A two dimensional finite element model was constructed to analyze the mechanical behavior of four unit fixed partial dentures (FPD) with a 2nd premolar abutment either employing a rigid or nonrigid connector and a 2nd molar abutment(Branemark implant, IMZ implants and natural tooth). Gap elements were used to model the clearance space of the nonrigid connectors and each components of implants. All FPDs with a implant abutment alter the patterns of stress distribution and displacement, but the magnitude of stress in the periodontium was not greater than that of the control. A FPD with rigid connectors induced the smaller stresses in the periodontium than a FPD with a nonrigid connector. A FPD with a Branemark implant exhibited the more desirable mechanical stress states as compared to the IMZ implants with IME or IMC.