title: The clinical value of membranes in bone augmentation procedures in oral implantology:  A systematic review of randomised controlled trials.
abstract: OBJECTIVE
  To determine the clinical value of membranes in bone augmentation procedures such as ridge augmentation with simultaneous (one-stage) and delayed (two-stage) implant placement, sinus augmentation surgery, ridge preservation and immediate implant placement.
  
  
  METHODS
  In April 2016, Embase, Medline (Ovid-SP), Cochrane Central, Web of Science and PubMed (as supplied by the publisher) were searched. There were no restrictions regarding language or publication date. Randomised controlled trials that reported membranes in bone augmentation procedures with a minimum follow-up period of 6 months after implant loading or that described geometrical changes of the bone graft at re-entry were included. Membrane placement had to be the only variable in the procedure. Outcomes were implant failure, complications, horizontal bone gain and resorption, graft resorption, defect height reduction, marginal bone loss around implants, aesthetic results and patient satisfaction. The results were pooled using fixed-effect models with mean differences (MDs) for continuous outcomes and odds ratios (ORs) for dichotomous outcomes.
  
  
  RESULTS
  After screening the titles and abstracts of 1843 papers, 32 potentially eligible articles were selected. Seventeen articles involving 10 trials were included in this review. These studies presented outcome data for 355 patients. Seven trials were considered to be at a high risk of bias, two at a low risk of bias and one at an unclear risk of bias. Insufficient evidence was found to determine whether there were differences in implant failure rates, marginal bone level changes, aesthetic results or patient satisfaction. For one-stage ridge augmentation (two trials; n = 52), there was evidence of more horizontal bone gain (MD: 0.84 mm, 95% CI: 0.46 to 1.21, P < 0.00001; two trials), defect height reduction (MD: 18.36%, 95% CI: 10.23 to 26.50, P < 0.00001; two trials), and prevention of graft resorption (P = 0.004; one trial) in favour of the membrane-covered group, although substantial heterogeneity was found for horizontal bone gain (Chi2; P = 0.05, I2=74%). There was insufficient evidence to determine whether any differences exist in two-stage ridge augmentation (three trials; n = 81), sinus augmentation (one trial; n = 104) and ridge preservation (one trial; n = 20). For immediate implant placement (three trials; n = 98), there was evidence of an increased defect height reduction in favour of the membrane-covered groups (MD: 6.25%, 95% CI: 1.67 to 10.82, P = 0.007; two trials), although with substantial heterogeneity (Chi2; P = 0.03, I2 = 79%). More complications were observed when a membrane was used (OR: 2.52, 95% CI: 1.07 to 5.93, P = 0.03; three trials).
  
  
  CONCLUSIONS
  There is insufficient evidence regarding the effects of membranes on bone augmentation procedures to support any definitive conclusions. Only 10 studies were included; they had limited sample sizes and short follow-up periods, and the majority were at a high risk of bias. However, no difference in implant failure was found, and the possible clinical value is still unknown, as long-term clinical parameters such as marginal bone loss, aesthetic results and patient satisfaction have been insufficiently studied. Conflict-of-interest and source-of-funding statement: The authors declare that they have no possible conflicts of interest. No funding for this review was received.
authors.forename: Brend P
authors.initials: BP
authors.lastname: Jonker
authors.forename: Maarten W K
authors.initials: MW
authors.lastname: Roeloffs
authors.forename: Eppo B
authors.initials: EB
authors.lastname: Wolvius
authors.forename: Justin
authors.initials: J
authors.lastname: Pijpe
mesh_terms: D000540:Alveolar Ridge Augmentation / Q000379:methods*; D016025:Bone Transplantation; D003758:Dental Implantation, Endosseous / Q000379:methods*; D006801:Humans; D008567:Membranes, Artificial; D016032:Randomized Controlled Trials as Topic
chemical_list: D008567:Membranes, Artificial