title: Effect of platform switching on peri-implant bone levels: a randomized clinical trial.
abstract: OBJECTIVE
  The concept of platform switching has been introduced to implant dentistry based on observations of reduced peri-implant bone loss. However, randomized clinical trials are still lacking. This study aimed to test the hypothesis that platform switching has a positive impact on crestal bone-level changes.
  
  
  METHODS
  Two implants with diameters of 4 mm were inserted epicrestally into one side of the posterior mandibles of 25 subjects. After 3 months of submerged healing, the reentry surgery was performed. On the randomly placed test implant, an abutment 3.3 mm in diameter was mounted, resulting in a horizontal circular step of 0.35 mm (platform switching). The control implant was straight, with an abutment 4 mm in diameter. Single-tooth crowns were cemented provisionally. All patients were monitored at short intervals over the course of 1 year. Standardized radiographs and microbiological samples from the implants' inner spaces were obtained at baseline (implant surgery), and after 3, 4, and 12 months.
  
  
  RESULTS
  After 1 year, the mean radiographic vertical bone loss at the test implants was 0.53±0.35 mm and at the control implants, it was 0.58±0.55 mm. The mean intraindividual difference was 0.05±0.56 mm, which is significantly <0.35 mm (P=0.0093, post hoc power 79.9%). The crestal bone-level changes depended on time (P<0.001), but not on platform switching (P=0.4). The implants' internal spaces were contaminated by bacteria, with no significant differences in the total counts between the test and the control at any time point (P=0.98).
  
  
  CONCLUSIONS
  The present randomized clinical trial could not confirm the hypothesis of a reduced peri-implant bone loss at implants restored according to the concept of platform switching.
authors.affiliation: Department of Prosthodontics, University of Berne, Berne, SwitzerlandDepartment of Oral Surgery, University of Witten/Herdecke, Witten, GermanyDepartment of Prosthetic Dentistry, Propaedeutics and Material Science, University of Bonn, Bonn, GermanyDepartment of Periodontology, Operative and Preventive Dentistry, University of Bonn, Bonn, Germany.
authors.forename: Norbert
authors.initials: N
authors.lastname: Enkling
authors.affiliation: Department of Prosthodontics, University of Berne, Berne, SwitzerlandDepartment of Oral Surgery, University of Witten/Herdecke, Witten, GermanyDepartment of Prosthetic Dentistry, Propaedeutics and Material Science, University of Bonn, Bonn, GermanyDepartment of Periodontology, Operative and Preventive Dentistry, University of Bonn, Bonn, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Jöhren
authors.affiliation: Department of Prosthodontics, University of Berne, Berne, SwitzerlandDepartment of Oral Surgery, University of Witten/Herdecke, Witten, GermanyDepartment of Prosthetic Dentistry, Propaedeutics and Material Science, University of Bonn, Bonn, GermanyDepartment of Periodontology, Operative and Preventive Dentistry, University of Bonn, Bonn, Germany.
authors.forename: Victoria
authors.initials: V
authors.lastname: Klimberg
authors.affiliation: Department of Prosthodontics, University of Berne, Berne, SwitzerlandDepartment of Oral Surgery, University of Witten/Herdecke, Witten, GermanyDepartment of Prosthetic Dentistry, Propaedeutics and Material Science, University of Bonn, Bonn, GermanyDepartment of Periodontology, Operative and Preventive Dentistry, University of Bonn, Bonn, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Bayer
authors.affiliation: Department of Prosthodontics, University of Berne, Berne, SwitzerlandDepartment of Oral Surgery, University of Witten/Herdecke, Witten, GermanyDepartment of Prosthetic Dentistry, Propaedeutics and Material Science, University of Bonn, Bonn, GermanyDepartment of Periodontology, Operative and Preventive Dentistry, University of Bonn, Bonn, Germany.
authors.forename: Regina
authors.initials: R
authors.lastname: Mericske-Stern
authors.affiliation: Department of Prosthodontics, University of Berne, Berne, SwitzerlandDepartment of Oral Surgery, University of Witten/Herdecke, Witten, GermanyDepartment of Prosthetic Dentistry, Propaedeutics and Material Science, University of Bonn, Bonn, GermanyDepartment of Periodontology, Operative and Preventive Dentistry, University of Bonn, Bonn, Germany.
authors.forename: Søren
authors.initials: S
authors.lastname: Jepsen
mesh_terms: D016301:Alveolar Bone Loss / Q000000981:diagnostic imaging* / Q000382:microbiology*; D016723:Bone Remodeling; D001862:Bone Resorption; D003758:Dental Implantation, Endosseous / Q000379:methods*; D015921:Dental Implants; D019250:Dental Implants, Single-Tooth; D005260:Female; D006801:Humans; D008297:Male; D008334:Mandible / Q000000981:diagnostic imaging / Q000601:surgery; D008875:Middle Aged; D011446:Prospective Studies; D011859:Radiography; D016037:Single-Blind Method; D018709:Statistics, Nonparametric; D016896:Treatment Outcome
chemical_list: D015921:Dental Implants