title: Bone healing with an in situ-formed bioresorbable polyethylene glycol hydrogel membrane in rabbit calvarial defects.
abstract: OBJECTIVE
  The aims of this study were to test whether or not the application of an in situ-formed synthetic polyethylene glycol hydrogel (PEG) used as a biodegradable membrane for guided bone regeneration with a variety of graft materials and ambient oxygen or hyperbaric oxygen (HBO) environments would result in enhanced bone regeneration, and to observe the histologic and histomorphometric aspects of bone healing of the calvarial defects with and without a PEG membrane.
  
  
  METHODS
  Thirty adult, skeletally mature, male New Zealand white rabbits were randomly divided into 3 groups of 10 animals each. Bilateral 15-mm-diameter critical-size defects were created in the parietal bones of each animal. Group 1 served as a control with unfilled bilateral calvarial defects, group 2 had bilateral calvarial defects filled with morcelized autogenous calvarial bone, and group 3 had bilateral calvarial defects filled with a biphasic calcium phosphate ceramic. One of the calvarial defects was randomly protected with a PEG resorbable liquid membrane in each animal. Five animals from each group underwent a course of HBO treatment (2.4 ATA 100% oxygen for 90 minutes 5 days a week for 4 weeks) and the other 5 served as control and did not receive any supplemental oxygen (normobaric). The animals were killed 6 weeks after their surgery, and their parietal bones were harvested. The specimens were analyzed with microscopic computerized tomography (microCT) scans and histomorphometrics.
  
  
  RESULTS
  The unfilled normobaric control bony defects did not heal, proving the critical-size nature of these defects. The presence of autogenous bone or bone ceramic in the defects increased the bone volume fraction and bone mineral density of the defects (P < .001). The presence of a membrane in the ungrafted and autogenous bone grafted defects resulted in a decrease in the corrected bone volume fraction (P = .002) but not in the bone ceramic grafted defects (P = .580). Bony healing of defects where the membrane was unsupported was compromised; the membrane did not maintain the desired bone regeneration volume with the unfilled and autogenous bone grafted groups. The PEG resorbable liquid membrane worked best with the bone ceramic material. HBO did not ameliorate the healing of the autogenous bone graft or ceramic filled defects in the 6-week time period of this study.
  
  
  CONCLUSIONS
  Although the PEG resorbable liquid membrane is easy to use and forms an occlusive layer, caution is recommended when using the membrane over an unsupported defect. HBO did not ameliorate bony healing with the membrane at the early 6-week time point. The authors recommend future assessment with HBO at the 12-week time point.
authors.affiliation: Oral and Maxillofacial Surgery and Anesthesia, University of Toronto, Toronto, Canada.
authors.forename: Craig C
authors.initials: CC
authors.lastname: Humber
authors.forename: G K B
authors.initials: GK
authors.lastname: Sándor
authors.forename: Joel M
authors.initials: JM
authors.lastname: Davis
authors.forename: Sean A F
authors.initials: SA
authors.lastname: Peel
authors.forename: Bozidar M B
authors.initials: BM
authors.lastname: Brkovic
authors.forename: Yong Deok
authors.initials: YD
authors.lastname: Kim
authors.forename: Howard I
authors.initials: HI
authors.lastname: Holmes
authors.forename: Cameron M L
authors.initials: CM
authors.lastname: Clokie
mesh_terms: D020341:Absorbable Implants; D000818:Animals; D001861:Bone Regeneration / Q000187:drug effects* / Q000502:physiology; D018786:Bone Substitutes / Q000494:pharmacology; D016025:Bone Transplantation / Q000379:methods; D002130:Calcium Phosphates / Q000494:pharmacology; D003131:Combined Modality Therapy; D048091:Guided Tissue Regeneration / Q000379:methods*; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000494:pharmacology; D006931:Hyperbaric Oxygenation; D008297:Male; D008567:Membranes, Artificial; D011092:Polyethylene Glycols / Q000494:pharmacology; D011817:Rabbits; D012886:Skull / Q000187:drug effects* / Q000502:physiology / Q000601:surgery; D014945:Wound Healing / Q000187:drug effects / Q000502:physiology
chemical_list: D018786:Bone Substitutes; D002130:Calcium Phosphates; D008567:Membranes, Artificial; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D011092:Polyethylene Glycols; C020243:calcium phosphate