Lasers in Endodontic: A review

Since the development of ruby laser by Maiman in 1960 & application of laser for endodontics by Weichman in 1971, a variety of papers on potential applications for lasers in endodontics have been published. Lasers have been a signi icant advancement in the ield of endodontics. Be it effective cleaning, root canal treatment, surgery etc. The lateral accessory canals and anatomical complexities have been a restraint in root canal procedure, for such cases lasers have been introduced to simplify the process & have good clinical results. As there has been a boon in the improvement of laser techniques, many latest lasers having a broad array of characteristics is accessible and can also be helpful in several areas related to dentistry. When compared with conventional techniques, laser treatments has been proven to be more advantageous. Thepurpose of this article is to summarize laser applications in endodontics, including their use in pulp diagnosis, dentinal hypersensitivity, pulp capping and pulpotomy, sterilization of root canals, root canal shaping & obturation & apicectomy. This article reviews the role of lasers in endodontics since the early 1970s & summarizes what future may hold for endodontics. With the potential availability ofmany new laserwavelengths andmodes, much interest is developing in this promising ield.


INTRODUCTION
Effective cleaning of canals of the root is the aim for performing root canal procedure. Conventionally manual instrumentation and chemical irrigation for cleaning and shaping of root canal have been used (Olivi et al., 2011) Presence of lateral canals with varying morphologies and dimensions, anatomical complexities and intricacy of irrigants penetrating in canals present laterally as well as complex branching of canals near apex, causes a restraint of endodontic therapy. Hence, Laser technology was introduced in endodontics to improve the conclusions gathered by the use of standard techniques by using light energy to increase the ability to clean and helps in removal of debris along with smear layer within the canals and hence leading to improvisation in the cleansing of the canal (Kimura et al., 2000). In 1971, Weichman & Johnson became the irst to use the laser in endodontics in an attempt to close the apical opening of foramen via Co2 laser. As there has been a boon in the improvement of laser techniques, many latest lasers having a broad array of characteristics has been accessible and can also be helpful in several areas related to dentistry. When compared with standard techniques, laser treatments has been proven to be more advantageous. According to results, it has been suggested that laser was proven effective for removing debris, smear layer, & also been a useful disinfection tool.

History
1917-Albert Einstein gave the theory of stimulated emission on which principle of the laser was based.
1964-Patel invented the co2 laser. It was the only laser which can be applied to hard as well as soft tissue (Karlovic et al., 2005).
1965-Stern and Sognnaes were the irst to report that ruby laser was responsible for vaporization of enamel (Rf and Rh, 1965).
1971-Weichman and Johnson reported the effectiveness of laser during root canal treatment for the irst time (Yamamoto and Sato, 1980). 1990-Diode lasers emerged which were semiconductor-based (Adrian et al., 1971).
1997-FDA gave clearance to Er:YAG laser and the Er,Cr:YSGG after 12 months.

Mechanism Of Action
An active medium produces a beam of laser that leads to the production of speci ic wavelength photons on stimulation via light/electricity. Some of the characteristic features being, monochromatic(beam composed of a single wavelength), unidirectional, coherent, which are being released via a medium which is active and stimulated. On production of the laser beam, it travels in a single path, although the different types of laser and the related conduction hardware may diverge the beam. Active media being a solid-state, gaseous state, or in a semiconductor state. Erbium laced yttrium, Er: YAG and aluminium are some of the solid active media which are crystal medium host drug in company with atoms which are capable of producing light and are excitable."CO2" being an accepted laser wherein the active medium remains preserved in a vacuum chamber. On stimulation by an electrical source, semiconductor present in diode laser emits the light(laser), [7] by a process called optical pumping. On absorption of a photon by erbium atom, the electrons get raised to a superior energy level. On returning to lower energy state, two similar electromagnetic waves are released, which can further excite a large number of atoms in the reaction, which results in a magni ication of the produced light. The active medium is surrounded by a mirror called resonator, which will further increase the light energy.
The output coupler is one of the mirrors is less than 100% re lective from where the light leaks and these photons from a beam of a laser. After the formation of the beam, with the help of beam transfer hardware, the beam is passed on towards the target tissue Table 1 (Lin et al., 2010).

Classi ication
According to Light Active Medium

3.
Bone cutting and lengthening of crown.

Laser application can be used in patients showing any of the below mentioned clinical indings.
Tooth with purulent pulpitis, lateral canals, teeth showing gangrenous changes in coronal portion and pulp of root, teeth showing peri-apical lesions and abscess, root resorption because of trauma or infection. Also for tooth which has undergone three months of treatment without any success. e. Removing the hyperplastic as well as pathological tissues from near the apices.

Thermal Consideration
When treatment was carried out of 45 seconds duration at 15Hz, it was observed that a temperature of 38 degree celcius was measured on surface of the root, this resultant parameter lied within the physiological limits. The low of blood around the root surface keeps the dental tissue more expeditiously cooled, this was considered that in an in-vivo situation. On treatment with ibre-optical waveguide in coronal direction the temperature on root canal wall decreases which assures that only marginal tissue is affected and hence no damage is expected.

Morphological Changes
On applying Nd:YAG with 15Hz/1.5W, the maximum part of dentinal tubuli closes because of inorganic melting. Smear layer removal occurs & (Gutknecht, 2007) by using 810nm laser diode comparable results can be expected. On application of Er:YAG laser, entire smear layer removal occurs while the tubuli of dentin remains open.

Disinfection Effect
Conventional alternate rinse in root canal preparation by sodium hypochlorite or hydrogen peroxide have been successfully proven to have a bactericidal effect (Suryavanshi et al., 2017). The only one to examine an 80% of reduction in bacterial count following 5 treatment sessions were BYSTROM et al. but only in root canals of upto ISO30 while the curve roots remained an exception.

CONCLUSIONS
In todays dental treatment procedures lasers are playing very important role, if used ef icaciously and ethically. As the advancement of much thin, elastic & long lasting ibres, application of lasers in root canal treatment is soon going to increase. Since laser technology came in the areas of dental treatment, the complicated techniques is becoming simpler with less consumption of time and hence improving ability to concern for patients. Due to relatively high cost laser devices are have limited access. Evaluation of studies on laser showed that Nd:YAG laser treatment was effective in replacing the customary procedures.