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Dental Specialties 6 - Oral Radiology

Also called an Oral and Maxillofacial Radiologist, an Oral Radiologist is concerned with diagnostic images for diagnosis and management of diseases of the lower face. 

When I was a dental student in Iowa, Oral Radiology was not a recognized specialty in dentistry in the USA.  However, it was a recognized specialty in Canada at the time.  Because of this, the University of Iowa had managed to entice a leading Oral Radiologist from Canada to teach us about images available to us in dentistry for aiding in the diagnosis of dental problems.  You might notice that I said aid in the diagnosis of dental problems.  I find that many of our patients believe that when a radiograph (x-ray) is done of a certain area, the problem will be obvious to all.  This is often not the case.  In fact, Oral Radiologists bristle at the term “read” a radiograph.  The information on a radiograph is often very subtle.  As such, it cannot be read.  Instead, the radiograph must be interpreted.  Clinical experience and the wisdom that usually comes with it aids immensely in accurately interpreting what is displayed on a radiograph.

There are several kinds of images that are useful in dentistry, the most important and common being images produced by x radiation.  Usually, the amount of radiation used to do a dental film is very small, further reduced by the use of lead shielding in the form of a lead vest.  The radiation dose can be further dramatically reduced by using digital radiography.  This is when a sensor is used instead of film and the image shows up within a few seconds on a computer screen instead of on film.  (The radiation used to make a dental image digitally is about 1/10 the amount used to make the same image using film.) There are several advantages to use of this kind of image over conventional film, the most obvious being that many items can be displayed to the patient on the screen that would be too small for the untrained eye to see on conventional film.  Diagnostic quality is very consistent using digital technology.  The images can be sent to a specialist instantly via the internet, and contrast and other parameters can be adjusted so that diseased areas can be seen more easily.

There are a couple of classes of Radiographs.  One is intraoral radiographs.  This is when a sensor or a film is placed inside the mouth for the image to be made.  Intraoral radiographs are done when accuracy is vital because what is being examined is small.  Another is extraoral radiographs.  This is when the sensor or film is located outside the mouth when the image is made.  This is typically done when a broad area is to be examined as when wisdom teeth are to be seen.  Usually the image seems out of focus in some areas and its resolution is lower than intraoral radiographs which are done when only a small area is to be seen or something very subtle is to be observed—like small dental caries (cavities).

There is a new kind of oral radiography which is often termed “Cone Beam”.  This is really like a CT scan for the teeth and jaws.  This is an up and coming technology.  It is quite useful when bone is to be located for the precise placement of implants.  The cost of one of these units is still prohibitive (over $300,000 for one unit), and the regulatory body in Ontario has not managed to see its utility as of yet so has not approved Cone Beam for use in Ontario.  Surely both of these factors will change in time, but until resolution is vastly improved, small cavities will not be able to be seen using one of these units.

There is still a lot of improvement we hope to see in the ability of dental radiography to diagnose small cavities.  With present technology, a cavity noted on a dental radiograph is still two to six times as large in the mouth as it appears on the best radiograph available for use in today’s dental office.  This is where clinical experience and careful clinical examination come into play.  Even so, Oral Radiography today is an indispensable adjunct to clinical examination when diagnosing problems in the mouth.  Radiographs allow the dentist to see and thus treat some oral diseases much sooner in their progression than waiting for those conditions to become large enough to be seen on a clinical examination alone.

A very careful dentist looking for a problem just beginning may have radiographs done when you are in the office and then look at them in a dark room later.  The dark room behind the dentist aids in seeing the subtle differences in the image in certain places that would help in diagnosing a problem to be fixed early while it is small rather than waiting until it is larger and easier to see later.

- This article was written by Dr. Mike Christensen and published in the Daily Miner and News, and Enterprise. Local Kenora News Publicatons (1998-2006)

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