Over the years, the researchers are continually investigating the laser applications in dentistry. The first laser used in dentistry was reported by Weichman and Johnson in 1971 who attempted to seal the apical foramen in vitro by means of high power infra-red laser. Although their goal was not achieved, sufficient relevant and interesting data were obtained to encourage further study. Since then many papers on laser applications in dentistry have been published with growing interest in the topic. In endodontics in particular acceptance of this technology by clinicians has remained limited, perhaps partly due to the fact that this technology blurs the border between the technical, biological and dental research (Figs 22.1A and B).
Lasers used in dentistry have emission wavelengths that range from 0.5 to 10.6 microns. They lie in either the visible or infrared, non-ionizing portion of the electromagnetic spectrum. Hence, they emit either a visible wavelength of light or an invisible infrared light. Excimer lasers fall in the UV region.
Laser medium consists of a resonant cavity with a power supply, a cooling system, and with control system to the unit. Lasers are named after the chemical elements, molecules or compounds that comprise the core or the active medium, that is stimulated. The active medium can be a container of gas as in case of CO2 laser a solid crystal rod such as an Erbium:YAG laser, or a solid state electronics in case of a diode laser. Stimulation for the production of laser is usually a beam of white light from a flash lamp or arc lamp, or monochromatic light from another laser; or it may be electric current in case of diode laser.
EMISSION MODES AND DELIVERY
Lasers emit light energy in three different basic modes.
A. Continuous mode: the beam is emitted continuously at one power level for the length of the time operator presses the foot switch.
B. Gated -pulse mode: laser energy is switched on and off like a strobe light by opening and closing the mechanical shutter in front of the beam path of a continuous wave every few milliseconds.
C. Pulsed mode: large energies are emitted for a short time, of a few microseconds usually, followed by a long time when the laser is off.
Lasers utilize different delivery systems, depend- ing on the wavelength of the laser and the access required at terminal target tissue. These include:
A. Articulated arms: These have joints that allow the arm to bend, made of tubes connected at joints where a mirror reflects a beam into center of the next tube without touching the inner surface of the tube.
B. Hollow waveguide: this is a flexible hollow tube that has an interior mirror finish the laser energy is reflected along this tube and exits through handpiece. These are much thinner than the articulated arms.
C. Glass fiberoptic cable: This is more flexible than a waveguide, smaller in diameter, with sizes ranging from 200 to 600 microns. Quartz optical fiber encased in a resilient sheath.
Wavelength of laser determines the modes of delivery as fiberoptic cables are not efficient at transmitting all wavelengths. Wavelengths of 300 nm to 2400 nm are efficiently transmitted by fiberoptic cables; whereas wavelengths above 2400 nm and below 300 nm are absorbed by quartz fiber and laser energy is converted into mere heat. Hence CO2 laser energy at a wavelength of 10,600 nm is absorbed after only a few millimeters traveling through optic cable.
Laser can interact with tissues in four basic ways.
A. Reflection: Off the surface without penetration or interaction of light energy with the tissue.
B. Transmission: Apportion of light may be transmitted through the tissue unchanged as if transparent to laser beam.
C. Absorption: Some of the light may be absorbed into a component of the tissue in which case there will be transference of energy to the tissue.
D. Scatter: The remaining light may penetrate the tissue and be scattered without producing noticeable effect on the tissue.
LASERS USED IN ENDODONTICS
1. Gallium-Aluminum (GaAlAs) Semiconductor Diode Laser
2. Helium-Neon (HeNe) Lasers
3. Nd: YAG Laser
4. Er: YAG Laser
5. Er, Cr: YSGG Laser
6. CO2 Laser
i. Gallium-Aluminum (GaAlAs) Semiconductor Diode Laser: Previous studies on semiconductor diode laser irradiation of dental pulp have reported no dental pulp damage High-power semiconductor lasers of 3 to 30 W have been developed, however, and soon will be applied to dental pulp treatment. To confirm the effect on dental pulp of high-power semiconductor diode lasers, histopathologic examination must be performed.
i. Helium-Neon (HeNe) Lasers: The commercial HeNe lasers of more than 15 mW have not been used for dentistry. There is no possibility of dental pulp tissue damage by this laser.
