Evaluation of Electric Discharge Machining to achieve Passive Fit of Implant Superstructure: An in vitro Study

Objective: To evaluate marginal discrepancies between cast implant superstructure and EDM processed implant structure. Materials and methods: For the purpose of this study, an experimental model was prepared on which nine cast implant superstructure in nickel-chromium were fabricated which was then subjected to EDM processing. One-screw test was used to verify fit of superstructure both preand post-EDM processing. Photo/Image analyzer was used to evaluate the marginal discrepancy. To reduce the error of measurement, nine readings were taken of each implant abutment junction, i.e. overall 324 readings preand post-EDM processing was made. Results: All implant superstructure fabricated by investment casting procedure in nickel-chromium alloy showed negative one-screw test, i.e. they were fitting actively on abutment head and were sitting passively after EDM processing. Mean marginal opening of cast implant superstructure before EDM processing was 95.93 microns and 22.76 microns after EDM processing. Conclusion: Nickel-chromium alloy can be used for fabrication of implant superstructure with EDM as programmed refining procedure to achieve passive fit.