IN-VITRO CHANGES IN CLIPS AND BARS USED TO RETAIN IMPLANT OVERDENTURES

Although implant retained overdentures are a less expensive alternativ e to fixed implant-supported prostheses in certain situations, problem s with retentive clips fracturing and needing frequent replacement hav e been reported. This study compared baseline and posttest retention o f metal and plastic clip-retained overdenture analogs and monitored su rface changes in bars and clips throughout the testing process. A labo ratory model was made with two implant analogs processed into an acryl ic resin platform to which three bars were fitted. Two overdenture ana logs were made and retained on the model with metal or plastic clips. Each bar-clip assembly was subjected to 5500 insertion and removal cyc les to simulate 3 years of in vivo insertion and removal. Although the differences in retention between metal and plastic clips and between clips before and after testing were statistically significant, it is q uestionable whether they are clinically significant. Neither clip frac ture nor loss occurred during this study, which suggests that it may b e functional or parafunctional loading and not repeated insertion and removal of an implant overdenture that may cause the stated problems.