Why dentists take x-rays?

http://www.webmd.com/oral-health/dental-x-rays-when-get-them

Dental x-rays are one of a common and effective diagnostic tools that dentists use. Dentists use them to confirm the health of patient's teeth, roots, bones and gums, that may otherwise missed with a simple oral examination. Often times, x-rays reveal early stage of tooth decay, infections, gum diseases and more. Dentists rely heavily on x-rays to help them determine which is the best treatment for the specific tooth for the specific patient. Prior to major dental procedures, such as tooth implant, braces, wisdom teeth extractions and root canals, x-rays are used to evaluate the necessity of performing suggested procedures and to check progress of the procedures. Early diagnose and getting proper treatment is the key in slowing down the progression of dental diseases, increasing the chance of saving the original teeth, avoiding pain and discomfort.