tooth or an in situ interaction; they are the nearest ones to the optimum situation when one considers the low availability of clinical endodontic fibers. Future improvements to laser fiber tips will result in suitable medium for the clinical use of the laser Er:YAG irradiation to vaporize debris and smear layer from the prepared root canal.
Supported by a grant from the secretariat of the Research Committee of the National and Kapodistrian University of Athens.
1. Mayer BE, Peters OA, Barbakow F. Effects of rotary instruments and ultrasonic irrigation on debris and smear layer scores: a scanning electron microscopic study. Int Endod J 2002;35:582–9.
2. Hulsmann M, Schade M, Schafers F. A comparative study of root canal preparation with HERO 642 and Quantec SC rotary Ni-Ti instruments. Int Endod J 2001;34:538–46.
3. Siqueira JF, Araujo MC, Garcia PF, Fraga RC, Saboia Dantas CJ. Histological evaluation of the effectiveness of five instrumentation techniques for cleaning the apical third of root canal. J Endodon 1997;23:499–502.
4. Anic I, Segovic S, Katanek D, Prskalo K, Najzar-Fleger D. Scanning electron microscopic study of dentin lased with Argon, CO₂ and Nd:YAG laser. J Endodon 1989;24:77–81.
5. Khan MA, Khan MFR, Khan MW, Wakabayashi H, Matsumoto K. Effect of laser treatment on the root canal of human teeth. Endod Dent Traumatol 1997;13:134–45.
6. Takeda FH, Harashima T, Eto JN, Kimura Y, Matsumoto K. Effect of Er:YAG laser treatment on the root canal walls of human teeth: an SEM study. Endod Dent Traumatol 1998;14:270–3.
7. Takeda FH, Harashima T, Kimura Y, Matsumoto K. Efficacy of Er:YAG laser irradiation in removing debris and smear layer on root canal walls. J Endodon 1998;24:548–51.
8. Harashima T, Takeda FH, Zhang C, Kimura Y, Matsumoto K. Effect of argon laser irradiation on instrumented root canal walls. Endod Dent Traumatol 1998;14:26–30.
9. Takeda FH, Harashima T, Kimura Y, Matsumoto K. A comparative study of the removal of smear layer by three endodontic irrigants and two types of laser. Int Endod J 1999;32:32–9.
10. Yamazaki R, Goya C, Yu D, Kimura Y, Matsumoto K. Effects of Erbium, Chromium:YSGG laser irradiation on root canal walls: a scanning electron microscopic and thermographic study. J Endodon 2001;27:9–12.
11. Shoji S, Hariu H, Horiuchi H. Canal enlargement by Er:YAG laser using a cone-shaped irradiation tip. J Endodon 2000;26:454–8.
12. Levy G. Cleaning and shaping the root canal with a Nd:YAG laser beam: a comparative study. J Endodon 1992;18:123–27.
13. Arrastia-Jitosho AM, Liaw LH, Lee W, Wilder-Smith P. Effects of a 532 nm Q-switched nanosecond pulsed laser on dentin. J Endodon 1998;24:427– 31.
14. Pini R, Salimbeni R, Vannini M, Barone R, Clauser C. Laser dentistry: a new application of Excimer laser in root canal therapy. Lasers Surg Med 1989;9:352–7.
15. Hibst R, Keller U. Experimental studies of the application of the Er:YAG laser on dental hard substances: I. Measurement of the ablation rate. Lasers Surg Med 1989;9:338–44.
16. Kimura Y, Yonaga K, Yokoyama K, Kinoshita J, Ogata Y, Matsumoto K. Root surface temperature increase during Er:YAG laser irradiation of root canals. J Endodon 2002;28:76–8.
17. Anastasopoulou N, Ziolek C, Serafetinides A, Lubatschowski H. Qswitched Er:YAG radiation transmission through fluoride glass fibers and dielectric-coated metallic hollow waveguides. Optics Commun 2000;186:167–71.
18. Serafetinides AA, Khabbaz MG, Makropoulou MI, Kar AK. Picosecond laser ablation of dentin in endodontics. Lasers Med Sci 1999;14:168–74.
19. Walsh JT, Flotte TJ, Deutsch TF. Er:YAG laser ablation of tissue: effect of pulse duration and tissue type on thermal damage. Lasers Surg Med 1989;9:314–26.
20. Rohanizadeh R, Jean A, Daculsi G. Effects of Q-switched Nd:YAG laser on calcified tissues. Lasers Med Sci 1999;14:221–7.
21. Neev J. Analysis of excimer laser interactions with hard tissue. In: Miserendino L, Pick R, eds. Lasers in dentistry. Chicago: Quintessence Pub, 1995:261–82.
22. Wigdor H, Walsh J, Featherstone J, Visuri S, Fried D, Waldvogel J. Lasers in dentistry. Lasers Surg Med 1995;16:103–33.
Laser_efficacy_on_root_canal_walls.pdf
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