EFFECTS OF FOCAL SPOT SIZE ON CARIES DIAGNOSIS WITH D-SPEED AND E-SPEED IMAGES

Annual measurement of the x-ray unit focal spot size has been recommen ded by the American Academy of Oral and Maxillofacial Radiology as par t of the dental radiographic quality control program. This study compa res the effects of focal spot size on caries diagnosis. Three x-ray un its with small, medium, and large focal spot sizes were used to produc e bite-wing images on extracted teeth mounted in acrylic bases. Random ized films were scored for lesion presence and depth by two general de ntists. Weighted kappa statistics were used to evaluate the agreement of reviewer caries diagnosis by film speed and focal spot size. Compar isons of caries calls with small versus medium and small versus large focal spot sizes produced weighted kappa statistics = 0.72 and 0.70, r espectively. Differences in caries calls were greater because of film speed rather than focal spot size. The results of this study suggest t hat the clinical significance of varied focal spot size is negligible. The value of annual measurement of focal spot size is questionable, a nd its recommendation should be revisited.