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Lsm Moritz Endodontics (Ktp)


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KTP Laser in Endodontics

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Lsm Moritz Endodontics (Ktp)

  1. 1. Lasers in Surgery and Medicine Innovative Wavelengths in Endodontic Treatment Ulrich Schoop, MD, DDS,1* Wolf Kluger, MD, DDS,1 Selma Dervisbegovic,1 Kawe Goharkhay, MD, DDS,1 Johann Wernisch, TD, PhD,2 Apostolos Georgopoulos, MD, PhD,3 Wolfgang Sperr, MD, DDS, PhD,1 and Andreas Moritz, MD, DDS, PhD1 1 Department of Conservative Dentistry, Dental School, Medical University of Vienna, A—1090 Vienna, Wahringer Straße ¨ 25a, Austria 2 Institute for Applied and Technical Physics, Technical University of Vienna, A—1040 Vienna, Wiedner Hauptstraße 8-10, Austria 3 University Clinic for Internal Medicine I, Department of Infectious Diseases and Chemotherapy, A-1090 Vienna, Wahringer Gu ¨ ¨rtel 18-20, Austria were capable of complete eradication of E. faecalis to Background and Objectives: The sanitation of the root a significant extent. There was no significant relation canal system and the adjacent dentin has always been a key between the temperature increase and the bactericidal requirement for successful endodontics. In recent years, effect. various laser systems have provided a major contribution to Conclusions: The present study demonstrates that both this aim, namely the Nd:YAG-, the 810 nm Diode-, the wavelengths investigated could be suitable for the disin- Er:YAG-, and the Er,Cr:YSGG laser. Numerous studies fection of even the deeper layers of dentin and equal the could prove their efficiency within the endodontic proce- results achieved by established wavelengths in state-of- dure. Recently, two new wavelengths have been introduced the-art endodontics. Lasers Surg. Med. to the field of oral laser applications: The KTP laser ß 2006 Wiley-Liss, Inc. emitting at 532 nm and the 980 nm diode laser. The present in vitro investigation was performed to evaluate the effects Key words: 980 nm diode; KTP laser; bacteria; endodon- of these laser systems focusing on their antibacterial effect tics; root canal in deep layers of dentin and their impact on the root canal dentin. INTRODUCTION Study Design/Materials and Methods: Two-hundred A crucial step within endodontic therapy is the disinfec- slices of root dentin with a thickness of 1 mm were obtained tion of the root canal and the three-dimensional network of by longitudinal cuts of freshly extracted human premolars. dentinal tubules. From the infected pulpal tissue bacteria The samples were steam sterilized and subsequently penetrate into the deeper layers of root dentin and pro- inoculated with a suspension of either Escherichia coli or pagate a periapical inflammation with subsequent destruc- Enterococcus faecalis. After the incubation, the samples tion of the adjacent connective tissues [1–3]. The sanitation were randomly assigned to the two different laser systems of the root canal including the most distant areas of the tested. Each laser group consisted of two different opera- tubular system can be regarded as a major challenge in tional settings and a control. The dentinal samples under- today’s endodontics and is of great importance for the went ‘‘indirect’’ laser irradiation through the dentin from prolonged preservation of endodontically treated teeth. the bacteria-free side and were then subjected to a classical The local microenvironment favors the selection of quantitative microbiologic evaluation. To assess the relatively few bacterial species which can survive and temperature increase during the irradiation procedure, proliferate being out of reach of the host’s immune additional measurements were carried out using a thermo- response. Even rinsing solutions applied during conven- couple. To assess the impacts on the root canal walls, 20 tional root canal treatment only partly affect those bacteria. additional samples underwent laser irradiation at two The pathogenic microorganisms are able to penetrate the different settings and were subjected to scanning electron root dentin up to a depth of more than 1 mm, whereas microscopy. disinfecting solutions only reach a depth around 100 mm Results: Microbiology indicated that both laser systems were capable of significant reductions in both test strains. At an effective output power of 1 W, E. coli was reduced by Wolfgang Sperr is the head of Department of Conservative at least 3 log steps in most of the samples by the tested Dentistry. *Correspondence to: Ulrich Schoop, MD, DDS, Department of wavelengths, with the best results for the KTP laser Conservative Dentistry, Dental School, Medical University of showing complete eradication of E. coli in 75% of the ¨ Vienna, Wahringerstr. 25a, 1090 Vienna, Austria. samples. E. faecalis, a stubborn invader of the root canal, E-mail: Accepted 23 February 2006 showed minor changes in bacterial count at 1 W. Using the Published online in Wiley InterScience higher setting of 1.5 W, significant reductions of E. coli were ( again observed with both laser systems, where the lasers DOI 10.1002/lsm.20331 ß 2006 Wiley-Liss, Inc.
