title: The alveolar ridge splitting/expansion technique: a systematic review.
abstract: OBJECTIVE
  The aim of this systematic review was to evaluate clinical, radiological and histological outcomes of the alveolar ridge splitting/expansion technique (ARST) with or without GBR.
  
  
  METHODS
  A screening of two databases MEDLINE (PubMed) and EMBASE (OVID) and hand search of articles were performed. Human and animal studies reporting on dental implants placed with simultaneous ARST up to May 31st 2014 were considered. Quality assessment of selected full-text articles was performed according to the ARRIVE guidelines and the Cochrane collaboration's tool to assess risk of bias.
  
  
  RESULTS
  Overall, 18 human and six animal studies (risk of bias: high/unclear) were included in this review. No randomized controlled trials were found. Due to the heterogeneity of study designs, definitions of success criteria, outcome variables, observation times and surgical procedures, no meta-analysis was performed. Reported survival (18 studies) and success (nine studies) rates ranged from 91.7 to 100% and 88.2 to 100%, respectively, with a mean follow-up of 1-10 years. Crestal bone level changes (∆CBL) in some studies indicate slightly higher bone loss before and after loading. Histologic and histomorphometric data from six animal studies confirm the crestal bone loss, particularly at buccal sites.
  
  
  CONCLUSIONS
  Within the limitations of this review, ARST seems to be a well-functioning one-stage alternative to extended two-stage horizontal grafting procedures. Data indicate that during healing and first year of loading, increased ∆CBL particularly at buccal sites must be anticipated. Additional horizontal GBR can help to preserve buccal bone height and width.
authors.affiliation: Department of Periodontology, University of Bern, Bern, Switzerland.
authors.forename: Mario A
authors.initials: MA
authors.lastname: Bassetti
authors.affiliation: Department of Oral and Maxillofacial Surgery, Lucerne Cantonal Hospital, Lucerne, Switzerland.
authors.forename: Renzo G
authors.initials: RG
authors.lastname: Bassetti
authors.affiliation: Department of Periodontology, University of Bern, Bern, Switzerland.|Robert K. Schenk Laboratory of Oral Histology, School of Dental Medicine, University of Bern, Bern, Switzerland.
authors.forename: Dieter D
authors.initials: DD
authors.lastname: Bosshardt
mesh_terms: D016301:Alveolar Bone Loss / Q000473:pathology* / Q000601:surgery*; D000540:Alveolar Ridge Augmentation / Q000379:methods*; D000818:Animals; D016025:Bone Transplantation / Q000379:methods; D003758:Dental Implantation, Endosseous / Q000379:methods*; D015921:Dental Implants; D016557:Guided Tissue Regeneration, Periodontal / Q000379:methods; D006801:Humans
chemical_list: D015921:Dental Implants
keywords: horizontal bone augmentation; ridge expansion; split-crest technique