EFFECTS OF ATTACHMENT CLIPS ON OCCLUSAL FORCE TRANSMISSION IN REMOVABLE IMPLANT-SUPPORTED OVERDENTURES AND CANTILEVERED SUPERSTRUCTURES

Attachment clips are commonly used to provide retention for removable implant-supported overdentures. In this study, the effects of attachme nt clips on occlusal force transmission in four implant-supported over dentures with cantilever extensions were investigated using beam theor y. Distributions of moments and of forces in overdenture, clips, canti levered superstructure, and implants were calculated as functions of p osition, number, and stiffness of attachment clips. Three-, four-, and five-attachment clip configurations were analyzed. Results showed tha t maximum bending moments and forces in all components are strong func tions of position, number, and retention of attachment clips, while th e effects of attachment clip stiffness are negligible. Increasing the number of attachment clips from three to five results in a significant decrease of maximum bending moments in the superstructure and implant . For a nide range of attachment clip positioning, the maximum tensile force on the implants is as high as half the applied load. At least o ne attachment clip for all configurations is also subjected to tensile force, which can cause it to slip out from the superstructure and inc rease maximum bending moment in the superstructure and implants.