  2. 2. 2 SCHOOP ET AL. [4,5]. In addition, bacteria like Enterococcus faecalis have then cut from the upper and medium third of the dentin adjacent to the root canal. The sample size was chosen in the capability to form intra- and extraradicular biofilms, order to simulate the irradiation conditions of prepared root which makes them even harder to control [6–8]. These facts canals in complete and intact teeth. To remove the smear are often responsible for those cases, which are therapy layer resulting from the cutting procedure, the specimens resistant from the beginning or end up as long-term failures were immersed in an ultrasonic bath with ethylenediami- after accomplished endodontic treatment. netetraacetic acid for 4 minutes, followed by three washes The introduction of lasers in endodontics helped to in physiological saline solution for a period of 2 minutes overcome the problem of the insufficient penetration depth each. The samples were stored in physiological saline of disinfecting agents. This new method dramatically solution at a temperature of 48C until further use. improves the effectiveness and success rate of root canal treatment. In general, dental lasers provide greater acces- sibility of formerly unreachable parts of the tubular Bacterial Inoculation network due to their better penetration into dentinal The samples were steam sterilized (Melatronic 23, tissues [9–11]. Scientific research was first conducted with Melag, Berlin, Germany) at 1348C for 10 minutes to remove the Nd:YAG [12–15] and the diode lasers [16–19], which all preexisting bacteria. Previous investigations [27] did gained widespread acceptance in the fields of laser-assisted not show alterations of the physical nature of the samples. endodontics. For both wavelengths, a high disinfecting Chemical alterations, particularly of the organic com- capability was reported. Lasers suitable for the preparation pounds of the dentinal tissues, cannot be excluded but of dental hard substances like the Er:YAG and the have to be accepted due to the necessity of a complete Er,Cr:YSGG underwent further development resulting in sterilization of the samples. However, this factor does not delivery systems also usable for root canal application. The affect the comparability of the samples. Following this step, according investigations indicate that these laser systems they were inoculated with 2 ml of either of the two test exhibit satisfying bactericidal abilities thus constituting strains, Escherichia coli (ATCC 25922) or E. faecalis (ATCC relatively new additions to the spectrum of lasers used in 29212) on one side by means of a micropipette. The initial endodontics [20–22]. inoculum was 108 CFU/ml, standardized by the same In a comprehensive study [23] four different laser dilution series which was used for the investigation of the systems, namely the Nd:YAG-, the Diode-, the Er:YAG-, actual samples. Incubation at 378C for 4 hours was carried and the Er,Cr:YSGG lasers, were compared under stan- out to allow the propagation of the bacteria into the dentinal dardized conditions. The study came to the conclusion that tubules, as described in a previous scanning electron all four tested wavelengths were able to disinfect the root microscopic evaluation [27]. canal dentin to a high extent and constitute valuable tools in up-to-date endodontics. Laser Devices In the meantime, new wavelengths have been estab- Two different laser systems were applied during the lished in dentistry. The diode wavelength of 810 nm has irradiation procedure: been complemented by a diode device emitting at 980 nm. In As a diode laser the ‘‘MDL 10’’ device (Vision GmbH, addition, the KTP laser emitting at 532 nm, representing a ¨ Goxe, Germany) was used. Emitting at a wavelength of frequency-doubled Nd:YAG device, has been introduced 980 nm, the laser can be operated in CW mode with an mainly for tooth-bleaching procedures. The abbreviation output power up to 2.5 W and in pulsed mode with a ‘‘KTP’’ stands for ‘‘Kalium-Titanyl-Phosphat’’ meaning repetition rate up to 1,000 Hz. Potassium-Titanyl-Phosphate. The second device used was a ‘‘SmartLite’’ KTP laser The present study was performed to evaluate the (Deka, Calenzano, Italy). It represents a frequency-doubled bactericidal effect of these novel wavelengths and to Nd:YAG laser and emits at a wavelength of 532 nm (visible compare their effectiveness to the other lasers tested in green). This laser can be operated in pulsed (up to 16 Hz) or the