Bicortical dental implantation technique was regarded as an alternative to internal sinus lift technique with bone grafting in dental implantation in atrophic maxillae. The purpose of this retrospective study was to evaluate the survival rates and bone stability of 6- and 10-mm implants in the posterior maxilla using bicortical dental implantation techniques after 1 to 5 years of prosthetic loading. A total of 53 patients received posterior maxillary implant treatments. Of these, 31 patients received bicortical dental implantation (group A), and 25 patients received traditional implantation (group B). Three patients received an implant with bicortical engagement and another implant without bicortical engagement. The survival rates were calculated, and the marginal bone heights were measured on radiographs at baseline and follow-up. The survival rate of group A was 100%. In contrast, the survival rate of group B was only 74.68%, with survival rates of 51.85% in the 6-mm implant subgroup and 93.33% in the 10-mm implant subgroup. In terms of variations in implant marginal bone heights, a significant difference was found only between the 6-mm subgroups in groups A and B. Significant intrasinus bone gain was found on the mesial and distal sides of the implants in group A. Application of bicortical dental implantation techniques with 6-mm implants could achieve better clinical outcomes in atrophic posterior maxillae.