by Leif Kullman
Planning to buy a new dental x-ray unit?
As a specialist in Oral Radiography I often get inquiries about unit requirements from dentists, who is planning to buy new radiographic units. There is a rather wide range of units available and the prices can differ a lot between the wellknown, established products and the more unknown. In this message I will not evaluate the different brands, only try to give the reader an idea of what you should think of, out of a quality aspect, when you buy a new equipment.
Today it is also natural for a presumed buyer as a first step, to ask himself if he should buy a digital unit or not. This is perhaps the most usual question and not intended to be the main subject of the present message. However, some comments cannot be excluded. The decision digital or not is influenced by several factors, for example the knowledge of the dentist and staff, their ambition for the future and the surrounding equipment and the economy of the practice. If there is a positive answer in these questions it can be time to go digital, but there is always time to wait a little more, better and probably cheaper digital units are produced all the time.
If the decision is taken to stick to the usual technique for some more time it can be useful anyway to check the following thing, when a new dental x-ray unit is bought:
The new unit ought to have a DC generator. Because then it will be able to use this unit in a digital system in the future (with an ability to very short, exact exposure times). A DC generator is generating a high quality direct current (constant potential) for the x-ray unit all the time. Thus minimizing the risk for generating low energy, not image creating, exposures. The kV of the dental unit should be at least 60 kV. The most optimal operating kV seems to be around 70 kV.
The following thing is also important to check up in the new equipment (notice that there can be differences between different countries due to their regulations) :
All x-ray units should have a collimator (also called PID; position indicating device) in form of a hollow cylinder with a rectangular (film shaped) or round cross section. This one should have a length so that the distance from focus to the patient will be at least 20 cm.
The diameter of this collimator should be not more than 6, but best is 5 cm and it should by preference be made of metal of course.
All units should have a total filtration corresponding to 2 mm aluminum (increasing filtration with increasing kV of the equipment). The mission for this is to take away low energy radiaton, radiation which else only should be left in the patient and not reach the film.
Finally, never forget that you also use a film, which is as fast as possible and that it is very important to keep a good quality in you darkroom work. A perfectly exposured radiograph is easily ruined due to bad darkroom procedures.