study cited above [23]. Following an identical study CW mode at an output power up to 3 W. design, the devices were evaluated with regard to their Each laser was equipped with a proprietary flexible effectiveness in the deep layers of dentin simulated by waveguide and fiber tip with a diameter of 400 mm and was indirect irradiation through dentin slices. This bacteriolo- operated in pulsed mode with a repetition rate of 15 Hz gical evaluation was complemented by scanning electron without any water spray or air cooling. The lasers were microscopy and temperature measurements. adjusted for an effective average output power of 1 W and 1.5 W measured directly on the fiber tip using a wattmeter MATERIALS AND METHODS (Field Master, Coherent, Auburn) before each irradiation Sample Preparation cycle. This procedure ensured stable and standardized irradiation schemes for each sample. Human premolars were cut into 1-mm thick longitudinal sections using a diamond-coated band saw (‘‘Trennschleif Laser Irradiation System,’’ Exakt, Norderstedt, Germany) under continuous water irrigation. The teeth had been freshly extracted for After incubation, the samples in both groups were orthodontic purposes and were obviously free from carious divided into nine subgroups, consisting of 20 specimens lesions. One hundred eighty slices measuring 2Â6 mm were each. Eight of these subgroups underwent laser irradiation;
  3. 3. INNOVATIVE WAVELENGTHS 3 the last group of 20 samples served as a control group for meter (TMG-1 device, manufactured by the Technical each test strain and remained untreated. University of Vienna, Vienna, Austria). The average value The following irradiation procedure was used with both and the standard deviation of the five measurements per lasers: the specimens were irradiated from the side oppos- laser/setting were calculated subsequently. ing the inoculated area in contact mode under constant Scanning Electron Microscopy scanning movement of the optical fiber at an angle of 15 degrees to the surface. The irradiated area thus showed Additional 20 samples were subdivided in four groups a cone-shaped outline resulting in a fluence of 6.7 J/cm2 for (two lasers at 1 and 1.5 W each) and prepared as described the samples irradiated at 1 W and 10 J/cm2 for the samples above (except for the bacteriological procedure). The irradiated at 1.5 W. One lasing cycle comprised five samples were then submitted to scanning electron micro- irradiations of 5 seconds each, with 15 seconds intervals. scopy in order to evaluate the morphological changes The irradiation was done by hand and always by the same induced by laser irradiation. The specimen were assessed investigator to ensure the comparability between the using an environmental scanning electron microscope sample groups within the actual study and the preceding (ESEM XL30, Philips, Eindhoven, The Netherlands) work- investigation [23]. No water or air cooling were used with ing with mild subpressure and without sputtering of the any device. samples, thus facilitating the assessment of native samples and the minimization of artifacts. Figures were made at Bacteriological Evaluation 100-fold, 500-fold, and 1,000-fold magnification. Upon irradiation, the specimens were placed into sterile Eppendorf tubes and 100 ml of physiological saline solution RESULTS were added. Each tube was then vortexed for 1 minute to Bacteriology remove the bacteria from the dentin and the dentinal Table 1 shows the results of the bacteriologic test tubules. The extracted fluid was diluted in log 10 steps. regarding E. coli and E. faecalis. Twenty microliters of each dilution were applied to culture Samples are rated in log steps of the colony counts ´ plates (sheep agar plates, Bio Merieux, Marcy I’Etoile, (CFU/ml), the laser device applied, and the specific France) and incubated for 24 hours at 378C. The colonies radiation powers. were then counted and the total number of bacteria (colony The results of the control group of both test strains forming units per milliliter of the extraction fluid) was showed colony counts ranging between 106 and 107 CFU/ml assessed. The lowest detection level of bacteria was 5Â102 CFU/ml. demonstrating a decrease of 1–2 log steps through the inoculation and incubation process. Temperature Measurements As far as E. coli is concerned, both wavelengths succeeded To assess the thermal impacts of the different wave- in a major reduction of the test bacterium even at the lower lengths and their possible