Purpose: To stabilize overdentures, a wide range of attachments to implants is suggested. Although there is evidence that denture stability is an important factor for patient satisfaction, there are no data on how these attachments may reduce denture mobility. It was the purpose of this study to compare the effects of different types of attachments on the mobility of implant-stabilized overdentures in vitro, designing a measurement device that could also be used in vivo. Materials and Methods: On an acrylic model with 2 implants in the canine areas, magnets were fixed to one of the implant abutments. Four Hall-effect devices were attached to the denture opposite the magnet, which allowed contact-free measurements of denture movements. Results: In vitro experiments loading an overdenture showed very small, largely insignificant differences in denture mobility when different bar or ball attachments were used. Geometric aspects of load application were more important than the choice of attachment. Conclusion: The measurements gave no guide to the choice of an attachment. The similarity of the attachments must be confirmed by in vivo measurements.