title: Peri-implant bone reactions to immediate implants placed at different levels in relation to crestal bone. Part II: a pilot study in dogs.
abstract: OBJECTIVE
  The aim of the present study was to evaluate bone-to-implant contact (BIC) and bone remodeling dynamics after immediate implant placement at different levels in relation to the crestal bone with two different implant designs in beagle dogs.
  
  
  METHODS
  The mandibular second, third and fourth premolars of six beagle dogs were extracted bilaterally and three implants were immediately placed in the hemi-arches of each dog. Randomly, three cylindrical and three tapered implants were inserted crestally (control group) or 2 mm subcrestally (test group). Both groups were treated with a minimal mucoperiosteal flap elevation approach. A gap from the buccal cortical wall to the implant was always left. Three dogs were allowed a 4-week submerged healing period and the other three an 8-week submerged healing period. The animals were sacrificed and samples were obtained. Biopsies were processed for ground sectioning. Histomorphometric analysis was carried out in order to compare BIC, de novo bone formation and bone remodeling.
  
  
  RESULTS
  All implants osseointegrated clinically and histologically. Healing patterns examined microscopically at 4 and 8 weeks for both groups (crestal and subcrestal) yielded similar qualitative bone findings. The total BIC mean value for the crestal group was 36.48 ± 3.4% and for the subcrestal group was 41.46 ± 4.2%. The mean percentage of newly formed BIC was greater with the cylindrical implant design (46.06 ± 1.09%) than with the tapered design (33.89 ± 1.72%). There was less bone resorption in the subcrestal group (test) than crestal group (control).
  
  
  CONCLUSIONS
  These findings suggest that apical positioning of the top of the implant does not jeopardize bone crest and peri-implant tissue remodeling. However, less resorption of the lingual crest may be expected when implants are placed 2 mm subcrestally. Moreover, higher BIC values were found in cylindrical implants placed subcrestally.
authors.affiliation: Department of General and Implant Dentistry, Faculty of Medicine and Dentistry, University of Murcia, Murcia, Spain.
authors.forename: Bruno
authors.initials: B
authors.lastname: Negri
authors.affiliation: Department of General and Implant Dentistry, Faculty of Medicine and Dentistry, University of Murcia, Murcia, Spain.
authors.forename: José Luis
authors.initials: JL
authors.lastname: Calvo-Guirado
authors.affiliation: Department of General and Implant Dentistry, Faculty of Medicine and Dentistry, University of Murcia, Murcia, Spain.
authors.forename: María Piedad
authors.initials: MP
authors.lastname: Ramírez-Fernández
authors.affiliation: Department of General and Implant Dentistry, Faculty of Medicine and Dentistry, University of Murcia, Murcia, Spain.
authors.forename: José
authors.initials: J
authors.lastname: Maté Sánchez-de Val
authors.affiliation: Department of Pharmacological Interactions in Dentistry, Dental School, University of Granada, Granada, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Guardia
authors.affiliation: Department of Pathology, School of Veterinary, University of Lugo, Santiago de Compostela, Spain.
authors.forename: Fernando
authors.initials: F
authors.lastname: Muñoz-Guzón
mesh_terms: D000539:Alveolar Process / Q000473:pathology / Q000601:surgery*; D000704:Analysis of Variance; D000818:Animals; D016723:Bone Remodeling; D001862:Bone Resorption / Q000473:pathology; D003758:Dental Implantation, Endosseous / Q000379:methods*; D015921:Dental Implants; D018772:Dental Marginal Adaptation; D017267:Dental Prosthesis Design; D004285:Dogs; D020007:Implants, Experimental; D008334:Mandible / Q000601:surgery; D016348:Osseointegration / Q000502:physiology; D010865:Pilot Projects; D011897:Random Allocation; D014945:Wound Healing / Q000502:physiology*
chemical_list: D015921:Dental Implants