It depends on the manufacturer and model.
Definitely an X-Ray tube in there, maybe the high voltage power supply,
and maybe some sensors.
You must provide the correct voltage for the correct length of time.
It sounds a bit dangerous to me without a schematic or wiring diagram,
and the correct knowledge of X-Ray techniques.
Keep in mind that even with a properly functioning machine the dentist
leaves the room to avoid multiple exposures.

Too_Many_Tools wrote:
I have a surplus xray dental head that I would like to reuse.

It has four wires entering it.

What is in a head like this and how can one use it for xraying items?

Any links to sites that describe how this device is constructed would
be appreciated.

Thanks

TMT