the purpose of the study is to compare the effect of different type of implant abutment connection system (external hexagonal, internal hexagonal and internal conical) of used implants under the overdenture in fatigue life of remaining bone of hemimandible.
Materials & methods: A three-dimensional finite element study model was constructed and duplicated three times. The model was composed of hemimandible screwed with reconstructive plate and restored by overdenture. The overdenture was retained by three implants of the same type of (IACS) at three positions. The only difference between the three models was the type of IACS used. Model (A) had implants of external hexagonal connection system, Model (B) had implants of internal hexagonal connection and model (C) had internal conical connection
Results: bone of internal hexagonal connection model showed largest number of fatigue life cycles, whereas external hexagonal connection showed smallest one and the values of internal conical connection model was intermediate
Conclusion: under the limitations of the current study, it may be concluded that using internal hexagonal IACS in implant supported mandibular overdenture rehabilitating hemimandible may be the most suitable type