When clinicians faced with an insufficient volume of supporting bone on ideally esthetic and biomechanical position for dental implantation, guided bone regeneration(GBR) was indicated. Although GBR has wide application at clinic, proper time of membrane removal remains qustionable in using non-resorbable membrane, such as non-expanded polytetrafluoroethylene(PTFE). The aim of this study was to compare the effect of maintenance period of PTFE membrane on bone regeneration in rabbit calvarial defects.

Eight adult New Zealand white female rabbits were used in this study. Four defects were surgically made in their calvaria. Using a trephine bur, 4 'through and through' defects were created and classified into 3 groups, which were consisted of control group(no graft), experimental group 1(autogenous bone)and experimental group 2(deproteinized bovine bone; OCS-B®). The defects were covered with PTFE membrane(Cytoplast®). Membranes were removed after 1, 2, 4 and 8 weeks post-GBR procedure in 2 rabbits repectively. All rabbits were sacrificed after 8 week post-GBR procedure. Specimens were harvested and observed histologically. The results were as follow;

1) The use of graft material and membrane was necessary in GBR procedure.

2) When PTFE membranes were removed early, the most favorable bone regeneration was revealed in experimental group I, followed by experimental group II and control group.

3) On GBR, it is recommended that membrane should maintain for 4 weeks with autogenous graft. As well, the use of xenograft need longer maintenance period than autogenous bone.

Further evaluations will be needed, such as histomorphologic research, more species and different kinds of graft materials. And on the basis of these studies, clinical researches would be required.