Q. How does it work?
A. When the X-Ray beam passes through the mouth, more X-Rays are absorbed by denser parts of the oral cavity  (teeth and bone ) than by softer tissues (gums and cheeks) before striking the film.  This will create an accurate image of the teeth and the surrounding areas after the film has been developped.

Q. How often should X-Rays be taken?
A. Whenever needed.  A thoroughful examination of a tooth (or teeth) always mandates good X-Rays of the said tooth or teeth.
In normal conditions, a set of full mouth dental X-Rays ia recommended every year to monitor changes that may occur during that time.

Q. What are he benefits of a dental X-Ray examination?
A. Many diseases of the teeth and surrounding areas cannot be seen by the dentist with naked eyes.  An X-Ray photograph may reveal:
-Small areas of decay between the teeth
-Infections in the bone
-Abnormalities of the teeth and the surrounding areas
-Some types of tumors
Finding and treating dental problems at an early stage can save time. money and unnecessary discomfort.  If you have a hidden tumor, X-ray radiographs may even save your life.

Q. Is dental X-Rays dangerous?
A. The risk of radiation exposure in dentistry is very minimal compared to its benefits.
We are exposed every day to radiation from various sources, including outer space, minerals in the soil, household appliances and environment pollution.  Some numbers to think about:

Dental radiographs:
-Bitewings (4 films)                                                         0.038 mSV
-Full mouth series (18 films)                                          0.150 mSV

Medical radiographs:
-Lower GI series                                                              4.060 mSV
-Upper GI series                                                              2.440 mSV
-Chest                                                                               0.510 mSV

Radiation from outer space in Denver, CO per year   0.510 mSV
Radiation in the US from natural sources per year      3.000 mSV

Q. Can pregnant women have X-rays taken?
A. The consensus opinion for dental X-Ray exposure in pregnant patients is that if dental treatment is to be provided during pregnancy, then radiographs required for that treatment are justified.  If treatment is to be deferred until after delivery, then radiographs should also be deferred.
There is no set limit for diagnostic radiation exposure of any patient.  This includes dental radiation exposure and pregnant patients.  It would be unreasonable to cause an important diagnostic to be  missed because of some arbitrary limit on radiadtion exposure.  On the other hand, it would be unreasonable too if unnecessary X-Rays are taken with no regards of the patient's medical conditions.