title: Crestal bone changes in macrogeometrically similar implants with the implant-abutment connection at the crestal bone level or 2.5 mm above: a prospective randomized clinical trial.
abstract: OBJECTIVE
  Crestal bone loss around dental implants is a criterion for success as this could prevent loss of implant and superstructure. The macrogeometry of the implant could influence bone remodelling when the implant-abutment connection is placed at crestal bone level or above. The aim of this study was to evaluate crestal bone remodelling in a randomized clinical prospective trial in macrogeometrically similar implants with the prosthetic connection at the crestal bone level and 2.5 mm above. The null hypothesis was that there was no difference in crestal bone loss after 1 year of early loading.
  
  
  METHODS
  Patients were referred to Academic Centre of Dentistry Amsterdam for implant placement. Patients were subjected to inclusion and exclusion criteria and received a minimum of two implants: an implant with the prosthetic abutment connection at the crestal bone level (minimized collar [MC], bone level) and one with the prosthetic abutment connection 2.5 mm supracrestal (long collar [LC], tissue level). The mesial or distal location of each implant type was blinded for the patient and randomized. The implants were loaded splinted after 3 weeks of healing. The primary outcome was bone-level change assessed after 1 year of loading.
  
  
  RESULTS
  Thirty-three patients fulfilled the inclusion criteria. Thirty-nine Thommen SPI ELEMENT LC implants and 39 MC were placed, and each fixed dental prosthesis was supported by one LC and one MC implant. The intraclass correlation of measures performed by the first and second X-ray examiner was as follows: on the mesial side of the MC implant 0.990 (0.980-0.995; 95% confidence interval [CI]), 0.980 (0.962-0.990; 95% CI) on the distal side of the MC implant, 0.979 (0.959-0.989; 95% CI) and 0.988 (0.978-0.994; 95% CI) on the mesial and distal side of the LC implant, respectively. The mean bone loss of the MC implant was 0.4 ± 0.4 mm. The mean bone loss of the LC implant was 0.2 ± 0.5 mm. The paired samples t-test showed a statistically significant difference (P < 0.05) between the MC and LC implants.
  
  
  CONCLUSIONS
  Dental implants at bone level show statistically significantly (P < 0.05) more crestal bone change after 1 year of loading than a tissue-level implant.
authors: Section of Oral Implantology and Fixed Prosthetics, Department of Oral Function, Academic Centre of Dentistry Amsterdam, Amsterdam, The Netherlands.
authors: Paul
authors: P
authors: van Eekeren
authors: Section of Oral Implantology and Fixed Prosthetics, Department of Oral Function, Academic Centre of Dentistry Amsterdam, Amsterdam, The Netherlands.
authors: Ali
authors: A
authors: Tahmaseb
authors: Section of Oral Implantology and Fixed Prosthetics, Department of Oral Function, Academic Centre of Dentistry Amsterdam, Amsterdam, The Netherlands.
authors: Daniël
authors: D
authors: Wismeijer
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016301:Alveolar Bone Loss / Q000473:pathology* / Q000503:physiopathology; D016723:Bone Remodeling; D059605:Dental Implant-Abutment Design; D019094:Dental Prosthesis, Implant-Supported; D005260:Female; D006801:Humans; D008297:Male; D008334:Mandible / Q000473:pathology / Q000601:surgery; D008437:Maxilla / Q000473:pathology / Q000601:surgery; D008875:Middle Aged; D011446:Prospective Studies
keywords: clinical research; clinical trials; imaging; radiology; soft tissue-implant interactions