Objectives: Output intensities (air-absorbed doses in air: Gy) were measured at the cone tip using six dental x-ray generators. Methods: The type 660 ionizing dosimeter (Victoreen, Inc.) was used. The flat probe, type 660-3, was set at the cone tip of each dental x-ray generator. Measurements at three exposure times, of approx. 0.3, 0.6 and 1.0s were repeated five times. The exposure time versus air-absorbed dose relationship and the air-absorbed dose rate, were obtained for each generator. The number of exposure time settings required to give an air-absorbed dose of less than 2.00mGy at the cone tip was evaluated for each generator. Results: Outputs of two generators which were furnished with a short cone (20cm focal spot to cone tip distance) were 3.38 and 6.95mGy/sec at 60kV, and 4.67 and 9.82mGy/sec at 70kV. Outputs of four generators with a long cone (30-35cm) were distributed in the range of either 1.50-1.68mGy/sec or 3.06-3.57mGy/sec at 60kV, and either 1.95-2.29 or 4.06-4.73mGy/sec at 70kV, respectively. The calculated outputs at 10cm beyond the cone tip with two generators with a short cone were included in this range. The number of exposure time settings to give absorbed doses of less than 2.00mGy was in the range of 43 to 70% for five generators. One of the six generators had the low output rate. Conclusion: This experiment using six dental generators clarified that there were two kinds of generators which were distinguished by the x-ray output intensity. Some dental x-ray generators had outputs in the range of approximately 1.5-1.7mGy/sec at 60kV, and approx. 2.0-2.3mGy/sec at 70kV at the tip of the long cone. Outputs with other generators were approximately twice of these values. These findings are useful to evaluate the doses absorbed by the patient's skin surface, which is the maximum for the patient at the intraoral radiographic examination.