ii. Neodynium Yttrium Aluminum Garnet (Nd: YAG) Laser: Because the Nd: YAG laser has a wide energy emission range, the clinician should take into careful consideration such parameters as the:
1. Exposure time
2. Power
3. Whether the laser emission is continuous or pulsed
4. The type of laser tip
5. Distance between the laser tip and the surface to be irradiated.
The characteristics of the individual target teeth must be considered at the time of laser therapy. For example, whether the tooth surface is enamel or dentin, the thickness between the carious surface and the pulp chamber, and the color of the target area all must be taken into consideration. Dental pulp tissue irradiated at 3 W and 20 pps for 0.5 second, at 2 W and 20 pps for 1 second, and at 1 W and 20 pps for 2 seconds by the pulsed Nd: YAG laser (ADL 300, ADL Inc., Chicago, IL) showed no adverse effects. When black India ink was applied to the tooth surface and laser irradiation was conducted at 2 W and 20 pps for 1 second, the temperature rise of the pulp chamber was less than 3°C and completely disappeared after 5 seconds. Laser anesthesia of dental pulp, sedative treatment of temporo- mandibular arthrosis, and laser acupuncture therapy as well as treatment of the hypersensitive dentin can be performed without producing dental pulp damage, severe pain or tissue burn.
iv. Carbon dioxide (CO2) Laser: The CO2, laser, similar to the Nd:YAG laser, can emit high energy. The dental pulp tissue is affected by parameters such as waveform, power, and time of laser exposure. The wavelength of the CO2 laser is easily absorbed in water. However, there is little carbonization or heat penetration on the surface of substances that contain water. If the substance contains no water, carbonization and crack formation occur easily on the surface of the substance. CO2 laser also is used for ablating dental pulp tissue and soft dentin. When ablating carious enamel and dentin, pain and pulp damage may occur depending on the laser power, the exposure time, and the wetness of the surface. Generally the CO2 gas laser should be used at less than 1 W for less than 1 second under anesthesia and under air cooling. If the tooth is treated under these conditions, dental pulp damage and postoperative pain may be avoided.
v. Er: YAG Laser: The 2.940 µm wavelength of the Er:YAG laser makes it possible to ablate hard and soft tissue under water spray. Previous investigators have reported no pulp damage if the cavity preparation is carried out under copious water spray. It is necessary, however, to spray water mist just under the hard tissue surface that is to be ablated by laser.
vi. Er Cr: YSGG Laser: The ErCr:YSGG laser also can be used to ablate hard and soft tissues because the wavelength is 2.780 µm, which is similar to that of the Er:YAG laser. It has been reported that dental pulp damage can be prevented if cavity preparation is performed under sufficient water spray. Too much water decreases the ablation ability of this laser, however.
vii. Argon Laser: The argon laser can be used to cure composite resin quickly. This laser also can be used to ablate soft tissue. Dental pulp damage may be avoided if laser irradiation is performed for a short time at 1 W, while maintaining the laser tip at a distance of approximately 10 cm from the tooth surface.
The following is a summary of the laser applications in endodontics investigated over the years.
Laser Devices, Techniques, Assessments and Mechanisms
Semiconductor Diode Laser
Various 30 mW GaAlAs semiconductor laser devices have been commercially developed for desensitization treatment. After drying the hypersensitive dentin as much as possible, the laser tip is placed in direct contact with the tooth surface, which is then irradiated for a period of 30 seconds to one minute. If the desired effect cannot be obtained, the treatment is carried out once after a couple of days. A shorter exposure time and, effectiveness are expected for the 3-W and 20-W semiconductor laser. Mechanism of pain reduction by the laser stimulation is thought to be clarified by electrophysiologic and laser transmission studies. These studies indicate local changes around the dentin and the nerve endings as well as changes in the central pulpal neuron.
HeNe Laser: A treatment method similar to that of semiconductor diode laser is used with 6-mW and 15-mW HeNe lasers. The clinical assessment and mechanism are thought to be identical to those of the semiconductor diode laser.
Pulsed Nd: YAG Laser
Laser stimulation is performed at the points of the same side as that of the tooth pain at 2 W and 20 pps for 1 to 2 minutes at about 10 cm. Exposure time should be only 10 seconds. With respect to clinical assessment, in cases of slight or mild pain, the percentage of reduction is 90 to 100 percent. In cases of severe pain, the percentage of pain reduction is less than 60 percent, however. The mechanism of pain reduction is to be the same as that for the semiconductor laser.
