Lasers in RCT & Endodontics

A Study on Root Canal Cleansing by Nd:YAG Laser with Black Dye Solution, J Oral Laser Applications 9 (2009), No. 2

Purpose: To investigate in vitro the removal of smear layer, plug, debris, and pulp tissue by Nd:YAG irradiation with different potencies and times, with or without black ink on the apical root canal wall. Materials and Methods: Twenty-five extracted human teeth were divided into 5 groups after endodontic treatment. G1: no laser irradiation, control; G2: Nd:YAG laser 1 W, 1 s, 20 pps, 50 mJ; G3: Nd:YAG laser 2 W, 1 s, 20 pps, 50 mJ; G4: Nd:YAG laser 1 W, 2 s, 20 pps, 50 mJ, black ink; G5: Nd:YAG laser 2 W, 1 s, 20 pps, 50 mJ, black ink. All teeth were sectioned and analyzed under light microscope and SEM. Results: Statistically significant differences were observed among the 5 groups, p = 0. 0027(p < 0.05). No significant difference was found between G1 (control) and G2 (1 W, 1 s), p = 0.8345 (p > 0.05), nor between G3 (2 W, 1 s) and G5 (2 W, 1 s, black ink), p = 0.0758 (p > 0.05). However, a marked difference was seen between G4 (1 W, 2 s, black ink) and G5 (2 W, 1 s, black ink), p = 0.0367 (p < 0.05). A statistically significant difference (p < 0.05) was found between G3 (no black ink) and G5 (black ink) regarding carbonization..

Apical extrusion of root canal irrigants when using Er:YAG and Er,Cr:YSGG lasers with optical fibers: an in vitro dye study.J Endod. 2008 Jun

Because of the potential for irritant reactions in the periapical region, irrigant solutions must be constrained within the root canal. We examined fluid extrusion beyond the apical constriction by pressure waves generated by pulsed middle infrared lasers using needles and Max-I-Probes (Dentsply) as controls. Both free-running pulsed Erbium: Yttrium Aluminum Garnet (Er:YAG) and Erbium, Chromium: Yttrium Scandium Gallium Garnet (Er,Cr:YSGG) lasers with bare or conical fiber tips at distances of 5 or 10 mm from the apex displaced fluid past the apex. Larger apical openings showed greater extrusion of fluid. The volume of extruded fluid was similar to conventional 25-G needles, but fluid was distributed further from the apex. Because pulsed lasers create pressure waves in irrigant fluids within the root canal, the potential for extrusion of fluid from the apex should be considered when assessing intracanal laser treatments in endodontics.

The use of the erbium, chromium:yttrium-scandium-gallium-garnet laser in endodontic treatment: the results of an in vitro study.J Am Dent Assoc. 2007 Jul

The use of the erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser has become accepted in the field of cavity preparation. The development of miniaturized and flexible fiber tips has allowed this device to be used in endodontics. The authors conducted an in vitro study to assess the effects of Er,Cr:YSGG laser irradiation on root canals. METHODS: The authors inoculated root canals with two bacteria, laser irradiated them at two power settings and subjected them to a quantitative microbiological evaluation. They used scanning electron microscopy (SEM) to assess morphological changes in endodontically processed and laser-irradiated root canal walls. They measured temperature increases on the root surface to determine possible thermal side effects. RESULTS: The bacteriological evaluation revealed a disinfecting effect in the root dentin samples that was dependent on the output power but not specific for the bacterial species investigated. SEM showed the removal of the smear layer from the root canal walls and the exposure of dentinal tubules. The temperature rise during irradiation was moderate when standardized power settings were used.
CONCLUSIONS: The Er,Cr:YSGG laser can be used to eliminate bacteria in root canals. It also effectively removes smear layer and debris from the canal wall. CLINICAL IMPLICATIONS: Practitioners can use the Er,Cr:YSGG laser to prepare root canals for endodontic therapy.

