This assignment applies to all translations of the Work as well as to preliminary display/posting of the abstract of the accepted article in electronic form before publication. If any changes in authorship (order, deletions, or additions) occur after the manuscript is submitted, agreement by all authors for such changes must be on file with the Publisher. An author's name may be removed only at his/her written request. (Note: Material prepared by employees of the US government in the course of their official duties cannot be copyrighted.

Purpose: The aim of the present study was (1) to test whether or not the application of an in situ formed synthetic hydrogel, made of polyethylene glycol (PEG) used as a resorbable membrane for guided bone regeneration, will result in more amount of bone regeneration compared with an uncovered defect and (2) to evaluate if it can prevent the soft-tissue ingrowth into alveolar defects. Materials and Methods: Two critical size defects were created in seven Wistar rats. In the right side, an in situ formed hydrogel PEG membrane (Straumann MembraGel) was applied into the defect and the left one was kept empty as a control. After 60 days, animals were sacrificed and the calvarial bone was removed. The area of newly formed bone was determined by histomorphometrical analysis. For statistical analysis, the Mann-Whitney-U test was applied to model the amount of new bone formation. Results: The quantitative histomorphometric analysis obtained a percentage of newly formed bone for the test defects of 61,8% +/-22,2% and 53,8% +/-22,9% in the control group. The observed differences were not statistically significant. Conclusions The experimental PEG membrane was biocompatible and prevented soft-tissue ingrowth. There were no statistically significant differences between the groups.