Fabrication of hydroxyapatite microparticles including silver nano-dots at grain boundary for long-term antimicrobial pr
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Fabrication of hydroxyapatite microparticles including silver nano-dots at grain boundary for long-term antimicrobial property Hiroaki Igashira1, Michimasa Kamo2, Masayuki Kyomoto2, Toshiyuki Ikoma1 1 Department of Materials Science and Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan 2 Research Department, KYOCERA Medical Corporation, 3-3-31 Miyahara, Yodogawa-ku, Osaka-shi, Osaka 532-0003, Japan ABSTRACT The antibacterial properties are useful to restrain inflammatory response caused by bacterial infection after implantation. The composites of hydroxyapatite (HAp) and silver nanodots, silver oxide or silver phosphate have been investigated; however there are still some disadvantage in sintering; 1) silver nano-dots grow large, and are not homogenously distributed, 2) silver nano-dots melt and remove, and 3) silver phosphate and silver oxide formed exhibit higher solubility than metal silver. In this study, the distribution of silver nano-dots in HAp microparticles sintered was controlled at grain boundary with a modified silver mirror reaction as a novel route. HAp microparticles adsorbed formaldehyde by a vapor deposition method were soaked in an ammoniacal silver nitrate solution and were then sintered. There was a single phase of HAp including metal silver at 6.4 wt% even after sintering. The silver nano-dots were homogeneously distributed inside the microparticles. The release profiles of silver ions in phosphate buffer saline were compared with a reference; the HAp microparticles were soaked into silver nitrate solution and were then sintered. The distribution of silver in the reference was not homogeneous and large silver microparticles were grown outside the particles at 6.3wt%. The elution amount of silver ions from the microparticles at 12 hours was one-eighteenth of that from the reference. These results suggest that the HAp microparticles including silver nano-dots at grain boundary will be suitable for a long-term antibacterial material. INTRODUCTION Dental implant is one of major treatments for loss of tooth when patients suffer from carious tooth, periodontal diseases, systemic diseases, an accident or aging. The implants generally have an osseointegrated ability on alveolar bone due to the surface modifications of titanium implants with hydroxyapatite; however, inflammatory reactions at peri-implant tissues (peri-implant mucositis or peri-implantitis) have occurred for 52 to 57 % patients during 5-10 years after implantation (late failures)1. Although the disease rates are really high, preventative measures are still not established and are controversy2. Bacterial peri-implant infections would cause inflammation accompanying with bleeding and suppuration, which are also caused for fracture of implants. There are a lot of therapeutic treatments for peri-implant infection. The scaling and root planning are the first line to prevent bacterial infections3. After infection, antibiotic treatments such as local delivery in peri-implant pocket by using tetracycli
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