|MadSci Network: Cell Biology|
The thumb rule that "rapid dividing cells are more sensitive" apply only for in vivo systems. For cultured cell lines, there are many other things that can influence radiosensitivity, such as their genetic makeup, total gene content and type of cell. You need large doses of the order of ~1Gy and above to clearly observe/demonstrate the cell killing in mammalian cells. Some mutant cell lines, such as AT1BR with ATM and other repair deficiencies, are known to show more radiosensitivity at low doses. However, for establishing a survival curve, you need a wide range of doses from low to high doses (i.e., exceeding 1Gy). Dental X-ray machines can not deliver such doses unless irradiated for prolonged time, which can damage the unit.
Nevertheless, it is possible to observe biological damage using this machine with other endpoints such as chromosomal aberration (dicentrics, breaks, etc.) in cultured cell lines as well as blood samples. A dose of 0.2 Gy and above can clearly demonstrate the damage. Look for the protocols to prepare metaphase spreads using blood samples or cultured cell lines. For simplicity, you can also try micronucleus preparation. If you have facilities at hand, other options are pulsed field gel electrophoresis, comet assay and many other molecular end points.
I guess, there is no scope for protocols here. Feel free to contact me if you need any. Nevertheless, they are available freely on net.
Try the links in the MadSci Library for more information on Cell Biology.