Should you do it? When is it recommended?
The advantage of doing such type of exam without any complaints, it is probably that you will find a cavity before it becomes painful...or to study the evolution of a problem. The disadvantage are the cost and of course, the dose. Although the small doses present in these exams, they are still there. I refer again to this webtool, where you can calculate on your own the risks: Xrayrisk Traditionally, dental imaging present intra-oral 2D images, but extra-oral are also possible, including 3D images (tomography) which are obtained with a CT scan. Nevertheless, complex exams such as pan-tomography or tomography should only be done in case there is a problem, not for check up...
The main problem with dental imaging is the lack of regulation (either for prescription or safety) and the training of the human resources for these exams. In imaging clinics, you have human resources with radiography studies and possibly even a physicist. In dental clinical, which human resources do they have?
For more information about the technology and challenges, this article is a good review:
Vandenberghe B, Jacobs R, & Bosmans H (2010). Modern dental imaging: a review of the current technology and clinical applications in dental practice. European radiology, 20 (11), 2637-55 PMID: 20544352