In vitro biocompatibility of fluorcanasite glass-ceramics for bone tissue repair.

Fluorcanasite glass-ceramics were produced by controlled two stage heat-treatment of as-cast glasses. These glasses were modified from stoichiometric fluorcanasite composition by either adding P(2)O(5) or altering the molar ratios of Na(2)O and CaO. Commercial bioactive 45S5 Bioglass(R) was also prepared in-house to evaluate the relative in vitro biocompatibility of fluorcanasite glass-ceramics. The scanning electron microscopy (SEM) images showed that cells had colonized the surfaces of fluorcanasite glass-ceramics to form a confluent sheet. Quantitative MTT assay results were in good agreement with the qualitative SEM observations. It was concluded that incorporation of excess calcium oxide or P(2)O(5) in stoichiometric glass composition improved in vitro biocompatibility. Controlled heat-treatment further improved the biological response of cultured bone cells to modified fluorcanasite glass-ceramics when compared with their parent glasses. Ion release and pH data suggested a strong correlation between solubility (in particular, Na ion release) and biocompatibility. Reduced solubility, Na ion release, and related pH effects appeared to be the principal mechanisms responsible for improvement in in vitro biocompatibility.

In vitro biocompatibility of a novel Fe2O3 based glass ionomer cement.

INTRODUCTION: Since their invention in the late 1960s, glass ionomer cements (GICs) have been used extensively in dentistry but recently they have also been utilised in ear nose and throat (ENT) surgery. Unfortunately, Al3+, a component of conventional ionomer glasses, has been linked to poor bone mineralisation and neurotoxicity. OBJECTIVE: The aim of the research was to modify a commercial ionomer glass composition by substituting Al2O3 with Fe2O3. METHODS: Glasses with the following molar compositions were fabricated: 4.5SiO2*3M2O3*XP2O5*3CaO*2CaF2 (M = Al or Fe, X = 0-1.5). The glasses were characterised using X-ray fluorescence (XRF) and X-ray powder diffraction (XRD). Cements were prepared using a standard ratio of; 1 g of glass powder: 0.2 g of dried polyacrylic acid: 0.3 g of 10% tartaric acid solution. Cement formation was assessed using a Gilmore needle and in vitro biocompatibility was investigated for novel cement formulations. RESULTS: XRF revealed that the Fe2O3-based glasses had Al2O3 contamination from the crucibles and also had undergone substantial F- losses. XRD gave peaks that corresponded to magnetite Fe3O4 (JCPDS # 19-629) in all compositions. Apatite Ca5(PO4)3(OH,F) (JCPDS # 15-876) was identified in P2O5 containing glasses. It was possible to fabricate cements from all of the Fe2O3-based ionomer glasses. Good in vitro biocompatibility was observed for the Fe2O3-based cements. CONCLUSION: Ionomer glasses may be prepared by entirely replacing Al2O3 with Fe2O3. Cement setting times appeared to be related to P2O5 content. Fe2O3-based cements showed good in vitro biocompatibility.

Biocompatibility of glass-ionomer bone cements.

Glass-ionomer cements (GIC) have been extensively used in dentistry for over 30 years. Due to their excellent biocompatibility in dental applications GIC have been formulated for medical applications. The past decade has seen some impressive advances in the development of medical GICs, however these advances have been matched by serious critical problems. This review examines the properties of GICs, which can influence their behaviour in a biological environment. The progress made and the problems encountered in the development of these bone cements will also be addressed. The review will conclude with the research currently being employed to optimise the biocompatibility of these important biomaterials. There is little doubt that GICs compare favourably with alternative bone cements for specific applications, based on in vitro and in vivo studies. There is however, a degree of risk inherent in the use of any medical device or biomaterial. GICs must therefore be used carefully and in accordance with the instructions that are based on a significant body of research data.

Devitrification of ionomer glass and its effect on the in vitro biocompatibility of glass-ionomer cements.

The effects of devitrification of an ionomer glass with a molar composition 4.5SiO(2).3Al(2)O(3).1.5P(2)O(5).3CaO.2CaF(2) on cement formation and in vitro biocompatibility were investigated. Differential thermal analysis was used to study the phase evolution in the glass, and to determine the heat treatments for production of glass-ceramics. X-ray diffraction patterns from glass frit heat-treated at 750 degrees C for 2h contained peaks corresponding to apatite (JCPDS 15-876), whereas for samples heat-treated at 950 degrees C for 2h apatite and mullite (JCPDS 15-776) were the major phases detected. Transmission electron microscopy (TEM) confirmed that apatite and apatite-mullite phases were present after heat treatments at 750 degrees C and 950 degrees C respectively. Glass and glass-ceramics were ground to prepare <45microm powders and glass ionomer cements were produced using a ratio of 1g powder: 0.2g PAA: 0.3g 10% m/v tartaric acid solution in water. In vitro biocompatibility was evaluated using cultured rat osteosarcoma (ROS) cells. Scanning electron microscopy (SEM) showed that cells colonised the surfaces of cements prepared using untreated ionomer glass and glass crystallised to form apatite (750 degrees C/2h). However, quantitative evaluation using MTT and total protein assays indicated that more cell growth occurred in the presence of cements prepared using ionomer glasses crystallised to apatite than cements prepared using untreated glass. The least cell growth and respiratory activity was observed on cements made with crystallised glass containing both apatite and mullite. It was concluded that the controlled devitrification of ionomer glasses could be used to produce GIC bone cements with improved biocompatibility.