IOSR Journal of Dental and Medical Sciences (IOSR-JDMS) e-ISSN: 2279-0853, p-ISSN: 2279-0861.Volume 18, Issue 11 Ser.9 (November. 2019), PP 33-46 www.iosrjournals.org DOI: 10.9790/0853-1811093346 www.iosrjournals.org 33 | Page LASER Physics& its Application in Dentistry – A Review Eshani Yeragi 1 , Kavita Pol Nalawade 2 , Saurabh Gotmare 3 , Kajal Mahajan 4 , Prajakta Yeragi 5 1Department of Periodontology, Y. M. T. Dental College, Mumbai 2 Department of Periodontology, Y. M. T. Dental College, Mumbai 3 Department of Endodontics, Y. M. T. Dental College, Mumbai 4 Department of Periodontology, Y. M. T. Dental College, Mumbai 5 Department of Pediatrics, New York Corresponding Author:- Eshani Yeragi. Abstract: Lasers has revolutionized the technology used in dentistry in this current era and is being utilized as a part of various dental treatment including its use in Endodontics, Periodontics, Oral Surgery, Oral Medicine as well as in Orthodontics.There are many types of LASERs available for use in dentistry. Henceit’s very important to understand the physics behind lasers as well as its applications. The objective behind this review article is to elaborate different types of LASERs as well as its physics behind it. Key Words- Laser, Maser, Specturm Of Light, Spontaneous Emission, Stimulated Emission --------------------------------------------------------------------------------------------------------------------------------------- Date of Submission: 05-11-2019 Date of Acceptance: 21-11-2019 --------------------------------------------------------------------------------------------------------------------------------------- I. Introduction „LASER‟ is an acronym for Light Amplification by Stimulated Emission of Radiation 1 . Most patients still associate the sound and vibration of the drill with pain. However, with the new inventions and advancements in this field, several options have become available to progressive dentists to allay fears and offer patients state of the art treatment. One such advancement is the advent of the laser technology presenting new vistas for dentists in fields of dentistry. A laser is a device which is built on the principles of quantum mechanics to create a beam of light where all of the photons are in a coherent state - usually with the same frequency and phase (most light sources emit incoherent light, where the phase varies randomly) 2 . Among the other effects, this means that the light from a laser is often tightly focused and does not diverge much, resulting in the traditional laser beam. The unique characteristics of the laser are that it is monochromatic, coherent and collimated. This allows concentration of tremendous amount of energy to a small area. With the development of thinner, more flexible and durable laser fibres, laser applications in endodontics have increased. II. History Of Laser The dental lasers of today have benefited from decades of laser research and have their basis in certain theories from the field of quantum mechanics formulated by Danish physicist Bhor(1900) 3 . The 1917 seminal paper by Einstein ZurQuantenTheorie der Starlung contained the elements for the conceptual basis for stimulated emission of radiant energy that was to form the foundation of modern laser physics 4 .When combined with the principles of the quantum mechanics promulgated by Niles Bohr and the fabrication of optical resonators known in the nineteenth century, Gordon and others, much later in the 1955, were the first to demonstrate the stimulation of microwaves wit hin the electromagnetic spectrum.40 years later, American Physicist in 1958, Schawlow and Townes 5 revealed that it was possible to stimulate emission of radiant energy in the form of photons and in the infrared and visible or optical portions of the spectrum extending the maser principle to the optical portion of the electromagnetic field, which rapidly led to development hence LASER (Light amplification by the stimulated emission of radiation).The first working laser was constructed by Theodore Maiman 5 in 1960 at the Hughes Research Laboratories in Malibu, CA, by exciting a ruby rod with intense pulses of light from a flash lamp. The first actual continuously generating laser was attributed to Javan and colleagues 6 in 1961 who used a mixture of helium and neon. In 1964, Patel at Bell Laboratories developed the CO2 laser 7 . The HeNe laser was of low power, but it advanced the concept of laser practicability by its continuous mode and continues to be used as a coaxial spotter for laser beams of more powerful lasers.