Reproducible X-ray projection geometry in edentulous patients

Objective: To evaluate a novel fixation system for reproducible radiography in edentulous patients. Methods: A conventional extra-oral fixation system was modified with a film holder and adjustable scales. For measuring reproductivity and angulation e rrors two rods and two balls were fixed on the alveolar crests of the maxil la and the mandible and angular variations were measured. One hundred radio graphs of a conventional phantom were taken by one of the authors and by te n dental students. The angular disparity was calculated and intra- and inte roperator precision determined. Results: The average time taken to assemble the fixation system was 4 min. The 95% confidence interval for precision of the single operator was less t han 2.5 degrees in both the maxilar and mandible. The 95% confidence interv al for precision of the ten students was less than 2.2 degrees for the maxi lla and 2.7 degrees for the mandible. Then was no significant difference (P >0.05) in interoperator precision. Conclusion: The never extra-oral fixation system appears to be a potential means of obtaining reproducible radiographs of edentulous patients.