by Leif Kullman
The value of dental radiographs.
Intraoral radiographs are regarded as an essential element in diagnosis and treatment planning in dentistry. For example, to be able to help a patient with a persistent ache in a tooth due to a deep filling or perhaps trauma, both which might have created an acute inflammation and necrosis in the pulp tissue, we prefer to be able to view possible periapical tissue changes such as a widening of the radiolucent image of the periodontal ligament space and alteration of the adjacent lamina dura. If no radiographs are available, or a radiograph without a sign of pathology, it can be difficult to verify the diagnosis clinically. The negative result though does not necessarily mean that no pathology is present.
It is likely of course that it will take some days after inflammation of the pulp is initiated, for enough soft and hard tissue destruction to have occurred to be imaged in the periapical region, but sooner or later - almost always - signs will be demonstrated if the tooth not is treated in an early phase of the disease process.
Several important factors can contribute to our failure to see a widening in the periodontal ligament space which might result in our patient experiencing a toothache for more days than necessary. I would like to comment upon some of these factors in my monthly message.
The radiographic quality
Film processing and the routines of the darkroom are very important. Studies have shown that radiographs are often underdeveloped (the staff are in a big hurry, and "we must not keep our patient waiting"!) As a result, the film will be too radiopaque (pale) and have poor contrast. The same effect may arise if we have old or exhausted chemicals. The developer can also be too cold. Adopting manufacturer recommended procedures will eliminate all these problems. That is; read the comments on the package of film and chemistry.
Another frequently observed film fault is fogging. It may be caused by poor or prolonged storage conditions past the expiry date. Don't forget to check the expiry date when they arrive from your supplier to ensure current "freshness" of film. Keep the film stored where it is shielded from radiation and at a constant temperature if possible.
The consequence of fogging will be a reduced radiographic film contrast.
The exposure factors and the equipment is seldom a reason for underexposure, and thus pale radiographs. On the contrary, often dentists sometimes use increased exposure time if the radiographs are processing too pale and of poor contrast. This can result in an overexposure and a burn-out effect on the edges of a thin object, for
example the apical lamina dura.
It is also best to view the radiographs when dry. Certainly, if initially viewed wet, films should be seen again dry. Films should also preferably be mounted in specifically designed film mounts (eg. Trollplast) to facilitate the reading and diagnosing. A viewbox and some kind of virtual magnification during reading is also strongly recommended. Some dentists also like to have access to a magnifying glass when reading the radiographs. An important reason for blurring of the apical area of a a tooth is if the film has been bent when it was positioned in the mouth. To eliminate the risk of film bending, intraoral specific film holders can be used.(should be used!)
The ability of the observer
Perhaps even more sources of errors might exist in this aspect than in the film handling and quality. We will only discuss some of the possible reasons for interpretation errors. As always the starting point for interpreting pathology is the observer's knowledge of normal anatomy. It is important for every clinician to realize that some patients have more mineralized trabeculae and compact bone than others, producing a different radiodensity of the periapical region for each patient. There are wide structural variations within the "normal" limits.
Knowledge of various pathological conditions, their development and course of progress is of course important. One must know the initial characteristics of a lesion and to be able to look for these early signs in the radiographs. There are several factors connected to the health and condition of an observer, that will influence the diagnosing. Among these the following can be mentioned: Sight of the observer and his/hers... shall we call it... diagnostic acumen and personality. There is much research showing wide ranges in diagnostic scoring between observers. Some being under- and other over-scorers. It has also been shown that there are great discrepancies that occur in an observer on different occasions. Which means that we have to count with both a large inter- and intraobserver variability. Man is not always consistent!
These are the more systematic factors that can influence an observer but there are also more casual or random factors. Such factors can be mood of the observer, commitment to the task, tiredness and so on.
Finally there are additional influencing factors from the environment and surroundings. For example, view films in a quiet and semi-darkened room. But that is also an individual variation and some clinicians can accept a more busy atmosphere, or have become accustomed to that environment. One wonders though if some things are missed in the interpretation. Finally, considering some of the comments above, it may also be concluded that a succesful interpretation of radiographs depends very much upon the clinician and his/her understanding of the image. No matter how good the film quality is, the various abilities of the human being involved in the diagnostic process are critical to the correct outcome.
Next month I will describe one or two interesting cases.
Leif Kullman
