The study of the new dentin lying method by CO_2 laser irradiation and hydroxyapatite paste

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The purpose of this study was k find out a possibility of sealing the dentin tubuli using CO_2 laser and hydroxyapatite paste.Hydinxyapatite paste (mixed paste of CaHPO_4 2H_2O, CaCO_3, and H_2O) was applied to the prepared smooth dentin surfaces, which made of extracted human teeth, and irradiated by CO_2 laser under conditions of 3W Rep. 10/1000 and 100/1000 second. Next, these samples were cut in vertically, then investigated and analyzed by scanning electron microscope (SEM) and Fourier transform infrared (FT-IR).In every sample, the layer in which has the structure that sealed dentin tubuli was observed by SEM, and also the rich band of Calcium and phosphorus was found by FT-IR.The ingredients of internal dentin tubuli were, however, not determined.As a practical study, cervical cavities were prepared to expose dentin on upper first premolars which were intended to extract for orthodontal treatment, with patients' permission. Then the hydroxyapatite paste was applied to cavities and irradiated by CO_2 laser under conditions of 3W Rep. 100/1000 second. After extracted, they were investigated by SEM and pathological samples which had treated with hematoxylin-eosin staining.The results of SEM investigation, the micrographs which were the same as extracted human teeth were observed. And results of pathological investigation, normal dentinoblasts and pulpal tissue were observed.By this study, it was suggested that the irradiation of CO_2 laser with hydroxyapatite paste can seal the dentin tubuli without pulpal damage and carbonized layer.