Replacing Teeth with Plastic

Dentists as well as their patients have long dreamed of the day when a pulled tooth could be replaced by another in the same operation. But so far, only a patient's own teeth have worked well when thus transplanted, and rare is the patient who happens to have a surplus tooth handy just when it is needed. Now Brown University's Dr. Milton Hodosh reports encouraging progress with plas tic implants, molded to the aching jaw as soon as the offending tooth has been pulled. To make sure that the implants will stand up under any conceivable strain, he is installing them in baboons, which think nothing of trying to chew the steel bars of their cages.

Humans First. Dental Surgeon Hodosh got the idea for implanting plastic teeth seven years ago and proposed a pilot study to authorities at Rhode Island Hospital in Providence. Ordinarily such research would begin with animals, but there was no money available for such a cautious start. Dr. Hodoshen listed 25 human volunteers.

Satisfied that a plastic called polymethylmethacrylate would be harmless and would form a good, strong tooth, he made molds of extracted teeth on the spot and filled the molds with plastic. After baking for about 15 minutes in a 500DEG oven, a tooth was rockhard, ready to be sandblasted smooth, sterilized and put into the gaping socket in the patient's mouth. There Dr. Hodosh fastened it in place--sometimes by a pin through adjacent bone, sometimes by a bridge attachment to neighboring teeth.

Some of those first implants are still going strong. But there have also been some failures, and with a series of grants from the National Institute of Dental Research, Dr. Hodosh has turned to animals to find out why. With Veterinarian Morris Povar and Pathologist Gerald Shklar, he has placed 125 implants in the mouths of monkeys and baboons.

Chewed-Up Steel. Dentistry on the vicious and powerful baboon is quite a trick. The beast is first squeezed into the bottom of a special cage, where it gets a heavy injection of tranquilizer. Then it can be hauled off to the operating table, where anesthetic is given as needed. As in human patients, new membrane forms around the implanted tooth, Dr. Hodosh reports, with no sign so far of inflammatory or cancerous reactions.

As positive evidence that the plastic teeth will hold up, the researchers exhibit a steel laboratory tray chewed into a shapeless mass by a baboon who did no damage to his implants in the process. Another baboon has three plastic implants supporting a two-tooth bridge in the front of his lower jaw; he has worn down the artificial teeth from savage chewing on metal caging, but they have not loosened. Not until his animal research is finished will Dr. Hodosh go back to making implants in human mouths.

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