Using computers to diagnose and plan treatment of approximal caries. Detected in radiographs.

Two of the authors developed a computer-based software system that is capable of diagnosing approximal caries and making decisions about restorative care. The system was compared with decisions made by a group of experienced clinicians. The results indicate that the clinician viewers overall correctly identified a similar number of surfaces as the software, but from viewer to viewer, there was more variability in the number of surfaces identified correctly than in those identified correctly by the software users. Software packages such as this have the potential to raise overall accuracy by increasing the consistency of treatment decisions over time.

Evaluation of off-axis projection geometry in dental panoramic radiography.

New electronic imaging capabilities afforded by the use of linear charged-couple device arrays allow acquisition of three-dimensional information through simultaneous recordings from multiple sensors situated at different fixed angles. In theory, the resulting data can be processed to yield images tailored to specific diagnostic tasks that can be produced and manipulated on demand after exposure. The first step to determine the practical potential of such a system in panoramic radiography is to demonstrate the degree to which specific changes in projection geometry can be used to improve performance of selected diagnostic tasks of clinical interest in dentistry. Hence, the purpose of this investigation was to explore the potential to reduce proximal overlap that exist in current panoramic radiographs and also to displace the blurred image of the spine from areas of diagnostic interest through the use of off-axis projection geometry of the slit beam of radiation. As the off-axis angulation increased, more embrasures in the different areas of the dental arches of skull specimens were opened; the effects of beam angulation in the number of open embrasures was statistically significant (ANOVA, p < 0.05). A hypothetical multibeam system significantly improved the projection geometry toward the creation of images that contain little, if any, proximal overlap when compared with the conventional bilaterally symmetrical projection geometry system (t test, p < 0.001). At 6 degrees off-axis projection angle, the system was able to clear completely the anterior area from the superimposing shadow of the spinal column. The results show that multibeam alternatives to the single beam projection can significantly improve diagnostic quality in panoramic radiographs.

Evaluating student progress through error reduction in intraoral radiographic technique.

A simple system was developed to collate the errors made when radiographic surveys are taken of the complete mouth. A radiographic critique form was used to evaluate each radiograph. This study used 1150 complete-mouth radiographic surveys made by junior dental students. From a total of 24,150 radiographs, 2238 were clinically unacceptable as a result of one or more errors in technique. No retakes caused by processing or mechanical errors were considered. The four major errors that were found in the study included cone cutting (11.17%), incorrect vertical angulation (11.75%), incorrect horizontal angulation (4.6%), and incorrect film placement (64.9%). Although expected, perhaps the most noteworthy finding was that there was a statistically significant difference between the performance of students during the first quarter as opposed to the third quarter of clinical training; this indicated the need for a minimum of twenty to twenty-five complete mouth radiographic surveys to achieve minimal technical proficiency.

Radiation exposure and distribution measurements for three panoramic x-ray machines.

1. Exposures to internal sites in the phantom varied as follows: Panorex, 0.3 mr to 2.4 r; Orthopantomography, 0.4 mr to 0.8 r; Panelipse, 0.2 mr to 1.4 r. 2. With the phantom exposed for a normal-density radiograph at 65 KVP, the average radiation exposure at the sites measured were for the Panorex, Orthopantomograph, and Panelipse respectively: 8, 13, and 4 mr at the pituitary gland; 22, 62, and 8 mr at the superior area of the parotid gland; 13, 8, and 5 mr at the thyroid gland; 343, 425, and 365 mr at the submaxillary gland; and 50, 154, and 272 mr at the base of the tongue. 3. External exposures to the phantom and patients were found to be in good agreement at the low KVP. At the high KVP (using patients who were larger than the phantom), exposures at lateral and posterior sites showed relatively good agreement between phantom and patients, while exposures at anterior sites were less in patients. 4. The average stray radiation measurement at 1 meter from the phantom during pantomography with the three machines was 0.125 mr per exposure cycle. Individual averages were: Panorex, 0.10 mr; Orthopantomograph, 0.13 mr; and Panelipse, 0.15 mr.