Guided tissue regeneration (GTR), or guided bone regeneration (GBR), can be considered as sub-areas of tissue engineering because the characteristics of newly forming tissue are commonly influenced as usual by the surgical intervention and more importantly by the morphology or topography of a biomaterial surface. Thus, in guided tissue regeneration no cell seeding and culturing is used, but the effect is reached via an implanted device, normally a membrane. The terms were first introduced in periodontal and oral applications, and in GTR the membrane is placed between the periodontal defect and the gingival tissue and in GBR the membrane is placed between the bone defect and the gingival tissues [1]. Later, the terms have been expanded to use in other fields, including repairing craniofacial bone defects [2–4]. Materials commonly used in GBR and GTR are membranes of GoreTex©R (non-resorbable PTFE membrane, needs to be removed in the long term), collagen and aliphatic polyesters (PLA, PGA, copolymers) [2,5–9]. Other materials, including polymer and hydroxyapatite membranes have also been studied for GBR [10]. Two different types of GBR-membranes having occlusive layer on one side and a layer with controlled porosity on the other side of the membrane were developed and studied here in vitro and in vivo.