Would it be a good idea to get a full mouth series x-rays prior to a 3d CT scan for possible implants? (2 different dds's)or, not really necessary?

Good idea. A 3d scan is really a must for the implants to determine placement of the implant. Dental xrays do not show the with or contours of the bone or actually display where the nerve or sinus is located. At this time dental xrays are better for diagnosis of cavities and some other conditions. Probably because dentist are more use to reading xrays.