The one common deficiency of the panoramic film and intraoral films discussed in the two previous articles is that they are two-dimensional. They show left and right and up and down very well but not in and out. This is critical information when contemplating implant placement and orthodontic tooth movement.
Since implants require bone on all sides to remain stable and healthy, it is essential to know if there is enough bone volume going from cheek side to tongue side. Often, when teeth are extracted or have been missing for a long time, this dimension can be significantly reduced. Fortunately, today, we have ways to regenerate this missing bone with various bone grafting techniques.
In the case of orthodontics (both traditional and Invisalign), the problem is most often crowding (there are too many teeth for the size of the jaw bone). One way to compensate for this is to expand the size (circumference) of the dental arch. What we don’t often realize is that, in the natural condition, there is often little or no bone on the outside (cheek side) of the teeth. We will talk more about this in an upcoming discussion about recession. In any case, this is not a problem for the teeth as long as there is no excessive force or trauma applied to the teeth since the gum can attach directly to the roots without having bone present. The problem develops when unnatural forces like orthodontics are applied to the teeth. When outward orthodontic forces are applied to the teeth that have little or no bone on the facial side, in an effort to expand the arch to make more room for the teeth, the end result can be teeth that remain loose after orthodontic movement is completed or where recession of the gum develops so that the teeth become excessively long in appearance. Subsequently, these teeth may become sensitive to touch or temperature and certainly do not look attractive.
Today we have a type of dental radiograph that can provide this third dimension. It is referred to as a Cone beam CT scan. With a minimum of radiation, compared to medical CT scans, these studies show us this missing third dimension (in and out or cheek side to tongue side) in one-millimeter slices through one or both jaws. Thus, potential problems with implant placement, sinus grafting, or orthodontic movement of teeth can be anticipated and corrected beforehand. Cone beam studies can also be useful in finding root fractures which are rarely visible on bitewing or periapical films. And they can be helpful to the endodontist (root canal specialist) in finding and then filling the multiple root canal passages that exist inside the teeth.
In the next article, some final thoughts about dental radiographs.