Apical extrusion of root canal irrigants when using Er:YAG and Er,Cr:YSGG lasers with optical fibers: an in vitro dye study.J Endod. 2008 Jun

The use of the erbium, chromium:yttrium-scandium-gallium-garnet laser in endodontic treatment: the results of an in vitro study.J Am Dent Assoc. 2007 Jul

The impact of an erbium, chromium: yttrium-scandium-gallium-garnet laser with radial-firing tips on endodontic treatment, Lasers Med Sci 2007

Radial-firing tips should allow a more homogeneous laser irradiation of root canal walls. The aim of the study was to assess the effects of erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser irradiation in conjunction with those newly designed tips. The investigation comprised bacteriology, morphological evaluations and temperature measurements. Root canals were inoculated with two test strains and laser irradiated with power settings of 0.6 W and 0.9 W and a repetition rate of 20 Hz. Subsequently, the samples were subjected to microbiological evaluation. The morphological changes of the canal walls were assessed by scanning electron microscopy. To reveal possible thermal side effects, we carried out temperature measurements. The bacteriological evaluation revealed a decisive disinfectant effect.
Scanning electron microscopy showed the homogeneous removal of smear layer from the root canal walls. The temperature rise at the root surface during the irradiation was moderate, yielding 1.3°C for the 0.6 W setting and 1.6°C for the 0.9 W setting. The investigations indicated that the Er,Cr: YSGG laser, in conjunction with radial-firing tips, is a suitable tool for the elimination of bacteria in root canals and for the removal of smear layer.

Ø Thermographical and morphological studies of Er,Cr:YSGG laser irradiation on root canal walls, Photomed Laser Surg. 2004 Aug

This study was performed to investigate the temperature rises on root surfaces and morphological changes on root canal walls of extracted human teeth after irradiation by erbium, chromium: yttrium, scandium, gallium, garnet (Er, Cr:YSGG) laser and to evaluate the efficiency in removing smear layer and debris from the prepared root canal walls in vitro. Background Data: No report on Er, Cr:YSGG laser effects under various conditions and specific tips for endodontic treatments has been reported. METHODS: Sixty extracted human teeth with single and straight root were used in this study. The teeth were prepared at 1 mm short of the apical foramen by a conventional technique using K-files. Fifty-four specimens were irradiated by Er, Cr:YSGG laser at the output powers of 2 W, 3 W, and 5 W for 7 sec with three fiber tips (200, 320, and 400 microm diameters). Temperature changes were recorded thermographically. All teeth were examined by light microscopy or scanning electron microscopy (SEM). RESULTS: Thermographic study showed that the average temperature rises on root surfaces were less than 8 degrees C. Observation by light microscopy revealed the ablation at the apical stop, and that by SEM indicated that laser irradiation at 5 W using a fiber tip with 400 microm diameter was efficient for removing smear layer and debris without carbonization or melting.
CONCLUSIONS: The results of this study suggested that the temperature rises during Er, Cr:YSGG laser irradiation at the parameters used in this study are minimal to cause the damage on periodontal and bone tissues. Moreover, it was suggested that it is efficient to remove smear layer and debris without causing any carbonization and melting.

Ø Le, et al.-1999-An evaluation of the CO2 laser for endodontic disinfection.-J Endod-25-105-8-

The goal of this study was to evaluate the bactericidal action of the CO2 laser on animal teeth infected with an endodontic bacterial species. After instrumentation, 24 freshly extracted incisors were inoculated with a known concentration of Actinomyces odontolyticus and incubated anaerobically for 18 h. The incisors were separated into three groups: group 1--untreated control teeth; group 2--teeth treated with 3% NaOCl; and group 3--teeth lased with a CO2 laser at 5 W using three successive 9.9 s irradiation periods with 10 s between treatments. For each of the three groups, 60 microliters samples were removed using gel loading capillary pipette tips, and the diluted samples were plated in triplicate on Columbia agar plates. After a 5- to 6-day incubation, the colony-forming units were counted, and the quantitative results were subjected to an analysis of variance. The results of this analysis indicated an average 85% decrease in the colony-forming units in the laser-treated group, compared with the control group. According to Fisher and Scheffe tests, the differences in the averages between the control and laser groups were statistically significant (p < 0.05). The NaOCl treatment was statistically superior to the CO2 laser treatment.,

