キトサン・β-TCP 糊剤のラット頭頂骨骨膜下埋入時における細胞組織化学的研究
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概要
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Recently, bone substitutes, such as hydroxyapatite (HAP) and β-tricalcium phosphate (β-TCP), have been reported. These artificial substances are available for bone augmentation. However, the use of these substances is not without problems ; they are difficult to handle and shape and are not retained well in the host tissue. Chitosan, a naturally occurring high molecular weight polymer stable in vivo like collagen, was mixed with these artificial substances. The use of chitosan paste made the artificial substances much easier to handle and to be retained in the tissue. The osteoconductive properties of a chitosan HAP paste have been assessed in the rabbit. In this study, we evaluated the response to placement of a subperiosteal implant using chitosan β-TCP paste on rat calvaria, and examined the tissue cytohistochemically for evidence of soft tissue infiltration within the chitosan β-TCP paste when it is inserted into living tissue with direct approximation to bone. Male Wistar rats were injected through the jugular vein with horseradish peroxidase (HRP) as a peptide tracer, after various durations of experimental implantation. Dissection of the experimental regions showed that chitosan β-TCP paste was not spread on the calvaria and was firmly incorporated in the connective tissue without mobility. Light microscopically, soft tissue rapidly infiltrated the chitosan β-TCP paste, but no evidence of toxicity for host tissue was noted in any of the specimens. The materials were encapsulated roughly in fibrous connective tissue with few inflammatory cells. Healing formation was observed on the side of the materials. Cytohistochemically, HRP was deposited in the chitosan paste. Macrophages were observed around the chitosan β-TCP paste and had migrated into the materials. Uptake of HRP was detected intracellularly as granular reaction products in most macrophages but was more prominent in macrophages directly in contact with the chitosan β-TCP paste. These peroxidase-positive endocytotic structures were dense bodies, micropinocytotic vesicles and multivesicular bodies. Foreign body giant cells were also seen around the chitosan β-TCP paste. Uptake of HRP was seen in foreign body giant cells as well as macrophages. In newly formed bone HRP was detected throughout the lacunae and intracellularly in most osteocytes. In the calvaria not all of the lacunae was positive for HRP. These findings suggest that endocytosed chitosan is incorporated into the lysosomal system of macrophages and foreign body giant cells and then digested intracellularly by the lysosomal enzymes. Macrophages and foreign body giant cells may play an important part in absorption of chitosan. In conclusion, chitosan β-TCP paste is a resorbable, non-toxic and osteoconductive substance useful as a bone substitute.
- 九州歯科学会の論文
- 1998-04-25
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