The diagnostic records that I typically take include a panoramic xray, a lateral cephalometric xray, periapical xrays of the upper and lower incisors, digital photos and impressions for study models.
The xrays that your general dentist usually takes (periapicals and bite-wings) capture the most detail and are good for finding cavities, checking bone levels around the teeth, etc. The panoramic xray does not have the same detail that the dentist needs but orthodontists use it because it allows us to see structures not visible on the more detailed films (relationships of roots to each other, inclination of teeth, impacted teeth, size of unerupted teeth, sinuses, jaw joints, third molars, jaw symmetry, etc.).
The lateral cephalometric xray is essentially an xray of your skull from the side view. On this xray, I evaluate the relationships of the top and bottom jaw bones and to the skull and soft tissue, growth pattern, jaw symmetry, and inclinations of the front teeth relative to their respective jaw bones and overlying soft tissue.
I take periapical xrays of the upper and lower incisors becuase these are areas that are usually not adequately captured by the panoramic xray (due to the way this xray is captured).
The digital photos allow me to evaluate such things as the smile line and lip posture, soft tissue support from the teeth and jaw bones, gum line, tooth size and shape, bite relationships, etc.
The study models enable me to see areas not viewable with the photos (posterior teeth not able to be photographed, looking at the model from the back to see the teeth from their inside surfaces and how they are inclined inside-outside-wise, etc.).