Ø Takeda, et al.-1999-A comparative study of the removal of smear layer by three endodontic irrigants and two types of laser.-Int Endod J-32-32-9-

AIM: The effects of three endodontic irrigants and two types of laser on a smear layer created by hand instrumentation were evaluated in vitro in the middle and apical thirds of root canals.
METHODOLOGY:: Sixty human mature extracted mandibular premolar teeth with a single root canal and a closed apex were distributed randomly into five groups of 12 teeth each. Whilst cleaning and shaping up to a size 60 master apical file with a step-back technique, the root canals were irrigated with 3 mL of 5.25% NaOCL and 3% H2O2, alternately, between each file size. Group 1 (G1) were control specimens that were irrigated with a final flush of 17% EDTA. The teeth in group 2 (G2) were irrigated with a final flush of 6% phosphoric acid, and group 3 (G3) with 6% citric acid. In the specimens of group 4 (G4) the root canals were irradiated with a carbon dioxide (CO2) laser, and specimens of group 5 (G5) were irradiated using an Er:YAG laser. The teeth were split longitudinally and prepared for examination by scanning electron microscopy.
RESULTS: Control specimens (G1) showed clean root-canal walls with open dentinal tubules in the middle one-third, but in some specimens thick smear layer was observed in the apical one-third. Specimens irrigated with a final flush of 6% phosphoric acid (G2) or 6% citric acid (G3) were cleaner than with 17% EDTA, showing very clean root canal surfaces in the middle one-third but in the apical one-third the smear layer was not completely removed, especially at the openings of the dentinal tubules. The specimens irradiated with the CO2 laser (G4) showed clean root-canal walls with the smear layer absent, charred, melted, recrystallized and glazed in both middle and apical thirds. The root-canal walls of the specimens irradiated with the Er:YAG laser (G5) revealed an absent smear layer with open dentinal tubules in the middle and apical thirds. Statistical analysis showed no significant difference in the cleanliness of root-canal wall between G1 and G2, and G1 and G3. However, there were statistically significant differences (P < 0.01) between G1 and G4, and G1 and G5 in the cleanliness of the middle and apical one-thirds of the root canals.
CONCLUSIONS: Irrigation with 17% EDTA, 6% phosphoric acid and 6% citric acid did not remove all the smear layer from the root-canal system. In addition, these acidic solutions demineralized the interbular dentine around tabular openings, which became enlarged. The CO2 laser was useful in removing and melting the smear layer on the instrumented root-canal walls and the Er:YAG laser was the most effective in removing the smear layer from the root-canal wall.,

Ø Koba, et al.-1999-Post-operative symptoms and healing after endodontic treatment of infected teeth using pulsed Nd:YAG laser.-Endod Dent Traumatol-15-68-72-

Forty-four teeth in 38 patients, diagnosed with chronic apical periodontitis, were endodontically treated. Root canals were shaped using a step-back technique with 5% NaOCl and 3% H2O2 as irrigants. In half of the teeth the canal terminus was irradiated with pulsed Nd:YAG laser (1 W, 15 pps, 1 s). All canals were then obturated with laterally condensed gutta-percha points and sealer, and final radiographs were obtained. Occurrence of spontaneous pain was recorded 1 day after treatment. Percussion pain was recorded after 1 week, and then at 3 and 6 months after treatment. Radiographic follow-up was performed at 3 and 6 months. Percussion pain was significantly less (P < 0.05) in the laser-treated group than in the control group, both 1 week and 3 months after treatment. Other differences between the groups were not significant. These results suggested that the clinical application of pulsed Nd:YAG laser might be advantageous for the treatment of infected root canals.,

Ø Koba, et al.-1998-Pulsed Nd:YAG laser application to one-visit treatment of infected root canals in dogs: a histopathological study.-J Clin Laser Med Surg-16-217-21-

