A device suitable for being implanted in a human or animal body and being equipped for material delivery within said body, the device further being suitable for fixation on or in hard tissue: wherein the device comprises at least one of a plug portion to be inserted in an opening in a hard tissue layer of the hard tissue reaching from a proximal, accessible to a distal, non-accessible side thereof and a cover portion to be positioned over a mouth of such an opening in the hard tissue layer, the plug or cover portion comprising a complete ring of a material having thermoplastic properties and being liquefiable through application of vibrational energy to the ring or to device portions adjacent to the ring, said ring being situated around a cross section of the plug portion or on a tissue facing surface of the cover portion, and wherein the thermoplastic material has a modulus of elasticity of at least 0.5 GPa and the device is equipped for transmission of vibrational energy to the ring or to the device portions adjacent to the ring for the purpose of liquefying at least part of the material having thermoplastic properties and to bring the material into contact with the hard tissue to form on re-solidification a complete sealing ring around the opening wherein the sealing ring is capable of sealing a region proximally of the hard tissue layer from a region distally of the hard tissue layer, and characterised in that the device comprises a material delivery portion and wherein the device is equipped for material delivery on a non-accessible side of the hard tissue layer, and comprises a container with a perforated, fenestrated or otherwise permeable wall portion on a distal side of the plug or cover portion (P, C) and a non-permeable wall portion on the proximal side of the plug or cover portion (P, C) prohibiting material delivery on the proximal side of the plug or cover portion (P, C), wherein the material delivery portion is arranged or arrangeable in the container. wherein the device comprises at least one of a plug portion to be inserted in an opening in a hard tissue layer of the hard tissue reaching from a proximal, accessible to a distal, non-accessible side thereof and a cover portion to be positioned over a mouth of such an opening in the hard tissue layer, the plug or cover portion comprising a complete ring of a material having thermoplastic properties and being liquefiable through application of vibrational energy to the ring or to device portions adjacent to the ring, said ring being situated around a cross section of the plug portion or on a tissue facing surface of the cover portion, and wherein the thermoplastic material has a modulus of elasticity of at least 0.5 GPa and the device is equipped for transmission of vibrational energy to the ring or to the device portions adjacent to the ring for the purpose of liquefying at least part of the material having thermoplastic properties and to bring the material into contact with the hard tissue to form on re-solidification a complete sealing ring around the opening wherein the sealing ring is capable of sealing a region proximally of the hard tissue layer from a region distally of the hard tissue layer, and characterised in that the device comprises a material delivery portion and wherein the device is equipped for material delivery on a non-accessible side of the hard tissue layer, and comprises a container with a perforated, fenestrated or otherwise permeable wall portion on a distal side of the plug or cover portion (P, C) and a non-permeable wall portion on the proximal side of the plug or cover portion (P, C) prohibiting material delivery on the proximal side of the plug or cover portion (P, C), wherein the material delivery portion is arranged or arrangeable in the container.