Lasers in Endodontics

Dr.Vinisha Pandey The first laser used in endodontics was reportedWeichman and Johnson (1971)who attempted to seal the apical foramen in vitro by means of high power infrared (CO2) laser. Although this goal was not achieved, sufficient relevant and interesting data were obtained to encourage further study. The development of new deliverysystems, including thin and flexible fibres as well as new endodontic tips, has made it possible to apply this technology to various endodontic procedures, such asPulpal diagnosis Pulp capping/pulpotomy Cleaning and disinfecting of root canal system. Obturation of root canal system Endodontic re-treatment, and Apical surgery The complex root canal anatomy and the limited ability of chemical irrigants to three dimensionally clean and disinfect the entire endodontic space, the use of lasers was seen as a possiblemeans of adjunctively enhancing the effectiveness of endodontic treatment. Scientific Basis The interaction of light on a target follows the rulesof optical physics.Light can be reflected, absorbed, diffused, or transmitted. The interaction of laser light with dentin occurs when there is optical affinity between them. This interaction is specific and selective, based on absorption and diffusion. The less affinity, the more light will be transmitted and/or reflected.The near-infrared lasers (from 810 nm to 1340 nm) have negligibleaffinity for water and the hydroxyapatite of hard dentaltissues and therefore penetrate to a large extent through dentinal tubules and are absorbed by the bacteria pigments. This allows for a bactericidal effect in deeper dentin layers. The mid-infrared lasers (2780 nm and 2940 nm) are primarily absorbed by water(and, to a lesser degree, hydroxyapatite) in the dentinal walls and their bactericidal effect, via photothermal energy, is more superficial. Their affinity for water in dentin also performs a certain amountof ablation of the superficial dentin as a result of the photothermal effect. The carbon dioxide laser (10,600 nm) has a strong affinity for water and especially hydroxyapatite. The inability of this wavelength to utilize a fiber-optic delivery system limits its utility in intracanal applications. In 1999 Kesler et al. evaluatedthe clinical use of a specially designed microprobe (coupled to a CO2) laserhandpiece) within the apical third and reported a level of success comparable to conventional endodontic treatment. The interaction of different laser wavelengths on different targets (such as bacteria, dentin,and irrigants), via absorption or diffusion, generates biological effects responsible for different therapeutic actions that can be summarized as: Photothermal effects Photochemical effects Photothermal effects inducing photomechanical and photoacoustic effects. Effects of Laser Light on Bacteria At different power levels, all laser wavelengths destroy the cell wall because of their photothermal effect. The initial damage takes place in the cell wall via alterations in the osmotic gradient leading to swelling and cellular death. Gram-negative bacteria, due to the structural characteristics of the different cell walls, are more easily destroyed with less energy and less irradiation than gram-positive bacteria. When erbium laser energy is delivered with very short pulse durations (less than 150 microseconds) in a liquid-filled environment, a shock wave phenomenon (photo-mechanical acoustic effect) can occur. A recent study reported a direct bactericidal effect related to this shock wave-like phenomenon; a bacterial kill of 73% was seen when distilled water was activated by PIPS for 30 seconds in an ex vivo infected root canal.