title: Comparison between freestanding and tooth-connected partially stabilized zirconia implants after two years' function in monkeys: a clinical and histologic study.
abstract: BACKGROUND
  Partially stabilized zirconia implants placed by a 1-stage procedure have been previously shown to obtain initial osseointegration under clinically unloaded condition. However, it is unknown whether freestanding and tooth-connected partially stabilized zirconia implants can maintain a long-term direct bone-implant interface.
  
  
  OBJECTIVE
  This study examined the possibility of the long-term stability of osseointegration around partially stabilized zirconia implants with a 1-stage procedure with different loading designs.
  
  
  METHODS
  Thirty-two partially stabilized zirconia implants were placed into the mandibles of 8 monkeys. Three months after implant placement, 3 types of superstructure were provided in each animal to obtain different concepts of support as (1) single freestanding implant support, (2) connected freestanding implant support, and (3) a combination of implant and tooth support. At 12 and 24 months after loading, clinical, histologic, and histomorphometric evaluations of peri-implant tissues were performed on 28 implants.
  
  
  RESULTS
  No clear difference in clinical features was observed among the different types of support. Direct bone apposition to the implant was generally seen in all groups. Histometrically, bone contact ratio ranged between 66% and 81%, and bone area ratio varied between 49% and 78% at 24 months after loading. These values showed almost no difference among single freestanding, connected freestanding, and implant-tooth supports of partially stabilized zirconia implants.
  
  
  CONCLUSIONS
  In a primate model, partially stabilized zirconia implants placed with a 1-stage procedure achieve long-term stability of osseointegration with the use of single freestanding, connected freestanding, and implant-tooth supports.
authors.affiliation: Hiroshima University School of Dentistry, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Akagawa
authors.forename: R
authors.initials: R
authors.lastname: Hosokawa
authors.forename: Y
authors.initials: Y
authors.lastname: Sato
authors.forename: K
authors.initials: K
authors.lastname: Kamayama
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001641:Bicuspid; D000044:Dental Abutments / Q000706:statistics & numerical data; D003722:Dental Alloys; D003758:Dental Implantation, Endosseous / Q000379:methods / Q000706:statistics & numerical data; D015921:Dental Implants / Q000706:statistics & numerical data; D017267:Dental Prosthesis Design / Q000379:methods / Q000706:statistics & numerical data; D005260:Female; D008251:Macaca; D008334:Mandible / Q000473:pathology; D008963:Molar; D013997:Time Factors; D015040:Zirconium
chemical_list: D003722:Dental Alloys; D015921:Dental Implants; D015040:Zirconium; C028541:zirconium oxide