Abstract
2nd Ever since the dental profession was established there have been many breakthroughs such as radiology, local anesthesia, air driven turbines, osseointegrated implant .... etc. that helped propel dentistry in its progress and made it possible to cover new areas that were not accessible before. the most recent technological breakthrough is the development and application of the Laser. the scientific physical basis and tissue effect of lasers have been discussed. it is very important to become familiar with basic principles and then select the proper laser for a specific clinical application. Although there is some overlap of type of tissue interaction each laser wavelength has a specific quality that accomplishes a specific treatment objective.