influence on the bactericidal setting of 1 W. At the higher power setting (1.5 W), the effect, temperature measurements were carried out. For impact is even more considerable, yielding 3–4 log steps. this purpose, five samples were used for each laser and Both lasers are equally effective in killing these bacteria. power setting. The dentin slices were mounted on an even In comparison, both devices encountered greater diffi- culties in eliminating the gram-positive E. faecalis. At 1 W thermocouple using a silicon-based heat-conductive com- pound (Dow Corning 340 Heat Sink Compound, Dow the KTP laser was capable of removing the germ to an Corning, Midland, Michigan). During the irradiation extent of 1–4 log steps, whereas the 980 nm diode laser procedure, which was carried out in the same way as the showed a reduction of only 1–2 log steps in the majority of irradiation of the inoculated samples, the maximum the samples. temperature increase (starting from a room temperature An increase in effective irradiation power to 1.5 W of 218C) was recorded by the means of a digital thermo- strongly improved the bactericidal effect of the lasers used. TABLE 1. Bacterial Counts of E. coli and E. faecalis: For Each Power Setting and Laser Applied the Number of Specimens With the According Range of CFU/ml Is Indicated E. coli CFU/ml E. faecalis CFU/ml Below Below detection detection 103 104 105 106 107 103 104 105 106 107 level level Control 12 8 12 8 Diode 980nm, 1 W 11 7 2 1 5 13 1 Diode 980nm, 1.5 W 15 4 1 4 2 8 6 KTP, 1 W 10 8 2 4 6 4 6 KTP, 1.5 W 15 5 10 5 4 1
  4. 4. 4 SCHOOP ET AL. TABLE 2. Temperature Measurements Device 1W 1.5 W 3.8 Æ 0.48C 4.7 Æ 0.28C 980 nm diode 4.1 Æ 0.28C 5.5 Æ 0.48C KTP The averages and standard deviations have been calculated from five individual measurements per laser and power setting. A reduction of E. faecalis below the detection level was observed in 50% of the samples irradiated with the KTP laser. On the other hand, the diode laser yielded a bacterial reduction by up to 4 log steps in a considerable number of samples. Fig. 2. Environmental scanning electron microscopic picture of a dentin slice. 980 nm diode laser, 1.5 W. Magnification  Temperature Measurements 1000. Table 2 presents the results of the temperature measure- ments. All the measurements were carried out at a room temperature of 218C, thus they refer to an initial sample dentinal surface, including melting, recrystallisation, and temperature of 218C. For instance, the value 3.88C stands the formation of micro cracks (Fig. 4). for a temperature rise to 24.88C. While the diode laser showed the lower temperature increases at both power settings, the temperature rise caused by the KTP device DISCUSSION only slightly exceeds those values. The persistence of bacteria in the three-dimensional Environmental Scanning Electron Microscopy tubular network of root dentin can be regarded as the main The diode laser irradiation at 1W seems to have little cause for the failure of an endodontic treatment [2,3]. The impact on the sample surface. Dentinal tubules remain pathogenic flora is usually constituted of approximately open and no signs of melting can be discerned (Fig. 1). equal portions of gram-negative and gram-positive bacteria When the irradiation power is raised to 1.5 W, first signs [24,25], sustaining the periapical inflammatory process. of melting and recrystallisation can be seen, first of all in The removal of these bacteria and their toxins is an the lower right corner of the picture (Fig. 2). indispensable prerequisite for a successful endodontics. KTP laser irradiation at an output power of 1 W shows During conventional root canal treatment with chemo- major morphological changes of the dentinal surface. The mechanical methods, infected pulp tissue, and layers of root majority of the tubules appears to be sealed due to melting canal dentin can only be removed to a certain extent. While and recrystallisation of the hard tissues (Fig. 3). root canal morphology limits the extent of mechanical At an output power of 1.5 W, the KTP laser irradiation preparation, chemical irrigants are only effective in dentin results in an almost complete transformation of the layers directly adjacent to the canal wall. As shown by Fig. 1. Environmental scanning electron microscopic picture Fig. 3. Environmental scanning electron microscopic picture of a dentin slice. 980 nm diode laser, 1 W. Magnification  1000. of a dentin slice. KTP laser, 1 W. Magnification  1000.
