Pre-surgical dental implant assessment: A comparison between plain-film conventional tomography and digital tomography utilizing a storage phosphor plate system

The purpose of this in vitro study was to compare the accuracy of three imaging modalities, conventional film tomography, brightness, contrast and/or gamma-enhanced digital tomography and inversion gray-scale digital tomography in identifying crucial anatomical structures in implant placement. The sample included seventy-one implant sites in the posterior mandible from eleven cadaver specimens. All images were produced with a Cranex-Tome tomographic machine. Six raters viewed each group of images in a separate session and identified the superior border of the mandibular canal and the crest of the edentulous ridge. One group of images was rated twice for intra-observer reliability assessment. All tomographic images per implant site were overlaid with a gold standard tomogram which was made in the same location after marking the crest and mandibular canal on the cadaveric specimen. The identification error was recorded as the distance between the raters' marked point and the gold standard point. A repeated measures analysis of variance revealed a significant main effect for the anatomical structure of interest, indicating that the raters' error in identifying the superior border of the mandibular canal was significantly higher than the crest of the ridge. The intra-rater reliability was higher for the crest of the ridge compared to the superior border of the mandibular canal. Although there were no statistically significant differences between the three modalities tested, conventional tomography was more accurate in the identification of the crest of the edentulous ridge and the superior border of the mandibular canal.