Stimulation method for the surface of dentin hyper- sensitivity: The laser parameter must be changed according to the degree of pain induced by air blast or tactile examination using an explorer. Laser parameters of 1 W and 20 pps for less than 0.1 second with black ink are recommended for this treatment. This method should be applied only after sufficient training and only after all other laser treatments have been tried. Assessment by this method shows the most effective results because of the morphologic changes produced in the dentin and the stimulation of the central pulpal neurons.
CO2 Laser
The effectiveness of this technique is less than that of the pulsed Nd:YAG laser, and the laser exposure technique is difficult to perform without inducing pain. Usually the laser is used at 0.5 to I W, and the end of the laser tip is moved quickly, maintaining a distance of 10 cm from the tooth surface for a couple of minutes, until the pain induced by an air blast disappears completely.
Stimulation Method on the Tooth Crown Surface
Carbon dioxide laser exposure must not be done on the dried tooth crown surface because not only pain, but also carbonization is induced. Sodium fluoride paste or petroleum jelly is coated on the tooth surface, and then the tooth surface is exposed to the CO2 laser to prevent the occurrence of pain and the carbonization on the tooth surface by the laser. Output powers used for the treatment ranged from 0.5 to 3 W, and a success rate of greater than 90 percent was reported.
Although this method is not recommended, it is not so difficult to perform if the laser exposure is done at 0.5 W under air cooling after painting sodium fluoride paste on the surface. A caries prevention effect is derived by laser irradiation with sodium fluoride paste on the exposed dentin surface. This method offers the highest effectiveness with pain reduction of dentin hypersensitivity of the three above-mentioned CO2 laser methods.
APPLICATION OF LASER IN INDIRECT PULP CAPPING
As lasers were introduced to dentistry, nobody thought that laser could perform the treatment of indirect pulp capping. The discovery of closure of dentinal tubules by laser energy and the sedative effects on pulpitis has led to the development of several new treatments that are soon to be put into practice.
Deep cavities, hypersensitive cavities, and cavities that require sedative treatment are some of the indications for this treatment. The outcome of pulp capping procedure whether direct or indirect is unpredictable and success rates ranging from 44 to 97 percent have been reported.
When using the pulsed Nd:YAG laser, it is necessary to combine the application of black ink to the tooth surface and air spray cooling to prevent dental pulp damage resulting from the laser energy provided by 2 W and 20 pps for less than 1 second on the area. Wound healing of the irradiated pulp seemed to be better than that of controls at 1 week and dentin bridge formation in the irradiated pulp was stimulated at 4 to 12 weeks after operation using Nd:YAG laser (Ebihara 1989).
The mechanism of this treatment has been proved by various studies that described the degree of dye penetration as having decreased after laser irradiation of the dentin surface. The mechanism of sedation by the laser is thought to be identical to that of sedation of dentin hypersensitivity.When using the CO2 laser, the dental tissue must not be irritated by exposure to high-energy lasers for long periods of time. In some cases, it is recommended that this laser be used with 38 percent silver ammonium solution. However according to a study conducted by S Jukie et al in 1997, no newly formed dentin was found over the exposed pulp tissue in the root canal openings 30 to 45 days after CO2 and Nd:YAG laser irradiation.
APPLICATION OF LASER IN DIRECT PULP CAPPING
As laser treatment has advantages with respect to control of hemorrhage and sterilization, laser use for direct pulp capping has attracted dentists' attention. Previous researchers reported that the indications for direct pulp capping are extremely limited. The diameter of pulp exposure must be 2 mm or less, and there must be no infection in the pulp. Further, research on this subject is anticipated.
When using the CO2, laser for this treatment, laser irradiation of the exposed dental pulp must be performed to stop bleeding and sterilize the area around the exposure. Laser irradiation should be performed at I or 2 W irrigating alternatively with 8 percent sodium hypochlorite and 3 percent hydrogen peroxide, for not more than 5 minutes.
Calcium hydroxide paste must be used to dress the exposed pulp after the laser treatment, after which the cavity should be tightly sealed with cement such as carboxyl ate cement. Final filling of the cavity is done after 6 months. The high success rate is thought to be due to control of hemorrhage, disinfection, sterilization, carboni- zation, and stimulation effects on the dental pulp cells. It causes scar formation in the irradiated area due to thermal effects which may help to preserve the pulp from bacterial invasion. In addition, the laser minimizes the formation of hematoma between the pulp tissue and the calcium hydroxide dressing allowing a close contact between the dressing and the exposed pulp. If Melcer's description of therapy for inflamed pulps with lasers is found to be valid, the indication of this treatment may become more widespread in the future.
