A Hard Decade's Work: Steps in the Invention of the Glass-ionomer Cement

It is, perhaps, important first to emphasize what the invention of the glass-ionomer cement was and what it was not. It was not mixing a dental silicate cement powder with a solution of poly(acrylic acid) and observing cement formation with pleasant surprise. This may be the story of the zinc polycarboxylate cement, but it is not that of the glass-ionomer cement. I did, in fact, carry out such a simple experiment in 1965. An intractable paste was formed which, although it thickened up significantly during the co-urse of mixing, subsequently hardened very slowly. It was a cement that perversely combined absence of working time with a prolonged set. Not a material for dentistry. But the glass-ionomer cement did, in a way, originate from this negative result; subsequent development was to revolve around this problem of an unsatisfactory setting profile. The glass-ionomer cement originated not from a single inventive event but rather from a series of innovative steps which went toward the development of a practical glass-ionomer cement. There was the long grind of an extensive study, where persistence proved the kev to success. But it was leavened by moments of elation at the unexpected discovery, invention, or insight. There were also moments of despair, when the problems seemed insoluble. Doubleday (1920) summed it up with rare insight: