Cement is a misnomer, as most often the word cement is used to describe something that adheres, or sticks together, two substances. Cement implies that the material sticks the implant into the bone. In reality, bone cement should really be called bone grout. The reason is that this material actually acts as a space-filler, to create a tight space for the implants to be held against the bone. Bone cement does not stick substances together, rather it fills the void between the implant and the surrounding bone.
Related: How Implants Are Held In Bone