Objective      To establish three-dimensional finite element models of the mandible and compare the effects of implant-supported splinted and un-splinted superstructures on stress changes of the mandible and implants of edentate patients.       Methods      The scanning files of clinical mandibular cone beam computerized tomography (CBCT) data and standard crown data were collected

and reverse engineering software was used to establish three-dimensional finite element models of mandibular implant-supported splinted and un-splinted superstructures. The stress changes of the mandible

implants and superstructures under normal bite force were analyzed with finite element analysis software (ANSYS).       Results      Under normal bite force

von-Mises stress of the cortical bone and cancellous bone of the splinted model was smaller than that of the un-splinted model. The vo-Mises stress of each implant of the splinted model was smaller than that of the un-splinted model

and the stress was more concentrated in the un-splinted model. The von-Mises stress of the splinted superstructure was larger than that of the un-splinted superstructure.       Conclusion      The implant-supported splinted superstructure has better protective effect on the mandible and implants but not on the superstructure itself as compared with the un-splinted superstructure in the biomechanical aspect.