LASER ABLATION AND ACCESSORY TREATMENT FOR VITAL PULP AMPUTATIONVital pulp amputation by laser therapy was one of the most highly anticipated laser treatments in endodontics because this treatment appeared to offer amputation of the pulp tissue at a satisfactory level. Control of hemorrhage and amputation of pulp tissue without producing pulp damage was not always easy in narrow root canals.
Previously CO2 laser was commonly used for pulp capping and amputation procedures. Even though it is possible to use only the CO2 laser, this requires significant time, and the pulp tissue may be damaged by the laser energy. A CO2 laser technique is carried out only for pulpal hemostasis,after which pulp amputation with an excavator or a bur is recom- mended.
When it is necessary to ablate the pulp tissue into the apical portion of the root canal, several laser exposures are required. As a result, the carbonization layer formed on the surface of the pulp tissue by the laser energy must be removed by irrigating alternatively with 3 percent hydrogen peroxide and 5.25 - 11 percent sodium hypochlorite.
Pulsed Nd:YAG laser should be used only for pulpal hemostasis, sedation orand inflammatory effects, and stimulation of the remaining pulpal cells but not for vital pulp amputation instead of an excavator or burs as heat produced by this wavelength damages the pulp tissue. The HeNe and low-power semiconductor diode lasers are alternative lasers for these purposes.ACCESS CAVITY PREPARATION AND ENLARGEMENT OF THE ROOT CANAL ORIFICE BY LASER
Currently Access cavity preparation has been performed by air turbine, and enlargement of the root canal orifice has been carried out using a Peeso reamer or a Gates Glidden drill or bur.
The Er: YAG and ErCr: YSGG laser, which ablate enamel and dentin, have been developed and improved. As a result, these lasers may soon replace the air turbine, Peeso reamer, and Gates Glidden drill as the primary method of treatment. Vital extirpation of infected root canals is one indication for these lasers. In particular, this technique seems applicable for cases in which the Peeso and Gates Glidden instruments cannot be inserted into the tooth because of difficulty of opening the mouth and for cases in which it is difficult to find the root canal orifices.
A new type of ErCr:YSGG laser has been developed and put into practice. If this laser is applied for cutting enamel and dentin at 5 W and 6 Hz under water spray, access cavity preparation and enlargement of root canal orifices can be performed easily. The laser can be transferred via optical fibers inside the root canal. Detailed examination must be done to prevent perforation into the periodontium and step formation on the root canal wall.
ROOT CANAL WALL PREPARATION BY LASER (FIG. 22.2)
A laser that can cut enamel and dentin with fine optical fibers has been developed, making it possible to remove pulp tissue and prepare root canals. Only straight and slightly curved canals are indications for applying this treatment. Equipment of Er:YAG laser at 8 Hz and 2 W produced by KaVo Co. (Ulm, Germany) to prepare root canals.
The laser tip must slide gently from the apical portion to the coronal portion, while pressing the laser tip to the root canal wall under water spray. During laser exposure of the apical portion at more than 1.0 mm from the root apex, the debris at the apical foramen must not be pushed into the periapical tissue. When the laser fiber is unable to be inserted into root canals, the laser treatment should be performed after carrying out the usual root canal preparation using reamers and files.
Various studies have shown the Er: YAG laser is capable of removing infected dentinal surfaces and the smear layer present after all forms of mechanical root canal treatment. For this purpose, the laser irradiation must be performed after or in combination with the usual root canal preparation. The orifices of the dentinal tubules are exposed facilitating a tight fitting root canal filling which is indispensable for a successful root canal treatment.
LASER APPLICATION FOR REMOVING PULP REMNANTS AND DEBRIS AT THE APICAL FORAMEN
The pulsed Nd: YAG laser was used for removing pulp remnants and debris that are deposited at the apical foramen. A power of 2 W at 20 pps for 1 second is recommended. A 5 second interval should be applied to the root canal wall or to the apical foramen. The effects of this laser irradiation on the apical foramen include sterilization, removal of pulp remnants, control of hemorrhage, and stimulation of cells surrounding the root apex as well as debridement of the surface.
Harashima et al (1998) used argon laser on instrumented root canals for 2 sec at the area of apical seat. The laser was activated during withdrawal strokes from the apical to the coronal area of the root canal. Four exposures were made of 15 sec each. The results of this study showed that argon laser irradiation had reduced intracanal debris.