OBJECTIVE: In this study, the effects of pulsed Nd:YAG laser irradiation during root canal treatment of infected teeth were investigated histopathologically in dogs.
SUMMARY BACKGROUND DATA: Effects of Nd:YAG laser on infected root canal treatment have not been reported in vivo.
METHODS: One hundred thirty-five teeth with a single root, including incisors and premolars, in 15 healthy adult beagle-strain dogs were used in this study. After inducing infection in the teeth, each root canal was shaped with at least a # 40 K-file, then the canal was irradiated using the following parameters: 1 W, 30 pps for 1 and 2 sec; 2 W, 30 pps for 1 and 2 sec. Efficacy of debris removal and evaporation on the root canal walls at 2 weeks, and the degree of inflammation of the periapical region at 2, 4, and 8 weeks after laser irradiation were examined histopathologically by light microscopy.
RESULTS: Effective debris removal was observed in all cases of the laser-treated groups. No evaporation was observed except at the conditions of 2 W for 2 sec. Inflammation of periapical region in the laser-treated groups was similar in the control group at 2 weeks, but was significantly less than that in the control group at 8 weeks (p < 0.05).
CONCLUSION: These results suggest that pulsed Nd:YAG laser is useful for one-visit root canal treatment of infected teeth in dogs, if appropriate parameters are selected, and this is a potential therapy for human apical lesions of teeth.,

Ø Kesler, et al.-1998-Histological changes induced by CO2 laser microprobe specially designed for root canal sterilization: in vivo study.-J Clin Laser Med Surg-16-263-7-

OBJECTIVE: Until now, no suitable delivery fiber has existed for CO2 laser endodontic radiation in the apical region, where it is most difficult to eliminate the pulp tissue using conventional methods. To overcome this problem, we have designed a microprobe that reaches closer to the apex, distributing the energy density to a smaller area of the root canal and thus favorably increasing the thermal effects.
METHODS: A CO2 laser microprobe coupled onto a special hand piece was attached to the delivery fiber of a Sharplan 15-F CO2 laser. The study was conducted on 30 vital maxillary or mandibulary, central, lateral, or premolar teeth destined for extraction due to periodontal problems. Twenty were experimentally treated with pulsed CO2 laser delivered by this newly developed fiber after conventional root canal preparation. Temperature measured at three points on the root surface during laser treatment did not exceed 38 degrees C. Ten teeth represented the control group, in which only root canal preparation was performed in the conventional method.
RESULTS: Histological examination of the laser-treated teeth showed coagulation necrosis and vacuolization of the remaining pulp tissue in the root canal periphery. Primary and secondary dentin appeared normal in all cases treated with 15-F CO2 laser. Gram stain and bacteriologic examination revealed complete sterilization. These results demonstrate the unique capabilities of this special microprobe in sterilization of the root canal, with no thermal damage to the surrounding tissue.
CONCLUSIONS: The combination of classical root canal preparation with CO2 laser irradiation using this special microprobe before closing the canal can drastically change the quality of root canal fillings.,

Ø Takeda, et al.-1998-Efficacy of Er:YAG laser irradiation in removing debris and smear layer on root canal walls.-J Endod-24-548-51-

The purpose of this study was to evaluate the efficacy of Er:YAG laser irradiation in removing debris and smear layer from prepared root canal walls. Thirty-six human extracted mandibular incisors teeth were divided into three groups. Group 1 (G1) was control specimens that were not lased. The teeth of group 2 (G2) and group 3 (G3) were irradiated by Er:YAG laser at different watt powers of 1 W and 2 W. The teeth were bisected and prepared for study in stereoscopic light microscope and SEM. Control specimens showed an amount of debris and heavy smear layer obscuring the dentinal tubules at all levels in the canals. The root canal walls irradiated by Er:YAG laser were free of debris, with an evaporated smear layer and open dentinal tubules. Statistical analyses showed significant differences (p < 0.01) in cleanliness smear layer between G1 and G2, and G1 and G3. However, there was no statistically significant difference between G2 and G3 in the cleanliness of the middle and apical one-third of the root canals. These results show Er:YAG laser is effective in removing debris and smear layer from root canal walls.,

