CDX, CDX-2 & CDX-3 Dental Tubes
CDX
CDX-2	CDX-3	The “CDX” (Coolidge Dental X-Ray Unit) introduced by G.E. in 1921, was the first totally protected (electrically and radiation-wise) dental unit, where a small bulbar Coolidge tube and all the electric transformers and circuits were oil-immersed in a compact hermetically closed metal housing. The Coolidge tube in the first CDX was described as “surprisingly small” compared to x-ray tubes in general use, and particularly when compared to the air-cooled dental right angle tube. The CDX tube is only 4”(10cms) long, and was rated 45 kV and 10 mA. As in early Coolidge tubes, the filament is a flat spiral inside a hemispheric cup.
This CDX-2 tube, is the 1930’s version of the first CDX tube, of the same shape and size, equally built of lead-glass with the exception of the output port, and where the line-focus principle was adopted allowing improved ratings (60kV and 10mA). The CDX-3 tube, of the late thirties or early forties, is similar in size and internal structure to the CDX-2 with a more “modern” shape, where the central part is cylindrical, with a ground-glass x-ray output port.

Comparative picture of the modern Philips Oralix x-ray tube, 2” (5cms) high, the internal structure of which is, like many present time dental tubes, highly similar to that of the CDX-2 and CDX-3. It is rated 65kV and 7.5mA.

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