title: The efficacy of a double-layer collagen membrane technique for overlaying block grafts in a rabbit calvarium model.
abstract: OBJECTIVE
  To analyze the outcomes of a single- and a double-layered collagen membrane on the efficacy of onlay block grafts in terms of bone resorption and augmentation.
  
  
  METHODS
  A total of 36 New Zealand white rabbits were used in this study. Calvarial bone blocks were obtained from one side of the parietal bone and fixed on the contaralateral side. The onlay grafts were covered with either no (C group), one (M1 group), or two (M2 group) layers of a non-cross-linked collagen membrane (BioGide((R))). After 2, 4, and 6 months of healing, rabbits were sacrificed and explanted specimens were prepared for histologic and histomorphometric analysis. At each period, the overall pattern of graft bone resorption and membrane biodegradation were examined histologically, and the sustained external form of grafted bone (%) and the remaining mineralized bone volume (%) were measured histomorphometrically.
  
  
  RESULTS
  The M1 and M2 groups exhibited decreased bone resorption compared with the C group at all periods. The M2 group had less graft resorption and a higher bone density of the grafted bone than the M1 group. In the M1 group, the collagen membrane was degraded partially or completely by 4 months and was absent at 6 months. Conversely, for the M2 group, the membrane body was retained up to 6 months.
  
  
  CONCLUSIONS
  Our results demonstrated that the collagen membrane used here can reduce graft bone resorption. Furthermore, the double-layer technique using non-cross-linked collagen membranes (BioGide((R))) can enhance the efficacy of the onlay block bone graft technique in terms of both bone resorption and augmentation compared with a single-layer collagen membrane.
authors.affiliation: Department of Periodontology and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea.
authors.forename: Su-Hwan
authors.initials: SH
authors.lastname: Kim
authors.forename: Do-Young
authors.initials: DY
authors.lastname: Kim
authors.forename: Kyoung-Hwa
authors.initials: KH
authors.lastname: Kim
authors.forename: Young
authors.initials: Y
authors.lastname: Ku
authors.forename: In-Chul
authors.initials: IC
authors.lastname: Rhyu
authors.forename: Yong-Moo
authors.initials: YM
authors.lastname: Lee
mesh_terms: D020341:Absorbable Implants; D000540:Alveolar Ridge Augmentation / Q000379:methods; D000818:Animals; D001672:Biocompatible Materials / Q000008:administration & dosage*; D001861:Bone Regeneration / Q000187:drug effects; D001862:Bone Resorption / Q000517:prevention & control*; D016025:Bone Transplantation / Q000379:methods; D003094:Collagen / Q000008:administration & dosage*; D003399:Craniotomy; D005500:Follow-Up Studies; D048091:Guided Tissue Regeneration / Q000379:methods*; D008567:Membranes, Artificial; D011446:Prospective Studies; D011817:Rabbits; D011897:Random Allocation; D012886:Skull / Q000601:surgery*; D014945:Wound Healing / Q000187:drug effects
chemical_list: C106416:Bio-Gide; D001672:Biocompatible Materials; D008567:Membranes, Artificial; D003094:Collagen