Ø Takeda, et al.-1998-Effect of Er:YAG laser treatment on the root canal walls of human teeth: an SEM study.-Endod Dent Traumatol-14-270-3-
The purposes of the study were to observe the morphological changes on root canal walls after instrumentation and irrigation, and assess the efficacy of conventional cleansing procedures and the effectiveness of Er:YAG laser in removing debris and smear layer from the root canal walls. Thirty-six endodontically treated human mandibular incisor teeth with single root canals were bisected longitudinally and divided into three groups of 12 teeth. Group 1 (G1) was left unlased as a control. The teeth of group 2 (G2 and group 3 (G3) were irradiated by Er:YAG laser (laser parameters were set at 1 W, 100 mJ/pulse and 10 Hz) for 3 s and 5 s. The teeth were prepared for scanning electron microscope study. Control specimens showed debris and heavy smear layer obscuring the dentinal tubules at all levels in the canals. The root canal walls irradiated by Er:YAG laser were free of debris, with an evaporated smear layer and open dentinal tubules. These results suggested that Er:YAG laser irradiation had an efficient cleaning effect on the prepared root canal walls.,

Ø Ramskold, et al.-1997-Thermal effects and antibacterial properties of energy levels required to sterilize stained root canals with an Nd:YAG laser.-J Endod-23-96-100-

Thermal effects and antibacterial properties of an Nd:YAG laser were studied to establish clinically safe levels of energy to deliver into the root canal and to determine the energy level needed to sterilize infected root canals. The results indicate that lasing cycles of 3 J-s for 15 s followed by a 15-s recovery interval can be continued for prolonged periods without risk of thermal damage to surrounding tissues. In vitro lasing of root canals inoculated with dark stained bacteria showed that two such lasing cycles sterilized only two out of eight canals, whereas when four cycles were used seven out of eight canals were sterilized. Guidelines for energy levels in endodontic Nd:YAG laser work are discussed, and base data for calculating appropriate energy levels are given.,

Ø Khan, et al.-1997-Effect of laser treatment on the root canal of human teeth.-Endod Dent Traumatol-13-139-45-
The purpose of this study was to examine the morphological and temperature changes of the apical portion of human extracted teeth treated by Nd: YAG, CO2 and Argon-lasers. Seventy-two single-rooted human teeth were studied. The root canals were prepared conventionally. Laser treatment of the apical portion of the canal was carried out by means of an optic fiber or metal tip. Temperatures were recorded thermographically. Two-thirds of the specimens were stained with black India ink and 36% silver ammonium fluoride solution. All specimens were irradiated by the three types of lasers at several intensities and the temperatures were recorded. Half of the specimens were prepared for the telescopic light microscope and for scanning electron microscopic observation, and the rest for histopathological examination by light microscope. The scanning electron microscopic evaluation showed that the laser energy vaporized the deposited debris, producing a glaze-like surface. The histopathological investigation revealed a tapered, enlarged apical lased area. All three laser devices were capable of vaporizing the debris in this way but the degree of morphological change was highly dependent on energy level and duration. The Argon-laser produced the highest temperatures.,

Ø Gutknecht, et al.-1996-Long-term clinical evaluation of endodontically treated teeth by Nd:YAG lasers.-J Clin Laser Med Surg-14-7-11-
It was possible for the patients to avoid surgical intervention in a number of complicated periapical endodontic situations by means of Nd:YAG laser-assisted sterilization. A WSR has only very good primary results and the long-term successes are very limited. Once a lesions has healed in the manner explained in this study, in other words, with regeneration of the periapical anatomy, there is a very good long-term prognosis. Laser technology is an instrument whose overall effects represent a decisive improvement in the efficiency of conservative endodontic treatment in fields that were previously outside our sphere of influence.