RESUMO
INTRODUCTION: Rectangular collimation is recommended in order to reduce radiation doses to patients. However, anecdotal reports suggest that it may result in more retakes, with a possible net increase in patient dosage. METHOD: To test this hypothesis, eight general dental practitioners were recruited to participate in a project. Each took 25 pairs of bitewing radiographs of patients before and 25 after fitting rectangular collimators to their x-ray machines. Double-pack films were used so that duplicates could be examined. These were assessed by a consultant oral radiologist according to the National Radiographic Protection Board (NRPB) grading system for positioning and general film quality. RESULTS: Initially, positioning quality was above the target level for six of the eight dentists; however, for all but one, this dropped after using rectangular collimation. General film quality was of a lower overall standard initially. Using rectangular collimation had an effect on general film quality but the direction and size of this varied among the dentists. CONCLUSION: It was concluded that amongst the participating dentists, although numbers of retakes increased by 7%, there would be a net reduction in dosage to patients following rectangular collimation.
