title: Comparison of Initial Implant Stability of Implants Placed Using Bicortical Fixation, Indirect Sinus Elevation, and Unicortical Fixation.
abstract: OBJECTIVE
  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).
  
  
  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).
  
  
  CONCLUSIONS
  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.
authors.forename: Andrea
authors.initials: A
authors.lastname: Hsu
authors.forename: Wook-Jin
authors.initials: WJ
authors.lastname: Seong
authors.forename: Ryan
authors.initials: R
authors.lastname: Wolff
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
authors.forename: James
authors.initials: J
authors.lastname: Hodges
authors.forename: Paul S
authors.initials: PS
authors.lastname: Olin
authors.forename: James E
authors.initials: JE
authors.lastname: Hinrichs
mesh_terms: D000328:Adult; D000368:Aged; D000539:Alveolar Process / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D015519:Bone Density / Q000502:physiology; D016025:Bone Transplantation / Q000379:methods; D054893:Cone-Beam Computed Tomography / Q000379:methods; D003758:Dental Implantation, Endosseous / Q000295:instrumentation / Q000379:methods*; D015921:Dental Implants; D017267:Dental Prosthesis Design; D017268:Dental Prosthesis Retention; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008437:Maxilla / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D008875:Middle Aged; D016348:Osseointegration / Q000502:physiology; D010865:Pilot Projects; D011446:Prospective Studies; D059546:Sinus Floor Augmentation / Q000295:instrumentation / Q000379:methods*; D014945:Wound Healing
chemical_list: D015921:Dental Implants