title: A within-implant comparison to evaluate the concept of platform switching: a randomised controlled trial.
abstract: OBJECTIVE
  To evaluate whether platform switching could preserve marginal bone around implants up to 6 months after loading.
  
  
  METHODS
  15 patients were selected for a randomised controlled trial. Each patient received one customised wide body implant, with the external hex connection located eccentrically, allowing an extra 1 mm switch on one side. The hex was positioned at random at the mesial or distal side and the implant was loaded after 6 months of non-submerged healing. Patients were examined at 3, 6 and 12 months after surgery, during which a radiograph was taken to evaluate bone levels. At 12 months, the mucosal thickness was measured using a perio-probe.
  
  
  RESULTS
  All implants survived and the mean overall bone loss, calculated from both the switched and non-switched side, was 0.39 mm (SD 0.33, range 0.00-1.45), 0.85 mm (SD 0.59, range 0.10-2.50) and 0.80 mm (SD 0.46, 0.26-1.89) after 3, 6 and 12 months, respectively. The bone loss continued up to 6 months but stabilised thereafter (P = 0.615). Significantly more bone loss was observed at the non-switched side compared to the switched side at 3 months (0.51 mm versus 0.28 mm, P = 0.019), 6 months (1.05 mm versus 0.64 mm, P = 0.002) and 12 months (0.94 mm versus 0.66 mm, P = 0.002). The mean mucosal thickness was 4.22 mm (SD 1.45; range 1.50-7.00), and was not significantly different between the switched and non-switched sides (P = 0.882). However, using a post-hoc analysis with the mean thickness as a threshold, the mean bone loss was only significantly different between switched and non-switched sides when the mucosa was thicker than 4.22 mm (P = 0.036).
  
  
  CONCLUSIONS
  The outcome of this randomised trial is in accordance with earlier studies suggesting that that platform switching decreases bone loss by 30%. Although the sample size was limited, it seems that the creation of a biologic width affects peri-implant bone loss to a significant extent and that platform switching is only effective when the mucosal thickness allows the establishment of a biologic width.
authors.affiliation: Department of Periodontology & Oral Implantology, University of Ghent, Ghent, Belgium.
authors.forename: Stefan
authors.initials: S
authors.lastname: Vandeweghe
authors.forename: Hugo
authors.initials: H
authors.lastname: De Bruyn
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods; D000328:Adult; D000368:Aged; D016301:Alveolar Bone Loss / Q000517:prevention & control; D000539:Alveolar Process / Q000000981:diagnostic imaging / Q000473:pathology; D059605:Dental Implant-Abutment Design; D015921:Dental Implants; D017267:Dental Prosthesis Design; D005260:Female; D005500:Follow-Up Studies; D005881:Gingiva / Q000473:pathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D019252:Radiography, Dental, Digital; D013499:Surface Properties
chemical_list: D015921:Dental Implants