  5. 5. INNOVATIVE WAVELENGTHS 5 bactericidal potential of Er,Cr:YSGG laser regarding E. coli and E. faecalis for the first time in a controlled in vitro study. In order to facilitate a direct comparison between the four laser systems tested in the study, the authors decided to operate all devices (including the Er:YAG and Er,Cr:YSGG lasers) without any air or water cooling. The present study was carried out to evaluate two wavelengths recently introduced to the fields of dentistry, namely the 980 nm diode- and the KTP lasers. To allow for a comparison between the lasers tested in the present and the preceding study, the same study design for the bacteriologic tests was pursued, including identical average power output and fluence values. Until now, little is known about the impacts of these wavelengths on endodontics. Romanos et al. tested the 980 nm diode laser for its ability to remove periodontal Fig. 4. Environmental scanning electron microscopic picture pocket epithelium in vitro [38]. The objective of another of a dentin slice. KTP laser, 1.5 W. Magnification  1000. in vitro study performed by Gutknecht et al. was to assess the bactericidal effect of the 980 nm wavelength on bovine teeth [39]. Using comparatively high power settings, the authors were able to eliminate bacteria within the bovine Kouchi et al. [4], bacteria are able to invade the periluminal dentin to a significant extent. dentin up to a depth of 1,000 mm, whereas the penetration In an early in vitro study Tewfik et al. demonstrated the depth of chemical disinfectants is limited to a range about impacts of the KTP laser on root canal walls [40] and 130 mm [5]. Due to this lack in penetration depth of the described the laser to produce an increased permeability of bactericidal agents, pathogenic bacteria survive and con- the root canal dentin by enlarging and cracking the orifices stitute the reason for therapy resistant cases and long-term of the dentinal tubules. Another in vitro study addressed failures in endodontic treatment. the use of the KTP laser as an adjunct to scaling and root With the introduction of lasers to the fields of conserva- planning [41]. The authors drew the conclusion that the tive dentistry, the endodontic procedure was enriched by a KTP laser could be applied without endangering the dental multitude of new treatment methods dramatically improv- pulp or sound periodontal tissues if it is applied at ing the chance for a successful treatment outcome. Lasers reasonable settings. In another study, Nammour et al. showed to be feasible and effective tools for the cleaning and performed temperature measurements on root surfaces disinfection of the root canal system. This holds true for the while irradiating root canals in vitro [42]. Though the Nd:YAG laser which has been assessed for its application in authors applied energy settings up to 4 W, the temperature endodontic therapy by many authors [12–15,26,27] as well rise on the root surface did not exceed critical values as long as for the diode laser [16–19]. In contrast to chemical as cooling times of 1 second were heeded. A study by irrigants, these lasers are extremely effective in deep layers Machida et al. focused on the influence of the KTP laser on of dentin. An explanation for this effect was given by the root canal surface and the extent of the temperature Vaarkamp et al. [10] and Odor et al. [11]. Their findings increase at the root surface in vitro [43]. Using scanning suggest that the dentinal tubules act as light conductors electron microscopy, the authors found out that KTP laser propagating the laser light even to remote areas of the root irradiation facilitated the removal of smear layer from the dentin. root canal surface. Thermography revealed the harmless- Another laser system proposed for endodontic therapy is ness of the procedure in reference to the temperature rise the Er:YAG laser, up to that time established as a device for on the root surface. hard tissue preparation [28–32]. The applicability of this The highest temperature rise yielded in the present laser for endodontic purposes has been described by Hibst study was 5.58C. One must bear in mind that the et al. [20] and Schoop et al. [21,22]. Another wavelength measurements have been carried out on isolated dentin mainly used for the preparation of dental hard substances slices instead of intact human teeth. Due to the lack of heat is the Er,Cr:YSGG laser [33,34,35] which has recently been used for endodontic purposes as well [36,37]. conduction into a greater volume, the slices should represent a rather ‘‘supercritical’’ sample shape compared In a comprehensive study, Schoop et al. compared the to complete teeth. In the examination cited above [42] the bactericidal abilities of these four different laser devices in authors utilized intact extracted human teeth and yielded a endodontics [23]. To facilitate a statement on the bacter- highest temperature rise below 78C on the root surface icidal effects in deeper layers of dentin, the authors when using a maximum energy of 4 W. This temperature inoculated dentin slices with two different test strains rise was regarded to be harmless for periodontal tissues and irradiated from the side opposing the inoculation site. by the authors. The temperature rise produced in the The study revealed that all tested wavelengths were able to present study was quite lower, even though thin dentin disinfect the dentin samples to a high extent, showing slices have been used instead of complete teeth. It stands the best results for the Er:YAG laser and illustrating the
  6. 6. 6 SCHOOP ET AL. REFERENCES to reason that this temperature rise should not produce any adverse effects when the tested laser systems are applied 1. Lopez-Marcos JF. Aetiology, classification and pathogenesis in vivo. of pulp and periapical disease. Med Oral Patol Oral Cir Bucal Both lasers showed a high impact on the tested bacteria, 2004;9(Suppl: 58–62); 52–57. 2. Nair PN. Pathogenesis of apical periodontitis and the causes particularly when the higher setting (1.5 W) was used. of endodontic failures. Crit Rev Oral Biol Med 2004;15(6): Regarding the present study and the previous results 348–381. [23,27], no obvious relation can be seen between the 3. Nair PN, Sjogren U, Krey G, Kahnberg KE, Sundqvist G. differences in temperature increase and the variability of Intraradicular bacteria and fungi in root-filled, asymptomatic human teeth with therapy-resistant periapical lesions: A the bactericidal effects of each wavelength. 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