CHAPTER 3 Implants to Facilitate Tissue/Organ Re generation 3.1 The Problem of the Missing Organ; Solutions 3.1 R e generation versus Repair 3.2 Matrices for Tissue Regeneration 3. 2.1 Chemistry 3.2.1.1 Synthetic Polymers 3.2.1.2 Analogs of Ex tracellular Matrix : Collagen- GAG Copolymers 3. 2.2 Pore Characteristics 3. 2.3 Degradation Rate