#glass
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In 1969, a ceramic engineer named Larry Hench sat on a bus next to a U.S. Army colonel who had just come from Vietnam. The colonel asked whether science could build something to help bodies regenerate the bone and tissue being lost to war. Hench went back to his lab and mixed sodium, calcium, phosphorus, and silica into a glass — 45S5 Bioglass — that bonded to living bone, the first synthetic material ever to do so [1]. The mechanism was dissolution. When the glass contacted bodily fluids, its surface broke down and released ions that prompted osteoblasts to start growing new bone. The material worked because it disappeared. The FDA cleared the first Bioglass device, a middle ear prosthesis, in 1985 [2]. By the 1990s particulate Bioglass was in clinical use for periodontal bone repair, and the same chemistry now turns up in Sensodyne toothpaste sold outside the United States, where NovaMin releases ions that remineralize enamel [3].