摘要Objective To evaluate the success rates of immediate and delayed placement of implants with respect to the causes of tooth extraction and implant positions.Methods A total of 310 dental implants (immediate implants∶ delayed implants=76∶ 234) were inserted into 80 patients. The types, sizes and positions of the implants and the causes of tooth extraction were recorded. We then investigated the relationship of implant loss with the causes of tooth extraction and placement methods. Results A higher failure rate was found for the implants in the posterior region of the maxilla, and when periodontitis was cited as a reason for tooth extraction. The overall success rates were 93.4% and 95.7% in the immediate and delayed implant placement groups, respectively, after a 2-year follow-up. No obvious relationship of success rate was observed with the implant placement method, cause of tooth extaction, and implants' position. Conclusion The immediate placement of implants into fresh extraction sockets could offer advantages over the delayed implant placement. It seems to be a safe and predictable method for patients.