title: Evaluation of a new biodegradable membrane to prevent gingival ingrowth into mandibular bone defects in minipigs.
abstract: OBJECTIVE
  The aim of this study was to test whether a synthetic, biodegradable membrane made of polyethylene glycol (PEG) can prevent soft-tissue ingrowth into alveolar defects.
  
  
  METHODS
  In each of 16 minipigs, three mandibular premolars were bilaterally extracted. Three months later, acute standardized defects (diameter 8 mm, depth 8 mm) were prepared. Four treatment modalities were randomly allocated to the defects: (1) PEG membrane plus collagen sponge, (2) polylactide (PLA) membrane plus collagen sponge, (3) collagen sponge alone, and (4) empty defect. Animals were sacrificed at 10 days (n=5), 21 days (n=5), or 2 months (n=6) after treatment. Qualitative and quantitative histological evaluations of soft-tissue ingrowth and bone regeneration were performed on nondecalcified ground sections. For statistical analysis, the Mann-Whitney-Wilcoxon test, the Kruskal-Wallis, and the paired t-test were applied. P-values were adjusted using the Dunnett-Hsu adjustment.
  
  
  RESULTS
  At 10 days, the PEG membrane group showed the least soft-tissue ingrowth (mean value -0.75 mm; range -1.35 to -0.10), followed by the PLA membrane group -0.18 mm (-0.80 to 0.44), the collagen group 0.04 mm (-0.65 to 0.73), and the empty defects 0.60 mm (-0.08 to 1.29). Statistically significant differences were observed between the PEG membrane group and the empty defects (P<0.05). At 21 days, the highest percentage of newly formed bone was found in the PEG membrane group (mean 28.4%; range 21.6-35.2) compared with 23.7% (16.9-30.5; PLA membrane), 15.2% (8.2-22.2; collagen group), and 21.6% (14.5-28.8; empty defects). Statistically significant differences were only found between the PEG membrane group and the collagen group (P<0.05). At 2 months, the tested parameters revealed no statistically significant differences between the groups.
  
  
  CONCLUSIONS
  The experimental PEG membrane applied in the present study successfully prevented collapse of the covering soft tissues to a degree similar to the PLA membrane. The combination of a collagen sponge and the PEG membrane showed the least soft-tissue ingrowth at 10 days and promoted more bone formation at 21 days.
authors.affiliation: Clinic for Fixed and Removable Prosthodontics and Dental Material Science, University of Zurich, Zurich, Switzerland. daniel.thoma@zzmk.uzh.ch
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Thoma
authors.forename: Gian-Andrea
authors.initials: GA
authors.lastname: Halg
authors.forename: Michel M
authors.initials: MM
authors.lastname: Dard
authors.forename: Reinhart
authors.initials: R
authors.lastname: Seibl
authors.forename: Christoph H F
authors.initials: CH
authors.lastname: Hammerle
authors.forename: Ronald E
authors.initials: RE
authors.lastname: Jung
mesh_terms: D020341:Absorbable Implants; D016301:Alveolar Bone Loss / Q000601:surgery*; D000818:Animals; D001861:Bone Regeneration; D003094:Collagen; D005260:Female; D005881:Gingiva / Q000502:physiology; D016557:Guided Tissue Regeneration, Periodontal / Q000379:methods*; D008567:Membranes, Artificial; D011091:Polyesters; D011092:Polyethylene Glycols; D011897:Random Allocation; D013552:Swine; D013556:Swine, Miniature; D013997:Time Factors
chemical_list: D008567:Membranes, Artificial; D011091:Polyesters; D011092:Polyethylene Glycols; C033616:poly(lactide); D003094:Collagen