This study was per formed to compare the efficacy of guided tissue regeneration （GTR） around dentalimplants immediately placed into extraction sockets by resorbable of nonresorbable membranes. Mandibular. P2

P3

and P4 of four aduIt beagle dogs were extracted bilaterally

and buccal standard defects were cre-ated and measured. Eighteen commercially pure titanium Steri-Oss implant fixtures were placed into thefresh extraction sockets. Four implants were untreated controls

four implants received polytetrafluoro-ethylene （e-PTFE

Gore-Tex） membranes

five implants received collagen membranes （ParaGuide）

andfive implants received polyglactin 910 mesh （Vicryl）. After l4 weeks

clinical measurements were takenand the dogs were sacrificed and all specimens retrieved for histologic and histomorphometric evaluation.The average gain in bone height was 2. 1mm for untreated control sites

3. 3mm for Gore-Tex sites

3. 8mm for collagen sites

and 1. 3mm for polyglactin 910 sites. The greatest gain in bone height and volume was seen for two sites that received Gore-Tex membranes and remained covered for the entire evalua-tion interval. The results of this study indicate that Gore-Tex and collagen membrane preduced gdri re-sults for GTR around Implants immediately placed into extraction sockets. Since collagen membrane doesnot cause obvious infection and does not need the surgical reentry for membrane removal

it can be a validalternative to Gore-Tex membrane to improve bone regeneration around dental implants

while polyglactin910 mesh seems not suitable to be used as GTR membrane in immediate implantation for its hIgh infectionrate.