A lot goes on in the mouth that we cannot see. Dental radiographs (x-rays) allow us to evaluate the hard structures of the mouth (principally teeth and bone) in a way that is not otherwise possible.
We all understand that dental radiographs are necessary to properly manage the health of our mouth and to maintain excellent function and appearance for a lifetime. We also know that radiation can be harmful. Unfortunately, we are exposed to it all the time, and no one knows at what point the cumulative exposure can produce harm. The question then is, how often should we have dental radiographs? Like everything else that is done in medical treatment and the use of prescription medications, it is always a balance between benefit and harm.
As mentioned in Part 1, Bitewing radiographs are frequently taken once a year by the general dentist during regular examinations to help check for new decay in the teeth and around existing restorations. Some people are more naturally resistant to decay. Based on previous history, these people could make a case for less frequent bitewing radiographs.
When it comes to periapical radiographs, because more films are required in a “full series”, there is more radiation than the four bitewing films, and they are also generally more expensive. This, however, is balanced against the need for the information about the roots and surrounding bone that is necessary to maintain the health and longevity of the teeth. The ADA recommends this type of radiographic study once every three years. This is probably a good balance between maintaining oral health and the longevity of the teeth and avoiding excessive radiation.
It still amazes me, after almost 40 years in practice, how we will take a full series of radiographs on a patient who practices good oral hygiene and comes regularly for periodontal maintenance visits and, on the surface, all appears to be well and there is no discomfort, and yet we will find infections developing under the surface. It would be impossible to provide our patients with excellent care without the benefit of these radiographs. In the same way, it often surprises people that have fillings and crowns on some of their teeth, that they can still get new decay beyond the filling and crown margins. It is always better to catch new decay early before it goes so deep that it enters and infects the nerve inside each tooth. This then requires root canal therapy (assuming the tooth can still be saved) and is usually followed by placement of a crown (cap) over the tooth, so it requires multiple visits and is costly.
When it comes to Panoramic Films and CT scans, these are usually taken on an “as needed” basis depending on planned work. Hopefully, these discussions have helped answer some of your questions about dental radiographs, including the different types and their unique benefits.