Comparison of Initial Implant Stability of Implants Placed Using Bicortical Fixation, Indirect Sinus Elevation, and Unicortical Fixation

Purpose: The aim of this study was to determine if self-threading dental implants placed using stopper drills to bicortically engage both the alveolar crest and sinus loor (bicortical ixation) achieved primary and/or secondary stability comparable to that of short implants only engaging alveolar crest cortical bone (unicortical ixation) or implants engaging both the crest and sinus loor but via greenstick fracture and grafting (indirect sinus elevation). Materials and Methods: Thirty-eight patients exhibiting 7 to 11 mm of bone coronal to the sinus loor as conirmed by preoperative CBCT were recruited. Forty-ive implants were randomly assigned to one of the placement techniques. No patient received more than two implants, which were placed in opposite sides of the maxilla while using different surgical techniques. An Osstell ISQ was employed immediately after implant placement to measure stability six times in a buccolingual dimension. Secondary stability was measured at stage-two surgery after a 3- to 6-month healing period. Results: The greatest primary implant stability was achieved via indirect sinus elevation. However, no statistically significant difference was found among the three surgical techniques (P = .13; bicortical ixation: 71.4 [standard error = 2.1]), unicortical ixation: 69.6 [2.1], indirect sinus elevation: 75.9 [2.3]). The three techniques had similar secondary stability (P > .999; 79.9 [1.2], 80.0 [1.2], and 80.0 [1.3], respectively). Baseline residual ridge height measured on CBCT was similar (P = .1; 8.8, 9.9, and 9.4 mm, respectively), but implant diameter and length placed in the maxilla differed (P = .03/P < .001; 4.7/11.4 mm, 4.3/8.1 mm, and 4.7/11.8 mm, respectively). Primary implant stability was significantly correlated to CBCT bone density (r = 0.37). Conclusion: Primary and secondary implant stabilities of bicortical ixation did not differ significantly from those of unicortical ixation and indirect sinus elevation. However, use of the bicortical ixation technique is warranted since it is simpler and more economical than indirect sinus elevation; plus, it allows for longer implants than the unicortical ixation while yielding similar secondary implant stability.