Your Dental Xrays
In order to make one of my instructors very happy I'm going to tell you the proper name for dental xrays--radiographs.  You will impress your dentist and hygienist if you use this word.  I don't know that you'll get better treatment, they'll just be impressed. 
First the definitions.  A full mouth set of radiographs is 14 films that will give us a picture of all of your teeth, the surrounding bone, in between your teeth, and the apices of your teeth--a fancy word for root tips.  This set consists of bitewing and periapical films.  These films are taken every 3 to 5 years depending on how prone you are to cavities.
Bitewings are the xrays that have the tabs you bite on and they will show us in between the back molars.  These radiographs are included in your full mouth set of films and are repeated yearly to every 18 months in order to check for cavities.
Periapicals are taken with a film holder and show us the roots of your teeth.  We generally take these to see the tips of the roots and look for abcesses.  An abcess is an infection at the root tip that indicates the need for a root canal therapy.
Panoramic films are one large xray that shows all the teeth.  The machine used rotates around your head in order to impose the jaw and teeth on the large film.  Sometimes these are taken in place of full mouth xrays.  They are more commonly used in oral surgery because they show unerupted teeth--those still in the jaw and will assist in the removal of impacted teeth, wisdom teeth, or teeth that are no longer able to be restored.
Your dental radiographs are kept at the dental office, however, they are your property.  If you need to go to another general dental office or are referred to a specialist, your films can be copied and you may take them with you.  The other dentist may want his own xrays, but they will make you aware of this at your appointment. 
You will need to converse with the front office to determine if you will have to pay for any of the films or if they will be paid for by your dental insurance.
Click the x ray to go to the FDA's radiography guidelines.