title: The controlled resorption of porous alpha-tricalcium phosphate using a hydroxypropylcellulose coating.
abstract: Tricalcium phosphate (TCP) ceramic is known in orthopedics to be a bioresorbable bone substitute. A porous TCP ceramic body also has high potential as a drug delivery system in bony defects. Porous alpha-TCP ceramic can be easily fabricated using conventional sintering of beta-TCP, since alpha-TCP is the thermodynamically stable phase at temperatures above 1 100 degrees C. However, the solubility of alpha-TCP is much higher than that of beta-TCP. Therefore, the dissolution of porous alpha-TCP progresses at a higher rate than bone repair. In the present study, we attempted to reduce the dissolution rate of porous alpha-TCP by employing an organic polymer coating. We fabricated porous alpha-TCP ceramic with a continuous 10-50 microm diameter pore structure by sintering a body made from a beta-TCP and potato starch slurry. The porous body obtained was coated with hydroxypropylcellulose (HPC), and then subjected to heat treatment. The chemical durability and mechanical properties of the body were examined before and after coating with the HPC. The dissolution of porous alpha-TCP in buffered solutions was reduced by coating with HPC and drying at 60 degrees C. The compressive strength of the porous alpha-TCP was also improved by coating with HPC. The results of in vivo experiments showed that some parts of the porous alpha-TCP ceramic coated with HPC remained in the canal of the tibia of a rabbit four weeks after implantation, whereas no residual was observed in a non-coated alpha-TCP ceramic. Coating with HPC was found to be effective for controlling bioresorption and improving the workability of porous alpha-TCP ceramic. The prepared porous alpha-TCP ceramic is expected to be useful as a novel material for bone fillers by incorporating it with drugs or osteoinductive factors.
authors.affiliation: Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5, Takayama-cho, Ikoma-shi, Nara 630-0192, Japan. kitamako@ms.naist.jp
authors.forename: Makoto
authors.initials: M
authors.lastname: Kitamura
authors.forename: Chikara
authors.initials: C
authors.lastname: Ohtsuki
authors.forename: Haruna
authors.initials: H
authors.lastname: Iwasaki
authors.forename: Shin-Ichi
authors.initials: S
authors.lastname: Ogata
authors.forename: Masao
authors.initials: M
authors.lastname: Tanihara
authors.forename: Toshiki
authors.initials: T
authors.lastname: Miyazaki
mesh_terms: D000818:Animals; D001672:Biocompatible Materials; D018786:Bone Substitutes; D002021:Buffers; D002118:Calcium / Q000737:chemistry; D002130:Calcium Phosphates / Q000737:chemistry*; D002482:Cellulose / Q000031:analogs & derivatives* / Q000737:chemistry*; D002516:Ceramics / Q000737:chemistry; D008422:Materials Testing; D008853:Microscopy; D008855:Microscopy, Electron, Scanning; D011817:Rabbits; D013696:Temperature; D013718:Tensile Strength; D013818:Thermogravimetry; D013977:Tibia / Q000473:pathology; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D014965:X-Rays
chemical_list: D001672:Biocompatible Materials; D018786:Bone Substitutes; D002021:Buffers; D002130:Calcium Phosphates; D002482:Cellulose; C008079:hydroxypropylcellulose; C018392:tricalcium phosphate; D002118:Calcium