The laser irradiation produced melted dentin surfaces and vaporized the debris and pulpal tissue remnants. This was enhanced in presence of diamine silver fluoride. Studies have shown that Er: YAG laser was more effective in removing the smear layer and debris on root canal walls than the argon or Nd: YAG laser. Potassium titanyl phoshate laser (532 nm) and argon fluoride excimer laser (193 nm) was able to remove smear layer and debris form root canal.
ROOT CANAL CLEANING AND IRRIGATION IN COMBINATION WITH IRRIGATORS AND LASERS
Some laser devices produce cavitation effects in root canals in a manner similar to that of the ultrasonic irrigator. At present, the effect is weaker than that of ultrasonic irrigation. This laser technique is likely to be improved in the future. Straight and slightly curved root canals as well as wide root canals are indications for this treatment.
The pulsed Nd: YAG laser, Er:YAG laser, and Er,Cr:YSGG laser are recommended. A power of 2 to 5 W usually is used for approximately 2 minutes. The laser irradiation is not carried out by the laser alone; a solution such as 5.25 percent sodium hypochlorite or 14 percent ethylenediaminetetra-acetic acid (EDTA) also must be used.
STERILIZATION OR DISINFECTION OF INFECTED ROOT CANALS
The laser is an effective tool for killing microorganisms because of the laser energy and wavelength characteristics. To prevent thermal damage to the periodontium surrounding the tooth, various techniques are considered and recommended. Infected root canals are an indication for this laser treatment, but application to extremely curved and narrow infected root canals appears difficult.
Pulsed Nd:YAG , argon, semiconductor diode, CO2, Er:YAG, and other lasers have been considered for use in this treatment. The pulsed Nd:YAG laser has been recommended for this treatment because of the ease with which the laser energy and laser fiber can be controlled.
To increase the effect of sterilization in the infected root canal, we placed about 38 percent silver ammonium solution into the root canals and irradiated the canals using the pulsed Nd:YAG laser at 2 W and 20 pps for 5 second. 5.25 percent sodium chloride or 14 percent EDTA also has been used.
It is believed that it is impossible to sterilize the root canals completely without sterilizing the surrounding periapical tissue completely. In the future, lasers in combination with certain drugs may perform sterilization by the laser. Chances of spreading bacterial contamination and dissemination from the root canal to the patient and the dental team via the smoke produced by the laser can be avoided by using strong vacuum pump system.
STRENGTHENING OF THE ROOT CANAL WALL USING A SILVER AMMONIUM SOLUTION AND THE LASER
Silver ammonium solution has been used in iontophoresis of infected root canals and in caries prevention by application to the primary caries. Teeth lased with 38 percent silver ammonium solution became difficult to fracture. Pulpless teeth are indicated for this treatment.
The pulsed Nd:YAG, CO2, semiconductor diode, and argon lasers are recommended as laser devices for this treatment. To prevent leakage of the 38 percent silver ammonium solution into the periapical tissue through the apical foramen, a cotton pellet should be infused with the solution and placed in the apical one third.
Usually this treatment is performed using a pulsed Nd:YAG laser at 2 W and 20 pps for 5 seconds in one root canal. If there are no clinical symptoms, root canal obturation is carried out. If clinical symptoms are present, however, the patient should be observed after dressing the root canal using calcium hydroxide paste. Because no fine flexible fiber exists for use with the CO2, laser, laser irradiation into the root apex is somewhat difficult.
CLOSURE OF APICAL FORAMINA OF ROOT CANALS BY LASER
If apical foramina of root canals are completely closed temporarily by laser beams, the result of endodontic treatment is changed drastically. Anic et al have attempted this method, but no researchers have resolved all of the problems involved with its application. Preliminary studies performed revealed that closing small apical foramina was possible using the pulsed Nd:YAG laser. Closure was attempted by combining light-curable composite resin and argon laser or combining sectioned gutta-percha points and a pulsed Nd:YAG laser, However, it was found that it was relatively easy to close the apical root canal.
LASER TREATMENT UNDER A FIBERSCOPE
Laser treatment under a fiberscope has been performed for some time in stomach surgery. In the field of endodontics, treatment under a fiberscope has been put into practice in Japan as well as the United States.
By combining these instruments, dentists can remove debris, pulp remnants, root canal polyps, fractured instruments, and root canal filling materials with the aid of visual feedback. Inspection of the prepared root canal wall, apical seal, Dentin Bridge, and size and location of perforations is easy using this method. The pulsed Nd:YAG laser is used for these purposes.
