title: Effect of platform switching on crestal bone levels around implants in the posterior mandible: 3 years results from a multicentre randomized clinical trial.
abstract: OBJECTIVE
  Evaluation of differences in the clinical performance and crestal bone levels between implants restored with single crowns with platform-matched or platform-switched abutments after 3 years.
  
  
  METHODS
  The study enrolled adult patients missing two or more adjacent teeth in the posterior mandible with natural teeth mesial to the implant site. Randomization followed open-flap implant insertion and the corresponding matching or switching healing abutments placed at surgery. Conventional loading was made with cemented crowns. Clinical follow-up took place annually after loading up to 3 years. Bone level changes were measured in standardized radiographs as the variation in crestal bone from one evaluation to the next.
  
  
  RESULTS
  Sixty-three patients with a total of 135 implants (66 platform matching, 69 platform switching) were analysed. From surgery to 36 months, mean bone loss was 0.28 ± 0.56 mm for the platform-switching group and 0.68 ± 0.64 mm for the platform-matching group. A statistically significant difference was found between groups (p = 0.002) with an estimate of 0.39 mm (0.15-0.64, 95% CI) in favour of platform switching.
  
  
  CONCLUSIONS
  After 3 years, platform-switching restorations showed a significant effect in the preservation of marginal bone levels compared to platform-matching restorations.
authors: Faculty of Medicine, University of Coimbra, Coimbra, Portugal.
authors: Salomão
authors: S
authors: Rocha
authors: Medical Centre of Johannes Gutenberg University of Mainz, Mainz, Germany.
authors: Wilfried
authors: W
authors: Wagner
authors: Schleswig-Holstein University Hospital, University of Kiel, Kiel, Germany.
authors: Jörg
authors: J
authors: Wiltfang
authors: Faculty of Medicine, University of Coimbra, Coimbra, Portugal.
authors: Pedro
authors: P
authors: Nicolau
authors: Medical Centre of Johannes Gutenberg University of Mainz, Mainz, Germany.
authors: Maximilian
authors: M
authors: Moergel
authors: Faculty of Medicine, University of Coimbra, Coimbra, Portugal.
authors: Ana
authors: A
authors: Messias
authors: Schleswig-Holstein University Hospital, University of Kiel, Kiel, Germany.
authors: Eleonore
authors: E
authors: Behrens
authors: Faculty of Medicine, University of Coimbra, Coimbra, Portugal.
authors: Fernando
authors: F
authors: Guerra
mesh_terms: D016301:Alveolar Bone Loss / Q000601:surgery; D003442:Crowns; D000044:Dental Abutments; D003758:Dental Implantation, Endosseous; D015921:Dental Implants; D017267:Dental Prosthesis Design; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008334:Mandible / Q000601:surgery*; D008875:Middle Aged
chemical_list: D015921:Dental Implants
keywords: bone level; crestal bone preservation; implant; implant success; platform match; platform switching; randomized clinical trial; standardized radiograph