{'fraction_non_alphanumeric': 0.06028833551769332, 'fraction_numerical': 0.04456094364351245, 'mean_word_length': 4.640394088669951, 'pattern_counts': {'":': 0, '<': 2, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Evaluation of a new biodegradable membrane to prevent gingival ingrowth into mandibular bone defects in minipigs.

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.


MATERIAL AND 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.


CONCLUSION
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.