In vitro interaction betweenprimary bone organ cultures, glass-ionomer cements and hydroxyapatite/tricalcium phosphate ceramics zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFED I.M. Brook, G.T. Cm@ and D. J. Lamb School of Clinical Dentistry, Uni&ity of Sheffield, Sheffield S 10 2.X UK Presented at B/ointeractions ‘90, Oxford, UK 2 l-23 August 1990 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Primary organ cultures derived from neonate rat calvaria were maintained for 2 wk and used to study the zyxwvutsrqponmlkjihgfe in vitro response of osteoblast and periosteal cells to the component and composite forms of three different glass-ionomer (polyalkenoic) cements, comparing them to densely sintered hydroxyapatite and tricalcium phosphate ceramics. Dualitative analysis by scanning and transmission electron microscopy revealed that osteoblasts colonized all the solid test materials, although there was a less favourable response to materials with a rough surface topography and to unset and fluoride-containing glasses. On solid materials migrated cells maintained their tessellated morphology and exhibited numerous micro-appendages anchoring them to the surface of the test materials. A collagen-containing extracellular matrix was elaborated on to the ceramics and set glass-ionomer cements, except for one (AquaCem). Mineralization of the extracellular matrix was seen adjacent to hydroxyapatite and tricalcium phosphate ceramics, that adjacent to the latter morphologically resembling bone. Keywords: Biocompatibility, bone, osteoblasts, glass-ionomer cements Glass-ionomer cements (GICs), developed by Wilson and Kent’ in 1969, are widely used as dental restorative materials. They are formed by reaction of an inorganic base (aluminosilicate glass) with an organic polyelectrolyte (alkenoic acid) such as poly(acrylic)acid. Setting occurs by the transfer of metal ions from the glass to the acid. GlCs are therefore hybrid materials and, when set, can be considered as a composite of glass particles in a hydrogel binding matrix’. Evaluation of the biocompatibility of GlCs has concen- trated on their dental applications. The in vitro3,4 and in viva 5 ’ response of the dental pulp to GlCs has been compared to that of other types of dental filling material and, when used as an endodontic sealer, the clinical response of bone-periodontium has been compared to traditional dental materials’,*. However, although a GIC (Ketac-0, Espe, Germany) has been evaluated as a possible cement for orthopaedic implantsg, none has been studied in the role of a possible bone substitute. The purpose of this in vitro study was to compare the initial responses of osteoblasts and bone to GlCs and representative ceramic materials currently used as bone substitutes. Correspondence to Mr I.M. Brook. 0 1991 Butterworth-Helnemann Ltd. 0142-9612/91/020179-08 MATERIALS AND METHODS Materials Three different GlCs were evaluated. Two were commercial dental luting cements Ketac Cem Radiopaque (Espe, Germany) and AquaCem (DeTrey, UK), both based on fluoroaluminosilicate glasses of general composition Si02, A1203, AIF3, CaF2, NaF and AlP04, reacted with a copolymer of poly(acrylic)acid/maleic acid and poly(acrylic)acid, res- pectively, and the third was a fluoride-free glass Mp4 (Pilkington, UK) composition by mass SiOz 30.8%, AI,O, 38.5%, CaO 28.6% and Na20 2.1%, reacted with poly(acrylic)acid L3(4) mol wt 28 500 (Laboratory of the Government Chemist, UK). The commercial materials were mixed as directed for dental use and the fluoride-free GIC was made up in volume fractions of 0.5 Mp4,0.2 E3(4) and 0.3 sterile distilled water containing 10% tar-taric acid to control the set. The set materials were fractured with a hammer and irregular pieces of material approximately 2 X 1 mm selected. Smooth rods (nominally 2 mm long, 1 mm in diameter) were produced by placing unset material in silicone moulds. The set material was stored for 1 wk at Biomatenals 199 1, Vo/ 12 March 179