title: Which surface properties enhance bone response to implants? Comparison of oxidized magnesium, TiUnite, and Osseotite implant surfaces.
abstract: OBJECTIVE
  This study compared the speed and strength of osseointegration and osteoconductivity between an oxidized experimental magnesium (Mg) implant, an oxidized commercially available TiUnite implant, and a dual acid-etched surface Osseotite implant. The aim was to investigate which surface properties enhance bone response to implants, and thereby to test a biochemical bonding theory.
  
  
  METHODS
  A total of 60 screw implants (20 of each design) were inserted through 1 cortex into the tibiae of 10 rabbits. Surface chemistry, oxide thickness, morphology, crystal structure, and surface roughness were evaluated. After healing times of 3 and 6 weeks, all bone implants were unscrewed with removal torque (RTQ) devices, and the bone specimens were subjected to histomorphometry.
  
  
  RESULTS
  RTQ values for Mg, TiUnite, and Osseotite implants were 27.1, 21.3, and 15.4 Ncm, with new bone formation values of 29%, 18%, and 15%, respectively, at 3 weeks. At 6 weeks the RTQ values were 37.5, 36.4, and 21.5 Ncm, with new bone formation values of 39%, 31%, and 26%, respectively.
  
  
  CONCLUSIONS
  Mg implants demonstrated significantly greater RTQ values (P = .008 and P = .0001) and more new bone formation (P = .031 and P = .030) than Osseotite at 3 and 6 weeks, respectively. Mg implants also showed higher RTQ values at 3 weeks and new bone formation at 6 weeks than TiUnite, but neither were significant (P > .05). TiUnite showed significantly higher RTQ values than Osseotite at 6 weeks (P = .001), but was not significant at 3 weeks (P > .05). Osseointegration rate (deltaRTQ/deltaweeks) was significantly faster for Mg (P = .011) and TiUnite (P = .001) implants between 3 and 6 weeks of healing time, but was not significant for Osseotite.
  
  
  CONCLUSIONS
  The results indicate that surface chemistry facilitated more rapid and stronger osseointegration of the Mg implants despite their minimal roughness compared to the moderately roughened TiUnite. This suggests potential advantages of Mg implants for reducing high implant failure rates in the early postimplantation stage and in compromised bone, making it possible to shorten bone healing time from surgery to functional loading, and enhancing the possibility of immediate/early loading.
authors.affiliation: Department of Biomaterials/Handicap Research, Institute for Surgical Sciences, Göteborg University, Göteborg, Sweden. young-taeg.sul@hkf.gu.se
authors.forename: Young-Taeg
authors.initials: YT
authors.lastname: Sul
authors.forename: Carina
authors.initials: C
authors.lastname: Johansson
authors.forename: Tomas
authors.initials: T
authors.lastname: Albrektsson
mesh_terms: D000818:Animals; D003461:Crystallography; D015921:Dental Implants; D003764:Dental Materials / Q000737:chemistry*; D017267:Dental Prosthesis Design; D004577:Electron Probe Microanalysis; D008277:Magnesium Oxide / Q000737:chemistry*; D008297:Male; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D016348:Osseointegration / Q000502:physiology*; D010012:Osteogenesis / Q000502:physiology*; D016062:Porosity; D011817:Rabbits; D013499:Surface Properties; D013977:Tibia / Q000601:surgery / Q000648:ultrastructure; D013997:Time Factors; D014025:Titanium / Q000737:chemistry*; D019415:Torque; D014945:Wound Healing / Q000502:physiology
chemical_list: D015921:Dental Implants; D003764:Dental Materials; C009495:titanium dioxide; D008277:Magnesium Oxide; D014025:Titanium