title: In vitro degradation and in vivo resorption of dicalcium phosphate cement based grafts.
abstract: There are two types of DCP: dihydrated (brushite) and anhydrous (monetite). After implantation, brushite converts to hydroxyapatite (HA) which resorbs very slowly. This conversion is not observed after implantation of monetite cements and result in a greater of resorption. The precise mechanisms of resorption and degradation however of these ceramics remain uncertain. This study was designed to investigate the effect of: porosity, surface area and hydration on in vitro degradation and in vivo resorption of DCP. Brushite and two types of monetite cement based grafts (produced by wet and dry thermal conversion) were aged in phosphate buffered saline (PBS) and bovine serum solutions in vitro and were implanted subcutaneously in rats. Here we show that for high relative porosity grafts (50-65%), solubility and surface area does not play a significant role towards in vitro mass loss with disintegration and fragmentation being the main factors dictating mass loss. For grafts having lower relative porosity (35-45%), solubility plays a more crucial role in mass loss during in vitro ageing and in vivo resorption. Also, serum inhibited dissolution and the formation of HA in brushite cements. However, when aged in PBS, brushite undergoes phase conversion to a mixture of octacalcium phosphate (OCP) and HA. This phase conversion was not observed for monetite upon ageing (in both serum and PBS) or in subcutaneous implantation. This study provides greater understanding of the degradation and resorption process of DCP based grafts, allowing us to prepare bone replacement materials with more predictable resorption profiles.
authors: Faculty of Dentistry, McGill University, 3640, Strathcona Anatomy and Dentistry Building, Rue University, Montreal, Quebec H3A 0C7, Canada. Electronic address: zeeshan.sheikh@utoronto.ca.
authors: Zeeshan
authors: Z
authors: Sheikh
authors: Faculty of Dentistry, McGill University, 3640, Strathcona Anatomy and Dentistry Building, Rue University, Montreal, Quebec H3A 0C7, Canada. Electronic address: yu.l.zhang@mcgill.ca.
authors: Yu Ling
authors: YL
authors: Zhang
authors: School of Chemical Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK. Electronic address: l.m.grover@bham.ac.uk.
authors: Liam
authors: L
authors: Grover
authors: Faculty of Dentistry, McGill University, 3640, Strathcona Anatomy and Dentistry Building, Rue University, Montreal, Quebec H3A 0C7, Canada. Electronic address: geraldine.merle@mcgill.ca.
authors: Géraldine E
authors: GE
authors: Merle
authors: Faculty of Dentistry, McGill University, 3640, Strathcona Anatomy and Dentistry Building, Rue University, Montreal, Quebec H3A 0C7, Canada. Electronic address: faleh.tamimimarino@mcgill.ca.
authors: Faleh
authors: F
authors: Tamimi
authors: Division of Orthopaedics, Department of Surgery, Faculty of Medicine, McGill University, 1650 Cedar Ave, Montreal General Hospital, Montreal, Quebec H3G 1A4, Canada. Electronic address: jake.barralet@mcgill.ca.
authors: Jake
authors: J
authors: Barralet
mesh_terms: D065966:Absorption, Physicochemical; D001826:Body Fluids / Q000737:chemistry*; D001843:Bone Cements / Q000737:chemistry*; D016025:Bone Transplantation / Q000295:instrumentation*; D002130:Calcium Phosphates / Q000737:chemistry*; D003343:Corrosion; D008422:Materials Testing; D016062:Porosity; D012995:Solubility; D013499:Surface Properties
chemical_list: D001843:Bone Cements; D002130:Calcium Phosphates; C485829:calcium phosphate, dibasic, anhydrous
keywords: Brushite; Cements; Dicalcium phosphate; In vitro degradation; In vivo resorption; Monetite