The benefits from the use of radiation are far greater than the associated biological risks. Because the effects of low radiation dose cannot currently be measured, the basic assumption made is that every dose of radiation is capable of inducing some potential biological damage. Hence it is recommended to keep radiation exposures that are necessary to meet diagnostic requirements to the minimum . Over the years efforts have been made to determine the most appropriate balance between the potential risk and the obvious benefits of radiation in diagnosis and treatment of oral diseases. These efforts to identify the acceptable balance have resulted in establishment of radiation protection standards by various national and international committees on radiation protection and safety and this book is a treatise on the same subject.