title: Ex vivo mechanical properties of dental implant bone cement used to rescue initially unstable dental implants: a rabbit study.
abstract: OBJECTIVE
  Dental implant bone cement (DIBC) was developed to rescue unstable implants at the time of placement. The purpose of this study was to compare the mechanical properties of bone-cement-implant interfaces of cemented implants that were unstable initially and bone-implant interfaces of self-threaded implants placed in rabbit femurs after various healing periods. Interfaces and failure modes were also characterized using histology and scanning electron microscopy (SEM).
  
  
  METHODS
  Eighty dental implants were placed in 20 rabbits. In each rabbit, two experimental and two control implants were placed in the right or left femur; one was in the distal epiphysis and the other in the cortical shaft. The experimental implants were cemented in loosely prepared bony sockets, while the control implants were self-threaded. The rabbits were sacrificed after varying healing periods. Magnetic pulse stability and push-in yield tests on ex vivo specimens measured secondary implant stability, 0.2% yield load, displacement, interface stiffness, and load at 100 μm. After loading tests, interfaces were evaluated with histology and SEM. Most analyses used mixed linear models.
  
  
  RESULTS
  The 0.2% yield load, interface stiffness, load at 100 μm, and secondary stability were significantly higher for bone-cement-implant interfaces than for bone-implant interfaces. Mechanical properties of bone-cement-implant interfaces plateaued at 1 week, with minimal change over the following 12 weeks, whereas bone-implant interfaces improved gradually. SEM and histology showed intimate bone-cement-implant interfaces without soft tissue intervention and mainly cohesive failures within DIBC. Secondary stability was significantly correlated with interface stiffness and load at 100 μm.
  
  
  CONCLUSIONS
  The results suggest that DIBC can provide early implant stability and mechanical properties superior to those of self-threaded implants while maintaining intimate interfaces without signs of osteonecrosis or soft tissue intervention.
authors.affiliation: Department of Restorative Sciences, School of Dentistry, University of Minnesota at Minneapolis, Minneapolis, MN 55455, USA. seong001@umn.edu
authors.forename: Wook-Jin
authors.initials: WJ
authors.lastname: Seong
authors.forename: Hyeon-Cheol
authors.initials: HC
authors.lastname: Kim
authors.forename: Soocheol
authors.initials: S
authors.lastname: Jeong
authors.forename: Dan L
authors.initials: DL
authors.lastname: DeVeau
authors.forename: Conrado
authors.initials: C
authors.lastname: Aparicio
authors.forename: Yuping
authors.initials: Y
authors.lastname: Li
authors.forename: James S
authors.initials: JS
authors.lastname: Hodges
mesh_terms: D000818:Animals; D001843:Bone Cements; D015921:Dental Implants; D017268:Dental Prosthesis Retention / Q000379:methods*; D003799:Dental Stress Analysis; D005260:Female; D005269:Femur / Q000601:surgery; D008855:Microscopy, Electron, Scanning; D016348:Osseointegration; D011817:Rabbits; D013052:Spectrometry, X-Ray Emission; D013499:Surface Properties
chemical_list: D001843:Bone Cements; D015921:Dental Implants