title: Comparison of push-in versus pull-out tests on bone-implant interfaces of rabbit tibia dental implant healing model.
abstract: OBJECTIVE
  This study aimed to investigate whether push-in and pull-out tests measure mechanical properties of the bone-implant interface differently, and which test is more sensitive to changes over the healing period.
  
  
  METHODS
  Two identical self-threading dental implants (3.3×8.5mm) were placed in medial surface of the proximal condyles of left and right tibias of 20 rabbits (40 implants total). Five rabbits each were sacrificed after 1, 4, 8, and 12 weeks of healing. Push-in test was performed on one side's tibia implant and pull-out on the other side's implant, at a rate of 6mm/min. Primary and secondary implant stabilities and tibia weight were measured on all implants.
  
  
  RESULTS
  The push-in test generated significantly higher failure load (p=.0001; 530N vs 279N), lower displacement at failure (p=.0003; 0.436mm vs 0.680mm), and higher interface stiffness (p<.0001; 1,641N/mm vs 619N/mm) than pull-out test. Failure load, stiffness, and secondary implant stability were significantly higher for longer compared with shorter healing periods, while displacement, tibia weight, and primary stability were not. Failure load and stiffness differed significantly for four healing times for the push-in but not for the pull-out test. Failure load was significantly correlated with secondary implant stability for both push-in (r=0.66) and pull-out (r=0.48) tests, but stiffness was significantly correlated with secondary stability only for the push-in test (r=0.72; pull-out test r=0.40).
  
  
  CONCLUSIONS
  The push-in test appeared more sensitive than pull-out to changes in mechanical properties at bone-implant interfaces during healing in rabbit tibia model.
authors.affiliation: Division of Prosthodontics, Department of Restorative Sciences, School of Dentistry, University of Minnesota, Minneapolis, MN, USA. seong001@umn.edu
authors.forename: Wook-Jin
authors.initials: WJ
authors.lastname: Seong
authors.forename: Shahrzad
authors.initials: S
authors.lastname: Grami
authors.forename: Soo Cheol
authors.initials: SC
authors.lastname: Jeong
authors.forename: Heather J
authors.initials: HJ
authors.lastname: Conrad
authors.forename: James S
authors.initials: JS
authors.lastname: Hodges
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D015921:Dental Implants; D017267:Dental Prosthesis Design; D017268:Dental Prosthesis Retention; D003799:Dental Stress Analysis / Q000295:instrumentation; D004548:Elasticity; D005260:Female; D009929:Organ Size; D016348:Osseointegration / Q000502:physiology*; D011817:Rabbits; D013314:Stress, Mechanical; D013499:Surface Properties; D013977:Tibia / Q000502:physiology*; D013997:Time Factors; D014732:Vibration; D014945:Wound Healing / Q000502:physiology
chemical_list: D015921:Dental Implants