Four calcium phosphate cement formulations were implanted in the rabbit distal femoral metaphysis and middiaphysis. Chemical, crystallographic, and histological analyses were made at 2, 4, and 8 weeks after implantation. When implanted into the metaphysis, part of the brushite cement was converted into carbonated apatite by 2 weeks. Some of the brushite cement was removed by mononuclear macrophages prior to its conversion into apatite. Osteoclastlike cell mediated remodeling was predominant at 8 weeks after brushite had converted to apatite. The same histological results were seen for brushite plus calcite aggregate cement, except with calcite aggregates still present at 8 weeks. However, when implanted in the diaphysis, brushite and brushite plus calcite aggregate did not convert to another calcium phosphate phase by 4 weeks. Carbonated apatite cement implanted in the metaphysis did not transform to another calcium phosphate phase. There was no evidence of adverse foreign body reaction. Osteoclastlike cell mediated remodeling was predominant at 8 weeks. The apatite plus calcite aggregate cement implanted in the metaphysis that was not remodeled remained as poorly crystalline apatite. Calcite aggregates were still present at 8 weeks. There was no evidence of foreign body reaction. Osteoclastlike cell remodeling was predominant at 8 weeks. Response to brushite cements prior to conversion to apatite was macrophage dominated, and response to apatite cements was osteoclast dominated. Mineralogy, chemical composition, and osseous implantation site of these calcium phosphates significantly affected their in vivo host response.
Four calcium phosphate cement formulations were implanted in the rabbit distal femoral metaphysis and middiaphysis. Chemical, crystallographic, and histological analyses were made at 2, 4, and 8 weeks after implantation. When implanted into the metaphysis, part of the brushite cement was converted into carbonated apatite by 2 weeks. Some of the brushite cement was removed by mononuclear macrophages prior to its conversion into apatite. Osteoclastlike cell mediated remodeling was predominant at 8 weeks after brushite had converted to apatite. The same histological results were seen for brushite plus calcite aggregate cement, except with calcite aggregates still present at 8 weeks. However, when implanted in the diaphysis, brushite and brushite plus calcite aggregate did not convert to another calcium phosphate phase by 4 weeks. Carbonated apatite cement implanted in the metaphysis did not transform to another calcium phosphate phase. There was no evidence of adverse foreign body reaction. Osteoclastlike cell mediated remodeling was predominant at 8 weeks. The apatite plus calcite aggregate cement implanted in the metaphysis that was not remodeled remained as poorly crystalline apatite. Calcite aggregates were still present at 8 weeks. There was no evidence of foreign body reaction. Osteoclastlike cell remodeling was predominant at 8 weeks. Response to brushite cements prior to conversion to apatite was macrophage dominated, and response to apatite cements was osteoclast dominated. Mineralogy, chemical composition, and osseous implantation site of these calcium phosphates significantly affected their in vivo host response. ᭧ 1998 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 43: [451][452][453][454][455][456][457][458][459][460][461] 1998 Keywords: calcium phosphate(s); brushite; hydroxyapatite; calcite; remodeling INTRODUCTIONb-tricalcium phosphate (b-TCP) and hydroxyapatite mixtures used as bone void fillers and preformed granules, and blocks of hydrothermally processed apatite used as Numerous calcium phosphates have been evaluated as bioscaffolding in nonunion fracture applications. The different materials in orthopedics with varying degrees of success calcium phosphate phases present in these materials range in diverse applications such as bone void fillers, ingrowth from phase pure crystalline materials to mixtures of amorsurfaces on metal implants, and carriers for bone growth phous glasses with highly crystalline phases. factors.1-6 These materials fall into a wide range of initial LeGeros showed in vitro that calcium phosphates such chemical and crystallographic composition, morphology, as b-TCP and dicalcium phosphate dihydrate (DCPD), and physical handling characteristics. Calcium phosphates commonly known as brushite, undergo transformation to used currently in orthopedics and dentistry include sintered apatitic calcium phosphate. 7 a-TCP has been shown to hydroxyapatite granules used as periodontal fillers, plasma transform to apatite in vivo. 8 Simkiss and Wilbur also sugspra...
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