抄録
It was previously reported that when hydroxyapatite having a high molar ratio of Ca/P was heated,CaO crystals precipitated in the matrix phase of hydroxyapatite. In this study using spherical hydroxyapatite (HAP) with a Ca/P molar ratio of 3.5, six different pre-heated samples were prepared. They included HAP samples heated at 800℃ for 60 min, 300 min, 720 min, and 1,440 min, and HAP samples heated at 900℃ for 60 min, 300 min, 720 min, and 1,440 min, respectively. These pre-heated HAP samples were subjected to immersion tests in a physiological salt solution for one week and the immersion tests were repeated for four weeks. Such pre-heated samples after immersion tests were further investigated by x-ray diffraction analysis, and dissolved amounts of Ca and P, changes in pH values and cell culture were studied.
Within the limitations of this in vitro study, the following conclusions were obtained.
1. After the first one-week immersion test, the HAP sample heated at 800 and 900℃ showed pH values of 11-12. The pH values of both sample groups decreased in a range of 9.1-9.7 after the subsequent immersion tests.
2. The dissolved amount of Ca after the fourth-week immersion tended to decrease, compared to those after the first-week immersion tests. On the other hand, the dissolved amount of P was not affected by either the temperature or duration of heating.
3. Some heat treatments obstructed cell multiplication as a result of performing cell cultivation for seven days. As cell multiplication was hardly obstructed by the heat treatment of this research, the treatment was effective. The living body reaction will be examined in future studies.