APICOECTOMY, RETROGRADE ENDODONTIC APICAL CAVITY PREPARATION AND PERIAPICAL CURETTAGE BY LASER
CO2 and Nd:YAG lasers have been investigated for apicoectomy, retrograde endodontic apical cavity preparation, and periapical curettage. Recently Er,Cr:YSGG laser was found to be more suitable for the treatment of soft and hard tissues. Apicoectomy, retrograde endodontic apical root end cavity preparation, and periapical curettage can be performed using this one laser device. Cases with continuing clinical symptoms, root canals with fractured instruments, and sinus tracts in which pus drainage cannot be stopped by the standard endodontic treatment are included among the indications for this treatment.
Researchers have been studying ways to solve these problems using lasers. A decrease in microleakage due to closure of exposed dentinal tubules after laser irradiation on the cut surface at the root end as observed by scanning electron microscopy at apicoectomy sites was confirmed in vitro. Er: YAG and ErCr: YSGG lasers are recommended for this treatment, but the cutting ability of the hard tissue by Er:YAG laser appears to be inferior to that of the ErCr:YSGG laser. The laser parameters should be determined based on the size and length of the root apex that is to be cut.
ROOT CANAL FILLING USING GUTTA-PERCHA OR RESIN AND LASER
Gutta-percha is thought to be melted by laser heat energy. Anic and Matsumoto, attempted to investigate whether it is possible to perform the root canal filling using sectioned gutta-percha segments and a pulsed Nd:YAG laser. This was shown to be possible by the vertical condensation method, but the technique required too much time. At present, this technique is not practical. Although a method combining argon laser and light-curable resin is in the literature. Proper application of this method requires further research.
REMOVAL OF TEMPORARY CAVITY SEALING MATERIALS, ROOT CANAL SEALING MATERIALS, AND FRACTURED INSTRUMENTS IN ROOT CANALS
Several methods have been used to remove temporary cavity sealing materials, root canal sealing materials, and fractured instruments in root canals, but there are no ideal methods.
Lasers are soon to be applied for these purposes. According to experimental results, it was easy to remove temporary cavity sealing materials made of zinc oxide, eugenol, or gutta-percha by pulsed Nd:YAG, Er:YAG, and ErCr:YSGG lasers; root canal sealing material made of resin or gutta-percha by pulsed Nd:YAG and Er:YAG lasers; and fractured reamers or files in slightly curved and wide root canals. In narrow curved root canals, however, there were many cases in which the laser tips perforated the root canal wall.
LASER TREATMENT OF PERIAPICAL LESIONS OF SINUS TRACT
Although sinus tracts almost always can be closed by standard endodontic treatment, a few cases require special treatment.
Laser techniques are in cases for which apico- cectomy or periapical curettage cannot be performed or for which standard endodontic treatment due to the presence of a deep post in the root canal are indi- cations for this treatment and also used to accelerate the wound healing. This treatment may be performed to accelerate wound healing in combination with endodontic or surgical treatment. Pulsed Nd:YAG and CO2 lasers are recommended for these treatments.
For the pulsed Nd:YAG laser, 2W and 20 pps are the recommended parameters and the fiber tip must be inserted into the tract and drawn slowly from the root apex to the exit through the sinus tract. This treatment generally is performed three or four times during one visit. When using the CO2 laser, the exit of the drainage must be ablated as deeply as possible at 1 or 2 W and under air cooling or local anesthesia. The aforementioned laser treatments are performed once or twice a week until the sinus tract disappears.
Other Applications for the Endodontic Treatment
A pulsed dye laser emitted at 504 nm was used for the removal of a calcified attached denticle (Rocca et al. 1994). CO2 and Nd:YAG lasers have been used for the attempted treatment of root fractures (Arakawa et al. 1996). However, regardless of the reapproximation technique, laser type, energy, and other parameters used,fusion of the fractured root halves was not achieved. Lasers (Ar, CO2, Nd:YAG lasers) have been used successfully to sterilize dental instruments (Adrian & Gross 1979, Hooks et al. 1980, Powell & Whisenant 1991).
Hence, it can be concluded that it is useful to use lasers for endodontic treatment, however, it is yet not possible to use it alone. With the applications of thinner, more flexible and durable laser fibers, laser applications in endodontics will increase.
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