Objectives: To analyze the diagnostic value of the clinical and radiographic investigation of the interface of two-piece implant systems under the variables crevice size of the microgap, clinical experience, radiograph exposure time, prosthesis design, and type of evaluation. Method and Materials: A simulated mandibular cast with five screw-retained implants (Straumann) providing three different prosthesis designs displayed artificially created proximal, visually inaccessible microgaps of unequal sizes or junctions without any measurable gap formation. Three groups of 15 investigators each with a different degree of clinical experience evaluated the implant-abutment interfaces of the cast clinically and radiographically. The investigation was conducted on the basis of a scoring form adapted from the receiver operating characteristic (ROC) 5-choice method. Radiographs were prepared in two exposure times (0.1 second, 0.2 second) for each junction. Radiographs of the initial situation without any measurable gap formation were shown as a control and to detect false-positive scores for each gap size. A 10-point SEM measurement of the junctions served for standardization purposes. Statistical methods included ROC analysis, kappa analysis, and a regression analysis (α = .05). Results: Gaps greater than 150.9 µm (P .001) were detected 227% more frequently and gaps greater than 189.7 µm 292% more frequently via radiographic examination. Kappa values were adequate for the radiographic examination and unsatisfactory for clinical examination. Prosthetic superstructure and exposure time did not adversely affect the diagnosis. Clinical experience improved the detection of microgaps significantly. Conclusion: A relationship between the size of microgaps and the examiners' ability to detect them can be established. Whereas tactile examination alone is not accurate enough, radiographic analysis affiliated with a certain degree of clinical experience possesses features for an adequate clinical management of restoration defects. Schlagwörter: abutment, clinical investigation, exposure time, implant, microgap, prosthetic superstructure, radiographic examination