title: Two human hydroxyapatite-coated dental implants retrieved after a 14-year loading period: a histologic and histomorphometric case report.
abstract: BACKGROUND
  Controversy over the long-term clinical effectiveness of hydroxyapatite (HA)-coated dental implants still persists, despite numerous clinical studies documenting high survival rates. Concerns about the degradation of the coating over the years have been raised; it has been speculated that resorption of the HA could produce a space between the implant and the bone with a resultant mechanical instability.
  
  
  METHODS
  Two HA-coated implants were retrieved due to a fracture of the abutment screws after a loading period of 14 years and were treated to obtain thin ground sections for histologic evaluation.
  
  
  RESULTS
  At low-power magnification, it was possible to observe that the HA coating was in contact with mature bone. No gaps or connective fibrous tissue was found at the implant-bone interface. No epithelial downgrowth was present. No acute or chronic inflammatory cell infiltrate was present at the implant-bone interface. No foreign body reaction was present in the peri-implant tissues. Some osteocytes were in direct contact with the coating. For implant 1, the percentage of bone-titanium contact was 25% +/- 2.1%, and the percentage of bone-HA contact was 35% +/- 1.4%. The total bone-implant contact was approximately 60%. The HA coating appeared to be resorbed in 46% +/- 3.2% of the implant perimeter, especially in the coronal portions of the implant. For implant 2, the mean percentage of bone-HA contact was 13% +/- 1.8%, and the mean percentage of bone-titanium contact was 15% +/- 2.3%. The total bone-implant contact was approximately 28%. The HA coating appeared to be resorbed for a mean of 68% +/- 4.1% of the implant perimeter, especially in the coronal portion of the implant.
  
  
  CONCLUSIONS
  No acute or chronic inflammatory cell infiltrate was present in the peri-implant tissues. No signs of coating infection, fatigue, or failure were observed in two specimens. The HA coating may not be susceptible to degradation or dissolution under long-term function.
authors.affiliation: Dental School, University of Chieti-Pescara, Chieti, Italy.
authors.forename: Giovanna
authors.initials: G
authors.lastname: Iezzi
authors.forename: Antonio
authors.initials: A
authors.lastname: Scarano
authors.forename: Giovanna
authors.initials: G
authors.lastname: Petrone
authors.forename: Adriano
authors.initials: A
authors.lastname: Piattelli
mesh_terms: D020099:Coated Materials, Biocompatible / Q000494:pharmacology*; D000044:Dental Abutments; D003758:Dental Implantation, Endosseous; D019250:Dental Implants, Single-Tooth; D003773:Dental Plaque; D020878:Device Removal; D017886:Durapatite / Q000494:pharmacology*; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008437:Maxilla / Q000166:cytology; D008875:Middle Aged; D016348:Osseointegration / Q000187:drug effects*; D013997:Time Factors; D014082:Tooth Fractures / Q000601:surgery; D016896:Treatment Outcome
chemical_list: D020099:Coated Materials, Biocompatible; D017886:Durapatite