An inflatable tissue expander or more permanent prosthesis, suitable for implantation in a breast, is provided. The tissue expander includes a puncturable, self-sealing anterior portion forming a fillable cavity, and posterior portion that is puncture resistant. The anterior portion includes a silicone-based elastomer material having a mesh embedded therein. The posterior portion includes a first composite guard and a second composite guard, each composite guard including an arrangement of puncture resistant members and a flexible substrate having a first side on which the puncture resistant members are disposed in a spaced apart fashion.