PP-1: Granulation tissue formation surrounding the material PP. (PP, 1-wk-specimen, ×100); PP-12: Granulation tissue with some necrotic tissue foci and inflammatory cell infiltration. (PP, 12-wk-specimen, ×100); PE-1: Proliferation of scattered granulation tissue around the embedded material PE. (PE, 1-wk-specimen, ×100); PE-12: The granulation tissue changed to fibrous tissue. (PE, 12-wk-specime, ×100); FE-1: thin layered fibrous capsule tissue around the material FE. (FE, 1-wk-specimen, ×100); FE-12: Thin fibrous layered tissue. (FE, 12-wk-specimen, ×100). M: Embedded material.