Comparison of initial implant stability of implants placed using bicortical fixation, indirect sinus elevation, and unicortical fixation

Andrea Hsu, Wook Jin Seong, Ryan Wolff, Lei Zhang, James Hodges, Paul S. Olin, James E. Hinrichs

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


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 floor (bicortical fixation) achieved primary and/or secondary stability comparable to that of short implants only engaging alveolar crest cortical bone (unicortical fixation) or implants engaging both the crest and sinus floor 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 floor as confirmed by preoperative CBCT were recruited. Forty-five 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 fixation: 71.4 [standard error = 2.1]), unicortical fixation: 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 fixation did not differ significantly from those of unicortical fixation and indirect sinus elevation. However, use of the bicortical fixation technique is warranted since it is simpler and more economical than indirect sinus elevation; plus, it allows for longer implants than the unicortical fixation while yielding similar secondary implant stability.

Original languageEnglish (US)
Pages (from-to)459-468
Number of pages10
JournalInternational Journal of Oral and Maxillofacial Implants
Issue number2
StatePublished - 2016

Bibliographical note

Funding Information:
This study was partially supported by Dentsply Implants IIS Grant (D-2010-021). The authors gratefully acknowledge Drs Heather Conrad and Jason Chong for their help in recruiting patients to this study, Mr Calvin Won-Young Chang for collecting and organizing data, and Dr Mansur Ahmad for his generous support in imaging. The authors would also like to express their gratitude for all residents and faculty members who performed the surgeries and restorations on their patients during and beyond the study. Research reported in this publication was supported by the National Center for Advancing Translational Sciences of the National Institutes of Health Award Number UL1TR000114. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Publisher Copyright:
© 2016 by Quintessence Publishing Co Inc.


  • Bicortical fixation
  • Initial implant stability


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