Image resolution in dental and maxillofacial radiography with the conventional and "free focus" imaging concepts.

An investigation of the resolution capability of conventional and "free focus" dental radiography on non screen film was completed. The over-all imaging performance of conventional and "free focus" radiography exposed with three types of dental x-ray machines was comparable. Conventional "long-cone" radiography produced better resolution than "short-cone" radiography. "Short-cone" radiography exposed with conventional compact dental x-ray machines provided similar or better image resolution than those exposed with larger, high-energy machines. The miniaturized dental x-ray machines used in "free focus" radiography for periapical type exposures gave a resolution which was similar to or up to 100 percent higher than in conventional "long-cone" periapical radiographs. Differences in path length of the x-ray beam during clinical applications of conventional and "free focus" radiography indicated a higher potential for image noise and degradation in conventional films. A potential for segmental variation in image resolution in surveys of the dentition was seen only in the conventional techniques. These characteristics must be balanced against a tendency to variable segmental magnification in free focus radiography. Indications, however, are that applications of "free focus" radiography may be able to improve the early diagnosis of dental disease. Periapical type surveys of the dentition produced by "free focus" radiography may require only two exposures instead of the 14 to 20 required in conventional periapical surveys and may contain characteristics of periapical as well as bitewing films. "Free focus" radiography represents an attractive alternative that may be able to accomplish substantial time savings in the practice of dental radiography.