[en] An inexpensive and simple test device was developed and used in a field study to evaluate entrance dose, dose to an intra-oral film, filtration and field size under routine conditions in more than 200 dental practices. The test device consists of two films of different speeds and a set of five thin copper filters for a filter-analytical determination of the radiation quality. Dentists were asked to expose the test device when examining a molar tooth. Together with a short questionnaire, describing the respective conditions of film exposure and processing, the test device was returned for development and evaluation. The main result was the evidence of a significant dose reduction compared to the findings of similar studies performed in 1970 and 1975. This reduction is due to a general shift to lower values and a complete disappearance of values above 45 mGy (5R) which in 1970 were still more than 15%. In the same way the number of facilities showing insufficient filtration or collimation had decreased. Nevertheless, a large spread of dose values could still be observed, ranging from 2.5 mGy (290 mR) to more than 30 mGy (3.4R) for the entrance dose. The most striking result, however, was that such an important parameter as the speed of the films used at the respective unit had no impact on the entrance dose. (author)