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in the present study, the toxicity of tooth ash, plaster and tooth ash/plaster mixture was evaluated by several in vitro experiments. For the evaluation of the toxicity, measurement of the pH of the test materials, cell viability test, measurement of the DNA synthesis rate, and agar overlay test were done. The results were as follows. 1)The pH of the plaster, tooth ash, and the mixture 6.76, 10.12, and 8.36 respectively. 2) Cell viability was narkedly reduced by plaster(by 7o%), by the mixture(by 83%), and less extent by tooth ash(43%). 3) DNA synthesis was completely inhibited in tooth ash-immersed nedia, partly inhibited(by 36%) in the mixture-immersed media. 4) By diluting the immersed media(1:4) with normal media the toxicity was reduced raising the DNA systhesis rate close to normal. 5) in the agaroverlay test, none of the test material showed significant toxicity except plaster which showed mild toxicity. In conclusion tooth ash/plaster moxture is thought to be a reatively biologically safe material.
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