Objective: CAD/CAM is based on optical or mechanical scanning of tooth surfaces. The aim of this in vitro study was to investigate the influence of three different scan sprays on the proliferation, viability, and adenylate kinase (ADK) release of human fibroblasts. Method and Materials: Three different scan sprays (ScanDry, ScanSpray Luer Classic, and CEREC Optispray) were tested in vitro to determine their effects on proliferation, viability, and ADK release of human periodontal fibroblasts. A defined amount of the test material was sprayed into 96 multiwell plates, dried, and incubated with fibroblasts. The LIVE/DEAD Viability Assay, a two-color fluorescence-based method, was used to determine the cytotoxic potential (the AlamarBlue Assay for the proliferation rate and the ToxiLight BioAssay for the release of ADK). Results: There were differences between the scan sprays concerning inhibition of the proliferation and viability of fibroblasts. All materials inhibited the fibroblast proliferation and viability compared with the control group (P .001), and there were also significant differences among the scan spray groups. The scan sprays led to a greater release of ADK, but a significant difference could be found only between ScanSpray Luer Classic and CEREC Optispray (P .009). Conclusion: The results of this study proved that the scan sprays do not induce a significantly higher ADK release than the control group. The inhibiting effect on the fibroblast proliferation can be attributed to a material-independent phenomenon. Further experiments are necessary to validate the present data. Keywords: CAD/CAM, CEREC, cytocompatibility, in vitro, optical scanning, scan spray