title: Microvascular response to the subperiosteal implantation of self-inflating hydrogel expanders.
abstract: OBJECTIVE
  Excessive stretching of the overlying soft tissue often occurs during the attempt at primary closure after bone augmentation. Preliminary soft tissue expansion may prevent such perfusion disturbances caused by stretching. The purpose of this study was to investigate the effects of using self-inflating expanders at different rates to expand overlying soft tissue prior to the bone grafting procedure.
  
  
  METHODS
  Two different hydrogel expanders with different inflation curves were used. For the experiments, 48 Lewis rats were divided into six groups of eight animals each. In four groups, the different expanders were implanted subperiosteally on the calvarium. In two of these groups, an observation window was implanted for intravital microscopy. In the other two groups, histologic analysis of the covering skin was performed. Intravital microscopy of the unexpanded periosteum and histologic analyses of unoperated rats served as control groups.
  
  
  RESULTS
  Following implantation of the expanders, intravital microscopic examinations showed that, irrespective of the expansion curve, periosteal microcirculation had stopped completely without reperfusion within 14 days. Histologic analyses of the soft tissues, however, showed a well-vascularized connective tissue layer clinging to the expander. The microvessel density measured was significantly higher above slowly inflating expanders (91.2 ± 8.8 vessels/mm²) than above rapidly inflating expanders (48.4 ± 2.7 vessels/mm²) or unoperated periosteum (60.4 ± 4.8 vessels/mm²).
  
  
  CONCLUSIONS
  Subperiosteal implantation of self-inflating expanders leads to complete ischemia of the periosteum. However, replacement of the periosteum by connective tissue takes place within 14 days; as a result of subcutaneous angiogenesis, this tissue may have a significantly higher microvessel density than healthy periosteum.
authors.affiliation: Department of Oral and Maxillofacial Surgery, Hannover Medical School, Carl-Neuberg-Strasse 1, Hannover, Germany. constuehmer@web.de
authors.forename: Constantin
authors.initials: C
authors.lastname: von See
authors.forename: Nils-Claudius
authors.initials: NC
authors.lastname: Gellrich
authors.forename: Kai-Hendrik
authors.initials: KH
authors.lastname: Bormann
authors.forename: Alexander
authors.initials: A
authors.lastname: Rahmann
authors.forename: Martin
authors.initials: M
authors.lastname: Rücker
mesh_terms: D000818:Animals; D003238:Connective Tissue / Q000098:blood supply; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D008297:Male; D008833:Microcirculation; D008856:Microscopy, Fluorescence; D018919:Neovascularization, Physiologic; D013516:Oral Surgical Procedures, Preprosthetic; D010521:Periosteum / Q000098:blood supply* / Q000601:surgery*; D051381:Rats; D011917:Rats, Inbred Lew; D015626:Tissue Expansion / Q000379:methods*; D015625:Tissue Expansion Devices
chemical_list: D020136:Hydrogel, Polyethylene Glycol Dimethacrylate