Background: Because of the durability, non-resorbable GBR membrane is believed to achieve the good outcome. But it need second-stage removal and have higher exposure rate. Resorbable animal collagen membrane is widely used as good operationality. But they remain have the risk of unknown pathogen. So we developed synthetic GBR membrane GMEM-B2 adopting resorbable copolymer P(LA/CL). It can offer longer resorption period and also have soft and flexible feature to follow and fit to the outline of bone tissue. Aim/Hypothesis: It is also known that stiff resorbable membranes promotes a similar degree of bone formation as non-resorbable membranes. In this study we checked the longer duration and biological safety of the prototype in in vitro degradation test and in subchronic toxicity test. Material and Methods: GMEM-B2 is consisted of copolymer of e-caprolactone and L-lactide (P(LA/CL)), which undergo hydrolysis in body fluids. It have bilayer (porous and solid) structure. Former is to face to bone for good integration, and latter is to block soft tissue invasion. In vitro degradation test was performed in accordance with the ISO158114:1999. In short, 13mm-dia. round specimen was soaked in PBS (pH 7.4), at 37℃ (n=4). Every 4 or 8w, they were rinsed and dried to check the mass loss. 50% mass loss period of GMEM-B2 was compared with GC Membrane (GC Corp.,) Subchronic toxicity test of GMEM-B2 was performed according to the ISO10993-6:2016 and ISO10993-11:2006. Briefly, both sexual of BrlHan:WIST rats were used (n=6). Samples were implanted for calvaria onlay and subcutaneous (Exposure margin:113). Also sham op. was performed as control. At 18w, as main test item, hematological and blood biochemistry data was determined, and test sites were examined macroscopically and histologically. Results: From in vitro degradation test, it is turned that mass of each group were decreased in a linear fashion from 8 w. Period of 50% mass loss was 28.8w for GMEM-B2 and 13.4w for GC Membrane. Then we determined 18w as the time point of the subchronic toxicity test (as the middle of active degradation phase) for GMEM-B2. Subchronic toxicity test, no animals showed sample-related toxic symptoms. There were only toxicologically negligible differences in hematological results. Macroscopic and histological test revealed no significant abnormalities and inflammation in all groups. In histologicals, the tissue reactions against the test strips were mainly foreign body reactions. Many giant cells were present on the porous layer side, and cellular infiltration, mainly macrophages, into the test strips was noted. But it is also suggested that substantial barrier properties of GMEM-B2 were not compromised at 18w. In the subcutaneous implantation sites, similar tissue reactions were observed. Conclusion and Clinical implications: It was found that the 50% degradation time of GMEM-B2 was twice as GC Membrane (degrades in 12-16w in vivo). And GMEM-B2 did not cause subchronic systemic toxicity and inflammatory reactions. Because in literatures, it is said that some commercially succeeded collagen GBR membrane degrades in 12w or less in vivo. Taken together these results, GMEM-B2 is presumed to have enough potential in clinical application.
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