Objectives: An in vitro model was used to assess the ability of standa
rd radiographic techniques to detect marginal overhangs of resin compo
site luting agents beside porcelain and resin composite inlays. Method
s: The radiodensity of five commercially available luting resins was d
etermined using ISO 4049 methodology, For four of the luting agents, a
rtificial overhangs (0.5 x 0.5 x 2 mm) were created at the cervical ma
rgin of standard resin composite and porcelain inlays. Radiographs wer
e recorded, using wax as a tissue equivalent, and the overhangs reduce
d incrementally in depth by 0.5 mm with serial images at each depth. T
he images were assessed in random sequence by three observers. Results
: There were significant differences between the radiopacity of the lu
ting resins. These correlated well with the ability of the observers t
o detect marginal overhangs adjacent to resin composite inlays. Conclu
sions: Even with the most radiopaque luting material, a substantial ma
rginal ledge could not be detected in association with a radiopaque re
sin composite inlay. The threshold for detection of the overhang was l
ower when using a radiolucent porcelain inlay.