Influence of implant types on the stress distribution of mandibular free-end removable partial denture

Objective: To study the stress distribution and displacement of mandibular free-end removable partial denture with diff-erent types of implants.Methods: 16 three-dimensional finite element models of implant-tooth-supporting Kennedy Class I removable partial denture were created.Effects of different types of implants(ITI Straumann and NOBEL ReplaceTM Tapered)were evaluated under vertical loading.The variation of displacement of periodontium under saddle and the stress of the bone around implants,the periodontal membrane of abutments and the residual ridge was analysed and compared among the type of implant.Results: No matter how the parameter of implants altered,the stresses within implants concentrated at the cervical cortical bone around implants.Maximum stress within cortical bone around the implant decreased with the increasing of diameter of the same type of implant,but the maximum stress and displacement of abutments and periodontium under saddle had no significant differences among the implant types.With the same variation of length(from 6 mm to 10 mm),maximum stresses within cortical bone around ITI Straumann implants with the diameter of 4.1 mm(or 3.3 mm) were lower than NOBEL ReplaceTM Tapered implants with 4.3 mm(or 3.5 mm).Conclusion: The stress distribution of periodontal membrane of abutments and periodontium under saddle were not affected by implant shape,length and diameter;more attention should be paid to diameter than to length for the choices among the same type of implant;shape may have more influence than diameter upon the peri-implant stress among different types of implants.